6x9 film being sucked forward? Medalists and other cameras

[Dan Daniel]

Has anyone ever encountered what looks to be the film being sucked upwards in a Medalists? Or in any other camera, for that matter. I think I had it happen once with a Moskva 5.

The idea, for those not familiar with it, is that extending a lens like on a folder with bellows or on a Medalist with the lens on an extending helical, creates a vacuum that pulls film slightly away from the pressure plate. Which in turn leads to an out of focus area. Someone I am talking with has a 'radial' focus issue, with the main OOF area at the center, the main line of the OOF being horizontal (running 9cm from left to right, not 6cm from top to bottom (landscape format and yes it isn't really 6cm or 9cm, I know). As if you tied a string to the center of the film and pulled up slightly.

When I had it on a Moskva 5, it was mainly straight, running in the 6cm short direction, about 1cm wide, slightly tilted from true vertical. As if the film was slightly crumpled or bowed forward as it moved across the image opening.

Any thoughts if the Medalist could create this amount of vacuum? Other experiences with film being distored by bellows, folders, etc.? Thanks.

Note: the example of the Medlaist distortion is subtle and would not hold up after reduction for jpg and posting here. Imagine an oval OOF area, max at center and fading back into focus at the outer edges leaving about 1cm in focus at the four central edge points

 

[Besk]

I make it a habit to "tension" the film just before exposure with my Afgfa Record 6x9 by advancing the film slightly.

Have never heard of a problem with a Medalist though. Maybe it is a problem with film itself.

 

[ic-racer]

The demon of medium format. Even cameras without bellows, the film can pop forward. Very characteristic image. Edges in focus but nothing in focus in the center (as the focal plane can extend behind infinity with the film popped forward in the center).

 

[John Wiegerink]

I learned long ago that drop-bed folders that snap open quickly are the worst offenders of the films inward bulge problem. The larger the format, the worse the issue usually is. I always use my free hand to let the bed and bellows open slowly as possible. As for the Medalist and film bulge? I've never seen it in all my time using the Medalist. I have seen it from improper respooling 120 onto 620 spools. I just respooled a roll using a 620 take-up spool as suggested here, and it went well. I'll take the Medalist II for a walk tomorrow.

 

[Dan Daniel]

John, can you say more on how you found respooling to affect film flatness? And how you correct for it? Thanks.

 

[Nicholas Lindan]

The problem isn't the film being 'sucked' but the film being pushed by greater air pressure behind it than in front of it. Unlike air pressure, a vacuum can not exert a force.

As the bellows opens the air pressure inside the camera goes down rather uniformly - pressure waves in air travel very quickly, the leading edge of the expansion moving at the speed of sound. Air will enter the camera for a second (or less) after the bellows open but the air pressure in the camera will be uniform.

To buckle the film there would have to be a large volume of air trapped between either the backing paper and the pressure plate or the film and the backing paper. This volume of air would have to be present before the bellows are extended - the volume of air would have to be such that the film would have to be already buckled before the bellows opened.

If, theoretically, the bellows could open at such a speed as to create pressure waves inside the camera the effect would be to increase the pressure exerted by the pressure plate on the film as a result of higher pressure air behind the pressure plate. This would, of course, not buckle the film.

Many film backs bend the film around a tight bend as it comes off the take-up spool. Hasselblads are possibly the worst offenders, but Hassies don't have bellows. OTOH, they do have problems with out-of-focus stripes if the film has been sitting in the back for a long period of time.

I have never seen a problem with film plane distortion in many years of experience with folders - albeit I have only owned Zeiss folders. If popping the bellows open on a folder was a problem with film flatness the engineers at the camera company would have been well aware of it and would have solved it a 100 years ago.

There may be reasons for loss of film flatness in MF cameras but I will have to vote that bellows extension isn't one of them.

In the case of the OP's original question about the Medalist - the slowness of extending the lens on its helical precludes the possibility of any differential air pressure inside the camera during the act.

 

[Besk]

The pressure plate does exert pressure on the film but on the lens side there is nothing holding the film back except around the edges.

For most of the folders there is a hole in the pressure plate - that is there so the numbers can be seen on the backing paper when loading the film and advancing it. If the folding camera is opened too fast, air must fill the void made. Some of that air can come from behind the pressure plate, through the hole and push against the film from behind. It doesn't take much air.

 

[gone]

It can happen on a folder, although I've never experienced it. Waiting until you have the camera open to snug the film up is always a good idea. But on cameras I've owned like the Super Ikontas that don't allow that and have an auto-stop on the film advance, I never saw any issues w/ film flatness.

A 6x9 folder would be more likely to exhibit the problem vs the smaller sizes.

 

[John Wiegerink]

The pressure plate does exert pressure on the film but on the lens side there is nothing holding the film back except around the edges.

For most of the folders there is a hole in the pressure plate - that is there so the numbers can be seen on the backing paper when loading the film and advancing it. If the folding camera is opened too fast, air must fill the void made. Some of that air can come from behind the pressure plate, through the hole and push against the film from behind. It doesn't take much air.

Bob, you are 100% right. At least according to me, anyway. That little hole in the pressure plate probably has much to do with the film being forced forward as anything. I have experienced the problem on two 6X9 folders. One was a Kodak with side-rail style pressure plate with no hole and another German folder with conventional pressure plate with hole. Both allowed the wind knobs to be slightly rotated after opening, which helps solve the problem. I just always gently open my folders as a habit now.

 

[John Wiegerink]

The problem isn't the film being 'sucked' but the film being pushed by greater air pressure behind it than in front of it. Unlike air pressure, a vacuum can not exert a force.

As the bellows opens the air pressure inside the camera goes down rather uniformly - pressure waves in air travel very quickly, the leading edge of the expansion moving at the speed of sound. Air will enter the camera for a second (or less) after the bellows open but the air pressure in the camera will be uniform.

To buckle the film there would have to be a large volume of air trapped between either the backing paper and the pressure plate or the film and the backing paper. This volume of air would have to be present before the bellows are extended - the volume of air would have to be such that the film would have to be already buckled before the bellows opened.

If, theoretically, the bellows could open at such a speed as to create pressure waves inside the camera the effect would be to increase the pressure exerted by the pressure plate on the film as a result of higher pressure air behind the pressure plate. This would, of course, not buckle the film.

Many film backs bend the film around a tight bend as it comes off the take-up spool. Hasselblads are possibly the worst offenders, but Hassies don't have bellows. OTOH, they do have problems with out-of-focus stripes if the film has been sitting in the back for a long period of time.

I have never seen a problem with film plane distortion in many years of experience with folders - albeit I have only owned Zeiss folders. If popping the bellows open on a folder was a problem with film flatness the engineers at the camera company would have been well aware of it and would have solved it a 100 years ago.

There may be reasons for loss of film flatness in MF cameras but I will have to vote that bellows extension isn't one of them.

In the case of the OP's original question about the Medalist - the slowness of extending the lens on its helical precludes the possibility of any differential air pressure inside the camera during the act.

I agree with almost everything you say, but all camera makers are not equal. Some of the older, not well known makers of cameras might not have corrected or even known there was a problem. Many of those makers of those old folders didn't survive for very long, like Kodak and Zeiss did. Kodak and Zeiss would have had time and finances to correct almost any issue that cropped up, but the other smaller companies might not have.

 

[John Wiegerink]

John, can you say more on how you found respooling to affect film flatness? And how you correct for it? Thanks.

Dan,
The biggest issue with respooling and I only speak for myself, is the tape line. There is no problem rolling onto the intermediate spool, whether it be a 120 or 620 intermediate spool. The issue is repooling onto the user 620 spool from the intermediate spool because you are winding the film backwards and must now feed the untaped edge onto the finish 620 spool so that there is absolutely no slight bulge in the film compared to the backing paper. You can think you have started the film's untaped edge tightly, but you won't know until you have completed winding the film to the taped spot on the backing paper. If you feel a slight bulge or unevenness, you have a problem. That's why I insert my finger between the film and the backing paper to slowly unattach the film from the backing paper and then wind on, keeping tension on the spool until the tape reattaches itself to the backing paper. That way I know for sure there is "NO" bulge in the film.
What happens if you just do a sloppy respool job? You will get a bulge where the film and backing paper are not in sync anymore. That bulge will distort the image or at least be blurry at that point in the film. As an example, many years ago I took a picture of my oldest sons Rocket football team with my Kodak Medalist II and repooled Fuji Velvia slide film. I didn't know much about the bulge issue then, but learned very quickly after I got the processed film back from the lab. One of the neighbor boys was on one end in the picture and when I saw him I couldn't believe my eyes. He had shoulders that were about 40 inches wide. The bulge in the film was exactly where he was standing, and the curve of that bulge made him look wider(distorted) than he really was. Luckily, my other shots were better. I showed his father and told him I was going to discard that one. He said, "I want it"! He actually thought it was kool that his little boy had shoulders that wide. I guess all things work out in the end, but I just as soon forgo the bulge thing. JohnW

 

[Sal Santamaura]

...Many film backs bend the film around a tight bend as it comes off the take-up spool. Hasselblads are possibly the worst offenders, but Hassies don't have bellows. OTOH, they do have problems with out-of-focus stripes if the film has been sitting in the back for a long period of time...

We're on somewhat of a tangent now, but I'm happy to see you posting what I've described for decades, often to the ridicule of Hasselblad users in particular. My solution with reverse-curl film backs has been to leave every other frame blank. However, there is reason for positive outlook on the horizon. Kodak introduced its 120 Gold recently on a polyester base, so other Kodak 120 emulsions might also transition to the new base. Unlike acetate, which takes a "set" on the feed roller and then bulges toward the lens, polyester remains flat despite being forced backward on its way to the gate. Fingers crossed.

 

[John Wiegerink]

We're on somewhat of a tangent now, but I'm happy to see you posting what I've described for decades, often to the ridicule of Hasselblad users in particular. My solution with reverse-curl film backs has been to leave every other frame blank. However, there is reason for positive outlook on the horizon. Kodak introduced its 120 Gold recently on a polyester base, so other Kodak 120 emulsions might also transition to the new base. Unlike acetate, which takes a "set" on the feed roller and then bulges toward the lens, polyester remains flat despite being forced backward on its way to the gate. Fingers crossed.

Sal,
That is good news for us Hasselblad users. When I shot weddings, I never started with a partially used roll in a back for that simple reason, but I also didn't go to the lengths of skipping frames when I shot weddings either. I have pulled partial rolls of film out of A12 backs that have sat for long periods of time. To say they had a crease or bulge is an understatement. Victor got almost everything right with the design, but that reverse curl back was not one of them. JohnW

 

[BrianShaw]

Sal,
That is good news for us Hasselblad users. When I shot weddings, I never started with a partially used roll in a back for that simple reason, but I also didn't go to the lengths of skipping frames when I shot weddings either. I have pulled partial rolls of film out of A12 backs that have sat for long periods of time. To say they had a crease or bulge is an understatement. Victor got almost everything right with the design, but that reverse curl back was not one of them. JohnW

For me this has been a non-issue... just never leave film in cameras for extended periods of time!

 

[John Wiegerink]

We're on somewhat of a tangent now, but I'm happy to see you posting what I've described for decades, often to the ridicule of Hasselblad users in particular. My solution with reverse-curl film backs has been to leave every other frame blank. However, there is reason for positive outlook on the horizon. Kodak introduced its 120 Gold recently on a polyester base, so other Kodak 120 emulsions might also transition to the new base. Unlike acetate, which takes a "set" on the feed roller and then bulges toward the lens, polyester remains flat despite being forced backward on its way to the gate. Fingers crossed.

Sal,
I also apologize for slipping off the "sucked film" topic. JohnW

 

[Dan Daniel]

I certainly have no problems with the detours. The overarching issue is film flatness, so other causes of problems are interesting.

John, as I read you, you are saying that the respooling 'bump found its way under the pressure plate at some point and in crossing the film gate caused an out of focus distortion area? So the 'bump' stayed in the feed area, before the image opening, but at some point it found its way out of the feed area and across to the takeup.

I am very familiar with the bump from respooling. I undo the original tape and roll the film over it to let it find its own way out. Then check the tape position afterwards to make certain that it set down smoothly.

 

[John Wiegerink]

Dan,
Yes, that pesky film bow/bump found its way over the rollers and under the pressure plate on the Medalist. It sat close to the right side of the film gate, but about a half inch in on the transparency.

Dan,
Sounds like you and I are on the same page when it comes to the tape. It's the best way and the most foolproof method I have found. I have never had the "bump" problem since adopting it. The Medalist II was supposed to go for a walk today, but she decided to take one more day off. Maybe tomorrow?

 

[Helge]

It’s really very simple:
Hone some mechanical empathy and don’t let the bed spring open unassisted. For a host of reasons. Only one of them being film flatness.

 

[Sal Santamaura]

Sal,
That is good news for us Hasselblad users. When I shot weddings, I never started with a partially used roll in a back for that simple reason, but I also didn't go to the lengths of skipping frames when I shot weddings either. I have pulled partial rolls of film out of A12 backs that have sat for long periods of time. To say they had a crease or bulge is an understatement. Victor got almost everything right with the design, but that reverse curl back was not one of them. JohnW

For me this has been a non-issue... just never leave film in cameras for extended periods of time!

Perpetuating the tangent for one more post, two decades ago I did a lot of experimenting on this subject. The time needed for acetate base 120 film to take a reverse curl "set" and bulge varies with ambient conditions. When it was warm and humid (like right now here), the bulge appeared after as little as 15 seconds. That finding in particular was what set off the Hasselblad users' vitriol against me.

 

[BrianShaw]

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