Saving JPEGS Many Times After Making Many Changes
Sep 7, 2016 08:01:11 #
We've all heard that every time a JPEG is modified and saved, it loses a bit of quality. I did a little experiment. I found a picture of my dogs and changed it and saved it 100 times. Then I took a crop out of the center. The first shot below is the original. The second one has been modified and saved 100 times. When I did the processing and saving, it was always with the previous copy, not with the original. The picture was 1.15 MB, taken a few years ago with a Nikon D90. You can draw your own conclusions.
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Sep 7, 2016 08:05:21 #
jerryc41 wrote:
We've all heard that every time a JPEG is modified... (show quote)
Frankly, I see no significant difference.
Sep 7, 2016 08:11:57 #
londonfire
Loc: NY to NC
Jerry, thanks for clearing up that myth. In fact, on my IPad I like the second pic better.
Sep 7, 2016 08:19:36 #
Leitz
Loc: Solms
jerryc41 wrote:
We've all heard that every time a JPEG is modified... (show quote)
I believe this is to be expected, but if you had modified and saved the original each time, your result would have been quite different.
Sep 7, 2016 08:24:08 #
Leitz wrote:
I believe this is to be expected, but if you had modified and saved the original each time, your result would have been quite different.
If I had modified and saved the original a million times, it would have been like modifying it once. Each modification would have been done from the original, so it would have been just one change and save. What I wanted to show was what happens when you modify an image, save it, open it, and modify it and save it again - many times.
I'm not trying to prove a point here - just showing the results of multiple saves.
Sep 7, 2016 08:28:23 #
jerryc41 wrote:
We've all heard that every time a JPEG is modified... (show quote)
Well, I think and this is my opinion as I see it, it doesn't mean it as It is, the second one has a bit of lost saturation. Having said that this something that can be modified.
Now about the lost quality, as far as I am know if you save and save always the same size, you should not get any less quality, but if you resize it even in the same document it will make a lot of difference when you enlarge it again.
A way to avoid this is to make the layer of the picture (in Photoshop ) as smart object and one can reduce and enlarge as he wants without any lost definition.
I hope I understood your thread right.
Sep 7, 2016 08:46:02 #
Sep 7, 2016 09:30:13 #
phlash46 wrote:
Look about the same to me. Cute Pugs!
The one on the right passed away, but we still have her sister (on the left), the little one, and a long haired dachshund.
Sep 7, 2016 09:57:59 #
Sep 7, 2016 11:14:53 #
Leitz wrote:
Without precise details of the modifications, I really cannot comment further.
Does it really matter?
Sep 7, 2016 12:00:41 #
It's like using a filter to protect your lens. Just one of the things "QUALITY" nuts like to point out that will lessen your pictures if you do it. I think most of us would get better pictures if we would stop worrying about such things and work on taking pictures to get what we want. For instance using the aperture to get the depth of field we need to have the picture say what we want. - Dave
PS - Jerry thanks for all you do to make the forum interesting!
PS - Jerry thanks for all you do to make the forum interesting!
Sep 7, 2016 12:31:49 #
First thing.... 2 is different from 1 (you did some weird correction and the dogs are not at the same place, flip the images to see the differences).
Second... To damage a JPG to need to open, save, close then reopen, save, close... 100 times will do it. Saving 100 times from the same open JPG will not make a bit of difference.
I repeated your experiment using (open save close - Best quality 100 ) and the results are horrific.
Myth? Man...
Second... To damage a JPG to need to open, save, close then reopen, save, close... 100 times will do it. Saving 100 times from the same open JPG will not make a bit of difference.
I repeated your experiment using (open save close - Best quality 100 ) and the results are horrific.
Myth? Man...
Sep 7, 2016 12:58:55 #
Since I was at it, just to show the difference between a JPG lossy format and a PNG unlossy format I converted the original to a PNG format and then open saved closed is 50 times...
Difference during conversion? None pixel wise (color/luminosity) size on disk grew from 609kb to 4.3mb
Difference during conversion? None pixel wise (color/luminosity) size on disk grew from 609kb to 4.3mb
Sep 7, 2016 13:04:29 #
Of note the JPG conversion from really lossy (609kb) to highest JPG quality compression made that file grow to 5.1 mb... PNG msade it grow to 4.3mb.
Comparing this to PNG you may now understand why PNG is a 'weapon of choice' when posting...
Comparing this to PNG you may now understand why PNG is a 'weapon of choice' when posting...
Sep 7, 2016 13:33:14 #
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