There has been much discussion on the topic of saving JPG image files and the need to save them as TIFF or other format to preserve quality. I am not making any scientific claim on this topic.
In the image below the image on the LEFT is as close to the original as possible.
The image on the RIGHT has been opened and SAVED over 50 times. Each time it was opened in Photoshop it was saved, closed, opened saved and closed.
The intention was to simulate repeated editing etc where it is rumored that JPG images would loose quality after being saved a number of times. I've compared the images at 400X magnification and cannot detect any discernible quality loss or artifacts. It's difficult to present the results in this forum due to low file size limitation.
This is not totally scientific but I don't think many of us would be opening and saving an image file over 50 times so I'm not going to worry about JPG files so much in the future.
ShakyShutter wrote:
There has been much discussion on the topic of saving JPG image files and the need to save them as TIFF or other format to preserve quality. I am not making any scientific claim on this topic.
In the image below the image on the LEFT is as close to the original as possible.
The image on the RIGHT has been opened and SAVED over 50 times. Each time it was opened in Photoshop it was saved, closed, opened saved and closed.
The intention was to simulate repeated editing etc where it is rumored that JPG images would loose quality after being saved a number of times. I've compared the images at 400X magnification and cannot detect any discernible quality loss or artifacts. It's difficult to present the results in this forum due to low file size limitation.
This is not totally scientific but I don't think many of us would be opening and saving an image file over 50 times so I'm not going to worry about JPG files so much in the future.
There has been much discussion on the topic of sav... (
show quote)
Thank you ShakeyShutter! I'm not from Missouri, but I have needed someone to show me the differences side by side. What I have done is save all my original pics in one spot and work on them in another and keep the saved hangers there. Now I can find something else to fret about! And thanks to UHH for all the great information.
ShakyShutter wrote:
There has been much discussion on the topic of saving JPG image files and the need to save them as TIFF or other format to preserve quality. I am not making any scientific claim on this topic.
Saved at what JPEG quality? And from what original file size?
Cheers,
R.
JimH
Loc: Western South Jersey, USA
It is my understanding that JPG images are only recompressed (and therefore subject to whatever amount of quality loss) when you actually EDIT them and re-save. Open/Save does not, in and of itself, cause a re-compression algorithm to be carried out. Therefore, you could conceivably open/save a thousands times with no apparent loss of quality.
JimH wrote:
It is my understanding that JPG images are only recompressed (and therefore subject to whatever amount of quality loss) when you actually EDIT them and re-save. Open/Save does not, in and of itself, cause a re-compression algorithm to be carried out. Therefore, you could conceivably open/save a thousands times with no apparent loss of quality.
Define "Edit" and I'll go that way.
Roger Hicks wrote:
ShakyShutter wrote:
There has been much discussion on the topic of saving JPG image files and the need to save them as TIFF or other format to preserve quality. I am not making any scientific claim on this topic.
Saved at what JPEG quality? And from what original file size?
Cheers,
R.
Original was a JPG out of a Nikon D70. About 2.9mb.
It was copied to the PC, lived there for a long time, copied to a special directory, copied once and that one was renamed.
The test file was then Opened in PS PS2 then Saved (not saved as) at highest quality. It was then closed, Opened, Saved, Closed etc.
For presentation a New page was created in PS, each file opened and placed on that page. It was saved... about 9mbs. This file was re-sized in FastStone resizer to be able to upload.
The objective was to simulate opening and saving the same file repeatedly as work progresses as we all advise newbies not to do.
ShakyShutter wrote:
There has been much discussion on the topic of saving JPG image files and the need to save them as TIFF or other format to preserve quality. I am not making any scientific claim on this topic.
In the image below the image on the LEFT is as close to the original as possible.
The image on the RIGHT has been opened and SAVED over 50 times. Each time it was opened in Photoshop it was saved, closed, opened saved and closed.
The intention was to simulate repeated editing etc where it is rumored that JPG images would loose quality after being saved a number of times. I've compared the images at 400X magnification and cannot detect any discernible quality loss or artifacts. It's difficult to present the results in this forum due to low file size limitation.
This is not totally scientific but I don't think many of us would be opening and saving an image file over 50 times so I'm not going to worry about JPG files so much in the future.
There has been much discussion on the topic of sav... (
show quote)
You must have missed the part in all the discussions about .jpeg saving where "editing" was discussed. As mentioned above, you have to make some changes to the file then save, then open it again to lose data. Take your example and make a minor change to each time you open it and you'll see what Jim was talking about.
tkhphotography wrote:
ShakyShutter wrote:
There has been much discussion on the topic of saving JPG image files and the need to save them as TIFF or other format to preserve quality. I am not making any scientific claim on this topic.
In the image below the image on the LEFT is as close to the original as possible.
The image on the RIGHT has been opened and SAVED over 50 times. Each time it was opened in Photoshop it was saved, closed, opened saved and closed.
The intention was to simulate repeated editing etc where it is rumored that JPG images would loose quality after being saved a number of times. I've compared the images at 400X magnification and cannot detect any discernible quality loss or artifacts. It's difficult to present the results in this forum due to low file size limitation.
This is not totally scientific but I don't think many of us would be opening and saving an image file over 50 times so I'm not going to worry about JPG files so much in the future.
There has been much discussion on the topic of sav... (
show quote)
You must have missed the part in all the discussions about .jpeg saving where "editing" was discussed. As mentioned above, you have to make some changes to the file then save, then open it again to lose data. Take your example and make a minor change to each time you open it and you'll see what Jim was talking about.
quote=ShakyShutter There has been much discussion... (
show quote)
Didn't miss anything in the discussions. As above, define edit and I'll re-run the test.
ShakyShutter wrote:
tkhphotography wrote:
ShakyShutter wrote:
There has been much discussion on the topic of saving JPG image files and the need to save them as TIFF or other format to preserve quality. I am not making any scientific claim on this topic.
In the image below the image on the LEFT is as close to the original as possible.
The image on the RIGHT has been opened and SAVED over 50 times. Each time it was opened in Photoshop it was saved, closed, opened saved and closed.
The intention was to simulate repeated editing etc where it is rumored that JPG images would loose quality after being saved a number of times. I've compared the images at 400X magnification and cannot detect any discernible quality loss or artifacts. It's difficult to present the results in this forum due to low file size limitation.
This is not totally scientific but I don't think many of us would be opening and saving an image file over 50 times so I'm not going to worry about JPG files so much in the future.
There has been much discussion on the topic of sav... (
show quote)
You must have missed the part in all the discussions about .jpeg saving where "editing" was discussed. As mentioned above, you have to make some changes to the file then save, then open it again to lose data. Take your example and make a minor change to each time you open it and you'll see what Jim was talking about.
quote=ShakyShutter There has been much discussion... (
show quote)
Didn't miss anything in the discussions. As above, define edit and I'll re-run the test.
quote=tkhphotography quote=ShakyShutter There ha... (
show quote)
As mentioned above, you have to make some changes to the file then save, then open it again to lose data.
tkhphotography wrote:
ShakyShutter wrote:
tkhphotography wrote:
ShakyShutter wrote:
There has been much discussion on the topic of saving JPG image files and the need to save them as TIFF or other format to preserve quality. I am not making any scientific claim on this topic.
In the image below the image on the LEFT is as close to the original as possible.
The image on the RIGHT has been opened and SAVED over 50 times. Each time it was opened in Photoshop it was saved, closed, opened saved and closed.
The intention was to simulate repeated editing etc where it is rumored that JPG images would loose quality after being saved a number of times. I've compared the images at 400X magnification and cannot detect any discernible quality loss or artifacts. It's difficult to present the results in this forum due to low file size limitation.
This is not totally scientific but I don't think many of us would be opening and saving an image file over 50 times so I'm not going to worry about JPG files so much in the future.
There has been much discussion on the topic of sav... (
show quote)
You must have missed the part in all the discussions about .jpeg saving where "editing" was discussed. As mentioned above, you have to make some changes to the file then save, then open it again to lose data. Take your example and make a minor change to each time you open it and you'll see what Jim was talking about.
quote=ShakyShutter There has been much discussion... (
show quote)
Didn't miss anything in the discussions. As above, define edit and I'll re-run the test.
quote=tkhphotography quote=ShakyShutter There ha... (
show quote)
As mentioned above, you have to make some changes to the file then save, then open it again to lose data.
quote=ShakyShutter quote=tkhphotography quote=S... (
show quote)
The question is "How much data should be changed?" one pixel, two? What would be considered the LEAST invasive or benign "edit" to make on each one?
ShakyShutter wrote:
tkhphotography wrote:
ShakyShutter wrote:
tkhphotography wrote:
ShakyShutter wrote:
There has been much discussion on the topic of saving JPG image files and the need to save them as TIFF or other format to preserve quality. I am not making any scientific claim on this topic.
In the image below the image on the LEFT is as close to the original as possible.
The image on the RIGHT has been opened and SAVED over 50 times. Each time it was opened in Photoshop it was saved, closed, opened saved and closed.
The intention was to simulate repeated editing etc where it is rumored that JPG images would loose quality after being saved a number of times. I've compared the images at 400X magnification and cannot detect any discernible quality loss or artifacts. It's difficult to present the results in this forum due to low file size limitation.
This is not totally scientific but I don't think many of us would be opening and saving an image file over 50 times so I'm not going to worry about JPG files so much in the future.
There has been much discussion on the topic of sav... (
show quote)
You must have missed the part in all the discussions about .jpeg saving where "editing" was discussed. As mentioned above, you have to make some changes to the file then save, then open it again to lose data. Take your example and make a minor change to each time you open it and you'll see what Jim was talking about.
quote=ShakyShutter There has been much discussion... (
show quote)
Didn't miss anything in the discussions. As above, define edit and I'll re-run the test.
quote=tkhphotography quote=ShakyShutter There ha... (
show quote)
As mentioned above, you have to make some changes to the file then save, then open it again to lose data.
quote=ShakyShutter quote=tkhphotography quote=S... (
show quote)
The question is "How much data should be changed?" one pixel, two? What would be considered the LEAST invasive or benign "edit" to make on each one?
quote=tkhphotography quote=ShakyShutter quote=t... (
show quote)
ok, you got me interested in running my own little test. If you don't object I will use your photos and run with it for a couple days; today I don't have much time but will start.
JimH
Loc: Western South Jersey, USA
Well, you have to make an "edit" that doesn't alter the optical characteristic of the photo, which rules out anything like contrast/sharpness/brightness adjustments. What you might try if your PP software has the ability, is to crop by just a couple of pixels in any dimension, and NOT do a re-sample, because I think that might jack up the compression. Then check the actual file size after you save it - it should be a couple dozen or hundred fewer bytes. Then do it again...lather, rinse, repeat. You should see a noticeable difference after about 20 edit/saves, if you're so inclined.
Like you said, most people don't open/edit/save the same same image that many times. But they don't need to needlessly worry about 'viewing' it any number of times.
tkhphotography wrote:
ShakyShutter wrote:
tkhphotography wrote:
ShakyShutter wrote:
tkhphotography wrote:
ShakyShutter wrote:
There has been much discussion on the topic of saving JPG image files and the need to save them as TIFF or other format to preserve quality. I am not making any scientific claim on this topic.
In the image below the image on the LEFT is as close to the original as possible.
The image on the RIGHT has been opened and SAVED over 50 times. Each time it was opened in Photoshop it was saved, closed, opened saved and closed.
The intention was to simulate repeated editing etc where it is rumored that JPG images would loose quality after being saved a number of times. I've compared the images at 400X magnification and cannot detect any discernible quality loss or artifacts. It's difficult to present the results in this forum due to low file size limitation.
This is not totally scientific but I don't think many of us would be opening and saving an image file over 50 times so I'm not going to worry about JPG files so much in the future.
There has been much discussion on the topic of sav... (
show quote)
You must have missed the part in all the discussions about .jpeg saving where "editing" was discussed. As mentioned above, you have to make some changes to the file then save, then open it again to lose data. Take your example and make a minor change to each time you open it and you'll see what Jim was talking about.
quote=ShakyShutter There has been much discussion... (
show quote)
Didn't miss anything in the discussions. As above, define edit and I'll re-run the test.
quote=tkhphotography quote=ShakyShutter There ha... (
show quote)
As mentioned above, you have to make some changes to the file then save, then open it again to lose data.
quote=ShakyShutter quote=tkhphotography quote=S... (
show quote)
The question is "How much data should be changed?" one pixel, two? What would be considered the LEAST invasive or benign "edit" to make on each one?
quote=tkhphotography quote=ShakyShutter quote=t... (
show quote)
ok, you got me interested in running my own little test. If you don't object I will use your photos and run with it for a couple days; today I don't have much time but will start.
quote=ShakyShutter quote=tkhphotography quote=S... (
show quote)
Let me e-mail you an original copy to start with. PM your address please.
ShakyShutter wrote:
As above, define edit and I'll re-run the test.
You've got to be kidding.
http://www.merriam-webster.com/dictionary/edit:Definition of EDIT
transitive verb
1
a : to prepare (as literary material) for publication or public presentation
b : to assemble (as a moving picture or tape recording) by cutting and rearranging
c : to alter, adapt, or refine especially to bring about conformity to a standard or to suit a particular purpose <carefully edited the speech> <edit a data file>2
: to direct the publication of <edits the daily newspaper>
3
: delete usually used with out
ed·it·able adjective
See edit defined for English-language learners »
See edit defined for kids »
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