[jepjepjep]

I am about to start editing photos, and using Lr (4) for the first time. Hence I have a plethora of questions regarding JPEGs and Lr 4. I apologize beforehand for the obscene length and possibly bad English.

I currently shoot RAW, but I have thousands of JPEGs. I would like to avoid losing the quality of those JPEGs (through resaving and recompressing needlessly), and be able to handle and edit them as efficiently as possible.


Could you please confirm or correct the following assumptions:

1. Lightroom 4 only resaves and recompresses JPEGs when you export them. Therefore, there are no losses to the quality no matter how much and how many times you edit them (either in Develop module or by altering metadata by adding keywords etc.) before exporting. Furthermore, the exported file is a copy and the original is left untouched, so you can keep working on the lossless photo in Lr.

2. Saving metadata (by saving manually or having the "Automatically write changes into XMP" -option on) to the XMP-space inside the JPEG file does not cause a resave and recompression of the JPEG in a way that would result in any loss of quality (it only modifies the non-image part of the file).

3. Point number 2 holds true even if you choose to include develop settings in the metadata by turning on "Include Develop settings in metadata inside JPEG, TIFF, and PSD files".

4. Saving metadata to the JPEG alters modified date as shown in Finder. There is no setting or convenient way to avoid this.

5. "Automatically write changes into XMP" and "Include Develop settings in metadata inside JPEG, TIFF, and PSD files" should be turned off, unless you also intend to edit those files in another program that understands the data (e.g. another copy of Lr, Photoshop, Bridge etc.).

6. Original JPEGs can be exported without recompressing and loss of quality by choosing to export as originals. In this case, no edits (white balance etc.) will be visible, but changes in metadata will be present (only) if the metadata has been saved in the JPEG as described in points 2 and 3.

7. JPEG files can be renamed on import or at a later point without recompression or loss of quality (even though this information is not only stored in Lr catalogue since the name is also changed in Finder etc.).

8. There are no advantages to converting a JPEG to a lossless format (e.g. DNG) if you plan on editing them only in Lr and then exporting the final versions.

9. Lens profiles only work on RAW images. However, you can alter the lens profiles to make them fully applicable to JPEGs as well. All you need to do is change "True" to "False" in the following line of the XMP file: [stCamera:CameraRawProfile] True [/stCamera:CameraRawProfile]

10. The JPEG file should never be resaved again as JPEG, but in Lr this is not even possible without exporting.

11. Creating virtual copies, moving between folders etc. doesn't cause recompression or loss of quality.


And a couple of additional questions:

A. Are there any (other) settings or practices I should be aware of or avoid in order to avoid losing JPEG quality?

B. Should the workflow with JPEGs differ in someway from RAW workflow in order to achieve maximum quality / efficiency.

C. Are there separate editing presets for JPEGs and RAWs? If so, can RAW presets be applied to JPEGs as long as the resulting look is pleasing?

D. Where could I find good JPEG lens profiles (for Pentax K-5 or Olympus XZ-1), free JPEG editing presets, and Lr tutorials on JPEG editing, such as how much you can tweak certain settings without going overboard etc.?


Thank you in advance!

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Last edited by jepjepjep; 03-09-2012 at 02:08 PM.

[JinDesu]

1. Lightroom 4 only resaves and recompresses JPEGs when you export them. Therefore, there are no losses to the quality no matter how much and how many times you edit them (either in Develop module or by altering metadata by adding keywords etc.) before exporting. Furthermore, the exported file is a copy and the original is left untouched, so you can keep working on the lossless photo in Lr.

Yes. Lightroom maintains the original JPEG and all edits are applied to a copy. In addition, all changes are kept as data and you can edit those changes based on the original file.

8. There are no advantages to converting a JPEG to a lossless format (e.g. DNG) if you plan on editing them only in Lr and then exporting the final versions.
As far as I can tell, this is true. Since Lightroom will not make changes to the original file, there is no reason to convert a JPEG to a lossless format for editing. Unless you like to just slow down your computer for no reason.

10. The JPEG file should never be resaved again as JPEG, but in Lr this is not even possible without exporting.
Yes.

11. Creating virtual copies, moving between folders etc. doesn't cause recompression or loss of quality.
Do you mean in Lightroom, or in general? If you are referring to moving a file, there is no "call" for the JPEG to be opened and resaved.

Thank you in advance!

Answered the stuff I could, most likely the easiest questions of the bunch. Minor point afterwards - I don't work in JPEG so I wasn't aware that the lens profiles didn't work on JPEG. I would imagine the corrections applied would still work on JPEGs (excepting chromatic abberation correction).

[jepjepjep]

Thank you for a quick reply, this was very helpfull. Hopefully someone else can take care of the other stuff.

As to creating virtual copies and moving stuff around etc, I suppose I meant both to an extent: creating virtual copies and moving the file in Lr and moving, copying etc. in Finder. I assume that none of these actions require recompression.

Thanks again!

[emalvick]

2. Saving metadata (by saving manually or having the "Automatically write changes into XMP" -option on) to the XMP-space inside the JPEG file does not cause a resave and recompression of the JPEG in a way that would result in any loss of quality (it only modifies the non-image part of the file).

Correct. No software should

3. Point number 2 holds true even if you choose to include develop settings in the metadata by turning on "Include Develop settings in metadata inside JPEG, TIFF, and PSD files".

Again correct

4. Saving metadata to the JPEG alters modified date as shown in Finder. There is no setting or convenient way to avoid this.

I'm not sure about this. It seems you should have a yes or no option, but I've never checked

5. "Automatically write changes into XMP" and "Include Develop settings in metadata inside JPEG, TIFF, and PSD files" should be turned off, unless you also intend to edit those files in another program that understands the data (e.g. another copy of Lr, Photoshop, Bridge etc.).

I'm not sure about whether it should be turned off (that is up to you). However, a good reason to leave it turned on, especially the develop settings is that if you end up with a corrupt database or you do work with another program down the road, you don't have to think about it. It acts as a back-up.

6. Original JPEGs can be exported without recompressing and loss of quality by choosing to export as originals. In this case, no edits (white balance etc.) will be visible, but changes in metadata will be present (only) if the metadata has been saved in the JPEG as described in points 2 and 3.

not sure on this one

7. JPEG files can be renamed on import or at a later point without recompression or loss of quality (even though this information is not only stored in Lr catalogue since the name is also changed in Finder etc.).

True, renaming is renaming. Doesn't have anything to do with the actual data in the file

8. There are no advantages to converting a JPEG to a lossless format (e.g. DNG) if you plan on editing them only in Lr and then exporting the final versions.

Probably true, but you might look outside the forum a bit. I saw someone give a reason for converting a JPG to DNG. I'm not sure it was a good one.

9. Lens profiles only work on RAW images. However, you can alter the lens profiles to make them fully applicable to JPEGs as well. All you need to do is change "True" to "False" in the following line of the XMP file: [stCamera:CameraRawProfile] True [/stCamera:CameraRawProfile]

Not sure...

10. The JPEG file should never be resaved again as JPEG, but in Lr this is not even possible without exporting.

You definitely don't want to resave over an original JPEG because it will start accumulating losses. Of course any time you edit a JPG in any software you've made a change and you have to save it somehow. You could save it to TIFF and even export to TIFF, but unless you plan on working on that image again, I don't think you have to worry about exporting a JPG once. The nice thing with LR is that you are not making changes permanent, so as long as you have your develop settings, you'll be able to start from an intermediate step. I actually take advantage of the snapshot tool quite a bit to save the history at different points, especially where I am exporting from. This allows me to start from the spot an export was made if I need to do more work on an image or try something new.

11. Creating virtual copies, moving between folders etc. doesn't cause recompression or loss of quality.

Correct. Virtual copies are virtual.

And a couple of additional questions:

A. Are there any (other) settings or practices I should be aware of or avoid in order to avoid losing JPEG quality?

Make sure you set the quality as high as possible when saving as JPG and don't accumulate changes. If you need photoshop, at least export an intermediate TIFF before you save the final image to a JPG.

Ultimately, if you are really concerned with quality and you are going through the steps of working in LR, you could just shoot RAW to begin with. A lot of the develop tools in LR will not work well on JPG. You'll really see where the losses are in your JPG's the first time you try to adjust blown-out highlights or fill in shadows

B. Should the workflow with JPEGs differ in someway from RAW workflow in order to achieve maximum quality / efficiency.

C. Are there separate editing presets for JPEGs and RAWs? If so, can RAW presets be applied to JPEGs as long as the resulting look is pleasing?

I don't see why not. Just realize that some of the develop settings may not do anything or may give surprising results. You'll have to test, yourself. The beauty of LR is that you can step backwards if needed.

D. Where could I find good JPEG lens profiles (for Pentax K-5 or Olympus XZ-1), free JPEG editing presets, and Lr tutorials on JPEG editing, such as how much you can tweak certain settings without going overboard etc.?


Thank you in advance!

Just to reiterate what I answered towards the end. It sounds like you are planning on investing a lot of time into your images. If that is the case, you should consider shooting RAW. LR can only do so much with a JPG. I'm not sure that you'll easily find an JPG specific presets or lens profiles. You should just take some of the RAW profiles out there and test them out. I find it hard to believe that a lens profile would be significantly different for a JPG vs. RAW unless a JPG is missing the lens info in metadata that LR needs. Again, I'd just test it out a bit. I find the included profiles for lenses work quite well. There are some nice all-around editing presets in the forum here if you search a bit.

[jepjepjep]

Thank you emalvick for a truly exemplary answer!

Oh, and I actually did start shooting RAW recently. However, I have thousands of unsorted and unedited JPEGs from a recent around the world trip, and I probably have to do something with those

[psychdoc]

If you are new to Lightroom, try renting this book from your library. But its good enough to buy. Its the LR3 version at present.

Amazon.com: The Adobe Photoshop Lightroom 3 Book for Digital Photographers (Voices That Matter) (9780321700919): Scott Kelby: Books

[Anvh]

Thank you emalvick for a truly exemplary answer!

Oh, and I actually did start shooting RAW recently. However, I have thousands of unsorted and unedited JPEGs from a recent around the world trip, and I probably have to do something with those

Simply load them into Lightroom and don't "resave them" just let them be unthouched with lightroom managing the edits in his cataloge.
If you want to show them to friends or print them it's very easy and fast to output them from lightroom to the format you need/want, so leave the XMP and stuff for what it is.

[Marc Sabatella]

Your assumptions are all basically correct. Just a couple of obervations:

4. Saving metadata to the JPEG alters modified date as shown in Finder. There is no setting or convenient way to avoid this.

Saving metadata to the JPEG *does* change the file, so of course it changes the modified date. Anything else would break backup utilities, disk space management utilities, etc. It's not nice to lie to a filesystem about such things. But if you don't mind the risk, I'm sure there re any number of utilities that would happy to lie to the file system for you by altering the file modified date after the fact. The question is, why on earth would you want to? File modified date is *supposed* to tell you when the file was modified. If you just want to know when the picture was taken, that's what the Exif date is for.

5. "Automatically write changes into XMP" and "Include Develop settings in metadata inside JPEG, TIFF, and PSD files" should be turned off, unless you also intend to edit those files in another program that understands the data (e.g. another copy of Lr, Photoshop, Bridge etc.).

Why turn it off? Seems like a simple safeguard again loss/corruption of catalog info to me.

10. The JPEG file should never be resaved again as JPEG, but in Lr this is not even possible without exporting.

Not sure what you mean by this. Saving an edited file over the original loses the original, so of course it's not a great idea in general if you have any expectation of working with the original again. But if you are saving an edited file as a *copy*, so the originl is preserved, there is no particular reason not to do so as a JPEG if JPEG is what you want. There is no real point in going with a less ideal file format just to avoid the miniscule loss in quality from the compression, if you use a reasonably high quality setting. Just depends on how much file space or flexibility you are willing to give up in order to avoid that miniscule loss, I guess.

A. Are there any (other) settings or practices I should be aware of or avoid in order to avoid losing JPEG quality?

In general, you obsess about this *way* too much. Just use the program as it was designed to be used, exporting to JPEg when you need a JPEG output, and all will be fine.

[jepjepjep]

Thank you everyone!