Astonish findings !

david-low

I maybe the last to know but I still think the majority are unaware of this. For many will think saving a jpg in Level 12 is the best (for PS). I knew from the super hero here mentioned Level 10 is good enough and I have been religiously adopting that. But for subsequent or multiple resaving, it is Level 8 ! Yes, read on, this gonna blow your mind.

We understand opening and resaving a jpg file repeatedly (even without any editing) will degrade the image. But little do we know saving in Quality Level 8 in Photoshop will render no adverse effect when opening and resaving multiple times.

The thread below which eventually prompt me to carry out my own experiment, provides a good technical feed where they recycle the image 1,000 times. It's quite a lengthy post but full of supporting evidence.
http://forums.dpreview.com/forums/read.asp?forum=1006&message=31964153

To convince myself, I went on to do my own findings and voila, its unbelievable. Yes, Quality 8 (high) other than any other Quality is the optimum choice for multiple resaves. As I do not know how to write an action in PS for it to self generate, I did the pain staking way of importing an image into CS5, no editing, resave, close file and repeat action one at a time, repeating 30 times from Level 8 to 12 and continue to 100 resaves for Level 8, 10 and 12. My presentation differs from above thread but similar conclusion, and hopefully gives everyone something to digest.

I also append a tabulation, by which it is evident that for every resaved, the file size gets progressively bigger, most evidently for Level 12. It goes to show the editor does add information (perhaps more artifacts generated as Quality Level goes higher) although no editing is done. I'm not sure saving in the highest quality in other editors is the best. You may like to test it out.

This post is not about dispelling not saving in raw or tiff. I know how to protect my native or master file. Its about how to get the most out of a jpg image.

Appreciate your comments.

Tables:



Sample Pic



Original 100% crop



Resaved at Level 8 (repeat 30 times)



Resaved at Level 9 (repeat 30 times)



Resaved at Level 10 (repeat 30 times)



Resaved at Level 11 (repeat 30 times)



Resaved at Level 12 (repeat 30 times)



Resaved at Level 8 (repeat 100 times)



Resaved at Level 10 (repeat 100 times)



Resaved at Level 12 (repeat 100 times)

Richard

Interesting results. I'm always intrigued when someone comes up with evidence that goes against the prevailing wisdom. I wonder though how jpg 8s compare to 10s when they are printed. Resampling 100 or even 30 times is not something that many of us would ever do. My understanding was that 10 prints just about as well as 12, and that was the reason it was the preferred value.

pathfinder

I think this has todo with the original file size. I think modern DSLR images, most of which are at least 10Mpxls, will be as the poster described.

But if you start with a 3 Kb image, it will tolerate this kind of treatment much more poorly!

When I read this thread this morning in my iPad I could see no difference between any of the images, whether saved as 8, 10, or 12.

Now I see that after 8 the images get worse with resaving, not better.

Not sure how to react to this, but since I never resave a jpg, it is not a great deal of concern to me (I think ).

david-low

Richard wrote: »

Interesting results. I'm always intrigued when someone comes up with evidence that goes against the prevailing wisdom. I wonder though how jpg 8s compare to 10s when they are printed. Resampling 100 or even 30 times is not something that many of us would ever do. My understanding was that 10 prints just about as well as 12, and that was the reason it was the preferred value.

You're right that a pic can never be tweaked so many times in practical terms. Otherwise, one should save in tiff in the 1st place. Its a good question how the printing stack up between 8 and 10. But my gut feeling is since at 100% crop looks good for 8 than 10, it should be better. Just forsake a bottle of wine and spend the money to prove it.

david-low

pathfinder wrote: »

I think this has todo with the original file size. I think modern DSLR images, most of which are at least 10Mpxls, will be as the poster described.

But if you start with a 3 Kb image, it will tolerate this kind of treatment much more poorly!

When I read this thread this morning in my iPad I could see no difference between any of the images, whether saved as 8, 10, or 12.

Now I see that after 8 the images get worse with resaving, not better.

Not sure how to react to this, but since I never resave a jpg, it is not a great deal of concern to me (I think ).

Most of my master file are actually jpg (after editing) and saved in IQ 10. For the last few yrs, I've been resaving to IQ 10 should I use my master file to re-tweak, and so far I've been happy with the quality as I seldom using the master to re-tweak more than 3 or 4 times.

But after this findings, I guess any further re-tweak I ought to resave in IQ8.

Technically its proven (at least viewing from the screen). Just have to do the last printing part to be conclusive. To some, its more a mind-set thing as there are still many people believing saving to the max using IQ 12.