Fog on 4x5 film

[Mahler_one]

Perhaps someone can find what, if anything, I am doing wrong. I own a Canham 4x5 metal camera. I am learning how to use the camera, and I have noted that the first 4 sheets I have developed have a vertical line of fog on each sheet ( running from top to bottom in landscape mode ) at the side away from the notches-i.e., where the dark slide exits the holder. I note that there is abit of "play " when the holder is inserted-that is, as the dark slide is pulled out the holder wants to move a bit with it until the film holder is caught in the "frame" against the back of the bellows. I suspect that such movement is somehow effecting the seal at the exit point of the slide from the holder, and that pressure on the film holder to keep it from moving will solve the problem. I would appreciate any advice, and thanks in advance. By the way, if my analysis is correct, is such film holder movement a feature of the Canham camera, or do all film holders have to be "kept in place" by pressure against the holder as the dark slide is removed

Thanks to any and all!

Edwin

[Monophoto]

Edwin -

The film holder should not move at all when it is properly inserted into the camera and held in place with the spring back.

Are you using new or old holders? If old, do they have a metal ridge near the end that the darkslides go into? If so, this ridge should fit into a groove machined into the camera back. The combination of the holder ridge fitting into the groove, and the force from the camera back on the holder, should lock the holder in place.

Many years ago, it was the practice for the ridge to be on the camera back to fit into a groove on the holder. So if you have very old holders with a groove rather than a ridge, that could explain your problem.

But if you holders have the ridge, then the problem has to do with how you are fitting them into the camera back. Most likely, this is a matter of practice - with practice, you will sense when the holder is in position for the ridge to fit into the groove and be locked down with the spring.

You implied that your camera is new to you. Is it brand new? Another possibility is that the spring tension on the back is not adjusted properly. That would be a very unusual situation but I have heard of it happening.

Finally, coming back to used holders - if your holders are very old, it is possible that they felt light traps are worn out. If that is the case, the best solution would be to simply replace the holders.

Incidentally, I find that the light trap on some of my holders will leak a bit if the camera is oriented so that the darkslide slot is facing the sun. I try to rmember to leave the darkcloth draped over the camera when it is in that position to minimize leakage.

[Mahler_one]

Louie....thanks for taking the time to write a long and instructive response. I have new holders. The camera is slightly used, but in excellent condition having just been serviced by Keith Canham ( whom I met while he was looking at the camera ). The spring seems firm, and the film holders make a very firm and reassuring "clunk" when they are pushed in, and such holders appaer to be very well engaged. Nevertheless, when I pull the dark slide the holder does indeed move about an eight of an inch or so until is is "caught" against the ridges of the frame surrounding the back of the bellows. To keep the holder from moving I note that I have to keep a finger on the edge of the holder whilst I pull the dark slide out.

Edwin

[Monophoto]

Edwin -

The other thing I would suggest is looking carefully at HOW to withdraw the darkslide.

I have a Polaroid 405 holder, and was getting some fogging at the edge of the frame. Eventually, I discovered that when the darkslide was fully inserted into the holder, it was so close to the back of the camera that when I tried to pull lit (with my fat fingers), I was inadvertently pulling the holder away from the camera (against the spring). Once I saw what I was doing, I was able to consciously change the way I manipulated the darkslide.

[Mahler_one]

Thanks to all who responded. I believe-and hope- I solved the problem. I spoke with Keith Canham who spent lots of time on the phone with me as we tried to trace possible sources of fog. After lots of probling and adjusting we think that the problem is that the film holder was not completely inserted behind the ground glass. There is one "detente" that can fool a "new user" into thinking that the holder is fully inserted. If the slide is pulled from this location fog will occur at the site where fog on my pictures was noted. The film holder has to be pushed into the second "detente" which is indeed fully inserted into the correct channel. Keith said that he was taught to hold one end of a camera while inserting the film holder from the other side, i.e., the "empty hand" offers additional support "against" force from the holder and allows one to push the holder in with some authority. As Mono suggested, the holder should be pulled out straight without any hesitation. One might also apply some pressure against the ground glass to keep the holder in the correct place as the slide is being removed. Of course, as I already knew, one might also consider turning the film back so that is faces away from the sun so that light can be prevented from entering as the slide is pulled.

I don't know how much my learning experience can be applied to the experiences of users of other cameras, but I suspect that other view cameras also have similar "quirks". Thanks to Keith for taking the time to patiently review previous solutions where fog was noted, and thanks again to all here who took the time to offer help and guidance.

Edwin