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Comment by aray | Hacker News Reader

I'd love to see some test images with that (just get a side-by-side with the app and a larger aperture camera).

As I understand what you're proposing, I'm not sure it would actually be closer to what a large-aperture camera would capture. The light field from the farther depth field should be convolving with the light field from the near depth field.

Still, side-by-side would be the best way to view these :) I'll do it later this weekend if I get the chance.

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Side by side comparison http://onionpants.s3.amazonaws.com/IMG_0455.jpg

Thanks! Great example. Does it look like the large camera is focusing a few inches back from the front of the ball and the Google Camera is sharpest at the center of the ball?

Edit: I was trying to look at the sharpness of features on the ball -- specifically the lettering on the left side.

Focus point of the large camera should be the exact center of the image. The center of the ball is a little out of focus as the center of the image is the top left of the ball. User Error :)

What do you mean, "the light field from the farther depth should be convolving with the … near"? Intuitively, grandparent post is right, the hair should be sharp.

Nope, in the left example the hair should be blurred even in the edges. But the blur should be such that the details in the background are preserved (it seems sightly off). The math behind this afaik is a variant convolution with depth dependent kernel + occlusion. So in the right the hair is sharp because the blurred background is occluded by the sharp hair, but in the left the frontier isn't sharp because the sharp background isn't occluding the blurry foreground.

Here's a comparison that illustrates the behavior of foreground blur (shot with a DSLR): http://i.imgur.com/986Iv2K.jpg

You'll notice that on the bottom image, even though the foreground leaves are out of focus, the blur does not apply to the background - details in the background are still sharp, even if partially occluded by the foreground blur.

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