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Michael R
19-Apr-2016, 11:39
Looking for feedback, advice, two cents etc. etc. I’m not big into DIY but I’ve cobbled together a couple of glass/registration negative carriers which work perfectly, despite being on the ugly side. I’m now looking into another glass carrier project. Forget about Newton rings etc. Off topic in this case.

I want to use coated optical glass. In the past I worked with Schneider on this. I ended up with some MRC filter glass (from B+W) filters for a 35mm carrier. For 4x5, had to go with single coated filter glass from their MPTV division.

I might simply go with Schneider’s stuff again, but I am exploring a few other options due to curiosity. I’d like multi-coated glass if possible. I first contacted Zeiss asking if I could get some T* coated flats. They wouldn’t entertain such a small order, but pointed me to some other companies that might. One of these is QIOPTIC. There are some others such as Edmund, PGO.

Anyone have any experience with glass? I can’t order directly from Schott, but I assume if a company specifically lists N-BK7 they are using Schott.

Seems like what I’m looking for are typically called “optical windows”, which are high quality borosilicate crown glasses, only flat instead of shaped into a lens element. These are not always made in the thickness you want. I need 1mm and 2mm. Then of course you usually have to choose a coating.

I think I am totally out of my league when it comes to dealing directly with this type of supplier. That is why I would much rather if a photo company like Rodenstock or Nikon would just sell me a custom cut piece of whatever they put in their clear filters. Is that possible? Schneider was relatively easy to work with but the MPTV filters are single coated.

Just thinking out loud. Appreciate any thoughts or experiences. Drew Wiley?:D Others?

Michael

Randy Moe
19-Apr-2016, 12:06
Why not explain your exact design and purpose in order to gain other's interest in the project.

If your ideas and desires strike a chord with more users, a group may be able to work together in purchasing.

Peter De Smidt
19-Apr-2016, 12:32
I'm not sure what your application is, but there are also anti-reflection coated glass used for picture frames and for architectural purposes. For example, http://www.framedestination.com/Picture-Frame-Glass.html

Oren Grad
19-Apr-2016, 12:34
Some years back, I went through a phase of experimenting with coated glass for contact printing. I used coated glass marketed for art framing - Denglas (no longer available) or Tru Vue AR. The problem, apart from cost, was that these products tend to have imperfections that may be irrelevant for the marketed application but were a problem for me. I ended up having to search through multiple pieces of glass to get satisfactory ones, and eventually that got old both for me and for the frame shop where I was buying the stuff.

In principle I would be interested in a source of coated or multicoated glass of assured optical quality, though I fear the cost would be very high, possibly prohibitively so depending on the size. Even if larger sizes were out of reach, I might still be interested in glass for a 4x5 carrier - a coated bottom glass would be useful for negatives that have a very smooth emulsion side. In any case, I'd certainly be happy to see someone look into this seriously, to find out what if anything is possible.

Michael Rosenberg
19-Apr-2016, 12:41
Check out Howard Glass company in Philly. They have optical glass, including Schott glass. I got some clear glass (no defects) and made a pin registration carrier. I got diamond drill bits corresponding to 21 guage cannulae, which I bought from Small Parts Inc. If you go down this route I can tell you how to drill the glass so it does not crack from the heat.

Mike

Peter De Smidt
19-Apr-2016, 13:01
Edmund optics has some, including AR coated plastic. The latter comes up to 250mm square.

Drew Wiley
19-Apr-2016, 13:30
Hoya does custom stuff. But I'm in agreement with Oren about coated picture glass. It's tricky to cut and edge, fragile, and I've never found it personally adequate for enlarging, though it sure beats ordinary float glass. Most of the Zeiss and other Euro glass I have, I've picked up surplus at random. That requires some luck. Coated acrylic might not stay flat under enlarger heat; but you can get it any size you wish, clear up to 4x8 ft sheets (if you have enough $$$). If you deal with Edmund, make sure its the Scientific division; they have about a thousand times as much stuff as their hobby catalog or website. Drilling glass for registration is almost hopeless if the glass is tempered. The correct type of Schott glass for that purpose allegedly isn't even made anymore. But there are other ways of positioning pins. Reminds me, I still have a tiny bit of work left on one of my 8x10 carriers; but at least the pins are in place correctly after holding my breath hoping the glass wouldn't crack in the process. The whole problem with MC is that it seem to behave like tempering and make drilling unrealistic. I should probably dig out a damaged MC filter and test again with my new specialized bits. I still have one more carrier to register; but it's for 4x5, so not an urgent project. Most of my 4x5 work doesn't need pin registration in carrier per se. Finding offset micropins is hell unless you cannibalize them from old Condit glass. My way of circumventing that is to locate one stainless micro-dowel into an exact hole, the other dowel in a very slightly oversized hole with a bit of wiggle room for the epoxy, with fully taped-down punched film strip holding the precise distance until the epoxy sets.

Drew Wiley
19-Apr-2016, 13:51
... I didn't know about Howard Glass. Looks like a great resource.

Bob Salomon
19-Apr-2016, 14:16
Qioptiq is Rodenstock, or at least, Rodenstock Photo Optical is one of Qioptic's divisions.

Michael R
21-Apr-2016, 08:02
Thanks for the thoughts and suggestions so far. Apologies for the post being somewhat muddled. I'll try to clarify and give some specifics. This project or research began a few years back when I wanted to build a registration carrier for 35mm. I started to think about glass quality (especially below the negative), and the Newton ring issue. All this combined led me on this quest (I'm not much of a gear guy but occasionally I'll get a bug in my head).

When I built the 35mm carrier, I decided I'd try to use the best glass I could reasonably get. This ended up being B+W Clear (007) MRC filters cut down to the rectangular dimensions I needed.

At that time I was also replacing my 4x5 carrier system with an Inglis setup, and thought about having Alistair install some multicoated glass. The MRC filter glass I used in the 35mm carrier doesn't come large enough for 4x5 so I began exploring other options. Schneider Optics sent me a sample of the single coated filter glass they use to make filters in their MPTV division. I also got Tru Vue to send me 8x10 samples of all their stuff, which I thought could be interesting because while their Ultra Vue glass might be good for the bottom, some of the non-glare matte surfaces might be useful on top instead of other anti-Newton glass options. In the end I didn't have the time or inclination at the time to explore further so I just ordered the stock carrier from Inglis.

Fast forward and I'm now looking into ordering a second carrier from Inglis, and again I'm thinking about possibly using fancy glass, at least on the bottom. Alternatively I might try to build a carrier. If I use the Inglis carrier, there are some design constraints: bottom glass 2mm, top glass 1mm, so my Schneider glass and Tru-Vue glass (or other glazing materials) can therefore only be used on the bottom.

That's why I started thinking about looking into other suppliers that can make optical quality flats with coatings/multi-coatings. But it is all very complicated.

Drew Wiley
21-Apr-2016, 08:18
Why not just try some glass from a basic old AN glass slide mount? I've got a bunch of 6x7 laying around somewhere, and when I first started out (pre-LF), did
successfully use this in an enlarger.

Michael R
21-Apr-2016, 08:27
Part of the reason was to use higher quality glass below the negative, and also to explore the possibility that multicoating (to reduce reflection) would help suppress the appearance of Newton rings without having an etched ANR pattern.

Drew Wiley
21-Apr-2016, 08:41
Depends on both the room humidity and the specific type of film. Some of these new thin emulsion films are downright slick on both sides. I can't comment on your own climate. Here on SF Bay it's foggy most of the year, and I've never had luck with mere coated glass, except for a older style sheet films. And in the latter case, the best results were with a special Zeiss glass that I've been utterly unable to replicate. Unfortunately, last year I chipped a sheet and had to replace it with another from removed from my contact frame, so don't have any more left from that original box. It must have been surplus from some custom scientific application, and was hell to cut. Odd sheet size too, approx 12x16, but otherwise ideal for 8x10 film. I find 35mm less a pain in the butt than 120 film, which tends to be thinner and have more of a curl, so needs exceptionally even pressure in the carrier. And again long ago, starting out, I used a miniature film punch matched to the alignment pins in the glass slides. Now it's all custom Condit punches and glass or stuff I have personally modified. I always register small film (35mm and 120) using a taped on strip of polyester film and the 4x5 punch pattern. The tape itself needs to be polyester (not acetate) for dimensionally
stability. There is a narrow, thin mylar graphics art tape excellent for this. I wouldn't waste any time on things like Denglas. You need a better coating than that.

Michael R
21-Apr-2016, 08:53
What polyester tape are you using? I've wondered about using tape even for 4x5. Obviously that wouldn't be the same system, more like the design Lynn Radeka uses. But I haven't gone there because my stuff works fine.

Re Denglas, I guess your saying any glazing material (Tru Vue etc etc) would be out of the question for you as far as coatings go? The specs on some of the Tru-Vue coatings look pretty impressive.

I find the Schneider MPTV filter glass frustrating. Why is it only single coated???

Drew Wiley
21-Apr-2016, 10:26
The standards for picture glass are different than for optics per se. The True Vue I tested was actually a hard clear titanium coating, versus the traditional soft violet magnesium fluoride single coating of Denglas and many early coated lenses. This stuff is also rather fragile compared to true optical flats. But back to tape... Prior to people doing stuff on keyboards, graphics-oriented art stores routinely sold a selection of narrow high-quality mylar tape for creating lines on board. This has been variously marketed under Line A Tape, Chart Tape, Art Line Tape, Striping Tape, etc. Seems to still be readily available on line, though the big art store around the corner still carries a small selection in black and silver. Don't confuse it with narrow masking tape, sometimes sold under similar names. This is relatively tough stuff. 1/8" or 3/16" wide seems best for attaching masks to film. There is a trick to getting good register. You want everything held dead
flat and immobile as you roll and crease the tape edge to edge. For small film (up to 4x5) I life a semi-flexible non-marring polyethylene Bondo spreader for
applying moderate pressure while doing this. If you need to do big film, I can explain that later.

Michael R
22-Apr-2016, 07:20
I guess it's all more or less a waste of time, but an interesting excercise nonetheless.

EdSawyer
22-Apr-2016, 09:36
Likely since that's all they needed. It's just for filters, and it's just for TV. Not exactly the most demanding needs. Multi vs. single coating is not a big difference. < 10% improvement generally. There was an article on it in Modern Photography a few years ago. I will try to find the scan/copies of it I have. Fairly extensive and scientific test.





I find the Schneider MPTV filter glass frustrating. Why is it only single coated???

Michael R
26-Apr-2016, 04:31
Well, so far this search isn't going very well. Schneider apparently doesn't carry the 2mm thickness anymore. I guess I should have acted on that at the time. So far, that was really the only economically feasible option. I've been looking at the Howard Glass site too. Great resource.

Bob Salomon
26-Apr-2016, 05:08
Part of the reason was to use higher quality glass below the negative, and also to explore the possibility that multicoating (to reduce reflection) would help suppress the appearance of Newton rings without having an etched ANR pattern.

Newton rings occur when a flat, smooth surface, like the base side of film, comes in contact with a flat smooth surface like glass, that is why they use etched or sprayed anti Newton glass, so the glass in contact with the Fl
Lim base is no longer smooth and flat. Coating or multi coating the glass won't prevent Newton rings since, unless that glass is etched or sprayed, it is still a smooth, flat surface. And, since a filter is within the optical path of the lens it has to be as flat and smooth as possible, unless it is a special effect filter.

Michael R
26-Apr-2016, 05:56
Newton rings form due to imperfect contact between two reflective surfaces - but reflection is required. Agreed, depending on other variables AR coatings won't totally eliminate the formation of interference patterns, but they can help.

On a more generalized note, I was thinking just about glass quality in carriers. We tend to go nutso trying to get the best enlarging lenses, but when using a glass carrier, give no thought to the quality of the glass between the neg and lens. I don't know of any carriers that come stock with anything other than standard soda lime float glass.

I know we're into minutiae here, but lots of things are.