Lightroom and JPEGs

I 99% of the time shoot RAW. But occasionally, I like to shoot JPEG for easy candids of the kids, etc. Once I play with it in Lightroom, what is the best way to save a JPEG to retain the best quality possible?

Any adjustments you make in Lightroom are non-destructive - That means the original file (either RAW or JPEG) is unaltered and the changes are only recorded in the Lightroom catalog. You don't need to Save these as they are stored in the catalog.

However, if you want a copy of the image with the adjustments to post online or send to family/friends then you need to export the image using Lightroom export dialogue.

Hi Dan...thanks for answering. Yes, I want to know what settings in the LR export dialogue to use in order to have the highest quality image for print and online use ie should I save as JPEG or TIFF? what quality? size? etc.

daystar wrote in post #18128427
Hi Dan...thanks for answering. Yes, I want to know what settings in the LR export dialogue to use in order to have the highest quality image for print and online use ie should I save as JPEG or TIFF? what quality? size? etc.

JPEG is fine; 80 quality (at least my print house won't take anything higher than that). Size, etc is dependent on your output needs. Personally, I just export full size and then upload to Flickr, and it resizes for the other uses (forum posts, etc).

ok, so forgive me if this is a dumb but I saw online somewhere (and if it's online it's gotta be true, right???) that saving an original JPEG as a JPEG that's been a little manuipulated will really reduce the quality of the image. Not true?

Every time you save a JPEG you reduce its quality: true.

However, a high-resolution, high-quality JPEG will take a few saves without major/noticeable loss (it won't just turn absolutely dreadful upon first re-save). Just don't keep saving them and saving them. You should see JPEGs as final files.

Ah, ok...thanks Alveric! Good to know a one-time save won't destroy the image.

daystar wrote in post #18128517
Ah, ok...thanks Alveric! Good to know a one-time save won't destroy the image.

You could just try it and see. It doesn't cost anything.

I ran some tests quite some time ago resaving a JPG several times, and had a hard time seeing any deterioration.

As far as the first several re-saves are concerned, the loss in quality is only visible at the pixel-peeping levels –and most people won't pixel-peep unless that attractive face came out too small in the 50-people group shot and they zoom in to 400%. Again, as long as you start with hi-quality JPEGs, you shouldn't be too concerned about. You're in trouble when you start with medium-quality JPEGs and go from there.

There are several issues to consider.

Opening and closing a JPEG has no impact on quality. Open the original, look at it, then close it. The file is unchanged.

Saving a TIFF or PSD image file as a JPEG results in the software attempting to compress it. This may result in some image degradation. How much the image quality suffers depends on what quality setting you use. If you save at 100% the image will likely suffer no visible damage. The lower the quality level the higher the compression - meaning that more data is lost and the image quality may suffer. Saving an image at 10% quality will have a major impact on image quality.

If you open an existing JPEG image file (the 1st generation file) in PS or LR and then select to Save As/Export and select JPEG as the format, the software will create a new file (2nd generation) and apply JPEG compression (to an image that has already been compressed). Even if you select 100% quality there my be a tiny (but almost unnoticeable) difference in image quality. If you then open the 2nd generation JPEG and select to Save As a new file you have created a 3rd generation file which will again have gone through the compression process. Repeat the process opening each new generation file and Saving As and eventually the cumulative damage may become noticeable. However you would probably have to save dozens of generations before the damage would be noticeable. Provided you keep the 1st generation JPEG image safe there is no valid reason why you would ever go through this many generations.

Note: If you open a JPEG, select Save As and then select to save over the original file, you have destroyed the original and replaced it with a 2nd generation file. Doing this repeatedly over time will reduce the image quality.... but as above you would need to go through quite a few generations to get to a point where the damage is noticeable.

Repeatedly opening the 1st generation image and saving multiple new copies will not result in any noticeable image degradation because each one will be a 2nd generation image.

Conclusion.
Yes cumulative saving of generations of JPEG will result in image degradation but you would have to do it a lot for it to be noticeable. Saving a JPEG and an image quality setting of below 50% will have a much greater impact on image quality.

When it comes to JPEG quality settings I actually did some tests using the Jeffrey Friedel plug in for LR, that produces an uncompressed 8 bit TIFF and a complete series of JPEG files at all the possible levels of compression, Adobe only provides 13 different levels of compression, despite some dialogues having scales from 0 to 100. Although at all levels of compression there are some barely measurable differences from the TIFF they are completely unobservable even at Q80 which corresponds to level 10 on the 0 to 12 scale. What is interesting is that the Q100/12 JPEG file, if it contains a lot of very fine detail can actually end up larger than the uncompressed TIFF file. The way that the JPEG system works is that moving down from the maximum quality by a couple of steps makes no difference to the size of the differences from the TIFF, it just changes the distribution, so you will see a difference between the JPEG files, but the effect compared to the original TIFF is inconsequential. What is important is that moving to Q80/10 makes a huge difference in the size of the file. A Q100/12 file will be pretty much the same size as the TIFF, while the Q80/10 will be between 40% and 60% smaller depending on image content.

Personally I export all my JPEG images at Q80/10 as I know that there is zero observable difference between that and an uncompressed 8 bit TIFF. If I am using 8 bit files I see no point in using TIFF for final image export for printing, since it really makes no quality difference. However if you can print in 16 bit, then I would use a TIFF file, the extra bit depth makes a huge difference in quality.

Alan

Wow! Thank you all for such in-depth explanations! That really helps me wrap my head around it.

That would require a Mac OS, since Windows does not natively support 16 bit printing (a RIP is required), and probably a Canon printer - a model that comes with an XPS driver. Regarding Epson it is unclear what the driver does, whether it retains the high bit depth or knocks it down to 8 bits. At any rate, it would probably also require one of their biggest and most expensive models.

As to the benefits, i.e. improved quality, opinions are divided but most of the experts seem to think the difference is tiny, not huge or even that 16 bit can be detrimental. For instance:
http://forum.luminous-landscape.com/index.ph​p?topic=89357.0

or this:http://www.steves-digicams.com …ke-2-16-bit-printers.html
and this:http://ddisoftware.com …ate/16-bit-printing/?wap2
Mike Chaney is the author of Qimage printing software.

BigAl007 wrote in post #18128631
... the extra bit depth makes a huge difference in quality.

tzalman wrote in post #18128852
... most of the experts seem to think the difference is tiny

Interesting...

Dan Marchant wrote in post #18128574
Repeatedly opening the 1st generation image and saving multiple new copies will not result in any noticeable image degradation because each one will be a 2nd generation image.

As a slight clarification to daystar (OP), the above is essentially what Lightroom does when you use the Export function.

The original file is never changed. When you Export, it will create a new file by rendering your original image plus your current set of Lightroom edits. The Lightroom edits are never saved onto the original file; instead, they're in a separate hidden file that's essentially "show me what my photo would look like if we made all these edits."

Every time you Export, you make a new 2nd-generation image and your 1st-generation image is preserved. Quality losses due to compression degradation are insignificant.