I could use some diagnostic help

bobwysiwyg · Sep 4, 2008

I'm still learning to use my 4x5. While on vacation I used the Cambo on this shot of a falls in the Keweenaw Peninsula. Since were were not likely to be back this way for a year or so, I shot two images with a one stop difference between the two.

Processed them both (along with two other sheets) in a Combo tank, using straight D76 for the appropriate time based on the temp. All but the image named Falls-1 turned out fine, well, sort of, but I can't explain the the diagonal nature of the line in this image. When compared to the second image, Fall-2 not only is there the line, but some overall fogging. At first I thought perhaps there was a diagonal, hairline, crack in the dark slide for that sheet, but checked it carefully and it is fine. As a matter of fact, double checked all four dark slides for the film holders I emptied and developed.

As I said, still learning, is there something I could have done during the shot in terms of film holder or camera handling that could account for this? Any input would be appreciated.

Photo Engineer · Sep 4, 2008

A beautiful case of light fog!

Nothing struck me at first, and I posted this, then I remembered where I had last seen something like this! I saw it when the film holder was squeezed too tightly putting it into (or removing it from) the camera.

PE

Nicholas Lindan · Sep 4, 2008

You have a split in the film holder. Upper right corner, as the holder is loaded into the camera and viewed from the back. Pull both slides from the holder and you can see from the seams how the holder is made from two halves around the central septum. A bit of prying with a pen-knife should reveal the split.

bobwysiwyg · Sep 4, 2008

Nick,

Never thought about the septum, but it certainly would make sense. Expose the first side and light leaks through to the other sheet. Unfortunately, just checked them. All seems as it should be.

PE,

So there is such a thing as "pressure" exposure or fogging?

ic-racer · Sep 4, 2008

I can't tell, is the film fogged to the edge or is the fogged area contained within the image frame?

bobwysiwyg · Sep 4, 2008

It's fogged right to the edge. It's quite evident at the hinge end, it extends below what would be the hinge edge when the hinge is closed.

Photo Engineer · Sep 4, 2008

bobwysiwyg said:
Nick,

PE,

So there is such a thing as "pressure" exposure or fogging?

It is not pressure fogging in this case, it is bending the dark slide enough to let light in, or twisting the frame to let light in. I've seen it happen.

Of course, the other answer is right as well but you have apparently eliminated that possibility.

I've thought of several others which include a small pinhole in the "flap" that allows the end to rotate. This plastic, rubber or paper piece (depending on age and repair) often goes bad and gets pinholes just like bellows.

PE

bobwysiwyg · Sep 5, 2008

Photo Engineer said:
I've thought of several others which include a small pinhole in the "flap" that allows the end to rotate. This plastic, rubber or paper piece (depending on age and repair) often goes bad and gets pinholes just like bellows.

PE

Thought, hmm, when I read this idea. Went back to the film holder in question. I know which holder, but not certain as to which side. I opened the hinged flaps almost all the way on both sides and indeed, there are strings of pinholes, if you will, along the flap joint. The appearance is along the lines of the fabric weave. However, as you close the hinge, by the time you reach 45 degrees, no more light shows through. In addition, some other holders that did not exhibit this problem showed the same thing, so I'm not sure that the issue. I'm either tempted to load two sheets in the holder in question and try to duplicate the problem or just toss the holder all together. I hate not knowing the answer.

Joe VanCleave · Sep 5, 2008

In the fogged image there's a large, black border on the left side, unexposed from the camera lens but still fogged from the lower left corner of the image. This is an important clue, I think.

The fogging could be caused by the film not being inserted all the way into the back of the film rails; when the flap of the holder is closed down, its pinching the film (sandwiching it between the flap and the left side of the holder); then when the darkslide is pulled out, in-camera, light can leak through the gap formed by the film being pinched between the end flap. A normally loaded negative shouldn't have an unexposed edge that's this wide. This is pointing to the source of your problem.

~Joe

bobwysiwyg · Sep 5, 2008

Joe VanCleave said:
In the fogged image there's a large, black border on the left side, unexposed from the camera lens but still fogged from the lower left corner of the image. This is an important clue, I think.

The fogging could be caused by the film not being inserted all the way into the back of the film rails; when the flap of the holder is closed down, its pinching the film (sandwiching it between the flap and the left side of the holder); then when the dark side is pulled out, in-camera, light can leak through the gap formed by the film being pinched between the end flap. A normally loaded negative shouldn't have an unexposed edge that's this wide. This is pointing to the source of your problem.

~Joe

Joe, nice call. I had forgotten completely to consider the upside-down and backwards business, still too accustomed to the 35mm world I guess. I think you are on to something, actually a couple of things. I have noticed the broad strip on one or two other sheets, I think I have to pay more attention to ensuring the sheets are fully inserted in the holders, and no, no partial removal of dark slides, I always remove the dark slides entirely.

I'm going to take a closer look at that holder around the dark slide slot to see if there are any irregularities. Starting to feel like a trainee detective.:rolleyes:

bobwysiwyg · Sep 5, 2008

Joe,

You put me on the right track, I believe I found the problem. In the questionable holder, one dark slide is almost 3mm longer than the other. As a consequence, even when pushed in all the way, the reinforced area under the handle (showing white and black for unexposed/exposed) never quite seats all the way closing off the slot. It's not enough to prevent locking the slide in place, but I'm sure this leaves enough of a gap such that light could enter particularly if one corner happens to get flashed by some direct sunlight.

Nicholas Lindan · Sep 5, 2008

bobwysiwyg said:
I opened the hinged flaps

Ah, do you load the holder into the camera from the left or the right? If from the left then I would hazard a guess the problem is at the flap end.

I am making an assumption - always a horribly risky thing to do - that the light hit the film when the slide was removed and the exposure made. It seems the ray of light that fogged the film is in the same direction as the sunlight in the image. Was the camera in the shade or the sun when the picture was made?

The point where the ray of light entered the holder should be evident by loading the negative back into the holder and seeing where the ray points to.

The problem I had alluded to earlier was the possibility of a split in the weld between the two plastic halves of the holder.

There is also the possibility that the problem has nothing to do with the holder or the camera - it could be something that happened at the factory.

I was having troubles of a like sort when I first started using a Sinar and it came down to not having inserted the film holder all the way. I only found that this was the problem by trying determinedly to duplicate it. In the old days I would have chucked the holder, but given the price that holders go for these days ... I have memories of old Graflex holders going for $1 each at the camera shows.

bobwysiwyg · Sep 5, 2008

I load either from the top, when appropriate for portrait-- an I remember, or from the right in this instance, and in this shot, camera was in the sunlight and slightly to my right. If this is the case, how do you avoid something like this when withdrawing the dark slide?

Joe VanCleave · Sep 6, 2008

As a safety precaution I always cover the camera with my dark cloth, then reach underneath to pull out the darkslide. I then wrap the darkcloth around the rear of the camera, so as to not obstruct the lens, but still to shield the film holder and film back from direct sun. After exposure, I re-insert the darkslide underneath the darkcloth. Then I consider it safe to unwrap the camera, etc. I have a collection of older film holders, and a WWII-era Speed Graphic (and a homebuilt wooden pinhole 4x5) that I've faithfully used with this methodology, and have no fogging issues.

Bob, the holder with the questionable darkslide, is it the darkslide itself that's too long, or is the slot in the flap-end of the holder obstructed with some debris, preventing the slide from being fully inserted? In either event, you'd want to ensure that the slide can be fully inserted, so as to seal off the felt light trap. That holder may also have a felt trap that's worn out, aside from the problem with the darkslide.

~Joe

bobwysiwyg · Sep 6, 2008

Joe VanCleave said:
Bob, the holder with the questionable darkslide, is it the darkslide itself that's too long, or is the slot in the flap-end of the holder obstructed with some debris, preventing the slide from being fully inserted? In either event, you'd want to ensure that the slide can be fully inserted, so as to seal off the felt light trap. That holder may also have a felt trap that's worn out, aside from the problem with the darkslide.

~Joe

Joe,

It's definately the dark slide that is too long. After measuring the gap at the slot end to come up with the 3mm, I compared it to several other slides (which all seat correctly) and it is indeed, too long.

Thanks for the tip on how to protect everything while light while pulling/inserting the slide. Another tip to be added to my ever increasing list.

Photo Engineer · Sep 6, 2008

As far as I can determine, a long dark slide should not cause a light leak. It should still seal at each end, it just will not be lockable by the key at the end.

A bad felt or rubber gasket at the entry end will also cause problems like this.

PE

bobwysiwyg · Sep 6, 2008

Photo Engineer said:
A bad felt or rubber gasket at the entry end will also cause problems like this.

PE

Wondered about the seal myself. I'll have to find a light to shine through there and see. Sounds like the holder, slide, etc. may be questionable enough to just relegate to the trash. I have enough "challenges" in terms of learning the 4x5.

Kirk Keyes · Sep 12, 2008

Looks to me that the holder was not seated fully into the camera, and a ray of light made it into the back.

I could use some diagnostic help

bobwysiwyg

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