Tutorial: Retaining RAW data

Discussion in 'Retouching and Post Processing' started by MiriamJ, Jun 22, 2007.

  1. We shoot RAW to get the most information available to us, but often we throw that information away prior to and in the editing process resulting in less detail and poor color. Here's some thoughts on editing with full information:

    File type:

    Set your RAW converter to convert to TIF rather than .jpg. A JPeg has less information than a TIF, first because there is a smaller bit depth, (less information per pixel). Also, even worse, a .jpg is a compressed file, which means that information is thrown away to save space. What this means in the end is posterization. I think of posterization as a lack of smooth transaction in detail.

    Here's an excellent, short tutorial that explains about posterization and also shows you what it looks like. http://www.cambridgeincolour.com/tutorials/posterization.htm

    While you're at it, set your RAW converter to 16-bit TIF, instead of 8-bit. Again, much more detail available resulting in a better edited photo.

    Color space:

    Another thing that helps is to use ProPhoto color space. A color space is the gamut, (the amount of colors available for your use). Unless you are using ProPhoto when you convert to TIF, you are using less colors when you are editing, which greatly affects the colors in the end.

    Check out this page: http://www.luminous-landscape.com/tutorials/prophoto-rgb.shtml , especially figure 3b, to see how many colors you are limited to when using another color space such as Adobe RGB.

    Additional information added 6/23/07: As Charles points out there can be posterization with too many colors. BetaRGB and processing in LAB color (image->mode->lab color) is better.

    However, if Beta RGB is not available, as Iliah points out in this exercise thread, you can use the ProPhoto color space, then temporarily assign, (not convert) a smaller gamut such as AdobeRGB. Another alternative is to go into your color settings and use a 20% to 30% desaturation setting on your monitor.https://www.nikoncafe.com/vforums/showthread.php?t=104110&highlight=prophoto Very interesting!


    Clipping:

    The other thing that helps is to be very careful in both your RAW converter and Photoshop to keep a close eye on the histograms to make sure none of your channels are clipped, losing valuable information. I think of a histogram as a display of my photo in graph form. This shows you what clipping looks like on a histogram, and will also give you more information on histograms. http://www.cambridgeincolour.com/tutorials/histograms1.htm Look around the middle of the page for a clipped histogram.

    Converting after editing:

    You will need some additional steps after you finish your editing in Photoshop. You won't want to finish as a TIF, the file's way too big and some viewers will not recognize it. Also, things like Internet Browsers, photoviewers, often don't recognize ProPhoto, and will display an off-color image.

    So, after the Photoshop editing is finished, first I rename and save the image as a full-sized, ProPhoto color space, 16-bit TIFF, because once you convert, you lose information that you will never be able to retrieve again.

    After this save, I resize the photo.

    Next, I make sure I'm working in RGB mode, (image pulldown->Mode->RGB color). Then I change my color space to sRGB (Edit->convert to profile->sRGB IECxxxxxxx), if I'm posting the photo to the internet or to my printer/paper type profile if I'm going to print. Next, I change my bit depth to 8-bit, so I'll be able to save as a .jpg. Image->mode->8-bits channel. Last, when I save the file, I save as a .jpg.

    Added 06/23/07. This I wasn't sure about: It just made sense to me, and I just now confirmed, it's best to convert to your intended color space and then to 8-bit.

    If you're printing, it makes sense to use a printer profile. Assuming your monitor is correctly calibrated, it corrects the photo so that information sent to the printer is correct. I use one downloaded from www.drycreekphoto.com for the printer at my local Costco. More information about color spaces and printer profiles can be found at: http://www.drycreekphoto.com/Learn/color_management.htm

    By the way, your output still will not be correct unless your monitor has been correctly calibrated. I'm using the inexpensive Huey that also resets my monitor according to the changing room lighting as I'm working.


    Hope this is helpful.

    This is just what I've picked up that has helped me. If anyone reading this finds any inaccuracies, I'd be grateful for the clarification. :)

    Added 6/23/07 Thanks, Charles for the help and Virginia for the suggestion.
     
    Last edited by a moderator: Mar 15, 2017
  2. cwilt

    cwilt

    Apr 24, 2005
    Denver, CO
    Large gamut color spaces such as Prophoto have their issues too. This has been discussed many times on here and that other place.
     
  3. Miriam, what a wonderful summary about the value of RAW images and how to use them effectively.

    I thought the information about histograms and clipping was excellent.

    The only thought I have in the converting and editing part is that sometimes, when editing, there are currently some issues with 16 bit images. Some of my PS plug-ins don't work with 16-bit Tiffs. I'm always at a quandary at this point, trying to decide whether to make a duplicate and create a "2nd master" tiff image with 8-bits for additional processing. I know this is a good idea, but sometimes, I cheat and just do the conversion.

    Thanks for putting this together.
    I'm sure many here will find it helpful.

    Virginia
    aka beaucamera

    BTW, you might consider adding something about color space and printing.
     
  4. Charles, thanks for the tip, I'll run over to the other place and see what I can learn.
     
  5. Thanks, Virginia!

    Yeah, I know what you mean about the 16-bit files with PS plugins. I use the 16-bit as much as I can and convert to 8-bit if I must. I wish all the plugins would use the 16-bit files.

    Good idea about the color space and printing. A definate area of confusion. I'll add that. Thanks for catching that.:smile:
     
  6. Thanks for doing this Miriam !! :biggrin:
     
  7. You're welcome, Mike! :smile:
     
  8. Charles, I've had some time to read and think about this. Could you check my reasoning and see if I understand?

    ProPhoto is a comparatively large gamut, so large that it's outside of what we can see on our monitor. Assigning a profile of a smaller gamut of colors, such as Adobe RGB doesn't change the photo at all, just the display. Assigning Adobe RGB displays the photo in the smaller gamut, so that we can see all the colors for editing purposes.

    I also understand another advantage to assigning a smaller gamut is increased luminosity.

    So, would a good workflow be to convert from RAW to TIF using the ProPhoto color space, assign the Adobe RGB color space, complete the editing, assign the ProPhoto color space, then convert to sRGB or your printer profile?
     
  9. cwilt

    cwilt

    Apr 24, 2005
    Denver, CO
    Not just beyond the monitors abillities but also beyond what the human eye can see. Along with some colors that don't exist. It takes a very high end monitor to cover the aRGB gamut. Most don't.


    When you say "assign" do you really mean assign, or do you mean convert? Different functions with different outcomes. When going from a larger space to a smaller one there is likely to be some error in the conversion. The bigger the difference in size the more the error could be. Color management is a very deep hole. :wink:

    Here is a link to some notes posted by Iliah. He has probably forgotten more about color than I will ever know. I personally process RAW to BetaRGB. Once in photoshop I do as much as possible in LAB. That includes softproofing.
     
    Last edited by a moderator: Mar 15, 2017

  10. what does LAB have to do with anything other than a different way to view color? As far as I know it didn't have anything to do with the color space... but I'm just wondering.
     
    Last edited by a moderator: Mar 15, 2017
  11. Robert

    Robert

    Jul 24, 2005
    Canada
    Thanks Mirium!! I've been reading and appreciate all the info you've put forward.:smile:
     
  12. Actually, I was careful to say "assign". My thinking is that by assigning, (not converting), you would be preserving the exact numbers of each pixel in the photo, but would have the advantage of working in a smaller color space. You could edit in a color space that you could actually see, then reassign the ProPhoto color space, again not making changes in the photo itself, but only the display. You would convert only after editing. As you say there is likely to be some error converting from a larger color space to a smaller one, so you would only do that at the very end, when you were saving for the intended use, for example, the internet or printing.

    Excellent! That'll be worth multiple reads to take it all in.

    I'm converting from RAW to ProPhoto because I'm pretty sure I remembered that Iliah suggested doing it that way, but I haven't been able to find a post or private message from him that said that, so I'm wondering if my memory is faulty.
     
    Last edited by a moderator: Mar 15, 2017
  13. cwilt

    cwilt

    Apr 24, 2005
    Denver, CO
    Did you see his drawing which shows LAB as the hub which all transforms pass through? Why add another conversion and take the chance of more errors. Its not just another way to view color. Its the separation of color and Luminance.
     
  14. cwilt

    cwilt

    Apr 24, 2005
    Denver, CO
    Now you risk banding.

    Both RAW convertors that Iliah has worked on uses BetaRGB space for output. Although, RPP does default to LAB.:smile:

    I did not mean to side track you. Just pointing something out.:smile:
     
  15. You're welcome, Robert. :smile: I hope you find it useful. As always, I'd be glad to help if I wasn't clear somewhere.
     
  16. Well, durn it! lol.

    Regarding this thread: https://www.nikoncafe.com/vforums/showthread.php?t=104110&highlight=prophoto

    Then Iliah wasn't suggesting that using temporarily assigning a smaller profile, (or changing the monitor settings) is a practical way to use ProPhoto?

    No sweat, you're making me use my gray cells. I think they were starting to atrophy. :eek::eek::eek: Thanks!:smile:
     
    Last edited by a moderator: Mar 15, 2017
  17. cwilt

    cwilt

    Apr 24, 2005
    Denver, CO
    I can not presume to speak for Iliah. For my dual monitor setup the main monitor is profiled for printing. White point around 85 and black point at 0.50 using native gamma. The secondary monitor is a standard profile that I use for web previews so that I can see what everyone else does.

    As I said, color management can be a deep hole. Few understand it fully. I like to think of color management as just a band aid fix. One that often doesn't stick.:wink:
     
  18. Oh, I know. I thought maybe you understood better what he was saying.

    Cool monitor setup.

    Epoxy on the band-aid? The link you gave us to Iliah's explanation is a great place to start. I think some of this stuff is actually starting to sink in.
     
  19. cwilt

    cwilt

    Apr 24, 2005
    Denver, CO
    I will quote something Iliah told me.....

     
  20. Charles, excellent!

    The white and black points is something I had learned to do on my own, because, like he suggests, I found I was blowing colors and highlights any time I tried an edit in Photoshop.

    This also helps explain why I'm so much happier with my edited photos when I convert to ProPhoto or BetaRGB over Adobe RGB, even though the conversions are less saturated.

    So, I'm not going to worry about what the converted picture looks like, as long as I finish up with something I like. Cool!:smile::smile::smile:
     
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