Saving as Jpeg

Out of interest we conducted tests through Adobe Photoshop on a couple of images, making successive Jpeg saves at particular quality settings to see how the image would degrade over a series of "Save As" thus overwriting the image each time. The results are unremarkable with very little change to the images even after 40 successive saves at low quality setting.
It was surpriseing the effect was not stronger given the hysteria that surrounds Jpegs, but then we were all led to believe half the world population would be killed by bird-flu the other year and that Kodak had 'stopped making film' - perhaps the same journalists are responsible? Despite this we would still advise that if you are working on an image over a number of sessions then save the images in non-lossy format, such as Photoshop or Tiff, until you're finished then save as Jpeg if you wish.

Reference notes
Best quality = 10/10 or 12/12 in Photoshop ( depending if the computer is PC or Mac )
Low quality = 4/10 in Photoshop
Lowest quality = 1/10 in Photoshop
Cropped images 300 pixels width, RGB, 8-bit, no Colour profile added

The x100 saves might not be exact...it was getting kinda boring but we hope you find the results interesting!


The original train image is not completely sharp and shows a little camera movement. The final 'small image enlarged too much' illustrates what can happen to detail is a small image is printed too large. Typically we have seen this with camera-phones ( that have small sensors and poor quality lenses ) or an image that has been cropped down to a small size.

Alistair Baird
Director
The Darkroom UK Ltd
2013

girl portrait
girl detail

Original image 25Mb (3.8Mb stored size)

Straight crop from original

girl detail 2

girl detail 2

Best quality x5 saves

Best quality x20 saves

girl detail 3
girl detail 4

Low quality x5 saves

Low quality x20 saves

girl detail 5
girl detail 6

Low quality x40 saves

Lowest quality x100 saves

train
train detail

Original image 11Mb (2.3Mb stored size)

Straight crop from original

train detail 2
train detail 2

Best quality x5 saves

Best quality x20 saves

train detail 3
train detail 4

Low quality x5 saves

Low quality x20 saves

train detail 5
train detail 6

Low quality x40 saves

Small image enlarged too much