6x17 panoramic advice

[flsurf]

I just completed a 6x9 camera and was interested in building one that was either 6x12 or 17. When I built the first camera it originaly had a frame size of 6x11, first negatives indicated that due to viginetting the image circle was closer to 6x8. I have been using the Mr. Pinhole download for determining focal length , pinhole size etc. In doing so I have not been able to determine a pinhole/focal length that would provide negative coverage for a 6x17 unless my focal length was 90mm plus. I have seen a number of cameras on various sites that seem to do this without having the 90-100mm focal length. The camera I built was 29mm and uses a pinhole of 0.010. Any suggestions?

Thanks

fl

[Steve Smith]

See my 6x12 link below (not pinhole though).

The limiting factor with pinholes is the ratio of pinhole diameter to material thickness. If you have a pinhole which is equal in diameter to the thickness of material, it will block any light from more than 45 degrees from perpendicular, limiting the field of view to 90 degrees. If you can use thinner material, there is less chance of vignetting. e.g. if the material thickness is one third of the hole's diameter, 143 degrees of coverage is theoretically possible.


Steve.

[flsurf]

Thanks for your reply and advice. I looked at the brass shim material package and found that the thickness was 0.010 which is the same dia. of the pinhole. I will be looking for something in the range of 0.005.
Your project is very nice, I had noticed it a few days ago. The film transport cartridge looks very adaptable to the pinhole camera. I wish you luck with the project. The camera that I built was my first, still trying to zero in on the exposure. First film was a bit thin so I will be doing a number of test shots during my next weekend.

Thanks again
fl

[keithwms]

Steve's point is spot on. Last time I made a pinhole, I used very thin copper sheet, in which you can make very nice pinholes and should be able to go very wide. I don't recall the thickness of copper I used, but it was like a foil... which is of course a bit flimsy, so I just cut a hole out of a more sturdy material (delrin) and taped the foil on there and voila.

[Hikari]

You can also control vignetting by curving the film plane. Too short a focal length will result in vignetting as the pinhole to film distance is very different from the center to the edge.

[SMBooth]

Also don't try and go to short of a focal length, 70mm with curve back is nice. For pinhole material, try going to local engineering shop and get brass shim.

[Mark Fisher]

Stainless steel shim stock goes down to .0005! Here is the McMaster Carr page that has stainless shim stock. .001 isn't too flimsy and not too difficult to make a hole in....definitely more difficult than pop can aluminum.