View Full Version : pinhole sharpness

25-Apr-2017, 14:03
so i've been doing a series of very long exposures of theatrical set builds and rehearsals. i'm using a laser pinhole with a stack of ND gels in front, to get exposures times ranging from 2 hours to 6 days.

now the exposures all look great, but i've reached a threshold of optimal sharpness that i'm unsatisfied with. i'm thinking of incorporating a lens, but i'm not sure if i should just get a glass lens with a shutter and stack even more NDs in front, or somehow make a frankensteined pinhole/lens chimera? i don't even know where to start doing research on that.

I know I'm not the first photographer to be doing long exposures like this, so I'm hoping somebody here has some experience.

here's some photographic evidence (dust included for scale):


Graham Patterson
25-Apr-2017, 15:01
Without knowing the pinhole to film distance and the size of the pinhole, it is going to be hard to judge if you are hitting practical limits. A 'stack' of ND gels would be better replaced by fewer, denser ones - the fewer surfaces the better. There is a practical limit on sharpness - the optics industry developed for a reason, after all 8-)

25-Apr-2017, 15:09
Pinhole photography has no sharpness. It is what it is.
You might consider using a lens.

Jim Noel
25-Apr-2017, 15:16
You are taking an already not tack sharp pinhole and multiplying it's softness with a stack of filter gels.

25-Apr-2017, 17:57
If your goal is just long exposures, just get a VERY dense ND filter and put it on the lens. If, for some reason you want to use a pinhole, you need to handle the pinhole in certains ways. Here are two websites to help you calculate the f-stop of your pin-hole(s) and the focal length(s) that will produce the optimal (i.e., sharpest) results:



Sharpness will depend on the diameter of the pinhole, as well as getting it focused correctly, which depends on its focal length.

25-Apr-2017, 18:35
Just to add my 2 cents. Finding a really slow film helps cut down on all the filters. Think copy film or inter-negative film, maybe even microfilm (but use a low contrast developer with the latter).

6 days?? I'd look at lengthening the pinhole to film distance which lowers the amount of light reaching a given spot on the film.

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25-Apr-2017, 21:42
the sample image is without any NDs at all. and i've used the mr pinhole calculator to construct my camera. the focal length is 90mm with a .3mm hole i believe.

i'm not necessarily married to pinhole, it's just the path of least resistance when i started to project. i've tried out copy film, but the box i have is quite fogged and has some fungus, so i'm reluctant to purchase more. are new batches being manufacture still?

25-Apr-2017, 21:49
i guess it's time to break out the view cam for this project. one of the reasons for going pinhole is how inconspicuous my camera was.

27-Apr-2017, 20:44
two things,

* one not mentioned is that (I believe) Sharp edged and thinner pin holes make sharper images. so if you can use a good loop or place the pin hole in an enlarger and check that the shadow is even and not jagged that would be a place to start. If you can use thinner material, try it and see what that changes.

* The other is roundness. It looks like you have a nice and round pin hole, which is also helpful (oval shaped and the fuzzy edges on the light-sources shown would not be equal.)

* ( I also second the motion to replace stacks of ND with a single ND if possible, but your example shows that the issue is there without the ND's to begin with)

And if you do have to go view camera, a view camera can be very inconspicuous too. Think kodak brownie type box with a compact 65 or 90mm lens. maybe paint the chrome bits black. Good luck!

Ted R
28-Apr-2017, 07:51
six days! ? vibration? thermal expansion and contraction?

28-Apr-2017, 08:28
Sharp edged and thinner pin holes make sharper images.

Not so sure about that. At f/45, f/64, f/90, there's a trade-off between depth of field increasing & sharpness decreasing due to the convergence of light waves. Pinholes aren't known for their sharpness.

six days! ? vibration? thermal expansion and contraction?

I guess this means it's best not to set up the camera near an aerobic workout fitness studio.

Inconspicuous cameras can be set up by using an oat box, chip can, even a duffel bag with internal support for larger film.

I'm not a fan of the secret camera simply because I dislike being photographed by all the electronic cameras that are so pervasive throughout society & believe you should have a person's permission.

I don't even like the "if you enter our premises you give implied consent" approach, but at least they're letting you know in some way.

28-Apr-2017, 09:29
The Mr. Pinhole app will only get you so far. Most of these types of apps are an educated guess, with a fudge factor. How about making a sliding box pinhole camera where you can test a range of distances to dial in a better degree of sharpness? After your testing, you could lock that length in place.

By the way, I had submitted this suggestion before the recent forum problems. I guess it got lost.....

Chauncey Walden
28-Apr-2017, 09:30
I wonder if preflashing the film would help?

Gudmundur Ingolfsson
28-Apr-2017, 10:32
There is a formula for the optimal pinhole diameter : 1/125 of the square root of the intended focal length (the distance from the pinhole to the film plane ).

28-Apr-2017, 12:19
I haven't looked into it personally, but I'm sure there's also some way of knowing the image circle if you wanted to build a 6x6 roll film camera vs. 4x5 camera.

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28-Apr-2017, 12:21
my cameras are not exactly secret, they're hung up in the catwalk in the back of the theatre with permission. main reason to conceal is that stage actors get neurotic about cameras, even if they give consent. i'm totally in agreement about not liking photos taken without consent. my style of dress is not exactly inconspicuous, and i annoyingly catch street photographers try and sneak shots of me and my friends all the time.

vibration used to be a concern early on in the project, but i've tinkered and built a steel plate onto the bottom of my camera that screws into a mount that is wrenched onto the lighting grid. while i can't prevent the grid from vibrating from environmental factors, it's very sturdy. expansion and contraction could certainly be an issue that i didn't think of, the sets i build are very susceptible to that too.

the six day exposures are only for the set-build and demolition periods, so it all tends to be a giant mess anyway. when i shoot the performances the exposures tend to only be 2-4 hours. so maybe i should do away with the pin altogether and just get a dark ND?

Jim Andrada
2-May-2017, 21:45
As someone said, pinhole and sharpness don't go together. Pinholes are really small and difraction is significant.