Image Plane: Is it flat or an arc?

I've always imagined the image plane as a giant bubble, in which the camera is located in the center and the picture captured is a section (arc) of the bubble. With a maximum aperture, the bubble would be very thin, resulting in a shallow depth of field. With a smaller aperture, the opposite.

But I am just guessing. I haven't had much luck with Google on this, so I'd really like to get some good data on this. Can anyone explain this to me or provide some links that would help?

It's a flat plane, parallel to the sensor in the body of the camera.

Take a picture of a brick wall with a very shallow DOF. The bricks in the center will be in focus, and the bricks at the edges of the frame will also be in focus. That wouldn't happen if the plane was a bubble.

Also:
http://visual-vacations.com …focus-recompose_sucks.htm


One more thing: when using a tilt-shift lens, I believe it's a flat plane that is NOT parallel to the sensor.

https://photography-on-the.net/forum/showthre​ad.php?t=621561

The sensor is flat, so the image plane is supposed to flat too. But the focal plane is often less than perfectly flat on lenses.

tkbslc wrote in post #12844607
The sensor is flat, so the image plane is supposed to flat too. But the focal plane is often less than perfectly flat on lenses.

Yep, "supposed to be" flat. Actually, most good lenses of modern design have a pretty flat plane of focus.

To get a really flat plane of focus one would want a macro lens, which are optimized for flatness of field for photographing documents.

-js

So I did some more reading, and I think I had it right all along. With a simple lens, the image created on the sensor would be a parabaloid, with only the center being in focus. It is the complex lenses that make corrections for lens abberations and make the image almost flat. This article explained it very well, with lots of tests to boot:
http://toothwalker.org​/optics/astigmatism.ht​ml

Your initial premise is correct...yes the sensor is flat but the image plane has an arc to it, a simple tape measure with one end attached to the camera with the other end swinging in an arc will illustrate this.
Didn't ya ever wonder why one cannot buy a wider angle lens that has little distortion, see MTF Characteristics here http://www.canon-europe.com …n/ef_lens_work_​iii_en.asp and that a telephoto lens has little distortion.
That telephoto lens has a very narrow AOV as compared to the WA glass allowing for the arc of that bubble to have less of an effect on that flat sensor in the form of distortion.

chauncey wrote in post #12851797
That telephoto lens has a very narrow AOV as compared to the WA glass allowing for the arc of that bubble to have less of an effect on that flat sensor in the form of distortion.

And I would assume that in general, telephoto lenses suffer less from all other lens abberations than WA lenses. So when comparing MTF charts, one should really compare it to similar focal length and aperture lenses.