Digital camera good for testing pinhole sharpness?

[keithostertag]

Before spending $$$ on 5x7 sheet film for a planned homemade pinhole camera, I thought I'd try using my existing pinholes on my digital camera to test their sharpness. I am not having much luck :-(

I have two sets of pinholes I bought years ago- one is evidently machine drilled and the other is claimed to have been laser drilled. I tried several from each set on a body cap and also using one or more extension tubes to give me a variety of focal lengths- but in every case the images are too blurry, not nearly as sharp as what I see other get with their pinhole film cameras.

Is there some reason a pinhole won't give a similar level of sharpness on a digital camera as it would on film?

I tried several pinhole diameters ranging from .05 to 0.5 mm, and focal distances of about 50mm (body cap) to about 100mm with extension tubes. I had a sunny day and use a tripod, so exposure and camera movement were not issues. According to a formula I am using I should get good results with a pinhole diameter between say 0.15 and 0.25mm for my chosen focal length range.

For those of you who have gotten reasonably good sharpness using pinhole, did it take you awhile to find just the right combo of pinhole diameter and focal length? Is it that particular, or is there something technically inappropriate for testing pinhole sharpness with a digital camera?

Thanks,
Keith

 

[wiltw]

The problem is how do you position the digital sensor at the FL distance from the pinhole?!

 

[awty]

Use the Mr Pinhole calculator for optimum focal length and pinhole size for your film size. https://www.mrpinhole.com/index.php
Buy a laser cut pin hole at the right size.
Build your camera.
Work your subject to the angle of view the calculator gives you.
Work your exposure to the calculated f stop taking in account reciprocity
Develop your film.......happy days.

 

[Oren Grad]

What size digital sensor are you using for capture, and how large are you viewing your captures on screen - or how large are you printing them, if that's how you're judging?

 

[keithostertag]

What size digital sensor are you using for capture, and how large are you viewing your captures on screen - or how large are you printing them, if that's how you're judging?

Hi Oren- using a FX Nikon, evaluating, so far, on the camera's screen since it is so obvious there seems little reason to view them on the computer yet.

As one example, the flange distance for Nikon F-mount (46.50mm) and when using three extension tubes I have a FL of very close to 136mm on the full 24x36mm format digital sensor, using Mr Pinhole calculator I should be using a pinhole with a diameter of 0.49mm ... so when I used the 0.5mm I should have been close.

 

[MattKing]

From my perspective, pinhole on something as small as a full frame 35mm sensor is fairly disappointing.
You may be expecting too much from the format.
The pinhole method essentially eliminates all but a tiny remnant of acutance, so if you are going to work with a digital file, expect to apply lots of artificial sharpening in order to bring some of that acutance back.

 

[keithostertag]

Thanks Matt. Yea, that's part of the reason I asked about the efficacy of using digital to evaluate the pinholes... 5x7 film is so expensive and I wanted to get some practice with the pinholes before using it on film. As I have played with it I can tell that exposure and subject distance also play into the outcome quality (along with light quality, etc). But at least I can get a little comparative value from using digital first as long as I can keep most of the variables constant. Part of the learning curve! Thanks to all who made comments!

 

[MattKing]

Consider photographic paper in a 5x7 camera instead.

 

[gone]

It may be difficult or impossible to get an idea of how film will perform going by a digital camera. Not sure of the reasons, there's probably lots of them. It may be be more cost effective and better all around to use a cheap 35mm/mf camera? Or use paper for film? Pinhole photography looks like one of those things that you figure out by doing it, the exposures and all are so different than your usually daily shooting, or at least my daily shooting. So anything that enables you to make more pics w/ less $$$ should be good to go.

 

[Oren Grad]

I've shot pinhole with my EOS R and also with 6x6 cm and 4x5 inch film cameras; the film gets contact printed. I'd say that the digital files from the EOS R tell me nothing useful about the way pinhole images behave on film - just such a different subjective character that there's no point trying to translate from one to the other, let alone try to use one to make fine judgments about optimal pinhole size for the other.

If film cost is an issue, why not do your initial tinkering with a smaller format? Based on that experience, you can decide whether and, if so, how far you want to push toward larger sizes. But you might find that a size smaller than 5x7 serves your purposes after all.

 

[MattKing]

To illustrate a point...
I have a Noons 6x12 pinhole camera. It is a beautiful thing. It is set up for 6x6, or 6x9, or 6x12 on 120 film. Much bigger of course than a 35mm frame.
I can make really satisfying darkroom prints from the negatives it provides, as long as I bump the contrast up a bit.
When I scan those negatives - which adds another bunch of variables - the unmanipulated scans look something like this:

After a bunch of digital jiggery pokery (specialized technical term), including ridiculous amounts of sharpening, the result looks more like this:

You are trying to use a digital camera to preview, but that gives you none of the jiggery pokery.

 

[DWThomas]

Every year I go through the Worldwide Pinhole Photography Day shot gallery and as a general rule it appears the larger the format, the sharper the image. There is probably a technical explanation to account for that, but I've not tormented myself with the numbers. I suspect something to do with diffraction following the absolute dimension of the pinhole, vs a larger format permitting a larger pinhole to get the same resolution proportions for tracing out an image. I have been intending to make a body cap pinhole adapter for my old EOS 40D to see how much is "just how it is" and how much is errors in craftsmanship, but have never gotten around to it. Among an assortment of home brew cameras, my latest has been an 8x10 in which I've been shooting X-ray film for pretty good results. The X-ray stuff is way cheaper than the name brand photo films in that size. (Of course there's no manufacturer specs for using it for conventional photography.)

I agree with the suggestion above to try using paper. Getting "photo quality" tone and contrast with that can be tedious, but it should be adequate to evaluate sharpness.

 

[RalphLambrecht]

Before spending $$$ on 5x7 sheet film for a planned homemade pinhole camera, I thought I'd try using my existing pinholes on my digital camera to test their sharpness. I am not having much luck :-(

I have two sets of pinholes I bought years ago- one is evidently machine drilled and the other is claimed to have been laser drilled. I tried several from each set on a body cap and also using one or more extension tubes to give me a variety of focal lengths- but in every case the images are too blurry, not nearly as sharp as what I see other get with their pinhole film cameras.
Panels work with digital cameras there is similar to the way they work with film cameras if not identical. You may have too high of an expectation to the sharpness of a pinhole image. What f/stop of a pinhole are you using?

Is there some reason a pinhole won't give a similar level of sharpness on a digital camera as it would on film?

I tried several pinhole diameters ranging from .05 to 0.5 mm, and focal distances of about 50mm (body cap) to about 100mm with extension tubes. I had a sunny day and use a tripod, so exposure and camera movement were not issues. According to a formula I am using I should get good results with a pinhole diameter between say 0.15 and 0.25mm for my chosen focal length range.

For those of you who have gotten reasonably good sharpness using pinhole, did it take you awhile to find just the right combo of pinhole diameter and focal length? Is it that particular, or is there something technically inappropriate for testing pinhole sharpness with a digital camera?

Thanks,
Keith