RAW/JPG 100% Crop Not Equal?

[tajomaru]

Hi all,

Interesting (maybe just boring and n00bish) question here - I just noticed that when shooting RAW + JPG, the JPGs looked cropped when compared to its corresponding RAW.

http://tajomaru.com/misc/crop_problem/crop.htm

Look especially at the edges:
* left edge, jpg has the letter "S" cropped, raw does not
* bottom edge, raw has more barcode showing
* right edge, the raw shows a more of a gap between the open cardboard lid at the bottom and the edge


What's going on here? Interpreting this, this must mean that the focal distance of the lens used to record the raw and jpg must be slightly different, which perturbs me to no end. The only other possibility is that the jpg is cropped in camera during recording. Not sure why that would be the case either. For what it's worth, this occurs with both my 10-22 and 24-70.

Any clues anyone? Thanks.

-James

[tim]

Interesting question, i'll be interested to see if anyone has an answer. I'll take a guess that it has something to do with the image processing. There are pixels around the edges of the image that are ignored by raw convertors, I remember that the guy who wrote photoshop wrote a little utility to get those back, there's a thread around here somewhere. Try a couple of different RAW convertors (CS2, RSE, DPP) and see if they're all the same.

[jfrancho]

It's a peculiar find, but the crop doesn't alter the focal length one bit. Remember, the .jpg is made from that raw file in the camera. Which raw + .jpg setting did you use?

[tajomaru]

Thanks for the reply guys.

I just tried all 6 RAW + JPG size settings. Turns out this problem is only manifesting itself with the smallest JPG (1728 x 1152) at both compressions. I just might throw this into the firmware-is-whack bin and forget about it.

[lostdoggy]

naah you just want to show off your new toys. You dog you. Congrats!!!!

[tzalman]

Interesting question, i'll be interested to see if anyone has an answer. I'll take a guess that it has something to do with the image processing. There are pixels around the edges of the image that are ignored by raw convertors, I remember that the guy who wrote photoshop wrote a little utility to get those back, there's a thread around here somewhere. Try a couple of different RAW convertors (CS2, RSE, DPP) and see if they're all the same.
Tim has it right. Both DPP and in-camera conversion crop the image slightly. The reason is that the demosaicing interpolation involves an inspection of the neighboring pixels in order to determine the best values for the new R, G or B amounts assigned to each pixel. Pixels close to or at the edge have incomplete neighborhoods and the interpolation is, therefore, less accurate, so Canon discards them. Several third party converters (RSE/RSP for one) retain them because in most cases the inaccuracy is hard to see at anything but extreme magnifications.
Elie

[Wilt]

The phenomenon of pixel croppoing is PROGRAM specific. I have a RAW, a camera JPEG and a Rawshooter Premium created JPEG file, and all three are cropped identically.

[SWPhotoImaging]

Hey, can you move those boxes, I can't see the TV!

[tajomaru]

Tim has it right. Both DPP and in-camera conversion crop the image slightly. The reason is that the demosaicing interpolation involves an inspection of the neighboring pixels in order to determine the best values for the new R, G or B amounts assigned to each pixel. Pixels close to or at the edge have incomplete neighborhoods and the interpolation is, therefore, less accurate, so Canon discards them. Several third party converters (RSE/RSP for one) retain them because in most cases the inaccuracy is hard to see at anything but extreme magnifications.
Elie
Elie, thanks for the reply. I can only assume you are speaking about jpegs when you talk about insufficient data for interpolation. Then my questions is this: If Canon's philosophy is to discard 'sloppy edges' in favor of maximum fidelity, why are they inconsistent in their handling of the middle and large sized jpegs (on the 30D) which appear to retain their edges (when compared to their respective raw)?