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Old 12-29-2007, 02:08 AM   #1
jkjack
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Default ThumbsPlus — JPEGs at "original quality"

i have been using thumbsplus for some years and had always assumed that clicking the "use original quality" option when saving an image file would result in no loss of quality. i have read today that is not the case. i have known for some time that saving files in jpeg involved a loss of quality but had assumed that "use original quality" meant that in this particular case the flie would be saved without loss. on looking into it further i found this in thumbplus help (image file of this save dialogue box is included):

"Quality. Select a quality value, between 20 and 100. Values between 50 and 95 are recommended. Values below 25 are likely to degrade the image far too much, and values above 95 make the file larger without any appreciable quality increase."

"Use original quality. Check this option to use the JPEG quality from the original image."

so although still not 100% clear i'm guessing that this means if the file were originally stored with a 95 quality value then it will be stored with that again (if that is the case, why didn't thumbsplus call this option by something like: "use original compression value" which to me is a lot less likely to be misunderstood than "original quality")

i've been working on image files for a photo book which were already barely usable quality-wise (using a powershot s3) and have spent a year (often crawling to get close enough to have a decent photo) and now have 400+ photos that are seemingly good enough that i had an offer to publish some in a book. so it is a tremendous disappointment to learn that over the year i have been repeatedly knocking the quality down each time i edited (and i did often as a means to try to get all i could out of a borderline photo).

please tell me i'm wrong about this (or if that is not possible just give me the bad news).

also, if anyone could clear up this confusion that remains:

a 2,064,503 size file directly out of the camera (powershot saves as jpeg) becomes a 3,746,780 size file when saved with the "use original quality" unchecked and quality slider set at the max 100 and sub-sampling at 1:1(see below for what thumbs help has to say about this) and the original file becomes a 1,980,730 size file when saved with the "use original quality" option check (sub-sampling is not available in this case). in the latter case, the quality slider automatically goes to 97% which i gather accounts for a file size a little smaller. in the first case, however, i am at a loss as to why there would be any loss as the file size is considerably larger. thumbs help below says that saving at the sub-sampling 1:1 is best for files out of the camera and suggests that this is best for digital pictures. so it seems to me that if file size and processing time are not a consideration, then there should be no loss in saving with this option.

anyway, as i used the "use original quality" option i guess the bottom line is that everytime i opened and worked on a photo to improve it, i was losing 3% quality-wise when it was saved. kind of 1 step forward and 2 steps (or more) back.

pardon the long post but i'd like to clear this up. i assume in the future i should save the files out of the camera with the 1:1 sub-sampling and then when editing them use the tiff (please correct me if i'm wrong). another option is that i have found a method to shoot in raw mode using the powershot and would appreciate any input as to whether this would be worth going to the trouble to try to do (incidentally, i tested this and did indeed take a photo that was in canon's crw format but zoombrowser will not open it - i assume because that format is not an option in the powerplus - anyone know of a freeware crw file editor and converter?)

FROM THUMBSPLUS HELP

"Lossless JPEG is not currently supported. For lossless storage of 24-bit images, use TIFF, PNG, JPEG 2000, Targa, BMP, or PCX." ok, fine, but why use the misleading "use original quality"?

"For photographic images (more suited for the JPEG format), there is almost no apparent quality difference between the different sub-sampling methods.

but later:

So, 1:1 does provide the most accurate color, but whether you really need to use the extra disk space or download time depends on the planned use of the JPEG file itself. For digital camera pictures, it is best to store the originals as 1:1 (the way they come in from the camera), but using 2:2 for the web or e-mail is acceptable. If you plan to do a lot of editing (especially over a period of time), try converting your images to TIFF to retain color accuracy and minimize the lossiness (JPEG artifacts) that occur with repeated edits and saves."

these statements seems contradictory to me...

after hearing some views from other forum members more experienced than me i intend to contact thumbsplus about changing this before someone else wastes the hours that it seems i have.

thanks for any info.
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Old 12-29-2007, 05:53 AM   #2
ktinkel
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Hi, jkjack — welcome to the forum.

I know absolutely nothing about Thumbsplus, though others here do. But because of the holiday, things are a bit slow, so it may be a few days before you get a response.

I work in Photoshop (and am a graphic designer, not a Photoshop wiz by any means). In general, when opening a jpeg image, I immediately save a copy in the .psd (Photoshop) format. That preserves whatever quality level the image had when I received it (whether it is adequate or not — but I do not make things any worse).

I edit that file and save it and/or versions of it in the psd format. When I am ready to use the image in a document, I save a version at the correct size and resolution for the job requirements, but the .psd version remains in my files in case I need it again.

Don’t know if Thumbsplus allows for working that way, but it is a conservative approach that preserves your options.

I hope one of our Thumbsplus mavens pops up with some more specific advice.

   
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Old 12-29-2007, 06:20 AM   #3
Andrew B.
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I can only guess at what they mean, and I don't think it is good to guess. I think you need to ask them if "Original Quality" turns off all compression. And ask them if this turns off all smoothing, or if you have to do that as well. Also, if it turns of anything else that that does anything but save it as it is.

But even if they said it saves as is, I would still not save to jpeg. I just don't trust the format for accuracy. I once did a test where I saved file to jpeg from Photoshop at 100 quality, just to see the result. And when I zoomed in at pixel level, things were not exactly the same. I can't say it was of less quality, but it was not the same. And that worries me.

This does not mean that the photos you have now are ruined. If changes happened, they might not be significant. But the recommended work flow is to never save work in progress to jpeg. If you make any adjustments to an image file (regardless of its original format) save it to a new TIF, and retain the original file as it is. Then, if you need a compressed jpeg as a final output file, copy the TIF to a compressed jpeg, and still retain the TIF and the original.

The only exception to this would be if you are working with a program like Photoshop, in which case you can save to the program's native format instead of TIF, while also retaining the original.

Last edited by Andrew B.; 12-29-2007 at 08:12 AM.
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Old 12-29-2007, 05:44 PM   #4
Hugh Wyn Griffith
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What version of Thumbsplus are you using? It's up to:

29 November 2007 Version 7 SP2 build 2251

It might be worth checking to see if the updates alter anything relevant.

   
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Old 01-03-2008, 06:53 PM   #5
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One thing occurs to me:

Open a previously unedited file from the camera, save it under a new name with the "use original quality" option checked and change nothing else.

Then use a file compare utility program to compare the two files; if they're identical or nearly so, you're probably ok.

If you don't have anything else handy, you can use FC from a command prompt window to compare the files.

   
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Old 01-05-2008, 08:01 AM   #6
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Quote:
Originally Posted by Steve Rindsberg View Post
…save it under a new name with the "use original quality" option checked and change nothing else.

Then use a file compare utility program to compare the two files; if they're identical or nearly so, you're probably ok.
I don't use ThumbPlus for editing or saving, but your suggestion made me curious. So I ran some quick and dirty tests.

1. Compare CRC. This changes, but what is the change. Could it be the image info inserted by the program.

2. Load JPEG, make no changes, save. Then place both images on layers in Photoshop and do a/b switching to look for differences. No apparent difference at normal viewing size. But zoom in 3200%, and I notice slight color differences (confirmed by RGB reading in Info Palette).

So in terms of an existing collection of photos that have been saved to jpeg with original quality, the differences are so slight they do not hurt normal use. But, do this again and again on the same photo and the color could shift enough to be obvious.
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Old 01-05-2008, 12:35 PM   #7
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So it sounds as though something's changing ...

The next step: is it a one-time change or a slight change every time the file's opened/saved?

A one-time change might not matter. A series of minor changes might well add up to unpleasantness.

   
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Old 01-05-2008, 08:28 PM   #8
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I did that test. It changed both times, moving in the same direction of color shift. So if one did this several times, it could cause noticeable shift. But then again, this was only a quick and dirty test. I would not write an article based on the tests.
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Old 01-06-2008, 09:14 AM   #9
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Quote:
Originally Posted by Andrew B. View Post
I did that test. It changed both times, moving in the same direction of color shift. So if one did this several times, it could cause noticeable shift. But then again, this was only a quick and dirty test. I would not write an article based on the tests.
Understood. But at least you know that "Original quality" does NOT mean "Same as original" (or at least that some other setting might affect the image as well).

   
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Old 01-07-2008, 09:16 PM   #10
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Hi, JK Jack.

ALWAYS keep your original JPEGs somewhere! Do a 'save as' or back them up to another drive or disk or a folder named 'originals' but do it. (I learned the hard way...)

In my experience you can save a good-quality JPEG (your 2mb out of the camera should be plenty good) ONCE, sometimes a couple times, without being able to tell the difference in most circumstances. After that...

test for yourself. After you stash the original, save a file onto itself as many times as you can stand to. Pick something with clear edges and color contrast.

I just did this with an 875k image from my husband's little Sony. "Original Quality" came in at 96%, which should, but didn't, make the new file larger. The picture is very sharp and bright, the edge of a red plastic hummingbird feeder and its hanging rod in the foreground.

Then I zoomed them both way out, synched, and couldn't see any difference. After I selected the little squares and did a 'save selection as' it occurred to me that maybe it was a fake save -- that if there was no change in the file it didn't really apply whatever it would have -- and I saved the 75x little chunk onto itself 10 more times. See what you think. What I think is if "original quality" on your photos was in the high 90's you don't have too much to worry about. But in future, PLEASE stash an original somewhere!

Some files come in way lower than this when "original quality" is checked. You can check that one out to see if you're muddying and jaggying up the photo saving onto itself.

Years ago, before the Cerious staff got so full of themselves (and TP wasn't such big business), I asked about this and got this advice:

Before editing, save files to TIF with LZW compression. This is non-lossy. Edit and save to your heart's content, then (if necessary) save to a JPEG again.

This is very space-intensive if you keep the TIFs around. They come in at 30 or more megabytes, almost the same as a PSD. It's nice to know that saving a JPEG onto itself once or twice isn't going to make all that difference -- for my husband's reports. I wouldn't do it for any of MY wonderful RAW-derived photos, of course!

I don't know that the camera make would make a difference, except in that that little Sony has a newer fancier sensor than my old Powershot A80. O. Q. was 96% on it, too, though, when I just looked.

Wonder what the Cerious trick is. I was really surprised -- I did this once before, almost certainly with a much lesser file, and it did muddy up some as I remember.

Hope this helps.
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