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Thread: Colour profiles

  1. #1
    Ausphotography Regular kaiser's Avatar
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    Colour profiles

    Hi everyone,

    Did a quick search but I am still a bit confused...

    Am PP pics to put on a DVD slideshow. The RAW (NEF) files are tagged as Adobe RGB and that is what I am working with in Capture NX2. When converting to jpeg should I changed the colour profile to sRGB if its going to be viewed on other people's LCD monitors or HDTVs?

    Also, in NX2, when given the option to change colour profile of a RAW image, there are several options given when you choose to convert profile, under a sub menu titled "Intent"

    these are: 1. Perceptual, 2. Saturation, 3. Colourmetric, 4. Absolute Colourmetric.

    Is there a particular option that I should be using? The default is perceptual.

    Thanks,

    matt.
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    Antipod jev's Avatar
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    Definitely convert into sRGB before exporting them yes. Rendering intent "perceptual" will result in a little softer looking images that are compressed in color if the source profile is bigger than sRGB, colorimetric just clips anything that doesn't fit the sRGB space. See here for the full story. It depends on what you want to emphasise, but usually perceptive is best when converting to TV's (they usually are too saturated anyway).
    Ciao, Joost

    All feedback is highly appreciated!

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    Thanks for that jev.
    So when converting the colour profile of a RAW file from Adobe RGB to sRGB during the jpeg conversion - I should be okay as long as I don't save that colour change to the RAW file. Ie. if I want to keep working with that RAW file in AdobeRGB later on?
    Cheers.

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    Antipod jev's Avatar
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    Yes, you should be okay with that workflow.

    Whether or not you could safely change the colorspace in NX2 depends on the converter. Since I don't use NX2 I cannot tell how it would affect the photo there but I think it's safe to assume that NX2 does not alter the actual RAW image but instead just adds information in a sidecar. In that case, you could safely work in sRGB in the NX2 software whilst still keeping the full color space. You could always try what happens using a copy of a RAW file ofcourse.

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    Thanks mate. In NX2 you can either "apply colour space" to an image or "convert to" colour space. The former option shows an immediate change to the image whilst the latter has no visual effect.
    I have NX2 defaulted with Adobe RGB workspace, I am able to convert to sRGB > save as jpeg - then revert to the original RAW file in AdobeRGB with no noticable losses.

    I'm still encountering issues when I upload images and view them here in Mozilla Firefox - they appear washed out with greyer blacks (if that makes sense) and a little desaturated. They were definately converted to sRGB and confirmed this when looking at the image properties. They look fine when I view them in NX2 or Preview on my desktop. I'm working off a glossy MacBook screen which doesn't help things at all. Makes me want a decent monitor even more.
    Thanks for the advice.

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    A royal pain in the bum! arthurking83's Avatar
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    Quote Originally Posted by jev View Post
    ....Since I don't use NX2 I cannot tell how it would affect the photo there but I think it's safe to assume that NX2 does not alter the actual RAW image but instead just adds information in a sidecar. In that case, you could safely work in sRGB in the NX2 software whilst still keeping the full color space. You could always try what happens using a copy of a RAW file ofcourse.
    that's how NX works. Regardless of what colour space you use for the RAW, it's convertible to any/either without any loss of colour.

    It's only when you create TIFF's and JPG's, that the colour space then may become an issue, mainly when you want high quality prints form pro labs or some such service.

    ** Annoyances! **
    In View NX you can set an option to convert jpgs to sRGB only, whilst maintaining adobeRGB for the NEF if you wish, but you don't get that flexibility in CaptureNX, which is supposed to be the fully featured image editor!?
    Problem is that you can't use ViewNX to convert NEF's that have been edited with CaptureNX!

    One day Nikon will fully realise all of the little incompetencies of their software, and find a company that knows how to create software properly!
    It's not really an issue as such, just annoying in some ways, and most certainly avoidable as the two softwares share code!


    ** NOTE!! **
    In CaptureNX when you're changing preferences in that colour management applet, make sure if you want to change the colour space that you tick the small box under the option to do so, where it says use this instead of embedded profile
    . If that's not box is not ticked, and you set it to convert your adobesRGB's to sRGB, they remain as adobeRGB even though you think they are being converted!
    (guess who that happened too! )
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    Antipod jev's Avatar
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    Quote Originally Posted by kaiser View Post
    In NX2 you can either "apply colour space" to an image or "convert to" colour space. The former option shows an immediate change to the image whilst the latter has no visual effect.
    Always convert, never assign. You want the colors to look the same (where possible) and that means the pixel values must be recalculated. Compare it to the speedometer in a car: in the civilized world, the speed shown on the speedometer is in km/h. In the USA, they still show miles/hr (mph). If you want to convert the speed information from km/h into mph, you need to divide the numbers by 1.6 (for convenience, in reality it's a bit more I think). That is what happens if you convert color spaces. If you just assign a colorspace, you'ld take the reading from the km/h speedometer and interprete that as mph - you'ld go a whole lot faster. In colorspace terms: assigning would keep the numbers but the colors look differently.

    I'm still encountering issues when I upload images and view them here in Mozilla Firefox - they appear washed out with greyer blacks (if that makes sense) and a little desaturated.
    That is weird. If you post an example (same image, once without conversion [thus, in AdobeRGB] and one with conversion [in sRGB]) we can have a look.

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    Quote Originally Posted by jev View Post
    Always convert, never assign. You want the colors to look the same (where possible) and that means the pixel values must be recalculated. Compare it to the speedometer in a car: in the civilized world, the speed shown on the speedometer is in km/h. In the USA, they still show miles/hr (mph). If you want to convert the speed information from km/h into mph, you need to divide the numbers by 1.6 (for convenience, in reality it's a bit more I think). That is what happens if you convert color spaces. If you just assign a colorspace, you'ld take the reading from the km/h speedometer and interprete that as mph - you'ld go a whole lot faster. In colorspace terms: assigning would keep the numbers but the colors look differently.
    That has cleared things up for me - thanks for explaining it in layman's terms I will post two examples of what's happening with my photos: first in Adobe RGB, second converted to sRGB.

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    Quote Originally Posted by arthurking83 View Post



    ** NOTE!! **
    In CaptureNX when you're changing preferences in that colour management applet, make sure if you want to change the colour space that you tick the small box under the option to do so, where it says use this instead of embedded profile
    . If that's not box is not ticked, and you set it to convert your adobesRGB's to sRGB, they remain as adobeRGB even though you think they are being converted!
    (guess who that happened too! )
    Box is ticked, thanks

  10. #10
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    aRGB, then sRGB underneath. What are you seeing? Both of these images look near identical on my screen in NX2.- but still both look a little washed out compared to viewing them on anything but the web.
    (I have tried this with the box in the colour managment applet of NX2 ticked and unticked).
    Attached Images Attached Images
    Last edited by kaiser; 10-06-2009 at 8:57pm.

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    Antipod jev's Avatar
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    Quote Originally Posted by kaiser View Post
    What are you seeing?
    Both are identical on my browserscreen (Firefox with color management switched ON). You can check if your browser is color managed here. If you have a slightly older Firefox browser, (3.0.5 or so) you may have to switch color management on manually:
    • Type about:config in the address bar.
    • Click the "I'll be careful" button.
    • Type color_management in the filter field.
    • Double click the gfx.color_management.enabled field to set it to true.
    • Restart Firefox

    Here's a good check: make a screenshot from the images in your browser. Now, cut out both images and put them on top of each other in seperate layers in photoshop, gimp or whatever editor you use. Now, add a mask on the top layer. If you draw in that mask, you make parts of the top image disappear - you should see a difference in color if there's a colorspace mismatch somewhere. In this case, it's not visible - meaning the color spaces are correct for the given images.

    Repeat using a non-color managed browser (Internet Explorer for example) and see the difference.

  12. #12
    Antipod jev's Avatar
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    I've done that experiment for you, just to show what's happening. The screendumps from FireFox showed no difference but the screendumps from Internet Explorer show the image below. Notice the difference in color in the yellow/orange bricks of the buildings on the right hand side? That is the difference due to color space mismatches... it should be okay if you use a color managed browser.
    Attached Images Attached Images

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    A royal pain in the bum! arthurking83's Avatar
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    they may tend to do that, sometimes mine do a little, but I don;t fret over them so much.

    As for any differences between each image.

    In firefox 3.x you can enable it to use colour management. So that ARGB and sRGB images look the same. Generally aRGB images will have a flat washed out look.
    Both images posted look identical to me, as I have enabled colour management(in FF)

    Checked the exif and both are saved as you said, so you got colour management figured out correctly!

    Capture NX is the best viewer for viewing NEF images. It could look nicer on your PC because of that??? Are you looking at the NEF or the jpg in Capture?

    I just had a peek at the jpg in Capture and it looks basically the same(as the uploaded images).

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    Ausphotography Regular
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    Woot! I have Firefox v3.0.10 on Mac but colour management wasn't tuned on by default. Changed it manually like you said Jev and now everything is sweet Thanks heaps.

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