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Thread: Colour difference

  1. #1
    Ausphotography Addict Lplates's Avatar
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    Colour difference

    I was going to post a comp entry but the preview showed the image to be both darker and with a different colour to my original. I then started a post in the forum with the same image and when previewed it looked like it should.
    Is there any reason for this? I've certainly never noticed it before.
    Glenda


  2. #2
    Arch-Σigmoid Ausphotography Regular ameerat42's Avatar
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    Gee! Make it hard, Llps
    Let's start with: how many times have you tried this, and has it happened each time?

    Then, how do you save the images? What do you use to process, and when you save,
    what is the default color profile or space? (Not the same, but either will do.)

    It only seems odd to me that it should differ when displaying on the (presumably) same
    browser.
    Last edited by ameerat42; 16-09-2016 at 2:09pm.
    CC, Image editing OK.

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    Never happened before today Am and tried a few times. I am working in ProPhotoRGB on Ps.

    Think of me as giving us both something to think about and keep that old grey matter working. As soon as I read your post it made me think as I have changed how I resize web images recently. So I went back and resized the image in the 'save for web' option and tried it on the comp upload and it was fine. Tried how I have been resizing recently again uploaded in comp and preview showed horrible colours. Next I opened the jpeg then I changed the colour profile to sRGB then resized and tried uploading it and it worked fine.

    What I still don't get is why the colour only looked horrible when previewing the comp upload and looked exactly as it should when previewing the same image on a normal thread post

    Haven't taken many photos lately but my bird posts yesterday were resized using the image resize rather than save for web, I didn't change the colour profile and the colours in them look fine. Another
    Last edited by Lplates; 16-09-2016 at 4:08pm.

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    Arch-Σigmoid Ausphotography Regular ameerat42's Avatar
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    Perhaps you're using Photoshop.

    If you USUALLY do a Save for Web, then the color profile and space in there are properly set.
    If you only occasionally do a Save As..., then you may need to check your color profile.

    Try a Save As on some image that you haven't previously saved.
    Look in the COlor section near the bottom of the dialog box.
    In ICC Profile does it show anything other than sRGB and ticked?
    If so, just un-tick that.

    Of course, if you don't use Pshop. then look for the equivalents.

    At some stage, also consider changing the global settings for color management in your editor.
    (Will describe as needed.)

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    Maybe I didn't explain myself properly in my reply.

    I am using photoshop (Ps) and my colour settings is set for ProPhoto RGB.

    I've recently changed from 'save for web' to Save as jpeg, then image>resize to required size then post. Using this method the photographs appear okay in normal threads but horrible in the preview for the comp section.

    I think my dialogue box looks a bit different to yours
    Screen Shot 2016-09-16 at 5.44.55 pm.png

    The first image was saved as per the screen shot
    _DSC0812B.jpg

    The was saved with the embed profile unticked
    _DSC0812B unchecked.jpg

    This was saved as per screen shot but in photoshop I used edit>convert to profile>sRGB
    _DSC0812B convert profile.jpg

    I went into the comp section and tried uploading the first image of these three and when I got to the preview stage it looked like the second image.

    I have no idea why it appears differently when previewing in the comp section to how it appears in a normal thread on the forum

    Guess for comps I will just have to remember to convert to profile or use the save for web option.

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    Administrator ricktas's Avatar
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    Do not embed the ProPhoto colour profile in comp entries. Save them as sRBG. We strip EXIF on comp entries so that members names, or other identifying information does not appear on the EXIF (embedded in it) to maintain anonymity.

    Comp entries are stripped of EXIF so then the internet (not just AP) assumes they are sRGB.

    So ensure comp entries are saved as sRGB before uploading, and the colourspace shift will not occur.
    Last edited by ricktas; 16-09-2016 at 5:40pm.
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    Arch-Σigmoid Ausphotography Regular ameerat42's Avatar
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    Ta Rick. That is the key.

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    Thanks Rick, that explains it. It was confusing me that threads were fine.

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    Administrator ricktas's Avatar
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    Quote Originally Posted by Lplates View Post
    Thanks Rick, that explains it. It was confusing me that threads were fine.
    That depends also on the browser the viewer is using. Most 'modern' browsers are colourspace aware and if EXIF exists on a photo then they read the colourspace and will render it correctly. However if someone is using a browser that is not colourspace aware, or uploads a photo saved in something other than sRGB, that they have stripped EXIF from, the browser will not know what colourspace to use and default to sRGB, creating a similar issue to what you experience.

    Thankfully most browsers are colourspace aware and generally things appear as intended.

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    Ausphotography Regular John King's Avatar
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    Gidday LP

    If I may make a suggestion - don't use PPRGB colour space with any 8 bit files, specially not with compressed ones ( .jpg ... ). 8 bit files simply do not have enough colour numbers available to adequately map such a very wide colour gamut as PPRGB without posterisation.

    If I am editing a RAW file in PPRGB-16 and decide to save a copy as a jpeg, I save the 16 bit file, convert the profile to sRGB-16, downsample to sRGB-8, then save as a JPEG at 100% quality.
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  11. #11
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    Thanks John, but I shoot in raw 99% of the time and use ProPhoto 16 bit

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    Ausphotography Regular John King's Avatar
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    ^ so do I.

    However, I shoot RAW + LSF JPEG (and have the camera set for aRGB for the JPEG).

    For almost all web uploads, I use the OoC JPEG and run it through a PS action I recorded years ago. Among other tedious tasks, this converts the OoC JPEG to sRGB. When finished, it saves the output file into the folder I upload images from. Saves a lot of work, even just for one shot, let alone 50 ...

    BTW, I rarely crop images. I force myself to concentrate hard on the composition in camera. I impose this discipline on myself because composition of form and colour has historically always been the weakest part of my photography. This disciplined approach has helped me to dramatically improve over the years according to those who routinely look at my photos.

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    I'm with John.
    ProPhoto on jpg files is a wasted effort, not to mention the added complication of the issues discussed in this thread.

    And FWIW: the use of ProPhoto on a raw file is meaningless anyhow, the only real reason ProPhoto is an advantage is if you're converting to TIFF(or PSD or whatever high quality image format you prefer), or working on a TIFF derivative as an intermediary step in your editing then saving that tiff file for future reference or something like that.

    If you're keeping the raw file, then it's all pretty much a wasted effort for 99.9% of us.
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  14. #14
    It's all about the Light!
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    FYI All members... The comp system strips all EXIF data from entries. {EXIF is saved as text internally in the comp system for the mods to see, but that is all}

    So if you enter a comp in anything other than sRGB (default for display without EXIF) then it will render incorrectly.

    This is why the comp system tells you to use sRGB.

    YOU MUST USE sRGB FOR COMPS!
    regards, Kym Gallery Honest & Direct Constructive Critique Appreciated! ©
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    The only thing I've changed in PP recently is how I convert and resize my PSD files for the web. In the 'save for web' option I have found the file size is often inaccurate - very annoying when I had saved just under 400 to find it wouldn't upload because it was actually just over and I'd have to return to Ps and redo. It never presented any problems until I decided to enter a comp. Rick and Kym have explained the reasons so I will just have to add one quick step for comp entries in the future.

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