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Thread: Jpeg Compression

  1. #1
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    Default Jpeg Compression

    I'm starting to suffer a number of rejections for Jpeg Compression, which is unusual as normally anything that I'm confident of sails through screening. I earn money from sports photography, use professional kit and have over a thousand images on the site so I like to think I know what I'm doing.

    However, jpeg compression is becoming a problem. This latest example was rejected for it as well as bad processing.

    https://www.jetphotos.com/viewqueued_b.php?id=6947641

    I genuinely don't see anything wrong with the image. I was going to appeal but thought I'd try posting here instead.

    My workflow is to shoot in raw, edit the image, and save it as a TIFF file. Editing is to crop, center, clone out dust spots and sometimes clone out traces of a vignette as I shoot with a fullframe camera and vignetting happens quite often. The last task before saving the tiff is to adjust the levels so that the exposure will be acceptable to screeners.

    The saved TIFF file is then used as a master to create two jpegs. One is the final image which I keep with all my other aircraft images. The second is the one uploaded to Jetphotos.

    To produce a jpeg for Jetphotos I resize the Tiff to 1200 pixels wide, sometimes recrop it to 16x9 to remove sky and then apply sharpening.

    At this point I equalize the image to check that no flaws have appeared. If none have, them I save the edited TIFF file as a jpeg. (Quality 12, baseline standard). All done in the current version of photoshop.

    The quality of the new jpeg file is never as good as the TIFF was but it usually passes screening. However, I'm finding that more and more are getting rejected for compression.

    What should I be doing differently?

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    JetPhotos.Net Crew LX-A343's Avatar
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    Quote Originally Posted by snddim01 View Post
    I'm starting to suffer a number of rejections for Jpeg Compression, which is unusual as normally anything that I'm confident of sails through screening. I earn money from sports photography, use professional kit and have over a thousand images on the site so I like to think I know what I'm doing.

    However, jpeg compression is becoming a problem. This latest example was rejected for it as well as bad processing.

    https://www.jetphotos.com/viewqueued_b.php?id=6947641

    I genuinely don't see anything wrong with the image. I was going to appeal but thought I'd try posting here instead.

    My workflow is to shoot in raw, edit the image, and save it as a TIFF file. Editing is to crop, center, clone out dust spots and sometimes clone out traces of a vignette as I shoot with a fullframe camera and vignetting happens quite often. The last task before saving the tiff is to adjust the levels so that the exposure will be acceptable to screeners.

    The saved TIFF file is then used as a master to create two jpegs. One is the final image which I keep with all my other aircraft images. The second is the one uploaded to Jetphotos.

    To produce a jpeg for Jetphotos I resize the Tiff to 1200 pixels wide, sometimes recrop it to 16x9 to remove sky and then apply sharpening.

    At this point I equalize the image to check that no flaws have appeared. If none have, them I save the edited TIFF file as a jpeg. (Quality 12, baseline standard). All done in the current version of photoshop.

    The quality of the new jpeg file is never as good as the TIFF was but it usually passes screening. However, I'm finding that more and more are getting rejected for compression.

    What should I be doing differently?
    Your rejected photo shows bandings in the sky caused by JPG compression. Contributing factors can also be some sort of noise reducing and of course saving with JPG settings not set to best quality.

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    Useful info here: https://forums.jetphotos.com/showthr...P-versus-PS-CC

    As before I am intrigued by the possibility that a full frame sensor at low ISO and an image reduced to a fairly small size (1200 wide) may have produced a sky so free of noise as to cause JPEG banding.

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    Quote Originally Posted by Quebec Golf View Post
    Useful info here: https://forums.jetphotos.com/showthr...P-versus-PS-CC

    As before I am intrigued by the possibility that a full frame sensor at low ISO and an image reduced to a fairly small size (1200 wide) may have produced a sky so free of noise as to cause JPEG banding.
    That picture was taken with a Nikon D4S, which is a fullframe, professional sports camera. I doubt it would have made any difference had I used my D5 which is the newer version and the current Nikon flagship model.

    The point here, which I think LX-A343 may have missed as I maybe didn't make it clear, is that neither the camera nor the editing produced banding. The TIFF file from which the rejected image was created is flawless, even when it's reduced to 1200 pixels. It's only when you convert the tif to jpeg that banding appears. To answer LX-A343s points, images are always saved at best quality and you don't need noise reduction when you're shooting on a bright sunny day in the middle of summer at ISO125)

    I can only think of two possibilities.

    1) There's a better method of converting tiffs to jpeg which I'm ignorant of and I'm hoping someone can enlighten me on.

    2) The current version of adobe photoshop CC is incapable of producing smooth sky jpegs to the standard that Jetphotos requires.

    Any ideas?


    EDITED TO ADD - Disregard the photo attached. I tried to append the tiff file, which the forum wouldn't allow me to do. I then tested to see if I could add a jpeg, which evidently worked. And now the forum won't allow me to delete the jpeg!

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    Quote Originally Posted by snddim01 View Post
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    The point here, which I think LX-A343 may have missed as I maybe didn't make it clear, is that neither the camera nor the editing produced banding. The TIFF file from which the rejected image was created is flawless, even when it's reduced to 1200 pixels. It's only when you convert the tif to jpeg that banding appears...
    TIFF are uncompressed and could have 16 bit colour, while JPEG is 8 bit compressed. The conversion to jpeg is exactly the point in the process when banding or blotching will appear. I've never seen compression artefacts in my TIFFs.

    Quote Originally Posted by snddim01 View Post
    2) The current version of adobe photoshop CC is incapable of producing smooth sky jpegs to the standard that Jetphotos requires.
    You are having the opposite problem, the image had such a smooth sky that the process of converting it to jpeg resulted in banding (discrete colour steps in lines running perpendicular to the general direction of the colour gradient). If there was more noise in the sky before the conversion to jpeg there would be no banding/blotching.

    The above is based on the many jpeg compression rejections to my name... I used to obsess over the skies in my pictures and was trying to get them nice and smooth but that just resulted in the problems above. Without any comments on my rejections it was a while until things clicked for me (I stopped messing with the sky and no more jpeg compression rejections) so at least you're ahead of the curve that way.

    Regards,

    Alex

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    How are you saving/exporting your JPEG? I would encourage you to use the "Save for Web (Legacy)" under the Export menu to get the maximum quality out of your JPEG. I was having some issues with compression a while back and it was a result of my JPEG not exporting at it's max quality. Using that save format solved that issue for me.

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    I made a quick tweak to the image in question. Ian, if you'd like, throw the attached version into the JP equalizer and see if there is still banding. At least the area between the wing and the fin seems pretty compression-free to me now.
    Click image for larger version. 

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    Quote Originally Posted by Quebec Golf View Post
    I made a quick tweak to the image in question. Ian, if you'd like, throw the attached version into the JP equalizer and see if there is still banding. At least the area between the wing and the fin seems pretty compression-free to me now.
    Click image for larger version. 

Name:	78221_1542821266_spread6.jpg 
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ID:	20026Click image for larger version. 

Name:	78221_1542821266_spread6_equalized.jpg 
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    Whatever you've done has certainly improved the image QG. I'm quite surprised at that as I would have thought that re-editing a saved jpeg would only make the quality worse.

    What process did you use?

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    Quote Originally Posted by kevincargo View Post
    How are you saving/exporting your JPEG? I would encourage you to use the "Save for Web (Legacy)" under the Export menu to get the maximum quality out of your JPEG. I was having some issues with compression a while back and it was a result of my JPEG not exporting at it's max quality. Using that save format solved that issue for me.
    I just use the normal "save as" with quality set to the maximum 12. I tried your suggestion and it does seem to reduce the banding. Thanks.


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    As I have mentioned elsewhere, if there is a very smooth/gradient transition in the sky that's causing that blocky compressed-like look, try saving as a 16-bit tiff, doing all of your editing and then re-sizing, and then as a final step convert it to an 8-bit jpeg. This will significantly reduce the appearance of banding in clear blue skies.

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    I'm quite surprised at that as I would have thought that re-editing a saved jpeg would only make the quality worse.
    Yeah I generally consider it bad practice but I have re-opened my finished jpegs before for small last minute tweaks and re-exported without any noticeable quality reduction.

    What process did you use?
    I used the Spread function in GIMP on the sky.

    I don't know what the PS name for this is, but it's the function that runs an X by X pixel sized gate (X defined by user) over the image area and shuffles the pixels within the gate at random. I started with a few passes of 10 by 10 but that wasn't making enough of a difference so I made a few more at 15 by 15. In essence, enough pixels got moved from one band to another to break up the appearance of discrete bands. Trading off noise for visible compression.

    This is very much a band aid solution and probably not a welcome addition to anyone's workflow, but it is something to keep in the toolkit.

    Ultimately, based on lessons from Brian's thread, I would recommend to double check that the RAW converter you're using doesn't have some noise reduction function turned on by default.

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    Quote Originally Posted by Quebec Golf View Post

    Ultimately, based on lessons from Brian's thread, I would recommend to double check that the RAW converter you're using doesn't have some noise reduction function turned on by default.
    It would appear that Adobe Camera Raw DOES have NR turned on by default. Between switching that off and using dlowa's pointer about 16-bit tiffs it appears to have removed the banding. I'm not sure which step was the crucial one; I'll do more experimentation at a later date.

    I also discovered an alternative solution, which is to mask off the aircraft and add a very small amount of noise to the sky. It degrades the visual appearance of the picture, but changing the opacity of the additional noise layer to around 10% brings it back up. This seems to be enough to prevent banding forming when you convert to jpeg.


    Thanks for your input and to the JP crew who've contributed to the thread.

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    JetPhotos.Net Crew LX-A343's Avatar
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    Quote Originally Posted by snddim01 View Post
    It would appear that Adobe Camera Raw DOES have NR turned on by default. Between switching that off and using dlowa's pointer about 16-bit tiffs it appears to have removed the banding. I'm not sure which step was the crucial one; I'll do more experimentation at a later date.

    I also discovered an alternative solution, which is to mask off the aircraft and add a very small amount of noise to the sky. It degrades the visual appearance of the picture, but changing the opacity of the additional noise layer to around 10% brings it back up. This seems to be enough to prevent banding forming when you convert to jpeg.


    Thanks for your input and to the JP crew who've contributed to the thread.
    I wouldn't start such post processing steps as masking the sky and so on. Stick with conventional editing. Many photographers bring up superb quality like that with the same or similar camera/software combo.

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