Jpeg quality when shooting RAW+Large Jpg

Just wondering, I noticed to day for the first time that if images are shot at "Large JPeg" their size is around 2.5Mb, whereas if i shoot RAW+Large Jpeg, the ".JPG" image results in a saved file of approx 1.5Mb.

Anyone know why this is? - as I would have thought that they should be the same filesize (they are the same dimensions)

I know I can re-create them from the RAW files, but I was curious why they were not the same - when surely, they should be?

TJ

Could it just be a matter of what you are shooting? ISO 100 gives smaller image size than ISO 1600 (by quite a lot) and a big blue sky will be compressed a lot smaller than something very detailed.

Good point, thanks Brad, I don't think the ISO was that different on the examples I viewed, but I'll take another look and let you know.

Interesting observation. Try shootong the same image twice (preferably on a tripod, and of a static image), and set the recorded format to RAW + Ljpg, then just Ljpg. I'm going to try myself later today and see what it gives me.

I notice some people shoot RAW and Jpeg. Why do both? Not critisizing, just curious...maybe I am missing something and should change to shoot both....

So I don't have to do a conversion if I need a quick CD of the shoot's results.

Stating the obvious, but you are comparing at the same JPG quality as well as size?

According to the manual a Large/Normal JPG averages 1.8MiB, and a Large/Fine one 3.6 MiB.

As for the question of why use both, I cannot easily preview raw files (I am on an older OS) so the JPG files are invaluable to being able to review and preview images.

But this Sunday as I was running out of card space so I switched to raw only to conserve space, then when I got home inspiration hit me. The raw files have an embedded JPG file for previewing (well technically they have two as there is a thumbnail as well),
so I just wrote a quick script that uses exiftool to extract that preview image to a file.

As the preview is the just a small JPG in normal quality anyway it is as good as selecting this option but without wasting space storing the JPG twice. Now when I copy the files from CF to hard disk I just run the script afterwards and the JPGs appear as if I shoot in RAW+S/Normal!

Michael.

Jon wrote in post #2234704
So I don't have to do a conversion if I need a quick CD of the shoot's results.

I'm glad to hear this mentioned. I've thought about that fact many times already. The fact that the .jpg is ready to go can really be a plus sometimes. But you better have the card memory to deal with it.

johnthebaptist wrote in post #2234996
I'm glad to hear this mentioned. I've thought about that fact many times already. The fact that the .jpg is ready to go can really be a plus sometimes. But you better have the card memory to deal with it.

18 days in Greece without re-using a card . . . but everything was also backed up to a laptop as I went, and I burned DVDs periodically.

If you have BreezeBrowser, you can extract a 30%-50% sized (or there abouts, depends on the specific camera) jpeg from Any Canon RAW file.. and it takes mere seconds to do a folder full. Since I only use jpegs for stuff where the IQ does not matter much, I shoot RAW only and use these extracted jpegs for emails etc..