. . . Of course it will work, your aperture will be small so exposure will be long. With pinhole you have the blurr confusion circle around the hole size, suposing subjet is far, a larger blurr circle if subject is close.
For a 1200mm focal you are to use a 1.5mm hole delivering f/822 . Here it balances optimal diffraction vs hole :
https://www.mrpinhole.com/holesize.php
Your image would have a 1.5mm blurr circle.
Pros: you only need a hole, a 1.5 mm one it's easy to make. Holes for smaller formats have to be better machined to do a good job.
Cons: low speed, 1.5mm blur for f= 1200. . . .
There are many recommendations for the correct diameter of any focal length in pinhole photography, often based more on theory or poor advice rather than on hands-on experience. Based on my experience, the optimum pinhole diameter for a 1200mm focal length would be about 1.3mm. This would resolve about 1 line pair/mm where the on-axis blur circle from geometric optics and diffraction phenomena are about equal. At that point, image blur is
less than predicted by both geometry and diffraction. As the pinhole diameter increases, geometry determines image blur. As the pinhole diameter becomes smaller, image blur increases in a less predictable manner due to diffraction. Also, interpreting image blur of standard test charts varies among different people.
Wide angle pinhole photography brings up other factors which affect one's choice of pinhole diameter. As the angle of coverage increases, some photographers may wish to slightly increase the pinhole diameter to improve sharpness towards the edges of the image despite enlarging the central image blur. A pinhole image has negligible drop-off in sharpness up to 20 degrees from the pinhole axis. By 40 degrees there is little loss In radial sharpness, but about 35% in tangential sharpness. By 50 degrees the radial sharpness has dropped of noticeably and the tangential sharpness by 60%. This demonstrates that wide angle pinhole cameras show substantial astigmatism in addition to the distortion that all wide angle cameras have. If we move in close with a well-designed wide angle pinhole camera while maintaining the same image size, the image blur decrease. That is one way of improving pinhole image sharpness if the subject permits.
Much of this information is based on 40-year-old photography. It is based on rather casual photography instead of the more rigorous work that would be more valuable to researchers. I don't even have a darkroom now. If the more inventive photographers on this site unite to pool their findings, we may become the new center for pinhole photography.
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