RAW image sizes

SwordAngel

Joined: 2006-09-25
Posts: 3

Posted: Tue, 2008-10-07 04:48

The following discussion is probably not directly related to Gallery2. Nevertheless, it is possibly of interest to those who shoot a lot of RAW photos and manage them in Gallery2.

I own a Canon 400D (or Digital Rebel / Kiss Digital X as they call it in other parts of the world) and I shoot almost all of my photos in RAW.

When I extract metadata from my RAW images using dcraw (e.g. "dcraw -i -v IMG_0001.CR2"), dcraw reports 4 sizes: "thumb size", "full size", "image size", and "output size". "Thumb size" and "output size" are relatively easy to understand: one is probably for the embedded thumbnail generated by the camera, the other is the dimensions after applying any option that has a scaling effect (e.g. the -h option for half-size colour image). When no scaling option is used, the "output size" is the same as the "image size". What puzzles me is the "full size" and the "image size". With my RAW images, the "full size" is always slightly bigger than the "image size": "3948 x 2622" vs "3906 x 2602".

Does anybody know what's up with the "full size" and the "image size"?

In a related note, Mac OS X Leopard's Finder application reports the same images to have dimensions of "3888 x 2588", which causes even more confusion.

I don't have images in other RAW formats (e.g. Nikon, Sony, Olympus, etc.). Would somebody test with those and report findings here?

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nivekiam

Joined: 2002-12-10
Posts: 4353

Posted: Tue, 2008-10-07 23:02

This may or may not help. Found it using a google search:
http://wildtramper.com/sw/cr2/cr2.html

Quote:

/***************************************************************************
* The Canon CR2 file format is an encapsulated TIFF shell having 4 IFD sets.
* These IFDs are different versions of the same image.

Quote:

* The first IFD is a low pixel count JPEG image, and for the Canon 5D its image
* size is 2496x1664.

Quote:

* The second IFD is another JPEG rendered image, and it is described by two
* TIFF Tags

Quote:

* The third IFD is another JPEG rendered image. In this case there are several
* TIFF tags, and these give the size of the image as 384x256.

Quote:

* The forth IFD is the sweet spot of the CR2 file. It is a lossless JPEG
* compressed image of dimensions the size of the camera's photo sensor.

There's more here: http://www.google.com/search?q=canon+cr2+4+image+sizes and here: http://www.google.com/search?q=canon+cr2+specification

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SwordAngel Joined: 2006-09-25 Posts: 3	Posted: Tue, 2008-10-07 04:48
	The following discussion is probably not directly related to Gallery2. Nevertheless, it is possibly of interest to those who shoot a lot of RAW photos and manage them in Gallery2. I own a Canon 400D (or Digital Rebel / Kiss Digital X as they call it in other parts of the world) and I shoot almost all of my photos in RAW. When I extract metadata from my RAW images using dcraw (e.g. "dcraw -i -v IMG_0001.CR2"), dcraw reports 4 sizes: "thumb size", "full size", "image size", and "output size". "Thumb size" and "output size" are relatively easy to understand: one is probably for the embedded thumbnail generated by the camera, the other is the dimensions after applying any option that has a scaling effect (e.g. the -h option for half-size colour image). When no scaling option is used, the "output size" is the same as the "image size". What puzzles me is the "full size" and the "image size". With my RAW images, the "full size" is always slightly bigger than the "image size": "3948 x 2622" vs "3906 x 2602". Does anybody know what's up with the "full size" and the "image size"? In a related note, Mac OS X Leopard's Finder application reports the same images to have dimensions of "3888 x 2588", which causes even more confusion. I don't have images in other RAW formats (e.g. Nikon, Sony, Olympus, etc.). Would somebody test with those and report findings here?
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nivekiam Joined: 2002-12-10 Posts: 4353	Posted: Tue, 2008-10-07 23:02
	This may or may not help. Found it using a google search: http://wildtramper.com/sw/cr2/cr2.html Quote: /*************************************************************************** * The Canon CR2 file format is an encapsulated TIFF shell having 4 IFD sets. * These IFDs are different versions of the same image. Quote: * The first IFD is a low pixel count JPEG image, and for the Canon 5D its image * size is 2496x1664. Quote: * The second IFD is another JPEG rendered image, and it is described by two * TIFF Tags Quote: * The third IFD is another JPEG rendered image. In this case there are several * TIFF tags, and these give the size of the image as 384x256. Quote: * The forth IFD is the sweet spot of the CR2 file. It is a lossless JPEG * compressed image of dimensions the size of the camera's photo sensor. There's more here: http://www.google.com/search?q=canon+cr2+4+image+sizes and here: http://www.google.com/search?q=canon+cr2+specification ____________________________________________ Like Gallery? Like the support? Donate now!!! See G2 live here
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RAW image sizes

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