I have a Canon Rebel T5. I can shoot in RAW or RAW+JPEG. When I shoot in the latter, it stores both a preview with the RAW file, as well as the JPEG.
I've been using Digikam to manipulate my photos, but converting from RAW to JPEG or png takes forever. I didn't seem to get much out of it (like fixing exposure), except for the cases where I set my camera to shoot in black & white. Then I have the RAW if I decided that I did want the actual colors.
I did notice that the RAW image tended to have a lot more noise, though running wavelet noise reduction seemed to produce image quality roughly equivalent to the embedded JPEG. But this seemed like I was just taking a lot of time when I could just shoot in JPEG and get the same result.
Though today, I just discovered how to use exiftool to extract the preview from my RAW file. To test it out, I shot RAW+JPEG, and extracted the preview from my RAW file. I got an interesting surprise - the extracted file was almost 1/3rd the size.
So then I ran ImageMagick's compare tool with fuzz. Using a fuzz value of 5% gives me almost no differences.
One difference I did notice is that the preview has almost no EXIF data. But surely it's not 4MB worth of EXIF data, right?
So why does it appear that there is little difference in the images, despite having two wildly different filesizes?