AdanteGuy

Do jpeg images deteriorate when used as a screensaver on a computer?

anderzander

From what I have learned over the years, JPEG's have improved but they still begin to degrade over time every time the files are opened, long term conservation is better with TIFF's. JPEG's don't have any value for me except to send as emails, or temp files for preliminary evaluations, never as finals.

jeep_daddy Loc: Prescott AZ

No, they do not degrade when viewed. The only time they degrade is when opened, changed, then saved again and again. To view them does nothing to them.

Fotoartist Loc: Detroit, Michigan

I've yet to see a comparison of before and after showing this degradation under normal use. It exists in theory but I haven't seen it in reality. I'm waiting for the evidence.

bsprague Loc: Lacey, WA, USA

If you expose JPEGs to light, they fade over time.

jeep_daddy Loc: Prescott AZ

bsprague Loc: Lacey, WA, USA

Glad you saw the humor!

mborn Loc: Massachusetts

NO!!!!

Rongnongno Loc: FL

No.

Your question does not belong in this section thought.

(Download)

bsprague Loc: Lacey, WA, USA

Which is correct. Screensavers read the file. In theory if you are editing JPEGs and save it multiple times there will be some degrading as the software "freshens" the compression. A fun exercise is to try it. Start with an original. Save it as Version 2. Open Version 2 and save it as Version 3. Repeat. When you get to about 20, compare it to the original.

Fotoartist Loc: Detroit, Michigan

Can you show us a comparison of this degradation in 20 steps? I've never seen one. You hear this all the time but you never see the evidence.

rmalarz Loc: Tempe, Arizona

The simple answer is no. They do not deteriorate over time. That is unless the medium on which they are saved deteriorates. Opening a jpg file does not change it. However, opening a jpg file and saving it will cause it to change, whether you've done any edits or not.
--Bob

bsprague Loc: Lacey, WA, USA

That's my point. When I did it a long time ago, I didn't see deterioration. Urban legends die hard.

rmalarz Loc: Tempe, Arizona

You don't need to save it but once to see changes to the file.
--Bob

Kuzano

I have tested this numerous times. The test is simple. It involves forcing the compression algorythm to run repeatedly on the same file and set a lower save guality each time. The image ALWAYS reduces in quality on a JPEG save. You control how much.

TEST:

Open a chosen JPEG
Edit the file any amount
"File" "save as" same name
Set file quality for example at 80 per cent.
Save to close.

There will be degradation, as pictures are discarded. Mostly imperceptible on one action.

Now, do this same routine a number off times using the same file name, a similar guality reduction, and a same "file save" as the same name.

The more times you do this and the more you reduce the quality of the save, the sooner visible degading appears. Again, always repeat on the same file.

Hence to limit degrade to one file, change file name. To limit degrade to minimal:

Always use new or original
Always set quality saved at 99 or 100 per cent
Always save new edit to :"file save""save".

The compression runs on Every Save. The image guality is controlled.

Compression/dgradation does NOT take place on JPEG opens, viewing or copies, moves, or other transfers not involving edits and/or saves.

20 Years of teaching this in Community College.