Pinhole and Xray film

[Shen45]

Does anyone use xray film for pinhole work? I made an experimental pinhole on the weekend and was really surprised by the results. I cut down some xray film I had and in bright sunshine got an exposure of 6 seconds which was quite a good negative. I'm not sure how xray film responds to long expures or for that matter how to calculate the exposure in less light so if anyone can offer any suggestions would be appreciated regarding exposure and reciprocity. The pinhole is about f220 on a 5x4 giving roughly 90mm.

Also, to get good coverage on a 10x8 and have the equivalent of a 150 mm lens any suggestion for pinhole size? I have the back from a 10x8 so I can see it becoming a pinhole camera in the not too distant future.

Steve

[UlbabraB]

Hi,

I use often Xray film in my 5x7 and 8x10 pinhole cameras, and usually I expose it 15-30 seconds in daylight. My 8x10 camera has a 150mm focal lenght and If I remember correctly the pinhole is 0,5mm, about F/290.

I never calculated the reciprocity effect of Xray film but usually I give one or two stops more exposure when >1s and develop with inspection to get the right density. I need very dense negatives for alt printing (Kallitypes, salt, carbon, etc) and xray film is almost prefect for the purpose.

[Jim Jones]

My experience suggests a pinhole diameter of about 0.4mm for a 150mm focal length for optimum on-axis sharpness with panchromatic film. I haven't tried X-ray film. If you use blue sensitive film, that diameter could be very slightly decreased. For better image edge sharpness, it could be increased with a loss of central sharpness. Quibbling over optimum pinhole diameter is less productive than experimenting to arrive at the results that best satisfies each photographer.

[Jim Noel]

Read five different books or articles on correct pinhole diameters and you will get five different answers!

[SMBooth]

Just apply a normal reciprocity factor to X-ray film.

[WayneStevenson]

I've used it in my Calumet 8x10. I didn't get technical with it. I just racked out my focus until I got good coverage with the hole I made. Which was made with tinfoil wrapped over a lensboard, and a sewing needle tip.