EXCERPT page containing first few paragraphs. 2020-07-12 21:05:14
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I built a crude camera obscura:
- Cardboard box with crude hole to stick the front of the lens out.
- Tracing paper for the projected image (paper taped over a hole cut in stiff gatorfoam.
- Photographed the image visible on the tracing paper.
I checked the image circle at 14mm, 18mm, 25mm and 35mm. I had only crude materials to work with, but I can be certain of the results.
The image circle projected by the lens has a soft outline, so precisely where it ends is somewhat ambiguous (stopping down a lens extends the image circle slightly and better defines its edge, but there is no way to stop down the Olympus 14-35mm because it uses an electronic aperture control).
Below is what I measured at infinity focus. Figure ±1mm depending on how one counts the blurry and vignetted edge of the image circle (which can be seen below).
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