Help with issue with 8x10 camera, Please?

[Ed Bray]

I recently bought an 8x10 Plaubel Monorail camera from a member on this forum. I took the opportunity this morning to take a couple of head & shoulders shots (not the shampoo) using my wife as the 'not too keen' subject matter.
For this image I set up the camera about 4 foot from the subject position and focused my 450mm f9 Nikkor lens, I was using Adox 25 and rated it at ISO50, exposure was 1/15 sec at f16 and this included a stop for bellows draw. I then rotary processed the film using Caffenol CM for 8 minutes at 24 degrees Centigrade and after fixing and drying I scanned the neg with my V750 at 1200dpi. I just put the neg on the platen and the heat during the scan caused the edges to curl a little and this can be seen in the slight blur and distortion in the corners.

http://i332.photobucket.com/albums/m338/EdBray/Nik450Nikkor.jpg

What I am really concerned about though is what looks like light leakage or possibly processing issues across the image which also seems to have crept into the rebates, this is definitely on the negative and not on the scanner glass.
I had a good look at the film holders, they are Fidelity Elites and in very good condition, I was doubtful that if light leaks they would have been caused there. I then investigated further and had a look where you insert the film holder into the camera behind the ground glass and it looked like there had previously been some foam or felt there in the past but had perished or been removed. I decided to have a further look and took the back apart removing both the ground glass and also the outer ground glass frame. I then discovered that there had been something there in the past as some form of light trap on three of the four sides of the inner frame, see image below:

http://i332.photobucket.com/albums/m338/EdBray/8x10back.jpg

So now for my questions, what would have been the likely light trap material? I have a large sheet of 1mm self adhesive felt, but would rather use the correct material so if it is foam could you give me an idea if it is 1.5mm or 2mm or open cell or closed please? Once I have added whatever is required to the other 3 sides, would adding a strip of 1mm felt to the fourth side help too or cause problems?

Is it likely the issue could have been from the processing? The other sheet didn't suffer from this and I have never had any other issues using Caffenol before when rotary processing, I make the developer up fresh about 15 minutes before use using distilled water, all volumes are weighed out using a 0.01g scale and I mix them fully before introducing the next ingredient.

TIA for your help.

Eddie.

[Mark Sawyer]

Hopefully someone with the same model camera will chime in, as that's who can identify the "historically correct" material. I suspect it's a very thin black felt or velvet.

The two key issues are the light leak and the same distance from the lens to the film as from the lens to the ground glass. I'd suggest removing the back from the camera and laying a straight-edge across the center of the back. Put in a film hoder with an old negative and measure from the straight egde to the center of the film. Then remove the film holder and measure from the straight edge to the ground glass. That should be the thickness of the material under compression.

[Ed Bray]

Thanks Mark, that's a good idea, I have a digital Vernier caliper so could use that to measure reasonably accurately.

[Andrew®]

Eddie, for what it's worth, I have a 4x5 Plaubel monorail with a similar looking back that the film holder is pushed against. There is no foam or felt between the film holder and the surround.

[Ed Bray]

Eddie, for what it's worth, I have a 4x5 Plaubel monorail with a similar looking back that the film holder is pushed against. There is no foam or felt between the film holder and the surround.

Thanks for the info Andrew but the 8x10 definitely had some, you can see the residue remaining along three sides of the frame.

[ic-racer]

The negative scan shows up as a positive on my monitor. When I flip it I see that there is some film fog in the rebate area, perhaps from a leak at the tape hinge of the film holder. This is evident in the upper right hand corner of the negative.

Secondly, I see uneven banding across the negative. I'm not familiar with Caffenol CM or using it for rotary processing. Have you tried commercial developer intended for rotary processing?

In terms of the camera back. Each view camera I have treats that area differently. The one most similar might be the metal-framed Horseman FA that uses what looks like neporpene rubber around the perimeter in the trough. The foam thickness is important so that it compresses when the film holder is inserted and the film holder rests on the metal frame, not the rubber. The wooden view cameras I have use velvet, not felt, for the light trap on the back.

[Ed Bray]

Thanks for your thoughts, I will have a look at them. Yes, the banding is evident on the rebate area.