Omega/Peak Enlarging tool question

[Bob Salomon]

Not all emulsions are the same, but a curl for 35mm was engineered so that when in camera, the pressure plate pressed the top of the curl down evenly and provided an even flatness... If you look along the edges of the film gate, there is a slight recess where most all of the film was flat, but a small edge past the perfs needed to not be pressed flat, as this would create an overall tension that could affect the rest of the flatness of the frame...

Color slides that were hot mounted were expected to have a crown so popping was minimal... When I hot mounted many E6 slides at a pro lab, the paper hot mounts allowed for this... The different thinner color films tended to somewhat alike, so if put in a projector, the auto focus feature hopefully did not have to do too much...

B/W films with thicker emulsions and bases were all over the place, but some more or less curl was there, but the final curl also had a lot to do with processing, wash times, drying, storage, etc...

The curling function seems to be going away these days, as many customers plan on scanning film very flat, but curled film is important for best film flatness...

Steve K

You do know, I hope, that I represented the largest maker of slide mounts in the world who invented what was called the Pako/Pakon glassless mounts?

In 1983 Gepe bought HP Marketing, the company that I was sales and product manager for and Gepe owned Geimuplast who invented the Pako mount. We sold those to labs here as the Geimuplast Quickslide mount.

We were part of the Gepe Group until they closed our USA division in 2015.

Films don’t bow the same during projection. That is why glass mounts worked the best, even the film positioning ramp in the plastic glassless mounts didn’t prevent popping.

[Jac@stafford.net]

[...]Films don’t bow the same during projection. That is why glass mounts worked the best

Glass mounted slides have always been superior for projection.

But this thread concerns enlarger negative stages. My two-bits, using a Leitz Valoy and Leitz IIa I have not found Newton rings. Perhaps I am lucky.

[Drew Wiley]

Steve, I have understood what you're explaining for a very long time, and it is a partially valid point, but it's relative to just how flat you need your neg. My own printing standards don't allow that variable or risk, even in 35mm. It would still be something of a gamble, even if the neg pops predictably one direction. When I first started out with my own under-equipped darkroom, I actually mounted my roll-film images into Gepe AN glass (both sides) mounts. That made a distinct difference in both overall focus accuracy and preventing any such shift later. That phase didn't last very long, because after about six month I wanted more serious darkroom equipment; but it taught me an important lesson. Bob also correctly points out how, even during slide shows, there was a real difference qualitatively when the slides were glass mounted. This might have been more obvious in med format presentations; but it was also true for 35mm. My brother (a pro LF photographer) in those days used to hang out with a very well-known Leica addict who routinely won international slide show competitions. That kind of activity might sound arcane today, but there was serious money in it back then, and it was a shortcut to prime shooting contracts as well. Anyway, those guys routinely put their slides into flat glass mounts, and bought high-end flat-field projection lenses to go with them. Otherwise, they weren't going to even be in the running. Wish young people today could see what projected chromes look like, instead of computer screen images. It would be a revelation.

[Bob Salomon]

Steve, I have understood what you're explaining for a very long time, and it is a partially valid point, but it's relative to just how flat you need your neg. My own printing standards don't allow that variable or risk, even in 35mm. It would still be something of a gamble, even if the neg pops predictably one direction. When I first started out with my own under-equipped darkroom, I actually mounted my roll-film images into Gepe AN glass (both sides) mounts. That made a distinct difference in both overall focus accuracy and preventing any such shift later. That phase didn't last very long, because after about six month I wanted more serious darkroom equipment; but it taught me an important lesson. Bob also correctly points out how, even during slide shows, there was a real difference qualitatively when the slides were glass mounted. This might have been more obvious in med format presentations; but it was also true for 35mm. My brother (a pro LF photographer) in those days used to hang out with a very well-known Leica addict who routinely won international slide show competitions. That kind of activity might sound arcane today, but there was serious money in it back then, and it was a shortcut to prime shooting contracts as well. Anyway, those guys routinely put their slides into flat glass mounts, and bought high-end flat-field projection lenses to go with them. Otherwise, they weren't going to even be in the running. Wish young people today could see what projected chromes look like, instead of computer screen images. It would be a revelation.

A former CEO of AT&T believed in slide presentations and that created the multi projector slide shows and that meant that slides had to be in registration and absolutely had to remain sharp on all projectors. That led to the creation of 3 pin, pin registered mounts and the birth of Wess Mounts and the Gepe Pro mounts and the pin registered cameras that produced these dupe slides.

Film pops under heat, even when the film is used in enlargers and projectors that conformed to the ANSI standards for temperature at the film plane.

If you want critically sharp results, in prints or slides you need proper alignment and glass carriers or mounts. Although since Gepe stopped their production glass slide mounts are becoming extinct.

BTW Drew, Several years ago Gepe offered MF mounts with only one AN glass and one plain glass due to too many users complaining of the AN treatment coming into focus when placed against the emulsion. They also, in 6x6 cm made one glass only mounts but they did not prove too be very popular.

[Pieter]

A former CEO of AT&T believed in slide presentations and that created the multi projector slide shows and that meant that slides had to be in registration and absolutely had to remain sharp on all projectors. That led to the creation of 3 pin, pin registered mounts and the birth of Wess Mounts and the Gepe Pro mounts and the pin registered cameras that produced these dupe slides.

Film pops under heat, even when the film is used in enlargers and projectors that conformed to the ANSI standards for temperature at the film plane.

If you want critically sharp results, in prints or slides you need proper alignment and glass carriers or mounts. Although since Gepe stopped their production glass slide mounts are becoming extinct.

Totally off-topic, but that reminded me of the time I went on the road during the mid 80s with a wide-screen, 9-projector presentation that was run by a special board and an audio tape with synch pulses. Hundreds and hundreds of slides, hours and hours to set up and register for a 15-minute show.

BTW Drew, Several years ago Gepe offered MF mounts with only one AN glass and one plain glass due to too many users complaining of the AN treatment coming into focus when placed against the emulsion. They also, in 6x6 cm made one glass only mounts but they did not prove too be very popular.

[LabRat]

I did AV for a spell, and Gepe was good, but issues would come up with some frames where the film would partially dry causing slightly moving waves or fogging, or could shift in the mount if not silver taped down or regstration mounts were used... Also using the TV 140 slide trays were out, and some Carousel projectors did not like shuffling around the glass mounted slides, but they did stay in focus much better...

Kinda better now not pulling together dissolve shows, but not the same look or vibe when the planets aligned... ;-)

Steve K

[Bob Salomon]

I did AV for a spell, and Gepe was good, but issues would come up with some frames where the film would partially dry causing slightly moving waves or fogging, or could shift in the mount if not silver taped down or regstration mounts were used... Also using the TV 140 slide trays were out, and some Carousel projectors did not like shuffling around the glass mounted slides, but they did stay in focus much better...

Kinda better now not pulling together dissolve shows, but not the same look or vibe when the planets aligned... ;-)

Steve K

Steve,

The Gepe mounts were made with glass that could float under the metal mask. This meant that the mounts were ventilated.
By using tape to hold the film in place rather then properly putting the film under the hold down slots in the mask you were exacerbating any waving or fogging, etc.

Gepe also made a mount called the Gepe Pin mount that had small bumps that pressed the edge of the fil into holes on the opposite side of the mount to ensure that film shot in any camera, pin registered or not, could not shift position. Then the also made the 3 pin, pin registered mounts in 2 mask sizes for 35mm and one for Super Slide images.

Yes, 140 magazines could not be used but if you read the Kodak tech release on slide jamming on Carousel projectors you would have found that slide jamming was most prevalent with the 140 trays. Wes’s and Gepe Pro mounts were also too thick to fit the standard 80 slide tray as well and required the Universal tray.

[Drew Wiley]

Bingo again, Bob. You are stirring up some memories. My first experiments with masking, before I was even into large format work, involved one of those little 6X7 Gepe punches along with the registration pins in their matching mounts, which would accept a two sheet sandwich of mask and original chrome (They were designed to accept the thickness of a script title slide sandwiched to an original). I still have that thing in a drawer somewhere. And yes, for 35mm, I had the Universal Carousel tray, and it's still on a shelf around here. The problem Steve brings up involves another variable, however, namely the dimensional stability of film. Those of us who have worked with punch and register systems over a long period know the distinct advantage of polyester film base (dimensionally stable) versus acetate (shrinks, unstable). Even the tape involved should be dimensionally stable mylar rather than acetate or vinyl. But I recall an old timer telling me that the best color photographs he ever saw were the old lantern slide shows involving three different aligned carbon arc projectors with respective RGB pan separation negs, and a different respective color filter on the front of each. But those must have been hot, slow affairs. Maybe not as bad as Aunt Maude giving a three hour slide show of her latest vacation to Peoria, however.

[Bob Salomon]

Bingo again, Bob. You are stirring up some memories. My first experiments with masking, before I was even into large format work, involved one of those little 6X7 Gepe punches along with the registration pins in their matching mounts, which would accept a two sheet sandwich of mask and original chrome (They were designed to accept the thickness of a script title slide sandwiched to an original). I still have that thing in a drawer somewhere. And yes, for 35mm, I had the Universal Carousel tray, and it's still on a shelf around here. The problem Steve brings up involves another variable, however, namely the dimensional stability of film. Those of us who have worked with punch and register systems over a long period know the distinct advantage of polyester film base (dimensionally stable) versus acetate (shrinks, unstable). Even the tape involved should be dimensionally stable mylar rather than acetate or vinyl. But I recall an old timer telling me that the best color photographs he ever saw were the old lantern slide shows involving three different aligned carbon arc projectors with respective RGB pan separation negs, and a different respective color filter on the front of each. But those must have been hot, slow affairs. Maybe not as bad as Aunt Maude giving a three hour slide show of her latest vacation to Peoria, however.

Yes, they delivered great color as long as the same process filter was used for taking and projection. But most of those filters were subject to fading.
Also, if you were shooting anything that could move, like leaves, waves, people, animals, etc. the results were not good at all.

[Drew Wiley]

There was also a specialized expensive version of the Nikon F series adapted to make the sprocket holes seat in exactly the same spot relative to each successive frame, along with matching slide mounts which registered via the sprocket holes themselves. A large AV distributor in SF carried this whole system. I've even seen Durst carriers made for sprocket hole registration. I suppose most of these were used on copystands for title slides. Now we've got computer projectors and Powerpoint presentations allowing marketing MBA's to communicate their sheer BS more efficiently and boringly than ever. But Bob, I'm equipped to do tricolor 8x10 film separations in the field, as well as print them in register. It's just a matter of stumbling onto the right subject on a windless time of day. Each of the three exposures is quite slow due to the sheer density of sharp-cutting separation filters. In the meantime, there's regular color film. For studio still life, a process camera with a built-in registration bar can be used. The local camera store (Looking Glass) has a beat-up old Devin tricolor camera on their conversation piece shelf.