Kodak Medalist unusual out of focus areas on negative

Hunter_Compton · Monday at 8:16 PM

I got a couple rolls of Kentmere 200 and wanted to test one of them using my (up to this point highly reliable) Kodak Medalist. Film was transferred onto one 620 metal spool and then back onto another in a method that I have used many times with Kodak Tri-X, Gold 200 and Ilford FP4+ and Pan F without issue.

Upon development I found frames 3, 4 and 5 had unusual and inconsistent out of focus regions towards the center of the frame. The other frames on the roll were tack sharp as I would expect from the 100mm f/3.5 Ektar on this camera. I verified the areas of improper focus are visible on the negative with a loupe and not just on the scan.

The frames in question were all shot at either f/8 or f/11, whereas this frame was shot at f/4 and is sharp across the frame as expected.

I'm not inclined to think this is a lens adjustment or rangefinder issue. My leading theory right now is the film is buckling or warping and the pressure plate isn't keeping it flat enough, but I'm curious to hear other peoples interpretations and why I'm only running into it now.

Full size TIFF files can be viewed here: https://www.flickr.com/photos/158396499@N04/albums/72177720326903841/

(Please disregard the dust and imperfect cropping, these are pretty much straight off the scanner).

BAC1967 · Monday at 11:41 PM

I just noticed the same thing on some shots with my Medalist from a few weeks ago. Ilford Delta 100 developed in Beerenol. I don't remember the settings, they were slow shutter speeds both done with a tripod. In the first one you can see the roof and top front of the building is a little out of focus. The rope below the roof which is on about the same plane as the upper portion looks to be in focus. The roof slopes back and looks out of focus but the right side of the building is in focus. The second shot looks fine.

Fort Borst Blockhouse by Bryan Chernick, on Flickr

Historic Borst Home by Bryan Chernick, on Flickr

koraks · Tuesday at 4:33 AM

Hunter_Compton said:
My leading theory right now is the film is buckling or warping

It's a film-flatness issue for sure. I don't think it's buckling as I'd expect to see the typical higher-density crescent shapes you get where the film kinks. This looks like a more smooth bulge on the film instead. It's probably only very slight. I suspect the hand-rolling has a lot to do with this and I imagine it can be pretty difficult to tightly roll everything up, consistently.

Harry Callahan · Tuesday at 5:34 AM

@Hunter_Compton:

The strange thing is that the plane of sharpness does not seem to be shifted anywhere. In your first picture the road sign in the foreground is unsharp - and the tree behind the house also is unsharp. If film flatness was impaired plane of sharpness should be shifted into the foreground or background it think...

But your problem might be depended on how long the film rests inside the camera after advancing. I once did take two shots of the same subject with a medium format camera, one with filter one without filter. The film had been put into the holder weeks ago and two or three pictures were taken, then the film was sitting in the holder for several weeks, then i took two pictures of the same subject within one or two minutes.
Sharpness of the first picture was a little lower in the middle of the picture, while sharpness of the second picture was excellent.
I can see that the subject you took at f4 is on the house (Dydon Deopt) you took at f8 or f11. If you took the picture of the house first and then quickly went to the sign at the house, giving the film only one or two minutes to rest in the camera after advancing you may have gotten better flatness - as the film had no time to "curl" after advancing.

Maybe you can reduce this problem by advancing the film just before exposure.

koraks · Tuesday at 6:41 AM

Harry Callahan said:
The strange thing is that the plane of sharpness does not seem to be shifted anywhere.

The film will have warped in the direction of the lens, decreasing the lens-film distance. This means the focal point will have shifted off into the distance, likely beyond infinity. A focal shift beyond infinity can never be reflected in the subject matter and everything will be out of focus.

What rival explanation do you offer that in your view would better explain the phenomenon?

Harry Callahan · Wednesday at 5:11 AM

I`m not saying that i have a better/different explanation, i was just surprised that plane of sharpness had disappeared from the film. I mean how much has film to warp towards the lens to get this effect with a subject being like 30ft away from the camera? When the lens is set at 30ft, setting it to infinity may move the lens 1mm closer to the film - so the warp of the film had to be more than 1mm to produce this effect...

...anyway my idea of solving this problem is based on film warping inside the camera, so i`m taking it. I was surprised that it can be that bad.

koraks · Wednesday at 5:21 AM

Harry Callahan said:
...anyway my idea of solving this problem is based on film warping inside the camera, so i`m taking it.

Yeah, i figured that too, although I wasn't quite sure whether you may also have been thinking about something related to moisture etc. Not that I think that's it, and I really think it's warping. I also understand your surprise, although given the small difference at the film plane between infinity focus and let's say 30-100ft out, I can see how a tiny bulge would create a significant problem. What I find more surprising is that it seems to be such a localized bulge, like a little mound. When film bulges, I'd expect it to create ripples, waves and ridges.

Harry Callahan · Wednesday at 5:42 AM

As the plane of sharpness did disappear entirely i was thinking for a minute that the film may had moved during exposure - like a slide popping when getting warm in the projector - but i consider this unlikely to maybe impossible. Also i was wondering whether the Ektar lens, which should be made from rare earth glass may somehow interact with the film, if the film had extended spectral sensitivity - but BAC1967 used a different film and Hunter_Compton got sharp results at f4 where interaction with the lens should be greater than at f11... so i settled rather fast for warped film.

Well, the Medalist is a medium format camera, so the focal length should be around 105mm. Going from 30ft to infinity may move the lens even more than 1mm - so the warp had to be pretty big.
Hm... the middle of the negative is where the film gate is farthermost - so the edges of the image are in focus but the middle isn`t... similar to a slide popping in its frame.

OAPOli · Wednesday at 8:08 AM

@Harry Callahan you're correct, a 100mm lens moves approx. 1mm from infinity to 10m (32ft).

A central bulge seems possible. Probably due to a fluke issue in the film re-spooling?

Dan Daniel · Wednesday at 8:35 AM

Any possibility that the lens tube sucked the film forward? I've had it happen with a Moskva 5 folder.

Not certain of the history of the camera in question. Is the spool fitting in the feed side chamber well? Any chance that you are using plastic reels in the feed side, i.e. the respooled roll? Or the spools from China with the small tabs on the outside of the end flanges? I wonder if there is some binding or such going on in winding that makes the film feed erratically, allowing for uneven tension and hence a little popping.

Most plastic reels are slightly too long and may bind in the feed side. The reels with tabs should not be used in a Medalist in my opinion. The tabs will hang on the lower positioning tab in the feed side and on both the lower spring and upper wind tab bushing on the upper side of the take-up chamber.

Check the silver roller right next to the film gate on the feed side. There should be a 'cut-away' at each end, where the main diameter is reduced, maybe 4mm long. I've seen Medalists (re?)assembled with a roller in this spot that had no end cut-aways. I think that the cut-aways allow the edge of the film to drop down a bit, setting film up for a 'pre-curve' with the film curled away from the lens, more prone to sit flat and not move toward the lens. A small item and I could be wrong about the function of the relief at the ends.

Harry Callahan · Wednesday at 8:47 AM

@OAPOli

Thank you for checking about the lens.
Re-spooling surely won`t improve film flatness, but i also wonder about film tension in the camera. If there was enough friction on both spools, the film couldn`t bulge a lot or at all - as the spools would hold the film under tension. Maybe there is something in the camera to exert friction on the spools which has gotten weaker during the decades creating this effect on several Medalist cameras.

@Dan Daniel

The Medalist is not a folder, the camera front is stationary. Also the picture of the "hardware" sign on the house is a rather close-up shot - to do this he had to move the lens forward, but this picture has no bulge at f4. Therefore i don`t think that the lens did suck the film forward - while a folder surely could when unfolding it.
But i think that some of the other points you brought up may apply.
To better find out Hunter_Compton had to tell us in which order he took the pictures and what time roughly passed in between shots - as i assume this bulge to form over time.

EDIT:

Just re-read that Hunter_Compton did state order of the problematic frames, but i also needed to know number of the "hardware" picture and rough timespan between picture 3-5, 2-3 and 5-6.

Dan Daniel · Wednesday at 9:25 AM

Harry Callahan said:
The Medalist is not a folder, the camera front is stationary.

All good points, but just to clarify, the Medalist does have the lens on a large helical tube that is extended for over an inch and can be retracted. Certainly not a spring-loaded door with bellows, of course. Some Medalists have very free-moving helicals that can move quickly. I doubt that there is enough air motion and vacuum to pull film forward but I thought it should be mentioned.

Harry Callahan · Wednesday at 9:35 AM

I see - now i understand why you suspected the lens to suck the film forward.

EDIT:

On the other hand as the film does bulge anyway (as i assume over time) not a lot of air suction may be needed to make it bulge even more. So the helical tube may make things worse if the film already has some bulge when setting up the camera.

Mr Bill · Wednesday at 10:39 AM

Hunter_Compton said:
My leading theory right now is the film is buckling or warping and the pressure plate isn't keeping it flat enough, but I'm curious to hear other peoples interpretations and why I'm only running into it now.

Hi, I can describe a method that I've used to check for a similar sort of thing on custom long-roll (100 ft) portrait cameras used by a former employer. It comes from Norman Goldberg's book "Camera Technology...," and worked surprisingly well. I actually did the test on a lark, so to speak, and surprisingly found that there was sometimes a significant "buckle" at a certain point on one end of the frame. Depending on how much tension was on the film at that point. The company actually went back and modified something like 5,000 film magazines to correct this previously unnoticed problem (in portrait work that particular part of the film frame is not significant). The fix was to relocate one particular roller (might have been the drive roller; I don't recall) by something like 10mm or so. This completely eliminated the buckle in film.

If you're serious enough about chasing down the problem to do a little work, just respond here and I'll describe in more detail. (Or anyone else with Goldberg's book book, feel free to describe.) You'll need a smallish beamsplitter (I'm thinking a piece of window glass would likely work ok), and then set up a little jig.

koraks · Wednesday at 11:24 AM

Mr Bill said:
there was sometimes a significant "buckle" at a certain point on one end of the frame. Depending on how much tension was on the film at that point.

Oh yeah, that makes perfect sense. Uneven tension distributed across the width of film, with more tension at the edges where rollers have better grip, will result in a ripple being pulled in the center. Something like this could be the case here, indeed.

Hunter_Compton · Wednesday at 12:28 PM

So as requested, the order of operations was as such. The film was respooled from the 120 spool, to a metal 620 spool, and then to another metal 620 spool. Nothing abnormal was felt during this process.

I then loaded the camera within a few minutes of doing this, and advanced to frame 1 to set the frame counter and cocked the shutter. The lens tube was collapsed and stayed collapsed, while I drove to my first shooting location, which took 45-60 minutes. I then extended the lens tube, and shot exposures 1-6. The time between most exposures was probably 5-10 minutes, except for between 5 and 6, the depot and hardware sign, which was maybe 2-3 minutes.

I then collapsed the lens tube, drove another 20 minutes or so, re-extended it and shot exposures 7 and 8, with about 5 minutes between those. In all cases the film was advanced immediately after the exposure was taken, as is my normal procedure with this camera.

I don't think the extension of the lens helical tube would cause the film to be sucked forward into the film gate, it has baffles to make it light proof, but the helical grooves in it mean it isn't very airtight, which is probably why the designers chose this method of focusing, as it eliminates the vacuum effect when bellows are normally extended from collapsed.

For those interested, here are what the rollers on the feed and takeup side look like:

Harry Callahan · Wednesday at 1:44 PM

Well then my theory doesn`t really apply as to my theory frame 1 and 7 also had to be unsharp.
I see small teeth on the roller close to the take-up spool, where the note is not to turn this roller. I assume these teeth to stitch into the emulsion, making the roller turn and probably driving the frame counter of the camera. These teeth could exert tension on the film edges.

Donald Qualls · Wednesday at 3:16 PM

Harry Callahan said:
I see small teeth on the roller close to the take-up spool, where the note is not to turn this roller. I assume these teeth to stitch into the emulsion, making the roller turn and probably driving the frame counter of the camera.

Can't say for sure on a Medalist, but that's exactly what such teeth do in a Kodak Reflex II -- I've had the frame counter apart on one (about fifty years ago).

Hunter_Compton · Wednesday at 3:23 PM

Yes, that's what the teeth do here too. Though it still poses the question as to why it's causing an issue here, and hasn't in the past. I think I'm going to check dimensions on the width of both the film and backing paper of this roll of Kentmere 200 in comparison to prior Ilford and Kodak rolls and see if there's any discrepancy.

Dan Daniel · Wednesday at 7:42 PM

The rollers on both sides look normal. The feed side roller issue I had a concern about is not happening here.

Just to be certain, when you say metal 620 spool, you mean original old spool with thin flanges and no protrusions, yes?

You might give the pressure plate a quick check that it has even pressure.

Beyond the discussion up to now, I am at a dead end. I've heard of the Medalist having flatness issues, even seen a couple of examples like yours, but don't know what the cause was and what resolved it.

Hatchetman · Wednesday at 7:46 PM

go with the most likely scenario which is your re-rolled film is messed up

Hunter_Compton · Wednesday at 7:48 PM

Dan Daniel said:
The rollers on both sides look normal. The feed side roller issue I had a concern about is not happening here.

Just to be certain, when you say metal 620 spool, you mean original old spool with thin flanges and no protrusions, yes?

You might give the pressure plate a quick check that it has even pressure.

Beyond the discussion up to now, I am at a dead end. I've heard of the Medalist having flatness issues, even seen a couple of examples like yours, but don't know what the cause was and what resolved it.

Yes, original Kodak 620 stamped metal spools with no protrusions. I looked at the pressure plate and all seemed normal, but I will check again. Given the Medalist was an exercise in maintaining film flatness by Kodak engineers, I'm surprised this issue occurs.

Mr Bill · Wednesday at 8:23 PM

koraks said:
Oh yeah, that makes perfect sense. Uneven tension distributed across the width of film, with more tension at the edges where rollers have better grip, will result in a ripple being pulled in the center. Something like this could be the case here, indeed.

I should have clarified that this was using 35 mm long-roll perf film, using sprocketed drive rollers. In other words, similar to common 35mm film cameras. If your idea that the uneven tension would just naturally pull a ripple in the center of the film was correct, then wouldn't all 35mm cameras do the same thing?

So it doesn't seem to make perfect sense anymore, right?

But my real point is that Norman Goldberg's test method immediately and easily "detected" the buckle in the film. As I expect it would in this case.

Dan Daniel · Wednesday at 9:24 PM

One last thing to check- the hinge pins. Are both pins on each side seating, sliding to the outer edge? Sometimes a pin will not seat. This could leave the back canted slightly (very slightly). The back is actually part of the spool positioning, as you can see by the small wear marks from the edge of the spools. So maybe the back wasn't quite seated, and maybe this would let the spool wobble a bit and spread some uneven tension into the film?

Pure speculation.

Mr Bill · Wednesday at 9:43 PM

Hunter_Compton said:
Yes, original Kodak 620 stamped metal spools with no protrusions. I looked at the pressure plate and all seemed normal, but I will check again. Given the Medalist was an exercise in maintaining film flatness by Kodak engineers, I'm surprised this issue occurs.

I would hazard a guess that it's related to something that you did, or perhaps something is out of square in your camera.

Let me pose a "thought experiment." Imagine that you have a flat bench with a slightly elevated block in the center. Then, two '620' film spools with film rolled midway between them. Image holding the two spools down against the plate, film crossing over the block, such that it roughly mimics the orientation inside of the actual camera. The film is close to flat (as it crosses the block, representing the film gate) and the two spools are close to parallel.

Now consider what would happen if you forced one of the spools off of the parallel axis such that the ends are closer/farther with respect to each other. Obviously (?) there will be too much (lengthwise) film between the close ends of the spools. So it's gotta bulge somewhere, right?

A second way to distort the film would be to cause an out of square parallelogram situation. Imagine that the base of the spools are against a reference plate. Then, while keeping the spools axes parallel, move one of them away from the reference plate. This is gonna put a sort of angular wave in the film between the spools. (If you can't visualize it just use a small strip of paper to induce the effect.)

Just a couple of ways to imagine the consequences of certain alignment issues.

Kodak Medalist unusual out of focus areas on negative

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