Center filter question - usage on different formats

[Steve Goldstein]

Suppose I have a center-filter designed for a certain focal length LF lens. Will I get similar results using that center-filter on a shorter lens and a smaller format if the angle of view for the two focal lengths on the two formats is roughly equal? This question goes the other was as well, moving to a longer FL on a larger format.

Here's a specific example to help clarify my question. A 90mm lens on 4x5 and a 50mm lens on 6x7 (rollfilm) have quite comparable fields of view. So would a center filter meant for the 90mm on 4x5 properly correct a 50mm on 6x7? I'm aware the lens must be well stopped-down.

What prompted this crazy idea? The 50mm Mamiya 7 lens has 67mm filter threads, as does the 90mm f/8 Super-Angulon. Mamiya never offered center filters but Schneider did, and it occurred to me the Schneider IIIa or IIIb (depending which version of Schneider's documentation one consults) could match the Mamiya's 50mm lens. There's also a similar angle-of-view relationship between the M7's 43mm and the 75mm f/5.6 Super-Angulon, both of which also have 67mm threads, so the Schneider CF-III might be a match there.

For an example going the other way, consider the 72mm SAXL (4x5) and 150mm Nikkor-SW (8x10). The have similar fields of view on their respective formats and both have 95mm filter threads. Maybe Schneider's IVb, meant for the 72, will correct on the Nikkor (assuming one could find both the center filter and the Nikkor).

[r.e.]

I have a Mamiya 7II, but not the 50mm lens. Could I ask why you want to use a centre filter with it?

[Steve Goldstein]

I was just thinking that if the fields of view are the same then the fallof may be the same, so would be mostly correctable with a CF. It’s not really a big deal for me with black-and-white, and I rarely use the 50mm anyway, but struck me as an interesting question.

[xkaes]

What prompted this crazy idea?

That's not a crazy idea or question at all. It's the angle of view of the lens -- along with the structure of the lens and the film format -- that make the difference. I'll give you an example.

I have a 47mm for 4x5" film AND a 12mm for 35mm. They have the same angle of view -- 120°. I use the same 77mm center filter because they have the same fall-off.

BUT, the film formats are comparable AND both of them are NON-retro-focus lenses. My other 35mm lenses are retro-focus designs and are not really helped as much by CND filters.

But much has a lot to do with personal opinion. Some people only use CNDs on 4x5" lenses wider than 90mm -- but they would if the same lens was used on a larger film format. I use a weak CND filter on my 105mm on 4x5" -- stronger on my 75mm, etc.

The choice is up to you.

Check out: http://www.subclub.org/fujinon/center.htm
(http://www.subclub.org/fujinon/center.htm)

[Drew Wiley]

It's more complicated than that. But without attempting a technical answer, one can always experiment to find out the truth, provided the two given lenses are actually similar in front diameter filter thread. For example, the same 82mm 1.5 stop ND CF I used for a 120 Super-Angulon worked superbly for my Fujinon 90 SW, and even for a 55mm Pentax 67 lens using an 82 to 77 mm adapter. But different designs of even the same focal length wide angle LF lens from the same mfg might call for completely different CF's due to significantly different amounts of falloff. It's also affected by how far you stop down the lens when the filter is in place.

[r.e.]

It would be interesting to know what Bob Salomon thinks about this question. I don't want to purport to speak for him, but he may say that centre filters are designed with specific lenses in mind and are not necessarily interchangeable between brands, or indeed within a brand, even for the same focal length.

As a result of reading Bob's posts on the subject, my own practice has been to use the specified centre filter for a particular lens, although on his advice I regard Rodenstock and Heliopan centre filters as interchangeable. However, I've also read posts by people who say that they have had no problems using, for example, a Schneider centre filter on a Rodenstock lens. I have not had to purchase a centre filter for a lens, such as a Nikkor, for which no centre filter has been specified because Nikon didn't make centre filters, and apparently didn't recommend a brand and model for its lenses.

[xkaes]

...centre filters are designed with specific lenses in mind and are not necessarily interchangeable between brands, or indeed within a brand, even for the same focal length.


That certainly would be news to Hoya, Marumi, Heliopan, and others that made lots of CND filters -- in various strengths and diameters -- without any specific lens(es) in mind.

[r.e.]

That certainly would be news to Hoya, Marumi, Heliopan, and others that made lots of CND filters -- in various strengths and diameters -- without any specific lens(es) in mind.

Bob Salomon's posts on centre filters address Rodenstock, Schneider and Heliopan centre filters for large format lenses. You can read the posts yourself. There are quite a few of them. Note also the second last sentence of post #5 above. As I said, some people say that they have not had a problem with interchangeability in specific cases. The very existence of these posts should tell you that this is regarded an issue, whether you regard it as one or not.

My own centre filters are the ones recommended by the lens manufacturer so I haven't had to try interchangeability personally, but I have a Rodenstock lens where different generations of Rodenstock centre filters made it necessary to look into the issue. Indeed, I had a message exchange with Bob on the centre filter for the lens in question.

[Alan Klein]

Center filters page https://www.largeformatphotography.info/filters.html


Dan Fromm's center filter selection/discussion page: https://galerie-photo.com/center_filters_for_large_format_lenses.pdf

[r.e.]

Dan Fromm's center filter selection/discussion page: https://galerie-photo.com/center_filters_for_large_format_lenses.pdf

That document is a useful compilation of publicly available information. Beyond that, I have reservations about it. If you look at Fromm's posts, his actual hands-on experience with these centre filters is quite limited. His position on the issue that this thread raises is stated in this sentence: "Schneider and Rodenstock center filters aren’t particularly lens-specific, their makers’ propaganda notwithstanding." He doesn't explain what the basis is for alleging "propaganda" nor what "particularly" means. It's just a single sentence, bald-faced assertion. At one point, I raised this sentence with him in a thread, but I didn't receive a response.

[Drew Wiley]

Generic center filters are an option, but those basically try to copy the most common possibilities, and are designed for similar amounts of falloff, which you should know in advance with respect to your particular lens before selecting one. This topic has been discussed over and over again. Look up some or Bob Salomon's posts on the subject; he's fairly expert at it, and would instantly contradict the notion that you can just go out and buy anything that fits the filter thread and walk away with a correct result.

[xkaes]

... you can just go out and buy anything that fits the filter thread and walk away with a correct result.

Like any piece of new-to-you gear, you should run some, at least minimal, tests to see how it works with your gear & approach. This is especially true with CND filters since it will probably come without any instructions:

http://www.subclub.org/fujinon/center6.htm

[Drew Wiley]

Huh? I said ... CONTRADICTS the notion that you can just go out and buy something, and think it's gonna work properly. Please don't chop my sentence in half and quote it out of context. Center filters can be expensive, and aren't the kind of thing you find at a local camera shop to test at a whim. It's important to do some homework in advance, or better if possible, buy a dedicated filter from the same manufacturer as your lens. But there is enough similarity between the designing of popular super-wides among the big four manufacturers that substitution can be realistic, especially since Nikon and Fuji don't market CF's of their own. All my own test involved over-developing the b&w sheet film to exaggerate any remaining falloff, if it were there; and then the corners of the sheet compared to the center was measured with a densitometer. In my case, the Nikon SW behaved exactly like the Schneider, and the Schneider CF worked perfectly.

[xkaes]

Sorry. I was trying to agree with you.

[Drew Wiley]

Yeah, bad day for me as far as misunderstandings go. Weather is starting to change and I had half my garden plans interrupted this afternoon. Oct is ordinarily our hottest month here, but the climate is showing showing signs of schizophrenia, with our first mountain snowfalls due in a few days, and hopefully rain here on the coast. So have tinkered on the computer too long today instead, though I did get some print toning done.

[xkaes]

I've found my darkroom to be an excellent escape many times myself. My blood pressure always drops the instant I turn on the safelights and the music!

[rawitz]

Suppose I have a center-filter designed for a certain focal length LF lens. Will I get similar results using that center-filter on a shorter lens and a smaller format if the angle of view for the two focal lengths on the two formats is roughly equal? This question goes the other was as well, moving to a longer FL on a larger format.

Here's a specific example to help clarify my question. A 90mm lens on 4x5 and a 50mm lens on 6x7 (rollfilm) have quite comparable fields of view. So would a center filter meant for the 90mm on 4x5 properly correct a 50mm on 6x7? I'm aware the lens must be well stopped-down.

The answer is yes and no! If the angle of view is the same for different film sizes (which means the lens focals are proportional different), a (filter-size) matching centerfilter will work equal on both. But as every lens-construction with same angle of view has different light-falloff curves, the result will not(!) be the same. LF wide-angle lenses are very different in construction than 35 or 120-film lenses.

In theory, and that has been said here, each WA lens needs a special centerfilter to correct its special light-falloff, and even more for each f-stop it needs a different filter, if a 100% correction is needed or wanted.

In practice, not even the lens-recommended CFs correct the light-falloff perfect, but only "approximatly". When I compare lens specs, for example the Super-Symmar XL 150mm light-falloff at the border of 385cm IC is more 4 f-stops for aperture 8 and 3 f-stops for aperture 22, but the recommended CF IVa has a correction of 1,5 f-stops (exposure 3x). So all avaiable CFs are undercorrected, and using different (but size-matching) CFs on the same angle-view lenses in sheetfilm or rollfilm, will only change the factor of undercorrection. So if you think you need a CF, every size-matching is better than nothing, but none gives perfect correction.

regards
Rainer

[Alan Klein]

It's said that color needs center filters more than BW. The falloff is more noticeable with color.

[xkaes]

The appearance of light fall-off also depends on the subject (some subjects look better with it), the amount of cropping under the enlarger, and other factors.

[rawitz]

It's said that color needs center filters more than BW. The falloff is more noticeable with color.

Oh, YES I see this in my LF color-negs, with are more sensible in densities than slides. What I found is not only radial light-falloff, but also radial color-shift what in BW is not an issue. I found ways to correct it in post, but have no theoretical explanation for this. Maybe anyone here has ...

[Drew Wiley]

Has nothing to do with color per se, Alan. It's entirely contrast-related. Because color chrome films have higher contrast than color neg films or the usable range of black and white films, the falloff issue is statistically more obvious in that case, but can also transpire in the other cases. Even in black and white images, some people enjoy a falloff or darkening toward the corners, some do not. In architectural photography, what is acceptable in a personal creative exercise might not be under contract to the designer, who might want a more objective rendering better suited for publication or his own portfolio.

Then you've got technical issues especially in color, like when falloff leads to color crossover shifts. I've even employed that error deliberately a few times for creative effect. But most of the time, I don't want it. But in black and white itself, some people reach a point on the characteristic curve where the film ceases to respond in a linear fashion, for better or worse, esthetically. The point in having tools like center filters is to understand what they're for, and when you need to use them. People who go around saying they're unnecessary for this or that genre, or this and that kind of film don't speak for everyone.

[xkaes]

Anyone ever use a CND filter with a pinhole?

[Alan Klein]

Has nothing to do with color per se, Alan. It's entirely contrast-related. Because color chrome films have higher contrast than color neg films or the usable range of black and white films, the falloff issue is statistically more obvious in that case, but can also transpire in the other cases. Even in black and white images, some people enjoy a falloff or darkening toward the corners, some do not. In architectural photography, what is acceptable in a personal creative exercise might not be under contract to the designer, who might want a more objective rendering better suited for publication or his own portfolio.

Then you've got technical issues especially in color, like when falloff leads to color crossover shifts. I've even employed that error deliberately a few times for creative effect. But most of the time, I don't want it. But in black and white itself, some people reach a point on the characteristic curve where the film ceases to respond in a linear fashion, for better or worse, esthetically. The point in having tools like center filters is to understand what they're for, and when you need to use them. People who go around saying they're unnecessary for this or that genre, or this and that kind of film don't speak for everyone.

What I've noticed with a 90mm and Velvia 50, if there's a blue sky, the falloff makes the edges darker blue. That's less acceptable than if it was a BW picture. With color it just makes the sky's color look uneven. With BW you get a vignetting effect which is more acceptable.

Here's an example with a 75mm:
https://www.flickr.com/photos/alanklein2000/50768568606/in/album-72157715763486212/

[Alan Klein]

Oh, YES I see this in my LF color-negs, with are more sensible in densities than slides. What I found is not only radial light-falloff, but also radial color-shift what in BW is not an issue. I found ways to correct it in post, but have no theoretical explanation for this. Maybe anyone here has ...

How?

[Steve Goldstein]

Anyone ever use a CND filter with a pinhole?

That’s an interesting idea! I guess you’d need to experiment with how far in front of the pinhole to place the CND.

[Bernice Loui]

That shade of "blue" is not only darker, it is a different shade of blue with graduated shade of blue and density changes... Typical of ALL color transparency films.

Previously posted example of 155mm Rodenstock Grandagon @f22_zero camera movement and on center, no center filter, 8x10 Agfachrome RS100 (closer to netrual color, not Velvia fantasy color) , Sinar 8x10 clear sunny day. Note the density AND color shift.
232209


B&W example, image previously posted on LFF..
Berlebach woodiee tripod & Gitzo head, Linhof Technikardan 23s with baggie bellows, 58mm Super Angulon XL @f16, 6x9 Super Rollex, 120 Ilford FP4, HC110...

58mm SAXL image circle is pushed to near it's limits of 40mm rise (mm scales on the TK23s aids in accessing how much image circle is being used or used up) coupled with front tilt of a few degrees and rear swing of a few degrees to bring the base/lower area of the image into what needs to be in focus and why a monorail with precision/accuracy is a GOOD thing as applying 1-2 degrees of camera movement is not that difficult, camera MUST stay put once set while the roll film back is swapped in place of the GG frame.

Note the light falloff of the 58mm SAXL which now acts as a graduated ND filter... or how a fixed given aspect of LF wide angle lens behavior can aid in image making..
232210

Need for a center filter can be greater for color transparency film due to the innate lower contrast range of color transparency film.. AND know the color layers can and will produce color shifts if their individual densities vary due to a long list of possible conditions and problems. As to fixing this post production via software.. What are the reference colors and how does the software alter color balance and density as a system?

Color negative film is lesser sensitive to this due to increased contrast range, yet color negative film remains subject to color shifts due to shifts in color layer density.

B&W film is strict density.. no color which is much a different can-O-worms..
Bernice



What I've noticed with a 90mm and Velvia 50, if there's a blue sky, the falloff makes the edges darker blue. That's less acceptable than if it was a BW picture. With color it just makes the sky's color look uneven. With BW you get a vignetting effect which is more acceptable.

Here's an example with a 75mm:
https://www.flickr.com/photos/alanklein2000/50768568606/in/album-72157715763486212/

[xkaes]

That’s an interesting idea! I guess you’d need to experiment with how far in front of the pinhole to place the CND.

That would be limited by the diameter of the CND filter (a wider filter could be placed farther out), and the size of the film/paper (smaller paper would allow for CND filter farther out). Maybe there is some sort of way to estimate it mathematically.

[rawitz]

Anyone ever use a CND filter with a pinhole?

Thats easy to answer. Provided you have a perfect flat pinhole, the lightfalloff is proportional to the cosinus-falloff by mathlaw. Thats much more than the modern WA-lenses, which by construction correct/minimize this falloff. CND will help you a bit, but less than with those lenses.

[rawitz]

How?

You have to make a linear-radial soft mask from image center to the edges and then use gradation tool (in Photoshop) for color correction.

[Greg]

Anyone ever use a CND filter with a pinhole?

Did so a number of years ago on my 11x14 very wide angle pinhole camera (with an effective focal length of 5 inches). CND was a Schneider IVa 3x. Ended up shooting three times with the filter mounted at three different distances behind the pinhole. Determining the exposure for the center of the negative was easy. Using a plain pinhole and the light falloff is consistently even from the center to the edges of the film. Adding the CND and the light falloff was not consistent, producing a "doughnut" like effect that I really couldn't see on the negatives, but was readily apparent on the contact prints. After shooting three sheets of HP5 plus and making contact prints, well experimenting by shooting 11x14 film gets expensive very quickly. I think it is very possible to do, but I would use paper negatives.

[Michael R]

Anyone ever use a CND filter with a pinhole?

Yeah ‘cuz the exposure times aren’t already long enough :)

[xkaes]

Yeah ‘cuz the exposure times aren’t already long enough :)

Not any worse than adding a green or red or orange or PL filter -- or a combination.

[xkaes]

Ended up shooting three times with the filter mounted at three different distances behind the pinhole.

I never thought of that. I was thinking in FRONT of the pinhole. That's where I put my 77umm contrast filters -- but I suppose it wouldn't make any difference????

[Greg]

I never thought of that. I was thinking in FRONT of the pinhole. That's where I put my 77umm contrast filters -- but I suppose it wouldn't make any difference????

The 11x14 pinhole camera has a sliding brass shutter in front of the pinhole. It was just easier to mount the CND filter behind the pinhole. In front of or behind... it shouldn't make any difference should it?

[Bob Salomon]

The 11x14 pinhole camera has a sliding brass shutter in front of the pinhole. It was just easier to mount the CND filter behind the pinhole. In front of or behind... it shouldn't make any difference should it?

Focus shift

[Greg]

Focus shift

"Focus shift" with a pinhole camera???

[Drew Wiley]

Once corner hue shifts occur with color films, it implies a degree of crossover of the dye curves themselves, in some cases so inextricably that one simply can't post-correct the color per se in PS just via a contrast tweak, or even a simple color correction applied to the affected area. Think of concrete - once it's mixed and sets up, it's almost impossible to actually separate the sand, cement, and gravel ingredients, even with a Jackhammer. So whenever possible, it's best to do the correction at the time of the shot itself. I get awfully tired of hearing people state they can do "anything" in PS, and then when they can't, they're the very ones cursing Kodak or Fuji for incompetence and selling such a lousy film.

[Alan Klein]

Once corner hue shifts occur with color films, it implies a degree of crossover of the dye curves themselves, in some cases so inextricably that one simply can't post-correct the color per se in PS just via a contrast tweak, or even a simple color correction applied to the affected area. Think of concrete - once it's mixed and sets up, it's almost impossible to actually separate the sand, cement, and gravel ingredients, even with a Jackhammer. So whenever possible, it's best to do the correction at the time of the shot itself. I get awfully tired of hearing people state they can do "anything" in PS, and then when they can't, they're the very ones cursing Kodak or Fuji for incompetence and selling such a lousy film.

That makes sense for color film. What about BW film?

[Drew Wiley]

Obviously no color crossover issues with black and white film, but the very real risk of losing all tonal gradation off in the nether corner regions. Might not bother anyone at all looking at a contact print or small enlargement of the image; but then, if they scale the same image up to a big enlargement, the emptiness might be quite annoying. All depends. There are no rules applicable to every situation. You decide.

But I like to take advantage of as much of the straight line of a film way down into the shadows as I can, especially in high contrast situations, because that often alleviates the need of "minus" or "pull" processing or otherwise compensating development which penalizes midtone tonality. That's all potentially usable real estate way down there, which I want present on the negative, and not preempted. More density can always be burned-in or over-developed during the printing step afterwards if desired. But if nothing is there in the neg at all, there's no recourse. You can't opt to print detail or shadow texture that's nonexistent on the neg itself.

[xkaes]

The 11x14 pinhole camera has a sliding brass shutter in front of the pinhole. It was just easier to mount the CND filter behind the pinhole. In front of or behind... it shouldn't make any difference should it?

I don't use a shutter, so that's not a factor for me, but if the CND filter is on the front, that could cause more glare/flare, I suppose -- but I use lens shades.

But depending on the subject a CND filter -- assuming it works -- may help or hurt the subject.

[Drew Wiley]

Any kind of wide angle photography is a pain in the butt facing the sun without an adjustable shade.

[Alan Klein]

That shade of "blue" is not only darker, it is a different shade of blue with graduated shade of blue and density changes... Typical of ALL color transparency films.

Previously posted example of 155mm Rodenstock Grandagon @f22_zero camera movement and on center, no center filter, 8x10 Agfachrome RS100 (closer to netrual color, not Velvia fantasy color) , Sinar 8x10 clear sunny day. Note the density AND color shift.
232209


B&W example, image previously posted on LFF..
Berlebach woodiee tripod & Gitzo head, Linhof Technikardan 23s with baggie bellows, 58mm Super Angulon XL @f16, 6x9 Super Rollex, 120 Ilford FP4, HC110...

58mm SAXL image circle is pushed to near it's limits of 40mm rise (mm scales on the TK23s aids in accessing how much image circle is being used or used up) coupled with front tilt of a few degrees and rear swing of a few degrees to bring the base/lower area of the image into what needs to be in focus and why a monorail with precision/accuracy is a GOOD thing as applying 1-2 degrees of camera movement is not that difficult, camera MUST stay put once set while the roll film back is swapped in place of the GG frame.

Note the light falloff of the 58mm SAXL which now acts as a graduated ND filter... or how a fixed given aspect of LF wide angle lens behavior can aid in image making..
232210

Need for a center filter can be greater for color transparency film due to the innate lower contrast range of color transparency film.. AND know the color layers can and will produce color shifts if their individual densities vary due to a long list of possible conditions and problems. As to fixing this post production via software.. What are the reference colors and how does the software alter color balance and density as a system?

Color negative film is lesser sensitive to this due to increased contrast range, yet color negative film remains subject to color shifts due to shifts in color layer density.

B&W film is strict density.. no color which is much a different can-O-worms..
Bernice

Don't movements affect where the vignetting winds up? So for example, if you shift, you might have more darkening on one side than the other which would look weird. Even with BW?

[Alan Klein]

You have to make a linear-radial soft mask from image center to the edges and then use gradation tool (in Photoshop) for color correction.

Egads. Has anyone done that? With color you have to deal with color shifts as well. Might be easier with BW, but then wouldn't movements shift the falloff areas forcing you to somehow move around a gradation template? Seems like a center filter is the way to go.

[Bernice Loui]

Yes indediee, knowing how the lens behaves coupled with camera movements as needed/as used is then figuring this into how the image could benefit can be a plus to the overall image.

If wide angle lens is a must with lowered light fall off, using a proper ND center filter is a non-option. This is why ND center filters are made, why they are used and why they remain a needed and in demand optical accessory.

IMO, the idea/belief post fix up via software is a maybe at best. What is done today, a good number of modern digital cameras apply lens aberration fix-up in camera post image capture.. This is a better way as the software fix-up is lens and image sensor system specific.. The designers here would know more about how get the best out of the overall lens/imager/post capture system than post process software fixiee..

For film, get the proper ND center filter for the specific wide angle lens, use it as needed is the proper solution.


Bernice






Don't movements affect where the vignetting winds up? So for example, if you shift, you might have more darkening on one side than the other which would look weird. Even with BW?

[Doremus Scudder]

Don't movements affect where the vignetting winds up? So for example, if you shift, you might have more darkening on one side than the other which would look weird. Even with BW?

Vignetting is really the wrong term here. Fall-off is better.

If you've got a center filter on your lens, shifting/raising/lowering the front or the back standards will make no real difference in densities at the edges/corners, since the fall-off is attenuated over the entire projected image circle by the filter. Without the filter, yes, you will end up with more fall-off on the side that you shifted toward. With black-and-white, one can deal with this by judicious burning (I'll start a thread about "center burning" someday). With prints from color negatives, similar adjustments can be made. For color transparency materials, you need the center filter if you don't want the fall-off.

Note that if you're planning on not using a center filter and correcting fall-off with burning at the printing stage, you still need to add enough exposure from what your meter tells you to get adequate shadow exposure in the parts of the image affected by the fall off (i.e., overexpose a stop or whatever the center-filter factor would normally be).

Vignetting caused by running out of image circle or by mechanical blocking (e.g., stacking too many filters) is a different issue and not really related to center filters.

Best,

Doremus

[Doremus Scudder]

Egads. Has anyone done that? With color you have to deal with color shifts as well. Might be easier with BW, but then wouldn't movements shift the falloff areas forcing you to somehow move around a gradation template? Seems like a center filter is the way to go.

You're right Alan, shifting (or raising/lowering) moves the optical center of the image on the film to an off-center position. However, if you can identify that point in the image, then you can do your burning or masking or whatever you do in Photoshop around that point.

I print analog with enlargers and do "off-center" graduated radial burns all the time. Either the point around which I should center my burn is obvious, or I've made a note of where it lies at the time of exposure.

If you've got the center filter, by all means, use it. It is the easier method and indispensable with transparency materials. However, many of us B&W only practitioners dispense with the filter and the extra bulk it requires (along with the need for larger filters to attach to it, if desired), and just deal with the fall-off in the darkroom.

Best,

Doremus

[Michael R]

You often end up making adjustments anyway. Center filters don’t fully correct for falloff.

[Drew Wiley]

With the specified combination of specific lens and matching recommended CF, at specified recommended working aperture, a CF can indeed perfectly correct falloff. I've densitometer tested for that. That doesn't mean your enlarger mixing box and its lens is itself perfectly even. But if one just routinely shot a particular WA lens, then its own falloff could be correctly by a matching amount of falloff in the enlarging system, that is, when printing negatives. Lots of old timers knew that. The mixing box diffuser could even be ground convex and fine-tuned for that. But it still wouldn't retrieve shadow detail in the corners of your image if it was so underexposed to begin with, due to falloff, that it's not even there.

Note my "fine print". We can't always use the ideal recommended working aperture, etc etc. Same when enlarging.

[xkaes]

Absolutely, and this is a method to deal with light fall-off even without a CND filter. If you take a picture of a scene with a lens showing light fall-off, the corners of the negative will be less dense. A normal print will produce dark corners. But if you use the enlarging lens wide open, the corners of the print will be lightened due to the light fall-off in the enlarging lens. This will not, of course, create any more detail in the corners -- because there wasn't that much in the negative, but it can make the print appear more normal.

And if you use a CND filter that isn't quite strong enough in the corners, you can use the same approach to improve things a bit.

[Alan Klein]

Absolutely, and this is a method to deal with light fall-off even without a CND filter. If you take a picture of a scene with a lens showing light fall-off, the corners of the negative will be less dense. A normal print will produce dark corners. But if you use the enlarging lens wide open, the corners of the print will be lightened due to the light fall-off in the enlarging lens. This will not, of course, create any more detail in the corners -- because there wasn't that much in the negative, but it can make the print appear more normal.

And if you use a CND filter that isn't quite strong enough in the corners, you can use the same approach to improve things a bit.

I don't print but rather scan. So I either accept the fall-off or use a CF.

[Drew Wiley]

There are post-scanning apps that let you correct for fall-off density-wise; but the same principles still apply, especially in color chrome photography. You can't correct every problem that way, especially certain crossover issues. So when in doubt, use a CF at the time of the shot itself.

[rawitz]

There are post-scanning apps that let you correct for fall-off density-wise; but the same principles still apply, especially in color chrome photography. You can't correct every problem that way, especially certain crossover issues. So when in doubt, use a CF at the time of the shot itself.

Yes, every fotosoftware (not only PS) today has an automated vignetting-filter, but it only corrects center-circular fall-off in brightness, not in color.

This summer I did many colorfotografy with a lightweight 8x10`fieldcamera and Super-Angulon 120mm lens, which IC of 285mm (plus 20mm tolerance) produces full light-falloff on the film. I used no centerfilter.
The good news are: mostly I did not even have to correct with standard vignetting filter, the inherent falloff IMHO was acceptable or even improved the picture:

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But there are shots like this with light-falloff plus some colorshift. As also the lens was upshifted, I had to make manually a filterlayer and use it as mask to correct decentered falloff plus colorshift (with gradation tool in PS). Its not a digital forum here, so I only show the steps here: the pic out of the scanner, the mask and the final result.

232295

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regards
Rainer

[Drew Wiley]

I've even used CF's for the wrong reason on enlarging lenses, to create a perfectly round falloff effect in the print itself, and do so more consistently than conventional corner and edge burning.

[Bernice Loui]

Light fall-off and color shift reduced, but re-shifted in color and density visible in the digitally transmitted version of these images.

Could be ok for some not ok for others...

IMO, what has happened today, digital coupled with software bending of digital images have become SO prevalent and everyday majority of folks that grew up on digital/software images today have fallen into the pit of believing anything image related can be done via software. A product of digits, web and software centric society/culture of today..

IMO, if controlling light fall off of wide angle LF lenses IS important, get and use the proper wide angle lens with it's matching CF-ND filter.. Get the image best possible on film and do as little if any fixing via software as possible. Cost of the proper CF-ND filter is nil compared to the cost of sheet film, processing, time spent (not recoverable), resources related to creating these images on film. It is false economy to exclude using the proper CF-ND filter if needed then try other means to fix what is not really fixable..

Another very real problem, what IS the point or metric of reference for color rendition on film and it's overall density.. There was a time in this color film stuff when there were absolutes in references for color rendition and density plus the innate color rendition personality of a given color film.. That has essentially vaporized today.. Neutral color rendition, hue, saturation and more is not always desirable as color is tied to emotions which can be bent by the image maker based on their image goals..


Bernice






But there are shots like this with light-falloff plus some colorshift. As also the lens was upshifted, I had to make manually a decentered BW-filterlayer and use it as mask to correct decentered falloff plus colorshift (with gradation tool in PS). Its not a digital forum here, so I only show the steps here: the pic out of the scanner, the mask and the final result.

232295

232297

232298

regards
Rainer

[Drew Wiley]

There might also be very real variables associated with the nature of the ND material itself in relation to pixel capture which behave differently than film. So, just like Bernice implied, a lot of folk nowadays wouldn't even realize it if it was there, because they're concept of color itself is so plastic. But if an architect or designer hires you to reasonably faithfully replicate the color they had in mind, and not your own creative fantasies, having an understanding of what is really going on can be essential.

I'm personally more annoyed how color outdoor photographers go out and largely preempt the beauty of actual color relationships in nature, and substitute their own obnoxious sticky-sweet digital honey and jam, because they haven't ever learned to actually LOOK at anything intently or contemplatively. No color film or paper ever invented can be termed actual visual reality; but there should at least be an attempt to communicate a deep personal impression of what was actually there, and not switch it out for just another kitchy overtly-colorized stereotype.

[Bernice Loui]

Having been severely "disciplined" into the importance of color rendition and much more relative to color images, then having a reasonable memory and understanding what accurate/neutral color rendition is much about.. taking "liberties" with color does not sit well. For others, color is another creative image expressive tool and means to an end..

IMO, better to fully understand what this color image stuff is all about then apply as needed to achieve those image goals.. For some this means absolute color accuracy/neutral color rendition others. completely "interpreted" color for eye poking effect.. There is should be and can be a place for both..



Bernice



There might also be very real variables associated with the nature of the ND material itself in relation to pixel capture which behave differently than film. So, just like Bernice implied, a lot of folk nowadays wouldn't even realize it if it was there, because they're concept of color itself is so plastic. But if an architect or designer hires you to reasonably faithfully replicate the color they had in mind, and not your own creative fantasies, having an understanding of what is really going on can be essential.

I'm personally more annoyed how color outdoor photographers go out and largely preempt the beauty of actual color relationships in nature, and substitute their own obnoxious sticky-sweet digital honey and jam, because they haven't ever learned to actually LOOK at anything intently or contemplatively. No color film or paper ever invented can be termed actual visual reality; but there should at least be an attempt to communicate a deep personal impression of what was actually there, and not switch it out for just another kitchy overtly-colorized stereotype.

[rawitz]

IMO, if controlling light fall off of wide angle LF lenses IS important, get and use the proper wide angle lens with it's matching CF-ND filter.. Get the image best possible on film and do as little if any fixing via software as possible.

Bernice

I agree

[rawitz]

Having been severely "disciplined" into the importance of color rendition and much more relative to color images, then having a reasonable memory and understanding what accurate/neutral color rendition is much about.. taking "liberties" with color does not sit well. For others, color is another creative image expressive tool and means to an end..

IMO, better to fully understand what this color image stuff is all about then apply as needed to achieve those image goals.. For some this means absolute color accuracy/neutral color rendition others. completely "interpreted" color for eye poking effect.. There is should be and can be a place for both..



Bernice

But the "new color photography" era in the 60th and 70th started with new enlarging/printing technics. William Egglestone introduced the DyTransfer, and the photographers now could compose color within analog "manipulation". Digital technic did not invent it.

[Corran]

majority of folks that grew up on digital/software images today have fallen into the pit of believing anything image related can be done via software.


Get the image best possible on film and do as little if any fixing via software as possible.

Anything one could possibly want to do CAN be done in software. You can redraw the entire image pixel-by-pixel if you want. It's not a question of "possible" but whether or not the effort or time is manageable/desirable. Which is where the second statement comes into play. That's a perfectly fine and reasonable thought.

That said, for color shifts related to fall-off, a simple color curve filter + mask can be used to fix that in just a couple of clicks. For those doing digital output it is reasonable to use the tools available to "fix" as necessary / desired any given fall-off or other issue. And of course many folks use fall-off or other "defects" (depending on how that is defined) for creative use / expression.

I continue to not bother with CFs, mostly.

[Alan Klein]

For whatever it's worth, a CF loses two stops.

[Drew Wiley]

The Schneider CF I sold you Alan is exactly 1-1/2 stops max density. A 2-stop offset is less common, but necessary for some extreme wides.

[Drew Wiley]

rawitz - Eggleston hardly introduced dye transfer. By the time he finally showed up there were six different corporations making DT supplies. It was a standard commercial process for those who could afford it, and had already been around in one form or another for decades. The big labs could even do mural sized ones. He didn't even do his own color printing. But those lovely little DT prints certainly did more justice to his eye than the recent large inkjet ones. At larger scale, his work is simply a duck out of water anyway - a misfit. I don't know if any new dye editions of his are being made in Germany or not, where the last bastion of that kind of DT service still exists, using its own proprietary materials and techniques.

[Drew Wiley]

Corran - it's not that simple at all. Sometimes falloff crossover creates inextricable "mud", especially with color neg film. The only way for the average person to correct that digitally is to essentially erase it and artificially paint back in, or "dither", the desired cleaner hue. I'd rather have the minor inconvenience of attaching a center filter than the arduous torture chamber experience of dithering. You have mentioned your alternate technique of waving a darkslide in front of the lens during long exposures. I only do that when being attacked by gnats; so it must be an acquired skill.

[Corran]

Drew, again, I'm not talking about convenience or not, but whether or not something is possible at all. My response is related to the idea that "digital photo editing software" can not be used to fix a perceived issue. This is patently untrue - the power and ability of digital editing is essentially limitless. Of course it may be smarter to use the prescribed tool if the issue is easily resolved this way instead!

As for waving a darkslide around, that's for "dodging" the sky at the time of exposure, and it works wonderfully as an alternative for a graduated neutral density filter. While I haven't tried it, perhaps a circular piece of mat black paper on a stick could be used like a dodging wand in the darkroom instead of a center filter for part of the exposure time? :rolleyes: Tongue in cheek!

[xkaes]

The Schneider CF I sold you Alan is exactly 1-1/2 stops max density. A 2-stop offset is less common, but necessary for some extreme wides.

And there are some CND filters that are 1/2 & 1 stop. I think even some 2.5.

http://www.subclub.org/fujinon/center5.htm

[Bob Salomon]

And there are some CND filters that are 1/2 & 1 stop. I think even some 2.5.

http://www.subclub.org/fujinon/center5.htm

Heliopan also offered a 3 stop center filter.

[xkaes]

It took me a while, but I finally found one at a decent price.

[Drew Wiley]

Yeah, Corran - every time I see an actual print with that kind of problem and they claimed they '"fixed it" in PS, that's exactly what it looks like, just like the stitches attaching Frankenstein's head are obvious. What's hypothetically possible, and what's realistic are not the same thing. I've done all kinds of convoluted fixes, especially in pre-digital restoration work, but was charging for all that time and sheer headache. Hollywood can even go back in and colorize old black and white movies. They look pretty odd; but it's just an example of what can potentially be done. The question is, is it worth it when a simple filter does it far more better in a mere fraction of the time? The average digital printer doesn't even seem to be aware of those kinds of problems, and when they are, usually blame the lens or the film. The really competent digital printers I know have also long recognized why center filters exist; they spend enough time fine-tuning things as it is, without yet another issue.

In other words, we agree on this point. But trying to untangle already mixed crossover "mud" is not something the typical person would even understand. Best not to mix it to begin with if it's going to be a visual problem.

[Michael R]

If it looks bad it just means it was badly done. It's not a "digital problem" at this point. That ship has long since sailed. Digital editing is a skill and art, just like darkroom work, and like darkroom work, most people suck at it. That's how every artform is and always has been. Don't blame the medium/tools.


Yeah, Corran - every time I see an actual print with that kind of problem and they claimed they '"fixed it" in PS, that's exactly what it looks like, just like the stitches attaching Frankenstein's head are obvious. What's hypothetically possible, and what's realistic are not the same thing. I've done all kinds of convoluted fixes, especially in pre-digital restoration work, but was charging for all that time and sheer headache. Hollywood can even go back in and colorize old black and white movies. They look pretty odd; but it's just an example of what can potentially be done. The question is, is it worth it when a simple filter does it far more better in a mere fraction of the time? The average digital printer doesn't even seem to be aware of those kinds of problems, and when they are, usually blame the lens or the film. The really competent digital printers I know have also long recognized why center filters exist; they spend enough time fine-tuning things as it is, without yet another issue.

In other words, we agree on this point. But trying to untangle already mixed crossover "mud" is not something the typical person would even understand. Best not to mix it to begin with if it's going to be a visual problem.

[Drew Wiley]

I'm not blaming the darn medium, Michael, just the cavalier mentality itself that comes with the territory these days. Please think about my analogy of mixed concrete. Heck, I've seen harvester ant colonies take apart even high strength concrete grain by grain, and eventually, over many years, find a way in. But how many people have that kind of patience? The whole instant-this, instant-that mentality prevails. But all the really good digital printers I know seem to need more time to perfect their files than the effort needed to achieve excellent results back in their darkroom days. High quality printmaking takes serious commitment either way, but not many like to bother anymore.

[Bernice Loui]

Over the course of human history, there has been a bent to apply the current "state of the art" technology as a means to solve age old questions (the humanoid brain was once believe to be a pump) and answers to age old questions.. and to varying degrees "problems".. And no, technology cannot and will never solve (all) the constant problems of humanity and the human condition.

As for using digital based imaging software to "fix" what are perceived as image flaws, sure it can be done.. Real question is to what degree and how much of the original image information recorded will be altered by the image software process and specific individual applying their personality making these "image corrections"... Image information not recorded at the moment the image was captured can never be recovered, it can be added via imaging software except that image information added can NEVER be what happened at the moment the specific image was recorded.. This topic begins to scratch the surface of information theory and laws of Thermodynamics..

Fix it post in image software, sure.. how much effort will be involved.. and to what point and metric of reference_?_

Given an image file of 100+ MegaPixles.. how much effort and more will be required to fix each individual Pixel_?_ one pixel at a time..
Or an example of there is an energy cost to creation of information and the information added can never be the same information that would have been recorded at the moment of recording..

As for color crossover in color films, this is a very real thing. Severe difficulty is, majority of foto folks do not know what color crossover is, why it happens, why it is Extremely difficult to fix post process or have any appreciation of how color crossover bends color rendition and much more in the color image be it print or color transparency or via video monitor.. There is little appreciation of proper and neutral color rendition and all related, just personal projection under the guise of "Artistic/Creative Expression"....

I'm still of the unpopular opinion that painters that work in color have a FAR deeper and greater understanding of the relationship between color/emotions/creative expression than fotographers today...

Lesson here, make the very best image capture/recording at the moment using the image recording tools (yes, this means using a proper ND center filter as and if needed) as needed as the "cost" to "fix it"post or later is not gonna be that easy or have any ability to recover information that is forever lost at the moment of image capture/recorded..



Bernice

[Michael R]

Maybe it's just that there's a lot more out there than in the pre-digital era, so there's obviously going to be a lot more crap to see, but that's normal. Particularly when it comes to colour, even back in non-digital times there really weren't very many people making their own prints, let alone good ones, so if you saw a good book or show of colour work by a respected photographer, odds are the printing/reproduction was done by custom/pro outfits, and it was always a specialty. Now, on the other hand, even people with relatively little scanning/editing/inkjet skill, time etc. can still make their own colour prints or images to display online. Some people are really good at it, most are not, and perhaps you're seeing a lot of the not good stuff.


I'm not blaming the darn medium, Michael, just the cavalier mentality itself that comes with the territory these days. Please think about my analogy of mixed concrete. Heck, I've seen harvester ant colonies take apart even high strength concrete grain by grain, and eventually, over many years, find a way in. But how many people have that kind of patience? The whole instant-this, instant-that mentality prevails. But all the really good digital printers I know seem to need more time to perfect their files than the effort needed to achieve excellent results back in their darkroom days. High quality printmaking takes serious commitment either way, but not many like to bother anymore.

[Drew Wiley]

Precisely, Bernice. I know how to fix certain crossover issues even in dye transfer printing. It's quite involved, and film specific. And that whole unwinding of the ball of yarn after the kitten already got ahold of it can be replicated using analogous tortuous digital steps instead. The practical issue, however, is that most such practitioners don't even recognize the problem or how it came into being; so how would they know how to untangle it? One can't just activate the usual instant apps to get there. Re-colorized or further saturated mud is still mud, and that will be obvious to a trained eye. Every decent painter knew that; but most color photographers apparently do not.

Michael - yeah, things were not any better back in the heyday of color darkroom work. Seriously good quality has always been the exception, always will be. But the medium is way more democratized today, for better or worse, so the good work might somehow eventually rise to the top of the general heap. But by then, the current generation of inkjet technology might itself have become arcane and obsolete, with something else taking its place.

[Bernice Loui]

Yep, color print and related color excellence was an a absolute exception, not the common offering back in the great Hey-Day of photochemistry based color images.. There were maybe 2-3 color labs in the SF bay area (this was commercial Big $ and much more foto district on the west coast) there were consistently any good and the results were decided by not just the materials and color original involved, the specific individual doing the color work had Huge to do with the end result.. There were folks that demanded/expected very specific color results, others and often the majority folks were simply not that demanding. It was a diverse client/customer base back then

Still of the opinion, majority of folks do not appreciate or know what absolute Fab color prints or images are.. For this vast majority, just good enough is enough..



Bernice



Michael - yeah, things were not any better back in the heyday of color darkroom work. Seriously good quality has always been the exception, always will be. But the medium is way more democratized today, for better or worse, so the good work might somehow eventually rise to the top of the general heap.