31 generations of JPEG's compared

31 Generations of JPEG’s compared

A test to show image degradation from 31 generations of JPEG exports in Adobe Lightroom. With each generation the previous exported image was imported to Lightroom then exported for a total of 31 import / export cycles. Presented here are the 1st generation vs the 31st generation image that originated as a 91mb TIFF scan. Testing was done with Lightroom 5

A bit strange arrangement, but it demonstrates how well hi resolution original outputs web size image after number of jpeg generations.

Old internet knowledge was that first generation is hi resolution, second is web size and later generations only degrade in quality while storage size may even grow and after eight generation image quality was concidered too low to publish.

Why the **** would you choose a near monochrome cyanotype image with almost no fine detail to 'demonstrate' JPEG losses?

And hasn't anyone that cares already done their own tests?

Why the **** would you choose a near monochrome cyanotype image with almost no fine detail to 'demonstrate' JPEG losses?

 

And hasn't anyone that cares already done their own tests?

I work from RAW, and all of my jpgs are generated from RAW. So I've never run any tests myself.

I work from RAW, and all of my jpgs are generated from RAW. So I've never run any tests myself.

You're obviously one of the people that care about image quality then Bob, but there are those who exclusively shoot JPEGs - I believe. And there are still people that blithely open those JPEGs, work on them and even more blithely save them as JPEGs again.... change their mind, open them, work on them some more, re-save them, etc.

Admittedly it would take a bit of patience and determination to repeat that process 31 times without noticing the degradation in quality.

3 or 4 iterations are usually enough to convince against using JPEGs for archival storage. That's apart from the fact that a single bit corruption can make JPEG file recovery near impossible.

Ideally you want to stick with the raw data and use JPEG as an iteration variant in sRGB for web/mobil devices where it is then useful. The cameras JPEG engine that processes the raw massively clips and compresses highlights. We often don't when editing the raw. This compression can clump midtones as much as 1 stop while compressing shadow details! People incorrectly state that raw has more highlight data but the fact is, the DR captured is an attribute of the capture system; it's all there in the raw but maybe not in a camera proceed JPEG. You can't edit what you didn't allow to be saved; color gamut or DR.

A raw capture that's 10 or 11 stops of dynamic range can be compressed to 7 stops from this JPEG processing which is a significant amount of data and tonal loss! So when we hear people state that a raw has more DR than a JPEG, it's due to the poor rendering or handling of the data to create that JPEG. The rendering of this data and the reduction of dynamic range is from the JPEG engine that isn't handling the DR data that does exists as well as we can from the raw! Another reason to capture and render the raw data, assuming you care about how the image is rendered!