(My dad lives just to the left of this image, I’ll be sending him this, he’ll love it!)

Cheers Phil!

Ian

Theoretically, if all light from the landscape were to enter the camera through the very same point (the size of one photon?), the image on the film side would be in perfect symmetry with the real world, and so the picture would be infinitely sharp.

But then again, (almost?) no light would make it through this pointhole, so I suppose that exposure time would have to approach infinite, too. Or maybe there are some weird quantum effects that I’m completely ignoring.

The rays aren’t parallel, it’s that there is minimal parallax due to the width of the aperture.

Yes, I was just going to complain about “pinhead astronomy” in my drive by comment. AFAIU a focus is where rays from an object point converge to an image point. The picture I get is that an ideal pinhole provides focus by mapping visible object points to image points onto (i.e. 1-1). In fact, I see that is the image [pun intended] provided in Wikipedia.

It seems to me the ideal model would explain if a pinhole camera has ideally an infinite (or perhaps indefinite) focal length, and inverts the image. I assume using the physical width of the aperture gives a correction to a best focal length. But if rays from small objects were “parallel” they would give no focus and tend to blur the image, wouldn’t they, besides not explaining image inversion?

But I’m not giving this a lot of thought due to time constraints, so I could be _very_ wrong.

A neat camrea none the less. Still, I’ll stick with Kodak, etc.

See also Tarja Trygg’s Solargraphy site for images like this from all over the world.

Flickr is loaded with pinhole camera aficionados, including quite a few groups. Quite a few people over there are building their own or modding everything from cheap disposables to DSLRs. Crazy fun.

Try this. Pick a very tiny object that you can focus on comfortably. Note its apparent size. Then touch index finger to thumb on both hands, like making an “OK” gesture. Now, bring both pairs together so that both index fingers and thumbs touch. You will observe an opening between the four digits. Press them tighter to reduce the opening and bring your eye closer to it. Make the small hole as small as you can see through and look at the object again.

Move the aperture and your eyes relative to the object until you have reasonable focus. Surprise! You now have a super power!

For more information on the physics of a pinhole camera, click on my name above this post.

P.S. Imagine what other advancements in the field of physics the Arabs might have achieved if they had not found religion in the form of Islam!

Click on my name for the Wikipedia article.

Also, I just finished reading your first book, Bad Astronomy. I really enjoyed it, and, while I knew tides were caused by the moon’s and the Sun’s gravity, I didn’t know what caused two tides a day until I read it from you. That’s not the only thing I learned, there were other things as well. So thanks!