Strange 7D File Size Issue

Ok, can't figure this one out and may just be a firmware issue but I haven't seen it on any of the firmware fix lists from Canon.

I wanted to see if the 7D noise was consistent among the three RAW file sizes. So I took 4 pictures. Two at the large 18MP size, indicated as 5184x3456 on the Q menu, and two at the medium 10MP size, indicated as 3888x2592 on the Q menu.

When I transferred them to my computer I noticed that Windows 7 read the file dimensions as all being 5184x3456, but their file sizes were different, 22MB and 13.5MB. When I opened the RAW files with FastPictureViewer, it read their dimensions as all being 18MP too. In addition to that, when I scrolled through the files they all looked identical at 100% zoom.

However, when I load them into DPP or LR, they show up as the correct 18MP and 10MP.

If the smaller photo is really 10MP, how does FastPictureViewer see it at 100% at the same scale as the 18MP? If its really 18MP, how is the RAW file size only 13.5MB as opposed to 22MB? What is going on?!

10MP, 100% crop with Fast Picture Viewer

HTTP response: NOT FOUND | MIME changed to 'image/gif' | Redirected to error image by FLICKR

HTTP response: NOT FOUND | MIME changed to 'image/gif' | Redirected to error image by FLICKR

My guess is that some of the "viewers" are showing you the embedded preview JPEG. The real RAW editors know what to do with the actual RAW file.

Hmm, so it may be that the camera is embedding the full 18MP photo in with the 10MP RAW? That would mean that its taking the full 18MP photo and down sizing it in camera and not changing how the sensor works. Interesting.

No, just the preview JPEG. The camera stores a preview JPEG inside the RAW file for display on the LCD as well as quick previews in some programs. I don't know if the preview JPEG is 18MP for an mRAW, but that was just a guess as a possibility.

Tiggity-T wrote in post #13853439
Hmm, so it may be that the camera is embedding the full 18MP photo in with the 10MP RAW? That would mean that its taking the full 18MP photo and down sizing it in camera and not changing how the sensor works. Interesting.

Absolutely! This is entirely a software operation, not hardware.

Love this site, learn something new everyday.

tzalman wrote in post #13853805
Absolutely! This is entirely a software operation, not hardware.

Exactly, the full sensor is indeed used and then the raw data resized down. Perhaps the embedded JPG is generated and stored first, then the raw data resized down afterwards. Interesting way to do it, instead of recording the raw, downsizing the raw, and then generate the JPG....

This is why people that swear shooting smaller raw sizes get better noise performance than full raw can be shown that it is no better than if you just shoot the full raw and later resize. There is nothing magical about the sensor in these modes, nor are there advanced algorithms that are binning the data so that noise is reduced. Just a resize and save!