Pinhole camera hole size verses shape

[stemked]

<p>Hi Folks.</p>

<p>I am working with a student doing some ultraviolet photography on flowers. About 6 months ago I go a pinhole lens for the project off ever trusty e**y. This is my first time ever using a pinhole 'lens'. Fooling around with the 'lens' I saw the image wasn't super sharp and put it under a dissection microscope. The hole is indeed very tiny, but it is not very round so I was wondering for good images with a pinhole 'lens' what parameter is most critical, hole size or shape. Or is the answer that both are equally critical?<br>

Thanks.<br>

Doug</p>

[chris_waller]

<p>Both. The hole must be very small and as near circular as is possible. For more info, look at Justin Quinnell's website. (<a href="http://www.pinholephotography.org/">http://www.pinholephotography.org/</a>)</p>

<p> </p>

[bobatkins]

<p>If you want the sharpest possible images (or the least blurred images anyway) the hole must be round and should be the optimum diameter which is (approx):</p>

<p>pinhole diameter = 1.9 * square root (focal length * wavelength)</p>

<p>where wavelength is ~ 0.000055mm (550nm) for visible light and maybe 0.000035mm(350nm) for UV light and "focal length" is the distance from the film/sensor.</p>

[matthew_moran]

Bob, I'm surprised that formula doesn't include anything

about the image size. Is the assumption that there will be

no enlargement?

 

Also, I think 550nm=0.00055mm (not 0.000055mm)

[DB_Gallery]

Thanks for posting this, I have been thinking about making a 16 x 20 pinhole that I can use litho sheet film in and do

contact prints...