Diminishing returns?

[Grandpa Ron]

I calculated the f stop on my camera as f 176. (4.75" ph to film / .027" ph).

While I am waiting to see the results of my first roll, I pulled out my 4x5 view camera. The focal distance is 8 inches, so the same pinhole would give me an f number of about 300.

I am experimenting with producing a .014" pin hole for an estimated F number around 570. It dawned on me that this may be like taking a picture on the planet Pluto with available sunlight.

So the question is, "is there a practical limit to the f number"'? What f number do most folk find to be the happy medium between best sharpest picture vs. time?

 

[MattKing]

So the question is, "is there a practical limit to the f number"'? What f number do most folk find to be the happy medium between best sharpest picture vs. time?

Diffraction also imposes a limit.
As does film reciprocity failure.

 

[Jim Jones]

The optimum pinhole diameter depends primarily on the focal length. For decades I've used the Pinhole Designer program (http://www.pinhole.cz/en/pinholedesigner/) with a user constant of 1.4 to determine this. That diameter can be a bit larger or smaller, depending on a photographer's preference. No pinhole image is perfectly sharp. The amount and quality of the blur can be varied slightly by using a slightly larger or smaller pinhole. The longer the focal length, the larger the pinhole. The distance to the subject also affects the optimum pinhole diameter. For a wide angle pinhole camera, some photographers may want a slightly larger pinhole to increase illumination in the corners of the image. The pinhole photography can be carried to extremes. One 110 x 32 foot pinhole image was made in 2006 (https://en.wikipedia.org/wiki/The_Great_Picture), but that's carrying things to far. The longest pinhole camera I ever used was 24 feet long to photograph a solar eclipse. It was rather awkward to handle.

 

[RalphLambrecht]

I calculated the f stop on my camera as f 176. (4.75" ph to film / .027" ph).

While I am waiting to see the results of my first roll, I pulled out my 4x5 view camera. The focal distance is 8 inches, so the same pinhole would give me an f number of about 300.

I am experimenting with producing a .014" pin hole for an estimated F number around 570. It dawned on me that this may be like taking a picture on the planet Pluto with available sunlight.

So the question is, "is there a practical limit to the f number"'? What f number do most folk find to be the happy medium between best sharpest picture vs. time?

I like to stay around f/180-256this may help further:

 

[RalphLambrecht]

in your case that's 0.5mm is about perfect giving youf/400 but a nice contrast picture and plenty of resolution for contact printing.