Check out these image editor images:
JPG Loss Comparisson
Image by Ant Smith
This image shows the impact of saving in JPG format.
The central image was saved as JPG and this was compared with the original by using a photoshop difference blending mode and a threshold mask – at threshold 1. This shows all of the pixels that differ by a lujinance level of 1 or more between the original and the first generation JPG copy. Note, this is without editing the original. This is the result of just saving the file. This first comparrison is top left.
The second image down on the left hand side was made in the same way, except using photoshop's Save for Web instead of Save. The differences are a little more pronounced.
The third image down shows just how different the save and save for web versions are.
All of this is repeated on the right, but here the original image is compared with 4th generation JPGs to show the cumulative effects. By the 4th generation the losses are become really quite apparent, and you can see how the Save for Web version degrades much more.
All this shows the lossy nature of JPG saves, and how image information is lost just by saving – even if you don’t edit. This all means it is strongly advisable to only save to JPG as the last thing you to do an image – always return to a lossless format if you need to do more editing.
Also note, because your image editor works internally with true bitmaps you can save to JPG several times in one edit session without introducing more degradation, because each save is calculated from the internal bitmaps. The cumulative losses only kick-in when you close the file (throwing away the internal bitmaps) and re-open it in between saves.
Mars, Exposed! (NASA, Mars, 2009)
Image by NASA's Marshall Space Flight Center
Editor's note: NASA's Curiosity Rover is scheduled to land on the surface of Mars on the evening of Aug. 5/6, 2012. (Read more here: www.nasa.gov/mission_pages/msl/index.html). In honor of this historic event, here are some breathtaking stills of the Red Planet.
Image caption: Image of exposed rock laters on Mars, seen by the MRO Mars High Resolution Imaging Science Experiment in the Argyre Region.
Image credit: NASA
More about Curiosity and the Mars Science Laboratory:
www.nasa.gov/mission_pages/msl/index.html
View the "Mars Landscapes" photoset:
www.flickr.com/photos/nasamarshall/sets/72157630860188338/
View the "Mars Landscapes" video:
www.nasa.gov/multimedia/videogallery/index.html?media_id=...
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These official NASA photographs are being made available for publication by news organizations and/or for personal use printing by the subject(s) of the photographs. The photographs may not be used in materials, advertisements, products, or promotions that in any way suggest approval or endorsement by NASA. All Images used must be credited. For information on usage rights please visit: www.nasa.gov/audience/formedia/features/MP_Photo_Guidelin...
Possible Cyclic Bedding (NASA, Mars, 2009)
Image by NASA's Marshall Space Flight Center
Editor's note: NASA's Curiosity Rover is scheduled to land on the surface of Mars on the evening of Aug. 5/6, 2012. (Read more here: www.nasa.gov/mission_pages/msl/index.html). In honor of this historic event, here are some breathtaking stills of the Red Planet.
Image caption: Image of possible cyclic bedding on Mars, seen by the MRO Mars High Resolution Imaging Science Experiment near iArabia Terra.
Image credit: NASA
More about Curiosity and the Mars Science Laboratory:
www.nasa.gov/mission_pages/msl/index.html
View the "Mars Landscapes" photoset:
www.flickr.com/photos/nasamarshall/sets/72157630860188338/
View the "Mars Landscapes" video:
www.nasa.gov/multimedia/videogallery/index.html?media_id=...
_____________________________________________
These official NASA photographs are being made available for publication by news organizations and/or for personal use printing by the subject(s) of the photographs. The photographs may not be used in materials, advertisements, products, or promotions that in any way suggest approval or endorsement by NASA. All Images used must be credited. For information on usage rights please visit: www.nasa.gov/audience/formedia/features/MP_Photo_Guidelin...
