8x10 contact prints compared to 4x5 enlargements?

[Certain Exposures]

I have a follow-up question based on this thread. (https://www.largeformatphotography.info/forum/showthread.php?172868-Have-any-of-you-downgraded-from-8x10-to-4x5-Why) Have you ever compared an 8x10 print from a 4x5 negative to an 8x10 contact print?

I wonder if an 8x10 contact print looks superior to a 4x5 negative enlarged to make an 8x10 print. I have FOMO.

I've seen a 4x5 enlargement several times (I own one of Nico's prints (http://nicosphotographyshow.com/prints)). I've never seen an 8x10 contact print. Unfortunately, I get the feeling that only making one could help me make up my mind.


This response from Maris (https://www.largeformatphotography.info/forum/showthread.php?172914-8x10-contact-prints-compared-to-4x5-enlargements&p=1678381&viewfull=1#post1678381) answers the thread to me:


I've enlarged lot of 4x5 to 8x10. Even "enlarged" a 8x10 negative to 8x10 and then contact printed that same 8x10 negative by way of comparison.
All the prints look absolutely superb but there are subtle differences in the prints made by projection compared to the one made by contact. It's due to flare in the projection system.
This is best seen as fine black lines in projection prints being slightly wider and fine white lines being slightly narrower compared to a flare free rendition by contact printing.
The effect is very small and can only be seen in side by side comparisons which in practice is not done except by people troubled by an inquisitive mind.

[bmikiten]

I think the difference is pretty dramatic. NOTE that some of this is purely based on projection through optics versus direct contact printing (no optics). I have several Weston 8x10s and they are some of the most amazing prints I've seen even when compared to current state of the art 4x5 projected images. In my personal work I see a sense of depth and what I can only describe as presence in the 8x10 contacts. I've never shot the same image with both formats and done the test but it might be fun to do.

[willwilson]

It's better but subjective. They have a feel which is different than an enlargement. You do cut out all the fudge factor, no lens, no alignment, less dust. I think a 4x5 contact can show some of these differences just smaller (tonality, smoothness, sharpness, etc.)

For me I do not produce 8x10 as a final size so 4x5 enlarged is my go to as I struggle to see differences between formats at larger print sizes (16x20 plus). I have been making more small prints these days, like 11x14, and have thought about going Brett Weston on things and getting an 11x14 setup for contact printing, but some of my favorite work he did was medium format so go figure.

My test print size is 8x10. They go in a binder for reference. An 8x10 mounted to 11x17 behind glass would be tough to discern if it is an enlarged 4x5 or 8x10 contact print.

I say test and decide for yourself. Contact printing is quite different from enlarging for me.

-=Will

[rfesk]

I have never seen prints side by side but I am willing to bet that a good printer could enlarge a 4x5 negative to 8x10 so that it would be difficult to tell them apart.

It will be interested also in others experience.

[Maris Rusis]

I've enlarged lot of 4x5 to 8x10. Even "enlarged" a 8x10 negative to 8x10 and then contact printed that same 8x10 negative by way of comparison.
All the prints look absolutely superb but there are subtle differences in the prints made by projection compared to the one made by contact. It's due to flare in the projection system.
This is best seen as fine black lines in projection prints being slightly wider and fine white lines being slightly narrower compared to a flare free rendition by contact printing.
The effect is very small and can only be seen in side by side comparisons which in practice is not done except by people troubled by an inquisitive mind.

[Neal Chaves]

I made contact prints when I first started in 8X10 but as soon as I had an 8X10 enlarger, I usually went right to an 11x14 print. If I needed an 8X10 for a publication, or multiple 8X10 prints from the same 8X10 negative, I make them 1:1 with my enlarger. There may be a barley deductible difference seen by someone with a loupe, but the ease of making the prints, the control over dogging and burning, the freedom from Newton's rings, dust, etc. has me favoring 1:1 optical prints.

[paulbarden]

It seems to me that you've already decided you want to go 8x10, but you are hoping someone else can push you over the edge (of the decision). You don't need anyone else's opinion for that. There are many reasons to stick with 4x5 or move to 8x10. The key is in knowing what you want to do with the format you've chosen.
For me, I am only contact printing large negs these days, and almost all are salted paper prints. I find 4x5 too small to be meaningful (for ME) and 8x10 is optimal. I also do 5x7 and I love that format for its aspect ratio. (I find both 4x5 and 8x10 to be too close to square for my liking.)

[Certain Exposures]

I think the difference is pretty dramatic. NOTE that some of this is purely based on projection through optics versus direct contact printing (no optics). I have several Weston 8x10s and they are some of the most amazing prints I've seen even when compared to current state of the art 4x5 projected images. In my personal work I see a sense of depth and what I can only describe as presence in the 8x10 contacts. I've never shot the same image with both formats and done the test but it might be fun to do.

Thanks for sharing


It's better but subjective. They have a feel which is different than an enlargement. You do cut out all the fudge factor, no lens, no alignment, less dust. I think a 4x5 contact can show some of these differences just smaller (tonality, smoothness, sharpness, etc.)

For me I do not produce 8x10 as a final size so 4x5 enlarged is my go to as I struggle to see differences between formats at larger print sizes (16x20 plus). I have been making more small prints these days, like 11x14, and have thought about going Brett Weston on things and getting an 11x14 setup for contact printing, but some of my favorite work he did was medium format so go figure.

My test print size is 8x10. They go in a binder for reference. An 8x10 mounted to 11x17 behind glass would be tough to discern if it is an enlarged 4x5 or 8x10 contact print.

I say test and decide for yourself. Contact printing is quite different from enlarging for me.

-=Will

Thanks - 11x14 is the perfect general print size to me too! That's part of why I'm inclined to stick to 4x5 and below. 8x10 enlargers are big and pricey.

You and I share the same interest in ULF. I looked into 11x14 cameras for contact printing. The bodies are just way out of my price range for a film camera. Film and developer costs would be irrelevant because I'd just shoot less frames and more elaborately planned projects. You lose a lot of spontenaity with something that unwieldy though.


I have never seen prints side by side but I am willing to bet that a good printer could enlarge a 4x5 negative to 8x10 so that it would be difficult to tell them apart.

It will be interested also in others experience.

Yes, same.


I've enlarged lot of 4x5 to 8x10. Even "enlarged" a 8x10 negative to 8x10 and then contact printed that same 8x10 negative by way of comparison.
All the prints look absolutely superb but there are subtle differences in the prints made by projection compared to the one made by contact. It's due to flare in the projection system.
This is best seen as fine black lines in projection prints being slightly wider and fine white lines being slightly narrower compared to a flare free rendition by contact printing.
The effect is very small and can only be seen in side by side comparisons which in practice is not done except by people troubled by an inquisitive mind.

Thanks! This response wraps up the thread. I'm glad someone else was as troubled as me :p.



I made contact prints when I first started in 8X10 but as soon as I had an 8X10 enlarger, I usually went right to an 11x14 print. If I needed an 8X10 for a publication, or multiple 8X10 prints from the same 8X10 negative, I make them 1:1 with my enlarger. There may be a barley deductible difference seen by someone with a loupe, but the ease of making the prints, the control over dogging and burning, the freedom from Newton's rings, dust, etc. has me favoring 1:1 optical prints.

Thanks. Is it generally easier to make a professionally finished contact print than an enlargement? Why is dodging and burning easier? I've done contacts and enlargements. I've never reflected on the relative difficulty. I still have more to learn about the darkroom.


It seems to me that you've already decided you want to go 8x10, but you are hoping someone else can push you over the edge (of the decision). You don't need anyone else's opinion for that. There are many reasons to stick with 4x5 or move to 8x10. The key is in knowing what you want to do with the format you've chosen.
For me, I am only contact printing large negs these days, and almost all are salted paper prints. I find 4x5 too small to be meaningful (for ME) and 8x10 is optimal. I also do 5x7 and I love that format for its aspect ratio. (I find both 4x5 and 8x10 to be too close to square for my liking.)

Haha, my heart yearns to hold big negatives. I'm resisting. 4x5 is definitely too small to me. I like printing on 11x14. 4x5 enlargers require so much space though. It makes me wonder if I could live with 8x10 (sometimes).

[G Benaim]

They really are different animals, and then there’s the further difference between enlarging papers and contact papers (azo and Lodima), which further distance the two options. A contact print, even a small one, will attract your eye in ways enlargements won’t. But obviously in an enlargement you will see much greater detail. It just won’t have the presence of a contact print. One further complication is enlarged negs for contact printing, an option I haven’t tried but people I know and respect have compared the results and are satisfied when compared to a straight contact print, you just have to tailor the neg to the intended medium. Best thing to do is to get your eyes in front of some contact prints and decide for yourself.

[Larry Gebhardt]

I’ve compared 5x7 contacts to 1:1 enlargements only a few times and the difference was possibly noticeable with a loupe but with my strong reading glasses I wasn’t picking up significant differences.

I have an 8x10 I was gifted, but it needs a new bellows. I’m curious to try it not for the size of the negative but for the size of the ground glass. The step up from 4x5 to 5x7 is nice when composing. The bulk in packing the camera is not.

Given the detail in a 4x5 negative I wouldn’t step up to 8x10 enlarged until my print side was significantly larger than 16x20.

[jnantz]

Certain Exposures what are your goals ? Differences can always be seen in everything, even identical twins .. but in the end differences don't really matter (unless that's the point).

[paulbarden]

Haha, my heart yearns to hold big negatives. I'm resisting.

Why?? If you believe you want to explore it, then do it. You will either find that your first 8x10 contact print is a life-changing revelation that sets you on a new path, or it doesn’t bring you what you hoped for. Either way, you won’t know until you’ve tried it for yourself.

[Alan9940]

Back in the 80's, I did a direct comparison between 4x5 and 8x10--same scene, same film, same processing, etc. I couldn't duplicate the focal lengths on each format exactly, but they were close enough. I contact printed the 8x10 and enlarged the 4x5 to 8x10 on the same paper, same processing. When viewed separately, each were fine photographs. But, when compared side-by-side the contact print was noticeably sharper and, more importantly, had a presence to it. Put simply, the contact print felt like you could "dive into it" while the 4x5 appeared behind glass. Very hard to describe, but you'd notice it right away given the same opportunity. I was so enamored with the "look" that the 8x10 became my primary format for the next decade. At 70 years young now, I still enjoy the format!

[xkaes]

Sounds like another, "You can see the difference if you compare them side-by-side with a loupe" conversations. In other words, in the real world, it makes difference. Give comparison shots to 10 random people and none of them with see any difference.

[Alan9940]

Sounds like another, "You can see the difference if you compare them side-by-side with a loupe" conversations. In other words, in the real world, it makes difference. Give comparison shots to 10 random people and none of them with see any difference.

No, not through a loupe. With my own eyes. And, I agree that it makes no difference in the greater scheme of things and I'm sure you're right that if you handed comparison shots to 10 different people, probably not one would see any difference, but I see/saw a difference. Seeing how I do my photography for my own enjoyment I'm the only one who needs to be satisfied with the final results. ;)

[Neal Chaves]

I’ve compared 5x7 contacts to 1:1 enlargements only a few times and the difference was possibly noticeable with a loupe but with my strong reading glasses I wasn’t picking up significant differences.

I have an 8x10 I was gifted, but it needs a new bellows. I’m curious to try it not for the size of the negative but for the size of the ground glass. The step up from 4x5 to 5x7 is nice when composing. The bulk in packing the camera is not.

Given the detail in a 4x5 negative I wouldn’t step up to 8x10 enlarged until my print side was significantly larger than 16x20.

As I mentioned above, I cobbled together an 8X10 enlarging camera as soon as I started working in 8X10. The largest print I have ever made is 20X24, and now I do not intend to silver print larger than 16X20. If someone wanted and was willing to pay for one of my burnt offerings at a size up to billboard, there are much better and more practical digital processes available I can contract for, starting with a high resolution scan of the original negative on equipment I would rather not own, maintain, pay for or be taxed on. Today I have two Beseler enlargers, a 4X5 with a color head I use to vary contrast on multi grade papers, and an 45VXL 8X10 with a W45 tube cold light head which I use with gels for contrast control. I don't make many 16X20s and those which I do, I wash by hand in trays. Everything drys on screens.

[Certain Exposures]

They really are different animals, and then there’s the further difference between enlarging papers and contact papers (azo and Lodima), which further distance the two options. A contact print, even a small one, will attract your eye in ways enlargements won’t. But obviously in an enlargement you will see much greater detail. It just won’t have the presence of a contact print. One further complication is enlarged negs for contact printing, an option I haven’t tried but people I know and respect have compared the results and are satisfied when compared to a straight contact print, you just have to tailor the neg to the intended medium. Best thing to do is to get your eyes in front of some contact prints and decide for yourself.

Agreed - I do need to look at some 8x10 contacts. I've been starting at my 4x5 contact.


I’ve compared 5x7 contacts to 1:1 enlargements only a few times and the difference was possibly noticeable with a loupe but with my strong reading glasses I wasn’t picking up significant differences.

I have an 8x10 I was gifted, but it needs a new bellows. I’m curious to try it not for the size of the negative but for the size of the ground glass. The step up from 4x5 to 5x7 is nice when composing. The bulk in packing the camera is not.

Given the detail in a 4x5 negative I wouldn’t step up to 8x10 enlarged until my print side was significantly larger than 16x20.

Thanks for that info. I still contemplate 8x10 sometimes because an 8x10 slide could make an excellent collectable art piece. 4x5 slides would be too small. Also, if someone did want a wall sized print then your 8x10 negative would be worth it.


Certain Exposures what are your goals ? Differences can always be seen in everything, even identical twins .. but in the end differences don't really matter (unless that's the point).

I'm still weighing the relative costs and tradeoffs between the two formats. My goal is to profitably create art for education, entertainment, and publication.


Why?? If you believe you want to explore it, then do it. You will either find that your first 8x10 contact print is a life-changing revelation that sets you on a new path, or it doesn’t bring you what you hoped for. Either way, you won’t know until you’ve tried it for yourself.

You're probably right. The entry cost of 8x10 is a barrier for me. Operating one would be affordable because I can develop and print on my own. The work I create is generally suited to something less unwieldy. I'd have to change my subjects. E.g. I can't see myself shooting 8x10 in conditions like this (a blizzard that shut down the city):

https://i.imgur.com/QbF2JYv.jpg
Note: I finally figured out how to post images like this!


Back in the 80's, I did a direct comparison between 4x5 and 8x10--same scene, same film, same processing, etc. I couldn't duplicate the focal lengths on each format exactly, but they were close enough. I contact printed the 8x10 and enlarged the 4x5 to 8x10 on the same paper, same processing. When viewed separately, each were fine photographs. But, when compared side-by-side the contact print was noticeably sharper and, more importantly, had a presence to it. Put simply, the contact print felt like you could "dive into it" while the 4x5 appeared behind glass. Very hard to describe, but you'd notice it right away given the same opportunity. I was so enamored with the "look" that the 8x10 became my primary format for the next decade. At 70 years young now, I still enjoy the format!

Thanks - a few people keep mentioning the 3-dimensionality. Keep enjoying it!


Sounds like another, "You can see the difference if you compare them side-by-side with a loupe" conversations. In other words, in the real world, it makes difference. Give comparison shots to 10 random people and none of them with see any difference.

Did you mean to say that it doesn't make a difference in the real world?


No, not through a loupe. With my own eyes. And, I agree that it makes no difference in the greater scheme of things and I'm sure you're right that if you handed comparison shots to 10 different people, probably not one would see any difference, but I see/saw a difference. Seeing how I do my photography for my own enjoyment I'm the only one who needs to be satisfied with the final results. ;)

I won't doubt you. The idea of making 8x10 slides or producing prints with that mysterious 3-dimensionailty keeps me coming back to this topic.

[neil poulsen]

I've never made the comparison, so I wonder if one could tell a difference between a 4x5 negative enlarged to 16x20, compared to an 8x10 negative enlarged to a 16x20. I suspect that it could be fairly obvious.

[bob carnie]

I can say from printing 4 x 5 and 8x10 negs that the 8x10 print at 20 x 24 size is much different than 4 x 5, notice I do not say better but different. Same goes for almost every method I print you can see a difference.

I think it boils down to the OP actually seeing both to see the difference. I like really hot peppers , my wife not so much , but she is a master chef and I appreciate her version of cooking, I kind of believe this for all types of prints, I respect others work even though its not maybe how I would print, but then again it is their print not mine.


I really think its silly to say one method is better than another.

[Mark J]

I think that would be harder to see. I've done enlargements from 6 x 9 cm to 16x20" and also from 5 x 7" ( rarely ) to 16x20", and there wasn't a lot of difference, although to be fair, the rollfilm was FP4 and the 5x7" was HP5.
However I do think there's something about contact prints, there's a similar thread on the FADU forum, and I am in the camp with Alan9940 on this.
I am trying to get a condenser head for my Meopta Magnifax at the moment, to try instead of the colour head, because I believe it ought to look a bit more like the contact print, given that the illuminating light is more directional.
I was watching a comparison of the two sort of heads by 'The naked photographer' on Youtube a couple of days ago, and he did a number of prints at different grades, and some with less development, for use with the condenser. At the end his verbal conclusions were that there wasn't much difference, but I disagreed very much- it seemed obvious that they were different even from viewing via the TV.

[xkaes]

....if you handed comparison shots to 10 different people, probably not one would see any difference...

Exactly my point. To whom it makes a difference? If it does to you -- GO FOR IT.

[jnantz]

I'm still weighing the relative costs and tradeoffs between the two formats. My goal is to profitably create art for education, entertainment, and publication.


sounds like fun !
don't forget to factor in how you are going to develop the film... 4x5 can be relatively easy, but 8x10 is a bit more difficult...
unless you've developed bit sheet film before, it can either be a piece of cake using hangers and tanks or lets just say not so much of a piece of cake ...
(the devil is always in the details)

[Erik Larsen]

Today I did do a comparison between an 8x10 contact and a 1 to 1 enlargement and to my surprise it was a noticeable difference between the two. I was using a color head for the light source with identical exposure verified by an enlarger meter. The contact print was noticeably more contrasty. I didn't try to match contrast on the enlargement as my curiosity was satisfied but I think I could add a bit of magenta to the color head to match the enlargement to the contact print. It was a lesson but nothing more IMO, I think I could be happy with either. As others have mentioned only you can be the judge....

[ic-racer]

My observation is the resolution of the 4x5 enlargement is half and the grain is twice as big.

[xkaes]

Today I did do a comparison between an 8x10 contact and a 1 to 1 enlargement and to my surprise it was a noticeable difference between the two. I was using a color head for the light source with identical exposure verified by an enlarger meter. The contact print was noticeably more contrasty. I didn't try to match contrast on the enlargement as my curiosity was satisfied but I think I could add a bit of magenta to the color head to match the enlargement to the contact print. It was a lesson but nothing more IMO, I think I could be happy with either. As others have mentioned only you can be the judge....

That's exactly the same as making a print from a condenser vs a diffusion enlarger. If you adjust whatever (exposure, development, filter, etc.) for either, you end up with the same result.

[xkaes]

My observation is the resolution of the 4x5 enlargement is half and the grain is twice as big.

And it should be -- if you are using a loupe. But the human eye at a normal distance can not detect that difference.

If I'm at five feet from an 8x10" print, there is no way I can tell if it is from an 8x10 contact print or a 4x5" enlargement.

[Neal Chaves]

That's exactly the same as making a print from a condenser vs a diffusion enlarger. If you adjust whatever (exposure, development, filter, etc.) for either, you end up with the same result.

The tint of the glass in the contact print frame probably affects the contrast of VC papers. Try the test with a graded paper.

[Drew Wiley]

There is no single generic answer. Depends on how well you do one or the other. A poorly fitted contact frame with dirty glass can be just as "lossy" as a cheap enlarging lens and untamed bellows flare. Lots of variables. But if you optimize both styles, yes, there will be an evident difference between an 8x10 contact and a 4x5 enlarged to 8x10. But which you prefer is up to you.

Glass tint is so minor that it has almost no effect with respect to VC versus old graded papers in a contact frame, Neal. My contact frame has thick Anti-Newton glass in it, and I use that for even contact color separation work. The offset is only about 4cc of color correction - nil by black and white standards. I have no problem contact printing with VC papers.

[Tin Can]

Good to know!

I will convert one of my contact printers to AN

and test

Thanks Drew



There is no single generic answer. Depends on how well you do one or the other. A poorly fitted contact frame with dirty glass can be just as "lossy" as a cheap enlarging lens and untamed bellows flare. Lots of variables. But if you optimize both styles, yes, there will be an evident difference between an 8x10 contact and a 4x5 enlarged to 8x10. But which you prefer is up to you.

Glass tint is so minor that it has almost no effect with respect to VC versus old graded papers in a contact frame, Neal. My contact frame has thick Anti-Newton glass in it, and I use that for even contact color separation work. The offset is only about 4cc of color correction - nil by black and white standards. I have no problem contact printing with VC papers.

[xkaes]

... yes, there will be an evident difference between an 8x10 contact and a 4x5 enlarged to 8x10. But which you prefer is up to you.


There won't be any difference at a five foot viewing distance. Get rid of your microscope and enjoy the real world of photography.

[Michael R]

There won't be any difference at a five foot viewing distance. Get rid of your microscope and enjoy the real world of photography.

Drew’s eyes have built-in microscopes and also filtration to match various standard illuminants. True story.

[Michael Kadillak]

Good to know!

I will convert one of my contact printers to AN

and test

Thanks Drew

Save your money because you do not need anti newton glass for contact printing because you only have one glass surface, not two as in a negative carrier. Standard 1/8" shop glass is perfectly adequate. I just changed the glass in my 8x20 and 11x14 contact print frames last week.

[Michael R]

I think what Drew is referring to is the potential for Newton rings to form at the interface between the film base and glass (since both of those surfaces are highly reflective (unless it is a film such as Tri-X 320 that has a bit of tooth). I would suggest starting with regular glass first.


Save your money because you do not need anti newton glass for contact printing because you only have one glass surface, not two as in a negative carrier. Standard 1/8" shop glass is perfectly adequate. I just changed the glass in my 8x20 and 11x14 contact print frames last week.

[xkaes]

Drew’s eyes have built-in microscopes

I'm glad I don't have that problem.

[Tin Can]

Have plenty of AN 11X14

Bought in lock frames a decade ago

I sold 2 long ago on this forum

Not selling any now




Save your money because you do not need anti newton glass for contact printing because you only have one glass surface, not two as in a negative carrier. Standard 1/8" shop glass is perfectly adequate. I just changed the glass in my 8x20 and 11x14 contact print frames last week.

[Michael Kadillak]

Have plenty of AN 11X14

Bought in lock frames a decade ago

I sold 2 long ago on this forum

Not selling any now

Just wanted to make sure that future readers of this post understand that having surplus anti newton glass and putting it to use is not the same as a necessity to contact print with it because anti newton glass is hard to get and is expensive. Shop glass works fine for this application. Only when you have two glass surfaces in relative close contact to each other does the "risk" of Newton Rings come into play and even then it is not a given that the phenomena could manifest itself. If it does, then you can deal with it at that time. Glossy paper (immaterial how reflective it is) and contact frame glass will never be a concern.

[Oren Grad]

I think what Drew is referring to is the potential for Newton rings to form at the interface between the film base and glass (since both of those surfaces are highly reflective (unless it is a film such as Tri-X 320 that has a bit of tooth).

Yup. In my darkroom, printing HP5 Plus using regular glass in a felt-lined spring-back contact printing frame reliably produces florid Newton's rings. Frame design doesn't matter - I've tried several.

[Sal Santamaura]

Just wanted to make sure that future readers of this post understand that having surplus anti newton glass and putting it to use is not the same as a necessity to contact print with it because anti newton glass is hard to get and is expensive. Shop glass works fine for this application. Only when you have two glass surfaces in relative close contact to each other does the "risk" of Newton Rings come into play and even then it is not a given that the phenomena could manifest itself. If it does, then you can deal with it at that time. Glossy paper (immaterial how reflective it is) and contact frame glass will never be a concern.

Michael had it right. Nothing to do with two glass surfaces.


...the potential for Newton rings to form at the interface between the film base and glass (since both of those surfaces are highly reflective (unless it is a film such as Tri-X 320 that has a bit of tooth)...

320TXP is a joy in that regard. If one likes its characteristic curve, contact printing it is most pleasurable.


...I would suggest starting with regular glass first.

I've never had any success, irrespective of ambient temperature /relative humidity, in avoiding Newton's rings when contact printing other films with glossy base sides. One workaround is to fix, wash and dry an unexposed, undeveloped sheet of 320TXP, then use it as a spacer between other films' bases and the non-anti-Newton glass in either a contact frame or enlarger negative carrier. Never a ring again in that configuration.

[Michael R]

Indeed, it’s hard to imagine how it wouldn’t be a frequent problem in contact frames. If there is imperfect contact, and there is specular reflection between the two surfaces, Newton rings will form around the contact area.

I wonder why we don’t read of this more in the writings of photographers who did a lot of contact printing (Weston, for example). Unless maybe the bases of old films were less shiny or something.


Yup. In my darkroom, printing HP5 Plus using regular glass in a felt-lined spring-back contact printing frame reliably produces florid Newton's rings. Frame design doesn't matter - I've tried several.

[willwilson]

Michael, I was thinking the same thing. Drew? Anyone? Thoughts?

[Oren Grad]

I wonder why we don’t read of this more in the writings of photographers who did a lot of contact printing (Weston, for example). Unless maybe the bases of old films were less shiny or something.

Yes, maybe retouching directly on the negative was more commonly done, and sheet films of that era were more often coated on bases with a "tooth" to accommodate that. I imagine it shouldn't be too difficult to confirm or disprove that as a historical assertion.

[Michael Kadillak]

Can't dispute results and if Newton Rings are manifesting themselves in your contact printing regiment, something needs to be fixed as that condition is clearly unacceptable. I have contact printed with T Max 400, FP4+, Delta 100, Efke 25 and Foma 200 on glossy paper (Azo, Ilford warm tone and Classic) through 1/8" shop glass over 25+ years and never had a problem.

Learn something new just about every day.

[Tin Can]

Is there any correlation between high and low pressure contact

I use 2 high pressure and one low. the low seldom

I am still working on my 20X36" with only heavy plate glass on low pressure foam

My job was flat surface examination using Surface RA tool and FujiFilm pressure sensitive

Wow, we can now buy it from eBay

https://www.ebay.com/itm/266027072370?chn=ps&norover=1&mkevt=1&mkrid=711-213727-13078-0&mkcid=2&itemid=266027072370&targetid=4581183927179149&device=c&mktype=&googleloc=&poi=&campaignid=418233787&mkgroupid=1241348861725295&rlsatarget=pla-4581183927179149&abcId=9300542&merchantid=51291&msclkid=d0727fb698eb150e59d91bf38e15628b

[bob carnie]

Drew’s eyes have built-in microscopes and also filtration to match various standard illuminants. True story.

Not to mention he has built in XY coordinate vision so he can record every position he has ever been in and enhanced densitometer fingertip BORG style fingers.

[Michael R]

Is there any correlation between high and low pressure contact

I use 2 high pressure and one low. the low seldom

I am still working on my 20X36" with only heavy plate glass on low pressure foam

My job was flat surface examination using Surface RA tool and FujiFilm pressure sensitive

Wow, we can now buy it from eBay

https://www.ebay.com/itm/266027072370?chn=ps&norover=1&mkevt=1&mkrid=711-213727-13078-0&mkcid=2&itemid=266027072370&targetid=4581183927179149&device=c&mktype=&googleloc=&poi=&campaignid=418233787&mkgroupid=1241348861725295&rlsatarget=pla-4581183927179149&abcId=9300542&merchantid=51291&msclkid=d0727fb698eb150e59d91bf38e15628b

Strictly speaking, contact is contact, so it would not matter how much pressure there is if the two surfaces are perfectly flat. However as usual we aren’t dealing with perfect things/conditions, so in reality high pressure, for example, can either help or make the problem worse, depending on the surfaces, how evenly the pressure is applied (ie you don’t want to distort flatness etc.).

My first suggestion if Newton rings are a problem was always to try using a sheet of fixed out TXP 320 as a spacer (for glass negative carriers as well) as Sal mentioned a few posts earlier, before investing in more costly alternatives that may or may not work - although with the prices of Kodak films these days...

Oren raises an interesting question regarding old timey films. Before small and medium format was a thing, we know retouching negatives was very common and basically standard practice in studio settings and such. Perhaps in those days more films had somewhat “matte” base coatings for this purpose - like TXP still does. Maybe this was just enough to prevent a lot of potential Newton ring problems from popping up. Maybe not. I don’t know.

I went down the rat hole (as is my custom) with this and tried a slew of things and inquiries, and seem to have been able to prevent Newton rings with multicoated filter glass (you need reflection to have Newton rings), but obviously there is no perfect BBAR coating so this is by no means guaranteed to work - and it is prohibitively expensive. I did it because (a) I’m an idiot, (b) I only needed big enough for 35mm to 4x5 negative carriers. The state of the art, as it were, would be to use glass with a sub-wavelength (“nano-structured”) anti reflective surface. Basically a much finer grained scattering surface than ANR glass. The type of thing lens manufacturers have been using (Nikon Nano Crystal Coat etc.). However for the time being it’s a no-go because those surfaces need to be in sealed settings.

Anyway that’s much more than anyone ever wanted to read about Newton rings lol.

I always meant to ask Christopher Burkett how he handles Newton rings since he does so much masking. Maybe Drew knows.

[Alan9940]

Strictly speaking, contact is contact, so it would not matter how much pressure there is if the two surfaces are perfectly flat. However as usual we aren’t dealing with perfect things/conditions, so in reality high pressure, for example, can either help or make the problem worse, depending on the surfaces, how evenly the pressure is applied (ie you don’t want to distort flatness etc.).

My first suggestion if Newton rings are a problem was always to try using a sheet of fixed out TXP 320 as a spacer (for glass negative carriers as well) as Sal mentioned a few posts earlier, before investing in more costly alternatives that may or may not work - although with the prices of Kodak films these days...

Oren raises an interesting question regarding old timey films. Before small and medium format was a thing, we know retouching negatives was very common and basically standard practice in studio settings and such. Perhaps in those days more films had somewhat “matte” base coatings for this purpose - like TXP still does. Maybe this was just enough to prevent a lot of potential Newton ring problems from popping up. Maybe not. I don’t know.

I went down the rat hole (as is my custom) with this and tried a slew of things and inquiries, and seem to have been able to prevent Newton rings with multicoated filter glass (you need reflection to have Newton rings), but obviously there is no perfect BBAR coating so this is by no means guaranteed to work - and it is prohibitively expensive. I did it because (a) I’m an idiot, (b) I only needed big enough for 35mm to 4x5 negative carriers. The state of the art, as it were, would be to use glass with a sub-wavelength (“nano-structured”) anti reflective surface. Basically a much finer grained scattering surface than ANR glass. The type of thing lens manufacturers have been using (Nikon Nano Crystal Coat etc.).

Back in the 80's when I first started contact printing 8x10 negs, I had a terrible time with Newton Rings. Lots of theories as to what caused them--reflections, uneven pressure, humidity, etc--and I tried everything to resolve the issue. I always thought the issue was mainly caused by light refractions caused by minute unevenness of the two surfaces.

I don't remember how it all began, but I got into a conversation with Ron Wisner about this problem which resulted in my sending him a sheet of 1/4" plate glass that he sent off somewhere to have a single coating (same stuff used on lenses) applied to one surface. I don't remember it costing me much because I think he thought of it as a technical challenge to solve. Anyway, lot story short...got the coated glass, tried it, not a single Newton Ring since! Been using the same piece of glass for 40 years now.

So, you may be on to something with that coating idea.

[John Layton]

Michael I'm also an idiot...and although I sense that there are quite a few of us here on this forum - I wish there could be more of us in the general population.

[Oren Grad]

Following up on Michael R's points:

The primary problem isn't the amount of pressure, it's that the pressure is uneven. The wood-and-felt backs of printing frames don't come close to spreading evenly the high pressure that the springs exert at their few points of contact.

As I've posted elsewhere, the most effective solution in my darkroom has been to skip the printing frame and use a plain glass "sandwich" - a large, thin piece of glass goes on the enlarger baseboard, then the paper, then the negative, and on top a thicker, heavier piece of plain glass.

I've tinkered with Tru Vue AR coated glass in print frames, with equivocal results. What brought those experiments to an end was that it was quite expensive, and difficult to find pieces without small coating flaws that would show up in prints. The local pro frame shop where I was buying the stuff humored me at first, but after a few rounds of inspecting samples to find clean sections of larger pieces that could be cut for me to purchase it became apparent that it was becoming a nuisance for them. This was quite a few years ago; perhaps the manufacturing process has improved since then.

[bob carnie]

FWIW we are contact printing inkjet negatives to silver, and Pt Pd using a very thick glass plate , to date we have not seen any issues with newton rings. We place the paper emulsion up on the baseboard lay down the inkjet negative (emulsion down right reading) and then lay down the thick glass to create the contact.

[Michael R]

Back in the 80's when I first started contact printing 8x10 negs, I had a terrible time with Newton Rings. Lots of theories as to what caused them--reflections, uneven pressure, humidity, etc--and I tried everything to resolve the issue. I always thought the issue was mainly caused by light refractions caused by minute unevenness of the two surfaces.

I don't remember how it all began, but I got into a conversation with Ron Wisner about this problem which resulted in my sending him a sheet of 1/4" plate glass that he sent off somewhere to have a single coating (same stuff used on lenses) applied to one surface. I don't remember it costing me much because I think he thought of it as a technical challenge to solve. Anyway, lot story short...got the coated glass, tried it, not a single Newton Ring since! Been using the same piece of glass for 40 years now.

So, you may be on to something with that coating idea.

Without getting into the weeds, two things are required for the interference pattern to form:

1. Different amounts of space between the surfaces (for example some space vs no space (ie contact))
2. Specular reflection between the surfaces

[Michael R]

FWIW we are contact printing inkjet negatives to silver, and Pt Pd using a very thick glass plate , to date we have not seen any issues with newton rings. We place the paper emulsion up on the baseboard lay down the inkjet negative (emulsion down right reading) and then lay down the thick glass to create the contact.

This is likely the best way without exotic measures. The nice thing about thicker glass is it applies more pressure but without deformation.

[Michael Kadillak]

Without getting into the weeds, two things are required for the interference pattern to form:

1. Different amounts of space between the surfaces (for example some space vs no space (ie contact))
2. Specular reflection between the surfaces

Still trying to wrap my head around this issue. Industry standard glass used in a contact frame is inherently designed for its universal use (the primary application in windows of homes) to be the perfect transmitter of light because any applied coating that would have a modest degradation of this transmission to facilitate a specular reflection event (like a modest one way mirror) and is just not there or should not be there. The consumer market would have a fit. Then on the other side the surface of a glossy photographic emulsion is capable of a reflective event? I would think that the manufacturers of these emulsions would have checked that box off decades ago knowing full well that it is entirely within the realm of possibility that consumers of their product could very well opt for contact printing if only as proofing their negatives and not be subjected to any adverse visual artifacts. I have never seen a film photographic emulsion that appeared glossy to my eyes. I have seen base side of film emulsions that are "glossy" but that is not in play (emulsion of paper to emulsion of the film contact). My instincts tell me something else is going on here. If it is possible please post the variables of your interference patterns (film, photo paper, light source) and what it looks like.

[Oren Grad]

I have seen base side of film emulsions that are "glossy" but that is not in play (emulsion of paper to emulsion of the film contact).

The problem is the interaction between the non-emulsion side of the film base and the contact printing glass, not the emulsion side and the paper. That's why the retouching base on TXP makes a difference.

[Tin Can]

and maybe why my 2X X-Ray does not have NR

advantage 2x

[John Layton]

Oren I like your glass sandwich - but no issues with halation from the bottom piece? I also think of Bob Carnie's method of laying a single sheet of heavy glass over the negative and paper, with everything resting on the baseboard.

At any rate...this has really got me thinking about those felt lined contact frame backs - and although I don't often do contacts these days, I'll try employing either yours or Bob's receipe for this purpose in the future. Many thanks!

Edit: as for newton's rings, I also find that these to show up surrounding what can sometimes become slightly raised "islands" of negative spotting media, especially when I've made a strong mix in the attempt to completely block light passage (attempting to mitigate those evil black spots on prints), as such strong mixes often contain undissolved particulates. Oh...how I wish there were a truly opaque solution available, to say nothing of one which would also maintain planarity with the negative (retouching) surface! I've torn so much hair out of my head about this, for so many years...that its a miracle that I'm not completely bald!

[Michael R]

As Oren indicated, the most common source of Newton ring problems, whether contact printing or using a glass negative carrier in an enlarger, is the interface between the glass and the base side of the film, since both are reflective. For example, typical float glass (as in a contact frame) reflects around 4% of incident light at each glass-air transition. Broadband anti-reflection coatings such as those used on camera lenses and filters bring this down to 0.5% or less.

Regarding the film emulsion surface, traditionally it is/was matte enough that it wouldn’t cause problems. Ilford films are a good example. However some films such as Kodak TMax have shiny emulsion surfaces (look at a sheet of TMX and it can be hard to tell which side is the base vs emulsion without the notch code). This means you can potentially get Newton rings on either side (or both!), a problem many people enlarging TMX with glass carriers have wrestled with. It can be problematic for people scanning negatives too. I remember Fuji Acros being similarly exasperating (I haven’t used Acros II so I don’t know if it still has those same surface qualities but it isn’t available in sheets anyway so not relevant in the context of contact printing.

It sounds like you simply haven’t run into the problem, which is a good thing! If it ain’t broke, don’t fix it, or as Ron Mowrey would say, “if it works, it works”.


Still trying to wrap my head around this issue. Industry standard glass used in a contact frame is inherently designed for its universal use (the primary application in windows of homes) to be the perfect transmitter of light because any applied coating that would have a modest degradation of this transmission to facilitate a specular reflection event (like a modest one way mirror) and is just not there or should not be there. The consumer market would have a fit. Then on the other side the surface of a glossy photographic emulsion is capable of a reflective event? I would think that the manufacturers of these emulsions would have checked that box off decades ago knowing full well that it is entirely within the realm of possibility that consumers of their product could very well opt for contact printing if only as proofing their negatives and not be subjected to any adverse visual artifacts. I have never seen a film photographic emulsion that appeared glossy to my eyes. I have seen base side of film emulsions that are "glossy" but that is not in play (emulsion of paper to emulsion of the film contact). My instincts tell me something else is going on here. If it is possible please post the variables of your interference patterns (film, photo paper, light source) and what it looks like.

[Oren Grad]

I like your glass sandwich - but no issues with halation from the bottom piece?

Happily, I've never seen any issues with halation. But I can't guarantee that for others. Contact printing is evidently so sensitive to local details of environment, materials and methods that it will often be necessary to try multiple approaches to find one that works. I can't prescribe any best practice for beginners in contact printing beyond being prepared for the likely need to tinker.

[Oren Grad]

However some films such as Kodak TMax have shiny emulsion surfaces (look at a sheet of TMX and it can be hard to tell which side is the base vs emulsion without the notch code). This means you can potentially get Newton rings on either side (or both!), a problem many people enlarging TMX with glass carriers have wrestled with.

Yes! I don't shoot much TMX, but I've seen Newton's rings coming from the emulsion side of 35mm TMX in the glass carrier for my LPL 4x5 enlarger, which has AN glass on top and regular glass on the bottom.


It can be problematic for people scanning negatives too.

This too. Interestingly, the instructions for my Epson V700 say to put film on the glass with the base side down, but also warn of possible Newton's rings. I do get rings, and so I scan with emulsion side down, despite whatever reasons Epson has for recommending the opposite. But for sheet film I use HP5 Plus almost exclusively. I don't know what I would do if I preferred TMX.


It sounds like you simply haven’t run into the problem, which is a good thing! If it ain’t broke, don’t fix it, or as Ron Mowrey would say, “if it works, it works”.

And this three. The take-home is just that one size doesn't fit all. If you've got an approach that works for you, count your blessings and enjoy being able to concentrate on making more pictures.

[Mark J]

It seems to me that people troubled by Newton's rings should be buying the anti-reflection coated picture glass that is now available. It shouldn't cost more than about $20 for a piece big enough for 8 x 10" and surround.
When I got my Meopta 6x9cm enlarger years ago, I got the lower (smooth ) glass in the neg carrier coated ( at work ...which is cheating.. ) to stop any problems with rings.
( edit : I know that glass against emulsion is less of a problem, but I did it anyway )

[Alan9940]

Without getting into the weeds, two things are required for the interference pattern to form:

1. Different amounts of space between the surfaces (for example some space vs no space (ie contact))
2. Specular reflection between the surfaces

This is exactly what I thought caused the issue and the coated glass resolved it for me.

[Erik Larsen]

I’m of the opinion rightly or wrongly that humidity plays a big role in whether or not you’ll get newton rings. I’ve never seen them in my darkroom either contact printing or my plain glass negative carriers where as people doing things exactly as I do struggle with the nuisance. My humidity is always desert dry. I kind of feel blessed to not have to worry.

[Mark J]

Back in the 80's .....I don't remember how it all began, but I got into a conversation with Ron Wisner about this problem which resulted in my sending him a sheet of 1/4" plate glass that he sent off somewhere to have a single coating (same stuff used on lenses) applied to one surface. I don't remember it costing me much because I think he thought of it as a technical challenge to solve. Anyway, lot story short...got the coated glass, tried it, not a single Newton Ring since! Been using the same piece of glass for 40 years now.
So, you may be on to something with that coating idea.

Sorry I missed your comment Alan.
Yes, this is the key to it. With shiny film base and glass on top you have two reflections of about 4% or 4.5% . The fringe pattern is only generated when the surfaces come to within 2 or 3 waves of light apart ( for white light illumination ) , however there is a faint fringe pattern generated, now I haven't got the maths to hand right now, it might only be about 10% brightness modulation, but it's visible.
If you coat ONE of these surfaces and have it only reflecting about 0.5%, then the fringe pattern contrast will drop AT LEAST by a factor of 10. It might actually be 100, I will check my 'book of important things' while i'm working this week, if i get chance.

[Michael R]

Yes! I don't shoot much TMX, but I've seen Newton's rings coming from the emulsion side of 35mm TMX in the glass carrier for my LPL 4x5 enlarger, which has AN glass on top and regular glass on the bottom.

Yup. TMX has long been my favourite film (along with TMY-2) in all formats - except for the shiny emulsion which became an intermittent Newton ring problem for me when I first began experimenting with glass carriers. It’s what prompted my investigations into various potential solutions.

I did some wacky things. For my first go at a home-made 35mm carrier I had Schneider Optics (the U.S. arm in NY at the time) cut me some rectangles out of couple of B+W MRC UV camera filters. Another good one was contacting Tru-Vue and asking if they had a sample pack of all their glazing materials - which they actually sent to me for free (a bunch of 8x10s). Some funny stories along the way.

[Michael R]

Humidity could be a variable.

I know one photographer who found he could usually avoid Newton rings if he wiped the glass with isopropyl alcohol.


I’m of the opinion rightly or wrongly that humidity plays a big role in whether or not you’ll get newton rings. I’ve never seen them in my darkroom either contact printing or my plain glass negative carriers where as people doing things exactly as I do struggle with the nuisance. My humidity is always desert dry. I kind of feel blessed to not have to worry.

[Greg]

Humidity could be a variable.

I know one photographer who found he could usually avoid Newton rings if he wiped the glass with isopropyl alcohol.

Kodak Lens Cleaner applied to the glass reduces Newton rings.
Windex applied to the glass seems to increase Newton rings.
Kodak Film Cleaner applied to the glass and the film seems to work the best for me.
The above said, humidity seems to be a major factor that I have yet to pin down...

[Sal Santamaura]

...Kodak Film Cleaner applied to the glass and the film seems to work the best for me...

Do you have a stash of the old stuff? The type containing heptane and 1, 1, 2 trichloro- 1, 2, 2 trifluoro ethane? :)

[Alan Klein]

Yes! I don't shoot much TMX, but I've seen Newton's rings coming from the emulsion side of 35mm TMX in the glass carrier for my LPL 4x5 enlarger, which has AN glass on top and regular glass on the bottom.



This too. Interestingly, the instructions for my Epson V700 say to put film on the glass with the base side down, but also warn of possible Newton's rings. I do get rings, and so I scan with emulsion side down, despite whatever reasons Epson has for recommending the opposite. But for sheet film I use HP5 Plus almost exclusively. I don't know what I would do if I preferred TMX.



And this three. The take-home is just that one size doesn't fit all. If you've got an approach that works for you, count your blessings and enjoy being able to concentrate on making more pictures.

Wouldn't the picture be reversed if you scan with the base side up? Maybe that's why Epson advises to scan that way. Of course, you can reverse the image after scanning.

[Serge S]

Possibly museum glass would help, as it is coated on both sides with an anti reflection coating?


Sorry I missed your comment Alan.
Yes, this is the key to it. With shiny film base and glass on top you have two reflections of about 4% or 4.5% . The fringe pattern is only generated when the surfaces come to within 2 or 3 waves of light apart ( for white light illumination ) , however there is a faint fringe pattern generated, now I haven't got the maths to hand right now, it might only be about 10% brightness modulation, but it's visible.
If you coat ONE of these surfaces and have it only reflecting about 0.5%, then the fringe pattern contrast will drop AT LEAST by a factor of 10. It might actually be 100, I will check my 'book of important things' while i'm working this week, if i get chance.

[Greg]

Do you have a stash of the old stuff? The type containing heptane and 1, 1, 2 trichloro- 1, 2, 2 trifluoro ethane? :)

Exactly... Over the past twenty or so years, I infrequently used it. If I could smell it then I didn't have proper or enough ventilation.

Back in the late 1970s and the 1980s, we used it in normally ventilated darkrooms of (here it comes) a State Health Center, Hospital, and University!!!

[Jon Shiu]

237979 Kind of cool looking patterns! Didn't show up in cyanotype print. Pictorico negative used.

[Tin Can]

Very good!




237979 Kind of cool looking patterns! Didn't show up in cyanotype print. Pictorico negative used.

[Drew Wiley]

Great stuff, tricholo. One type of it was originally developed as an anesthetic! Then it was discovered how well it would clean movie film, or remove chewing gum from vinyl flooring without attacking the vinyl. Janitors used a lot of it, even mopped floors with it. Sometimes they'd be found dead lying on the floor the next morning, asphyxiated due to the fact trichloro is heavier than air, and concentrated near ground level. Then it was added to outdoor stains in lieu of paint thinner because it wasn't smog-forming. Painters sometimes passed out and fell off ladders; and I knew of an electrician who accidentally burned down a house due to its use nearby, and him getting woozy. I had a heated argument with a Dow chemist about it once, who of course claimed it was harmless. Within two years, that whole category of chemicals was nationally banned from commercial use.

[Drew Wiley]

Serge - Museum glass is NOT anti-Newton glass; nor is any other picture framing glass.

[Mark J]

He didn't say it was Anti-Newton glass. He said it was AR-coated glass, as is some picture-framing glass, if you ask nicely and hand over a bit more money.

[Drew Wiley]

It was spoken in the context of reducing Newton rings for scanning purposes. The only reason an expensive OPTICALLY COATED picture glass slightly reduces the risk of rings is that it takes an exceptionally flat kind of float glass to evenly accept a coating. Perhaps the acceptable quantity PPG makes has gone up due to optical coatings now being used in relation to highrise window temp control. Dunno. The coated picture kind is thin and fragile anyway, and difficult to relieve the edges of, while the thick type is really a sandwich with a UV control film in between, much like a sandwich-style Tiffen UV lens filter. Meanwhile, cheap acid-etched non-glare picture glass has the enirely wrong kind of etching for these purposes. But there are specific threads on this topic, so I'll leave it at that. But just like lenses, you can't use just any cleaner on optically coated picture glass. And they differ with respect to specific coatings. The last of it I have on hand was clear titanium coated, and anything containing ammonia is a no-no. The first type, Denglas, had a purplish magnesium coating resembling early lens coatings. None of these suppressed rings in my case. Only real AN glass did. The specific thick AN glass in my contact frame was made in Belgium, but is no longer available.

[jimskelton]

I just built an 8x10 camera out curiosity as to how much better it is than 4x5. I shoot paper negatives, which don't contact print the best, so I tried a b&w reversal, directly shooting the photo onto paper, bleaching the developed "negative", then fogging and redeveloping. The image jumps out of the photo. I'll upload a scan, but it doesn't really represent what it looks like in real life. I've enlarged 4x5 to 8x10 and this is quite a bit better than that, or anything else I've done. Of course, the downside is that you only have one copy...

238008

[Alan Klein]

Great stuff, tricholo. One type of it was originally developed as an anesthetic! Then it was discovered how well it would clean movie film, or remove chewing gum from vinyl flooring without attacking the vinyl. Janitors used a lot of it, even mopped floors with it. Sometimes they'd be found dead lying on the floor the next morning, asphyxiated due to the fact trichloro is heavier than air, and concentrated near ground level. Then it was added to outdoor stains in lieu of paint thinner because it wasn't smog-forming. Painters sometimes passed out and fell off ladders; and I knew of an electrician who accidentally burned down a house due to its use nearby, and him getting woozy. I had a heated argument with a Dow chemist about it once, who of course claimed it was harmless. Within two years, that whole category of chemicals was nationally banned from commercial use.

When I was in basic in the USAF, the sergeant had about four of us paint a large storage room. No windows or any ventilation. By the time we got done a couple of hours later, I was high from breathing all that paint. I'm sure it was the old type of stinky lead paint that is no longer used.

[Michael R]

Drew - just regarding optical AR coatings there is no requirement that the glass be of any particular surface flatness quality. High performance BBAR coatings are ubiquitous and relatively trivial at this point. Better flatness is always a better thing for trying to prevent Newton rings but the reason optical AR coatings help (or at least should help) prevent them is that there is less reflection at glass-air transitions. Theoretically if you could reduce reflection to 0,Newton rings could not form.


It was spoken in the context of reducing Newton rings for scanning purposes. The only reason an expensive OPTICALLY COATED picture glass slightly reduces the risk of rings is that it takes an exceptionally flat kind of float glass to evenly accept a coating. Perhaps the acceptable quantity PPG makes has gone up due to optical coatings now being used in relation to highrise window temp control. Dunno. The coated picture kind is thin and fragile anyway, and difficult to relieve the edges of, while the thick type is really a sandwich with a UV control film in between, much like a sandwich-style Tiffen UV lens filter. Meanwhile, cheap acid-etched non-glare picture glass has the enirely wrong kind of etching for these purposes. But there are specific threads on this topic, so I'll leave it at that. But just like lenses, you can't use just any cleaner on optically coated picture glass. And they differ with respect to specific coatings. The last of it I have on hand was clear titanium coated, and anything containing ammonia is a no-no. The first type, Denglas, had a purplish magnesium coating resembling early lens coatings. None of these suppressed rings in my case. Only real AN glass did. The specific thick AN glass in my contact frame was made in Belgium, but is no longer available.

[Certain Exposures]

I just built an 8x10 camera out curiosity as to how much better it is than 4x5. I shoot paper negatives, which don't contact print the best, so I tried a b&w reversal, directly shooting the photo onto paper, bleaching the developed "negative", then fogging and redeveloping. The image jumps out of the photo. I'll upload a scan, but it doesn't really represent what it looks like in real life. I've enlarged 4x5 to 8x10 and this is quite a bit better than that, or anything else I've done. Of course, the downside is that you only have one copy...

238008

This is one of the reasons why my heart still wavers on this topic. I want to experiment with that reversal process. 4x5 and 5x7 prints would be far too small.

I'm reading everyone's replies slowly. I'll respond to more later.

[Sal Santamaura]

Drew - just regarding optical AR coatings there is no requirement that the glass be of any particular surface flatness quality. High performance BBAR coatings are ubiquitous and relatively trivial at this point. Better flatness is always a better thing for trying to prevent Newton rings but the reason optical AR coatings help (or at least should help) prevent them is that there is less reflection at glass-air transitions. Theoretically if you could reduce reflection to 0,Newton rings could not form.

Wow, you mean the curved surfaces of lenses can actually accept AR coatings? Incredible! :D:D:D

[Drew Wiley]

Don't be a wiseacre again, Sal - (I should be ignoring anything you post, and generally do, though you often have interesting and useful things to say). Clear titanium coatings were first developed as a dramatic improvement over brass lacquers for expensive door hardware. I know the story quite well. If something like that turned up SoCal in the early 90's, typically Malibu, we probably shipped it there. That was vac deposited onto complex shapes, but obviously opaque things. I was on the ground floor of marketing that. But we were also one of the largest window dealers in the West, and likewise at least got into the early discussions about the technical issues with optically coating glass windows relative to e-issues. An as an engineer, just like most engineers I've known, you might not be aware that window washing crews don't use optical wipes like for camera lenses, cleaning just a few square inches at a time. The older magnesium coatings like Denglas used weren't realistic for windows, or really ideal for AR picture glass either. And to get a flawless look on a transparent medium with clear titanium imposed a new challenge. And if you were an architect, and not an engineer, I'd probably have to explain that windows are intended to be transparent. They don't teach that in the Architecture Dept here at UCB, perhaps CalPoly. Anytime someone looks out a window at UCB, a brick or bottle gets thrown at them, so they keep the shades closed. Or else one of the peregrine falcons nesting on the Campanile tries to fly in and collides with the glass. We don't want that either.
And if the windows are left open, the falcons will collide with pictures inside and scratch the optical glass, which is expensive to replace.

More to the point: Perfectly even vacuum deposition atop huge flat pieces of glass in high volumes, intended to be cut down afterwards, imposes a very different mechanical and industrial engineering challenge than coating lenses. Go argue with PPG about it, not me. I have enough trouble affording any kind of serious picture glazing these days.