Optimal sizes of pinholes

[Greg]

In what I consider the "bible" of pinhole Photography (PINHOLE PHOTOGRAPHY Rediscovering a Historic Technique by Eric Renner) is a list of the optimal diameters for pinholes for focal lengths ranging from 10mm to 1,000mm. I've noticed that in the current line of the various pinhole cameras offered on the EBay, the pinholes are usually a lot smaller than the recommended optimum sizes. Purchased an 8x10 pinhole camera in which the pinhole was a whole lot smaller that the recommended size. I enlarged it to the recommended size and my negatives appeared "sharper". I'm trying to get to the point of where my images look like "sharp" pinhole images... but definitely not images taken with glass optics.

My pinholes are made by drilling pinholes in .002" Brass Shim Stock. I also darken the sides of the pinhole aperture with a black Sharpie. Definitely cuts down on reflections from the raw cut/drilled brass stock on the outsides of the drilled hole. Lately have tried drilling pinholes in the aluminum soda cans are made of. It seems to be thinner than .002" but don't have an accurate measuring device to confirm that.

Would love to know other's experiences in achieving optimal pinhole sizes.

[LabRat]

From the turn of the Century books, they all agree that the best results come from the larger the format (over 11X14)... Then the pinhole becomes much less critical...

I had started experiments using larger pinholes with simple lenses that had very promising test results, but didn't get back to it yet... (There is enough light to compose with the pinhole removed, and a nice blend of image qualities of each...

Or consider trying single elements that are stopped way down (I'm using these now)...

Steve K

[Jim Jones]

My experience with Pinhole Designer suggests using a user constant of 1.4 for determining optimum pinhole diameter. Perhaps a larger constant will be better for quite wide angle coverage.

[Greg]

My experience with Pinhole Designer suggests using a user constant of 1.4 for determining optimum pinhole diameter. Perhaps a larger constant will be better for quite wide angle coverage.

Does the constant of 1.4 refer to .014% of the focal length for the diameter of the pinhole?

[rbiemer]

Does the constant of 1.4 refer to .014% of the focal length for the diameter of the pinhole? I shouldn't speak for some one else, but I believe that Mr. Jones was referring to the ability to change the equations in the Pinhole Designer program. There is a place to change one of the terms in the formula the program uses for its calculations. 175304
I have approached this a bit differently: I have a set of numbered drill bits (#61 through #80) and base my focal length around those. And my practice is to use brass sheet of .002" and then, with a fairly large sewing needle, dimple the sheet. Then drill almost through, then sand/polish the dimple til the hole is just visible. This gives me, I hope, a very thin edge to the pinhole.
One other thing I will note is that soda/beer can aluminum is much harder than the sheet brass. That material has been "work hardened" by the
process of forming it into the can. As well, it's not very flat to start out. Too much trouble for me--not sure how many drill bits I've broken when trying to use this stuff. A better alternative, I think, is to use the aluminum pans that some store bought baked goods come in. Around here that means Entemann's Danish or coffee cakes. Decently flat, not too difficult to work, and you get danish to snack on before and after your "lens" making.

Rob

[Jim Jones]

Rob is right. I was referring to the constant used in Pinhole Designer. The default Lord Rayleigh constant was derived by a physicist rather than by a photographer. It may have been based mostly on mathematical considerations. He also may have favored a larger than optimum pinhole diameter because of the slow photographic emulsions of the 1800s.

[Jim Jones]

This graph I made many decades ago may be of interest to photographers interested in pinhole performance. It was done while researching wide angle pinhole performance, and is less applicable to more traditional photography. It is limited by the wide spacing of pinhole apertures and by potential errors in interpreting lens resolution chart tests and in translating from the original data to this graph. The Rayleigh Constant is that as used in Pinhole Designer. Note that the highest resolution of the four curves uses a user constant in Pinhole designer close to the default Rayleigh Constant. Sometimes optimum optical test bench performance does not precisely relate to the most pleasing photograph images.
175306

[Greg]

Update: Bought an 8x10 pinhole camera that had a focal length of 125mm. Camera, as described by the maker, came with a pinhole of 0.0120". Thickness of the brass stock unknown. Initial test exposures looked terrible to me.

Looked at the Pinhole Designer program , but unfortunately need a PC to run it and all I use are Macs.

Thanks to rbiemer's #5 post, proceeded as follows: I got some .002" brass shim stock and drilled (#78 drill size) a 0.0160" hole in it. Placed a ball peened hammer face up, placed the drilled pinhole dead center on it, and struck the pinhole with another ball peened hammer. Pinhole became smaller so drilled it out again. Did this a couple of times till the edges of the pinhole were extremely thin. Blackened the brass with a sharpie and gently rounded the pinhole out with a needle several times. Made up an exposure table and attached it to the pinhole camera. Attached image (actual contact print looks lot better/sharper than the scan) is one of the first images I took with my "modified" camera.... I was very lucky, this is just the image quality I was looking for. Thanks rbiemer for your post.
Greg

[rbiemer]

Update: Bought an 8x10 pinhole camera that had a focal length of 125mm. Camera, as described by the maker, came with a pinhole of 0.0120". Thickness of the brass stock unknown. Initial test exposures looked terrible to me.

Looked at the Pinhole Designer program , but unfortunately need a PC to run it and all I use are Macs.

Thanks to rbiemer's #5 post, proceeded as follows: I got some .002" brass shim stock and drilled (#78 drill size) a 0.0160" hole in it. Placed a ball peened hammer face up, placed the drilled pinhole dead center on it, and struck the pinhole with another ball peened hammer. Pinhole became smaller so drilled it out again. Did this a couple of times till the edges of the pinhole were extremely thin. Blackened the brass with a sharpie and gently rounded the pinhole out with a needle several times. Made up an exposure table and attached it to the pinhole camera. Attached image (actual contact print looks lot better/sharper than the scan) is one of the first images I took with my "modified" camera.... I was very lucky, this is just the image quality I was looking for. Thanks rbiemer for your post.
Greg

Greg,
Happy to offer what little I know and glad it helped! There is one other on-line calculator page that might be useful:

http://www.mrpinhole.com/calcpinh.php

Lots of different claculators there and several ways to approach this. HOWEVER, if you are getting results you like--and that example you've shared is pretty good, I think--then just keep making photos!

Rob

[jp]

One theory of mine... A smaller pinhole size will proportionately allow more blue rays and diffract longer more visible light in relation to whatever it's smaller than. As film has gotten more pan than blue sensitive, maybe the bigger pinhole options make more sense for sharpness for the longer wavelengths our film is good for? The test would be to send colors through various pinholes with a dichroic enlarger or other pick your color non-led source (as leds do not evenly generate a spectrum of light) and onto a white board or screen to see how colors react (rays versus diffraction) to the pinholes.

[Jim Jones]

jp is right: the more sophisticated pinhole diameter charts and formulae do allow for film color response. My tests with infrared through blue sensitive films confirm this.