Anti-Newton Glass and Huge Enlargements

[Ian Grant]

So it seems the ultimate is wet mounting with regular glass. That must be an awful mess with 4x5 but I'll be doing so few very large prints I suppose it might be worth the effort.

Personally I wouldn't dream of wet mounting. I actually don't like glass carriers and never use them with LF film, I know Bob Carnie would disagree but it's always worked perfectly for me even with 10x8 negatives. I do you glass in the lower half on my carriers for 120 and the metal mask in the top, I guess I wouldn't be adverse to glass in the lower part of an LF carrier it's just that in 40 years of printing LF the carriers have always been glass less.

Ian

 

[Ronald Moravec]

Tex AN glass goes top only. Bottom is clear glass. I have made 16x prints from 35 mm and tex does not show. Does not show with slide projector either.

From 4x5. No way a problem.

 

[DREW WILEY]

I don't think Ctein wet mounted negs for enlarger use. Don't recall anything like that in his darkroom, which was quite basic. You could ask him. He does fluid mounting for scanning 120 film, however. He might have a few odds n's ends of dye transfer punches etc left, probably no dyes or film. He sent me an e-mail recently linking me to someone overseas scraping together supplies for a potential DT lab; but I should have my own little DT line
up and running in the next few months.

 

[Ian Grant]

I don't think Ctein wet mounted negs for enlarger use. Don't recall anything like that in his darkroom, which was quite basic. You could ask him. He does fluid mounting for scanning 120 film, however. He might have a few odds n's ends of dye transfer punches etc left, probably no dyes or film. He sent me an e-mail recently linking me to someone overseas scraping together supplies for a potential DT lab; but I should have my own little DT line
up and running in the next few months.

While it's possible I misread what Ctein wrote wet mounting has been used for enlarging for about 90 years, although I would think by very few people. Ctein was definitely using wet mounting for scanning but I think also for enlarging for a while. I remember because I was quite surprised and it was later I bought a 1927bBJP Almanac with the bit about wet mounting 35mm negatives (1926) for the highest quality results.

Ian

 

[RalphLambrecht]

I realize AN glass has little effect on relatively small prints but what about HUGE prints? Does that fine granularity of the AN glass ever show in really big prints?

I have never seen it

 

[Europan]

I think SPUR is Gigabit

No, it isn’t.

Gigabitfilm or Gigabit film in English is a family of special films together with a
proprietary developer formula, developed by Detlef Ludwig, Kreuzau, Germany.

It is true that Heribert Schain and Detlef Ludwig know each other well.

There was Gigabit 25 ISO as sheet film, 4" × 5". There was Gigabit 32 ISO as 35mm perforated film. There still is Gigabit 40 as 35mm and 16mm perforated films. I have introduced Gigabitfilm to cinematography in 2002 in 35mm and in 2005 in 16mm, respectively. I had a commercial lab specialised in black and white from 1999 to 2008. I want to reopen a film lab as soon as I have the means and Gigabit shall be among the offers from day one on. C-41 and E-6 shall also be available.

I’m on the dole.

 

[RobC]

No, it isn’t.

Gigabitfilm or Gigabit film in English is a family of special films together with a
proprietary developer formula, developed by Detlef Ludwig, Kreuzau, Germany.

It is true that Heribert Schain and Detlef Ludwig know each other well.

There was Gigabit 25 ISO as sheet film, 4" × 5". There was Gigabit 32 ISO as 35mm perforated film. There still is Gigabit 40 as 35mm and 16mm perforated films. I have introduced Gigabitfilm to cinematography in 2002 in 35mm and in 2005 in 16mm, respectively. I had a commercial lab specialised in black and white from 1999 to 2008. I want to reopen a film lab as soon as I have the means and Gigabit shall be among the offers from day one on. C-41 and E-6 shall also be available.

I’m on the dole.

Thankyou for clarifying that.

 

[RobC]

read the "Enlarging Devices / Enlarging" section on second page of attached pdf which has something to say about negative carrier glass and AN glass which is interesting. But if you need film flatness to keep neg within enlarger lens depth of field for the maginification and aperture you are using, then I think that trumps what it has to say. But if your negs stay flat without glass then thats always a better way to go. If you're not sure about enalrger lens depth of field then there are online calculators for macro work I think.

Note: An enlarger is a macro camera. The negative is "the subject" and focus at the negative is within depth of field and not depth of focus. Depth of field is very very narrow with the enlargement ratios used in printing. Down to fractions of a millimeter in many cases.

 

[DREW WILEY]

For best results, one wants everything on the enlarger perfectly adjusted, and the lens itself at an optically optimal f-stop and SHALLOW depth of field with focus only on the emulsion itself if possible. Stopping further down in order to accommodate uneven film will just compromise all that fuss you underwent using a special fine emulsion to begin with.

 

[MartinP]

I do you glass in the lower half on my carriers for 120 and the metal mask in the top, I guess I wouldn't be adverse to glass in the lower part of an LF carrier it's just that in 40 years of printing LF the carriers have always been glass less.

Whenever I look at 120 film it curves concave on the emulsion side. Before I found a clear lower-glass, I have used successfully the neg carrier with AN-glass in the top to 'squash' the film down on to the alloy 'glassless' masking-plate. Wouldn't doing it the other way round just lead to a neg bulging upwards?

Decades ago, one enlarger in the lab where I worked had a glassless 4x5" carrier, which seemed to work adequately with the stiff polyester film, while everything bigger had double-glasses. The 8x10" film would almost certainly sag in the middle without some sort of support.

 

[DREW WILEY]

120 film is the worst. Thin flimsy acetate that does indeed tend to curl. Can't imagine printing it without a precision glass carrier. I was spotting some
prints last night made by boosting the contrast of 120 negs way up with VC paper, practically to the limit. And yes, an Apo Rodagon lens was used, along with AN glass on both sides. These are so precisely in focus that with strong reading glasses I can detect the film grain itself perfectly crisp right out to the corners of the print, but not a trace of AN texture anywhere, not even on smooth skies, not in any of these prints.

 

[tedr1]

Some numbers:
150mm lens with 6X enlargement
F5.6 depth of field at neg = 0.0590mm so +or- 0.0295mm
F11 depth of field at neg = 0.226mm so +or- 0.113 mm
F22 depth of field at neg = 0.899mm so +or- 0.449 mm

150mm lens with 10X enlargement
F5.6 depth of field at neg = 0.0685mm so +or- 0.0343 mm
F11 depth of field at neg = 0.267mm so +or- 0.123 mm
F22 depth of field at neg = 1.07mm so +or- 0.535 mm

At F22 you could quite easily run into problems of AN Glass being in focus. Much less likely at F11 and very unlikely at F5.6

So to help avoid the problem, keep aperture as wide as is practical to give sharpness.

But finer grained AN glass is less likely to be visible if it is in focus.

Thank you for posting this information. I am interested because I am currently checking the alignment of my enlarger and I am curious about the accuracy of precision required. In my case the neg is 6x7cm and the lens 90mm, I would be interested to see the numbers for this case, could you please make the formula available?

Ted

 

[RobC]

upto what enlargement factor

 

[tedr1]

thank you, the examples used previously 6x and 10x are suitable

 

[RobC]

6x7 negative

neg thickness 0.12mm ( but emulsion thickness is much less than that)

90mm lens with 6X enlargement
F5.6 depth of field at neg = 0.0591mm so +or- 0.0295mm
F8.0 depth of field at neg = 0.120mm so +or- 0.06 mm
F11 depth of field at neg = 0.226mm so +or- 0.113 mm
F16 depth of field at neg = 0.476 mm so +or- 0.238 mm

90mm lens with 10X enlargement
F5.6 depth of field at neg = 0.0685mm so +or- 0.0342mm
F8.0 depth of field at neg = 0.138mm so +or- 0.069 mm
F11 depth of field at neg = 0.261mm so +or- 0.130 mm
F16 depth of field at neg = 0.553 mm so +or- 0.276 mm

you can get the free software to do the calcs (once you've worked out how to use it) from:

http://www.winlens.de/index.php?id=70

top tip: as soon as you start the software, maximise its window size to full screen becasue there is a bug and depth of focus panel doesn't work if window isn't maximised.

 

[tedr1]

thank you very much, I appreciate your help (I probably won't investigate the software, not my strong point)

Ted

 

[RobC]

pretty narrow window to work within.

 

[tedr1]

I notice that the results are very similar for 6x7 with a 90 and 4x5 with a 150.

The numbers seem to show the DOF increases as the magnification increases. Using the thought process of imagining the enlarger as a macro camera and comparing this to a conventional macro camera setup, this seems counter-intuitive, I would expect that as the magnification increases (in this case the lens moves closer to the negative) the DOF would shrink. Perhaps my thinking is incorrect (wouldn't be the first time )

 

[ced]

Wet mounting is not such a big hassle.
If you use a few drops of lighter fuel (Ronson or Zippo etc) and tape off the edges allround to keep air out and fuel in.
It evaporates with no damage whatsoever to the neg.
Oil mounting is messier but also does no harm when cleaning(dipping) the whole neg into a small bath of petroleum ether.
Both these methods eliminate scratches & craters where the light is bounced about causing dark spots & or scratches picked up in the print.

 

[RobC]

I notice that the results are very similar for 6x7 with a 90 and 4x5 with a 150.

The numbers seem to show the DOF increases as the magnification increases. Using the thought process of imagining the enlarger as a macro camera and comparing this to a conventional macro camera setup, this seems counter-intuitive, I would expect that as the magnification increases (in this case the lens moves closer to the negative) the DOF would shrink. Perhaps my thinking is incorrect (wouldn't be the first time )

I think its to do with the minimum circle of confusion in the print which gets bigger as the aperture gets smaller and therefore dof able to produce that is bigger than you think. I worked with smallest possible theoretical CoC at each aperture and magnification.
If I used same CoC for both 6X and 10X then yes dof gets smaller with greater magnification. But lenses don't work like that. CoC is dependant on effective aperture and not aperture set on lens so at F11 and 6X its F55 and at 10X its F99 and at F99 CoC due to diffraction and rayleigh limit is much bigger and therefore dof able to remain within it is wider. At least that is I what I think is the reason.
When you get into macro magnifications things behave differently than in non macro magnifications.

 

[tedr1]

Thank you. The fundamental message seems to be that DOF at the negative with lens wide open is of the same order as the film base thickness. This places high demands for precision on the parallelism of the negative and paper planes if sharpness is to be maintained. I am new to medium format work, having previously done a lot of modest enlargements of 35mm on a simple enlarger and taking a lot for granted!

 

[RobC]

correct. Enlargement alignment is very important. Both lens being perpendicular to negative and paper and neg being parallel with each other. But closing down gives a margin of error. However, with AN glass you may see the AN glass grain if you do that. I seem to be the only one who has actually seen it. Don't know if thats becasue I'm the only one who was looking close enough for it or becasue I had closed down aperture too much or whether my Durst AN Glass is especially grainy.

 

[DREW WILEY]

Also has something to do with what you have had to drink in the past half hour. Maybe that's how the early Impressionists saw everything in colorful
blurs and swatches. They had quite an absinthe habit. But no, those magical anti-Newton fairies and gremlins have never appeared to me yet. In this
part of the world, we're better known for alien landing and bigfoot sightings.

 

[Arklatexian]

I realize AN glass has little effect on relatively small prints but what about HUGE prints? Does that fine granularity of the AN glass ever show in really big prints?

Old-N-Feeble, I know no one knows better than you that South Texas extends from El Paso to where the Rio Grande flows into the Gulf of Mexico. Which area do you live in? If you are far enough West where things are dry, you might not even need AN glass. If you live near the coast, you probably will need AN like where I live. There is another answer however. When you build your darkroom, be sure to include an window unit or some other air conditioner to take the moisture out of the air. That is what I have done. I set the unit on 68 F and my darkroom stays dry and confortable to work in. This is, of course, for summer which is at least 6 months long most years. In Winter the air is usually drier....This does not answer your question but might help...Regards!

 

[Old-N-Feeble]

oldtimer, I'm south of San Antonio just a few miles north of Floresville. I'll definitely have heat, A/C and humidity control in the darkroom... both to increase or decrease humidity as needed. BTW, unfortunately, I live on a dirt road and dust is a SERIOUS issue so I'll be filtering the air as best I'm able also.