Finney Pinhole Cap

[jmal]

Not sure if this is the right forum, but here it is. After being very intrigued by Guillaume Zuilli's 35mm pinhole lith's, I discovered Finney's body caps. However, after scouring the web for examples of photos, I get the feeling that I can just defocus my camera and get the same effect. Of course, GZ's photos have their own personality that goes beyond equipment, but... Am I wrong? Is there something more to a pinhole cap for 35mm than this? Thanks.

Jmal

 

[rwyoung]

No you can't just defocus and get the same effect as a pinhole cap. A pinhole is a pinhole. A defocused image is just that, a defocused image. A pinhole image is focused however the limit of resolution is a function of the pinhole diameter.

You can make your own pinhole cap using a "body cap" which you may already have. When computing the pinhole size, there will be an optimum size as a function of the wavelength you want to focus and the distance to the film plane.

Google around for "pinhole designer" and use that for your calculations. You can measure from the lens flange on the front of your camera to the film plane. Remove film from camera, and fire the shutter on B to open the shutter and lift the mirror. Be careful you don't scratch things up. If you don't want to measure, 40mm is a good compromise focal length.

As to the wavelength of light to use for the calculation, well, again you have to compromise. Lots of people are using B&W photo paper so they tend to pick "blue" at 550nm. Can't really go wrong with that. But if you really want to get crazy with it, look at the spectral response chart of your film and work from its peak.

Lots of other comments can be made about making pinholes and if you need help, post again to this thread and I'll try to answer questions.

Or, just go buy a cap. On eBay, "pinholebilly" is a good source and cheaper than Finney (satisfied customer, no other relationship).

 

[jmal]

Thanks for the info. I guess in some cases the lack of resolution appears similar to an unfocused image. I also noticed that the poor images I saw online were primariliy done with a digi. I found some that I liked and, go figure, they were BW film. Also, I had never thought of the portion of the light spectrum that a pinhole might be optimzed for. Interesting.

Jmal

 

[rwyoung]

You can get VERY sharp images from pinhole apetures. I have a few in my gallery here and over at Flickr there is a pinhole group with lots and lots of examples. All over the "spectrum" so to speak. Not to steer too much traffic away from APUG but here is the link to give you some ideas:

http://flickr.com/groups/pinholers/

Mostly I use B&W photo paper in home made cameras but I've also done several using a modified Polaroid MP4 (kind used for passports and evidence documentation) on Polaroid and Fuji peel-apart materials. The Fuji colors in particular were very vibrant and the images are quite sharp. Also made some pinhole lens plates for large format cameras and had very good results. The long exposures and film reciprocity can produce some fun images!

Digital bodies with pinhole caps tend to produce images with all the sensor dust visible and I've also noticed a lot of color artifacts in them.