Question of RAW conversion to JPEG

[cokethenwpepsi]

So I know the basics of a RAW file, I just have one simple question.
If you take a RAW photo, download it from your camera or card to your computer, edit it in a RAW editor, then open it in Photoshop and save it as a JPEG (for web upload or whatever), is any detail lost in that conversion even though it was originally taken and edited as a RAW file?

[enrigonz]

yes, I'm afraid....

None of my jpegs look as good as the RAW files, sometimes you'll have a hard time noticing in the beginning but after some time you'll be able to notice

[cokethenwpepsi]

So with that clarified, what advantage does RAW have that wouldn't be lost in a jpeg conversion?

[derangedhermit]

Originally Posted by cokethenwpepsi

So with that clarified, what advantage does RAW have that wouldn't be lost in a jpeg conversion?

jpeg is a distribution and display format, not a working format. Editing with RAW files (or TIFF files, or PNG (lossless compression), or Adobe PSD format...) lets you keep higher image quality throughout the editing process. When you are finished editing, then you can output a jpeg for putting on the web.

[Peano]

Originally Posted by cokethenwpepsi

So with that clarified, what advantage does RAW have that wouldn't be lost in a jpeg conversion?

When you shoot jpeg or convert a raw file to jpeg, anywhere from one-third to one-half of the image data is thrown away. In many images, that wouldn't make any difference at all. But in the ones that count, it can make all the difference.

Shadow details that are blocked in the jpeg can often be recovered in the raw file. On the other end of the spectrum, highlight details that are blown in the jpeg can often be salvaged from the raw file.

In some cases, I do one raw "exposure" for the midtones, a second for the highlights, and a third for the shadows. By bringing all three into Photoshop and blending them using layer masks, I can get a much higher dynamic range than could be had from a straight conversion to jpeg.

[cokethenwpepsi]

So if you were to take a photo in RAW and were able to recover shadow and/or highlight detail then convert to jpeg, you would then have a jpeg with shadow and/or highlight detail, rather than if the image had originally been shot in jpeg, in which case those details would be permanently lost? So basically the question that nags me is: when a RAW file is converted to jpeg, then the modifications made before conversion are not lost, correct?

[Peano]

Originally Posted by cokethenwpepsi

So if you were to take a photo in RAW and were able to recover shadow and/or highlight detail then convert to jpeg, you would then have a jpeg with shadow and/or highlight detail, rather than if the image had originally been shot in jpeg, in which case those details would be permanently lost? So basically the question that nags me is: when a RAW file is converted to jpeg, then the modifications made before conversion are not lost, correct?

Correct. If you keep the raw file, it remains unchanged. You can't make any permanent changes to a raw file. All edits go as instructions into a little "sidecar" text file. When you save it as a jpeg, those changes get "baked into" the jpeg.

[cokethenwpepsi]

Excellent. Thank you for clearing that up for me.

[tonylong]

I'll just add to your question about detail.

If you convert from a Raw file to a full-size high-quality jpeg the compression that gets applied is minimal and you will have a full resolution pixel-wise so detail will be retained. I know the earlier poster said that "after a while" he noticed a difference but I doubt it is actual detail "missing" because all the pixels are reproduced in the jpeg. I'd be interested in seeing a 100% crop of the Raw and a jpeg that was converted at full size and high quality showing detail loss.

But when you resize an image during a conversion to a jpeg or tiff or whatever for, like you mentioned something like saving for the Web, you are throwing pixels away, and that means that finer detail will just disappear.

And, at lower quality settings you are eventually going to see other issues -- not detail loss as such but the lower the quality the more strange "artifacts" can be seen. This also happens when you save, open and re-save a jpeg multiple times -- eventually it can have a pretty ugly affect.

So, a good workflow is to do all you can in Raw, then, if you need to work on an image in Photoshop you can, and then if you have a project that you want to keep as a "working project" the "best practice" is to save as a tiff. At the point that you actually need to save for the Web, email, print, whatever is when you save the jpeg at the right size and quality for your intended use.

[cokethenwpepsi]

Awesome. Also, is the sharpening applied to a RAW more effective or advantageous in any way over sharpening jpegs?

[tzalman]

Originally Posted by cokethenwpepsi

Awesome. Also, is the sharpening applied to a RAW more effective or advantageous in any way over sharpening jpegs?

The designers of Lightroom, where the conversion from linear RAW space to the skewered gamma corrected space of a rendered format is done only as the last step in the workflow, claim that any image adjustment is better if it is done in linear space - including sharpening and noise reduction. The difference might not be apparent if all you ever do is post to Facebook and print 4x6s, but the larger you print the more important the quality of the editing becomes.

[tonylong]

Elie, could you give some specific info about this, like how different approaches might give different results?

[tzalman]

Tony, the reason that I qualified the above by saying that this is the LR designer's claim rather than making a flat statement of fact is that I am not entirely convinced. It seems to me that as long as the white point and black point are not clipped a 16 bit tif will contain all the RAW data and any alteration (editing) of that data can be done as well. OTOH, I understand that for manipulations of linear data the algorithms are simpler. If this makes them better I'm not qualified to say. Maybe Peano or others more knowledgeable than me will have comments.

[enrigonz]

When you throw out 50% of information in an image, you will loose detail, if you have a good eye you can see it. Is the same a MP3 compression, most people wouldn't notice the difference between and uncompressed or a less compress file over a 128kb MP3 file but I sure can. Is all about what you're eyes and ears get used to seeing or hearing, after a while you get use to it and it really doesn't matter for most, we train our eyes and ears to"make up" for the lost details and those details are filled by us in our sub-conscience one way or another. Lots of scientific studies have been done on stuff like this, easy to look up.

[tonylong]

Originally Posted by enrigonz

When you throw out 50% of information in an image, you will loose detail, if you have a good eye you can see it. Is the same a MP3 compression, most people wouldn't notice the difference between and uncompressed or a less compress file over a 128kb MP3 file but I sure can. Is all about what you're eyes and ears get used to seeing or hearing, after a while you get use to it and it really doesn't matter for most, we train our eyes and ears to"make up" for the lost details and those details are filled by us in our sub-conscience one way or another. Lots of scientific studies have been done on stuff like this, easy to look up.

If you resize the image or highly compress it then yes, you lose a lot of detail. But a fresh conversion to a full-size jpeg at high quality should not result in noticeable detail loss and a very minimal and unnoticeable amount of artifacts.

But, like I said, it would be informative if you could post a couple comparison photos -- a screen shot of a 100% view of a Raw file with a 100% crop of a full-sized high quality jpeg showing loss of detail would help us to give an objective analysis instead of subjective opinions!