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When I use ImageMagick's identify command to look at the quality of the JPEG from my camera's RAW+JPEG mode, I see 95.

When I use the same to look at the JPEG preview that has been directly extracted from the RAW part of the same RAW+JPEG photo, I see 81.

The two photos look the same on a macroscopic scale, but indeed do differ at the pixel level, and the embedded one is around 1/3 the size (in bytes).

I can't decided which one to use, or if I should even care. Assuming I have the time for batch extraction but don't have the time to develop these manually, is there any reason for me to continue shooting in RAW+JPEG mode and keep the standalone JPEGs, or should I go ahead and just mass-extract all the embedded JPEGs from the RAW files? Is the difference ever significant?

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  • \$\begingroup\$ What is the disadvantage of continuing to shoot RAW+JPEG? The file sizes of the jpegs are dwarfed by the file sizes of the raw files. If you don't have time to do any manual development, why not just shoot in the highest quality jpeg setting and forget raw altogether? You don't need to extract anything and you have a higher quality image at the end of your workflow while using much less storage space than saving raw files and then extracting lower quality jpegs. \$\endgroup\$
    – Michael C
    Commented May 27, 2016 at 4:35
  • \$\begingroup\$ @MichaelClark: The RAW file was 25 MB, the JPEG was 5.6 MB... that means every 4 JPEGs that I avoid allows me 1 extra RAW file. That's not "drawfing". \$\endgroup\$
    – user541686
    Commented May 27, 2016 at 4:38

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To concentrate on what you should do, I suggest you stick to the raw+jpeg. Worst case you need another card and storage is cheap. Do you actually ever get close to filling all your cards? If not, you don't need to worry.

My reasoning is that, like you (by the sound of things) I like to print or otherwise use a lot of my pictures as shot. But sometimes a picture is worth a bit of work that benefits from the raw. This is true for anything from wildlife to family snaps.

With family pictures in particular, being able to send the as-shot jpeg immediately to relatives is good, if they then printed it out big with jpeg artifacts it would annoy me when I saw it.

There is a clue in your question: "raw preview". That really is all it's good for.

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  • \$\begingroup\$ +1 to the advice... also, something I just discovered is that not all previews are the same dimensions as the actual image. One of my camera's preview is the same size, but the other's is much smaller. So they're not equivalent in that sense either. \$\endgroup\$
    – user541686
    Commented May 27, 2016 at 9:29
  • \$\begingroup\$ +1 to the practical advice here. Since I don't like to keep all my eggs in the same basket, these days I have trouble buying cards as small as I'd find ideal, anyway. \$\endgroup\$
    – mattdm
    Commented May 27, 2016 at 14:12
  • \$\begingroup\$ @mattdm me too. \$\endgroup\$
    – Chris H
    Commented May 27, 2016 at 14:14
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Although the context is different, this is fundamentally a question of the difference in compression levels. ImageMagick identifies them as 81 and 95 — that's not a standard number, but it's generally true that 95 is "pretty high quality" and 81 is "medium-low quality". The issue of RAW vs. JPEG is a red herring here; it just happens that the embedded preview uses high compression by default. You can probably get the other , separate JPEG to be similarly compressed by changing your camera's settings.

So, then, this is really basically the same as Is it worth using Pentax's Premium JPEG quality setting? (whether or not you are using Pentax).

From my answer there:

Demonstration of Pentax's four JPEG quality levels, with red flowers Demonstration of Pentax's four JPEG quality levels, with white flowers

where the low-quality (RAW preview) image is probably somewhere around the level of ★, while your separate "95" JPEG is probably like ★★★ (or maybe ★★).

My guess is that either:

A. Your subjects happen to be friendly compression and don't show significant artifacts; or

B. You're not looking closely enough. (What are jpeg artifacts and what can be done about them? will help you recognize what to look for).

If you decide you're happy with the results (for example, if you're really only going to be looking at them at that "macroscopic" scale you mention), and you keep the RAW images as a fallback, using the lower quality JPEGs is just fine. Just be aware that some scenes — like this high contrast red vs. blue — will be worse than others. For some situations, as my previous post suggests, you may want even higher-quality JPEGs.

Also, if you ever edit and re-save the JPEG, the degradation will be much worse (while it's almost negligible when working with 99- or 100-quality images).

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    \$\begingroup\$ +1 but please note that my question was slightly different than whether the higher-quality JPEG is worth it in general. Rather, it was whether I would have any reason to keep it around when I also have the RAW there, assuming that I can extract the preview from the RAW directly but don't have time to postprocess lots of photos. My takeaway from your answer seems to be that it's basically "no, you can discard them"... however, I'm noticing that some metadata isn't in the embedded JPEG, so I might lose more than just a little bit of quality. Do you have any comments on such losses? \$\endgroup\$
    – user541686
    Commented May 27, 2016 at 7:44
  • \$\begingroup\$ Btw, for future readers: the easiest way to "notice" the difference between the two JPEGs without zooming (ugh, I hate saying "notice", since it's basically forcing yourself to to see) is to tilt an LCD monitor with a low viewing angle very strongly and look at an area with generally similar colors, like the sky. The lower-quality photo will have fewer colors (and hence sharper changes between them) whereas the higher-quality one will blend more smoothly. Otherwise, it's usually pretty imperceptible. \$\endgroup\$
    – user541686
    Commented May 27, 2016 at 8:18
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    \$\begingroup\$ I think it is, fundamentally, the same as whether higher-quality JPEG is worth it in general. Or, at least, the same as whether to export using lower compression when you have the RAW files too. If you're only viewing at low resolution online and only making small prints, high compression and low quality is probably fine, so, sure, you could save a bit of memory card space and later batch processing time by extracting the embedded previews. If you want to preserve metadata, you could use exiftool to copy that from the RAW as part of your process. \$\endgroup\$
    – mattdm
    Commented May 27, 2016 at 12:44
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Assuming I have the time for batch extraction but don't have the time to develop these manually, is there any reason for me to continue shooting in RAW+JPEG mode and keep the standalone JPEGs, or should I go ahead and just mass-extract all the embedded JPEGs from the RAW files?

If you can extract the preview and you are okay with its quality, then no, you should not keep the camera generated JPEG (or keep the JPEG that is of better quality). But if you do not have time to postprocess and are okay with letting the camera make the editing decisions for you and produce an inferior image (less data) compared to the the RAW, then just shoot in JPEG mode and save the save the storage space and avoid the dilemma.

If storage space is of no concern and you want to have the ability to go back to the image at a later time and make a different (better) JPEG than the camera's software has produced, then you should continue to shoot and store both RAW+JPEG.

This way if at some later time you decide that the images you want to use to showcase your talent as photographer are an important tool/resume worthy of your time to post-process you can invest in the time to make the best possible image.

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