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View Full Version : G1 Digital Zoom - How exactly does it work?


Kid Moe
5th of June 2001 (Tue), 09:21
Ok, here is the thing. I have a G1 and I am wondering how it processes the following situation.

Say you max out the optical zoom (3x) and take a picture at the highest resolution (2048x1536).

Then, you go into photoshop (or whatever editing software) and crop the picture 512 pixels from the right and left and 384 pixels from the top and bottom. So now you have a pic that is 1024x768. I would reason that this would be equivalent to a camera that has a maximum resolution of 1024x768 and an optical zoom of 6x.

Now say you are lazy, and don't feel like doing this in photoshop everytime you wanted 6x Zoom at 1024x768. If instead you max out the optical zoom (3x) and set the digital zoom at 2x and take a picture at 1024x768, will you end up with the same result as above? Or will using the digital zoom ALWAYS diminish the quality of the output.

Put in another way, when using 2x digital zoom at half the maximum resolution does the camera

A) save the picture at 2048x1536 in its internal buffer and then crop the image. (No loss in image quality)

B) save the picture as 1024x768 in its internal buffer and THEN process the 2x Zoom on the 1024x768 image causing image degradation.

So in essence, can it be said that the canon has 6x optical zoom at 1024x768 and 3x optical zoom at 2048x1536?

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Kid Moe

Pekka
5th of June 2001 (Tue), 09:36
Kid Moe wrote:
Now say you are lazy, and don't feel like doing this in photoshop everytime you wanted 6x Zoom at 1024x768. If instead you max out the optical zoom (3x) and set the digital zoom at 2x and take a picture at 1024x768, will you end up with the same result as above? Or will using the digital zoom ALWAYS diminish the quality of the output.
Digital zoom resizes the image in camera. I don't know if the resizing algorithm in camera is same quality as in Photoshop, you could test that and tell us. Have you also checked if the zooming in affects automatic exposure? I suppose the exposure is measured from whole scene regardless of file size.

Put in another way, when using 2x digital zoom at half the maximum resolution does the camera

A) save the picture at 2048x1536 in its internal buffer and then crop the image. (No loss in image quality)
I don't think so.

B) save the picture as 1024x768 in its internal buffer and THEN process the 2x Zoom on the 1024x768 image causing image degradation.
I vote for this option.

If you really want to know what G1 does internally, it's quite easy to set up a controlled test target and test this behaviour and examine the results in Photoshop. I have never used digital zoom so it has never occurred to me to test how it works :)