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Old 12-29-2007, 02:08 AM   #1
jkjack
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Join Date: Dec 2007
Posts: 1
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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