Margulis LAB Color Book - Reading group

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  • jfriendjfriend Scripting dude-volunteer Posts: 24,828Registered Users Major grins
    edited September 26, 2006
    maggieddd wrote:
    OK thanks. I wasn't sure what to think of the final histogram. Why would photoshop change scale on the histogram?
    The image definitely looks better, at least in my opinion.
    It probably changes the scale to try to accomodate the spike of pixels at the far left end of the final histogram and that made everything else look lower. The area under the histogram is constant at the same scale so when the area suddenly looks a lot smaller, Photoshop must have changed the scale.
    --John
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  • ruttrutt Cave canem! Posts: 6,511Registered Users Major grins
    edited September 26, 2006
    maggieddd wrote:
    another question. How can I learn how to use Blend if setting?

    See chapters 7 and 8 especially. My summary of chapter 8 might help.
    If not now, when?
  • maggiedddmaggieddd Beginner grinner Posts: 5Registered Users Beginner grinner
    edited September 27, 2006
    rutt wrote:
    See chapters 7 and 8 especially. My summary of chapter 8 might help.
    thank you. chapter 8 was very helpful.
  • MyerMyer Big grins Posts: 25Registered Users Big grins
    edited October 27, 2006
    Blend If - maggieddd
    maggieddd wrote:
    another question. How can I learn how to use Blend if setting?

    I've been slowly going through the book and wanted to get through all of this thread before jumping in. I'm becoming an LAB convert. Must be some sort of religion.

    I read no more than 2-4 pages a day and many are re-read and re-read. I'm somewhere around page 225.

    It took me a while to figure out Blend if. While I'm still not comfortable thinking/applying it, this is the way it works.

    First, you can select either the L, a or b channels to apply.

    Picture two layers; one above the other. The top layer is all you can see.

    You'll notice that the end points of the upper and lower sliders are spread to their maximum width.

    By pulling in either end point of the top slider towards the other side, you allow the bottom to peek through anywhere outside the two points on the sliders.

    Splitting an end point merely makes the transition from top layer to bottom layer smoother.

    Now, moving one or more of the end points of the lower slider works differently. When you move an end point of the bottom slider, you force anything not between the end points of the bottom to take precedence over the top layer.

    Now, an example. If you have two layers. On the top layer you have a green letter "T" and a magenta letter "T". On the bottom layer use the same colors but the letter "B" in both colors. Top letter directly over bottom letters.

    Call up the Layers Options (double click the layer). Select channel "a" (Green/Magenta).
    You should see to letters "T" (green and magenta).

    If you slide the top left hand end point to the middle, you should exclude the top green color and the green "B" should show through (you excluded anything outside the top end points. Now slide that end point back to the left end. You should see both letters "T".

    Slide the bottom left slider to the middle. Now, you should see a green "B" and megenta "T" (you forced the bottom green letter to show through by forcing anything outside the two end points to take precedence).

    The top slider is used to allow the bottom to show through outside the end points and the bottom slider forces the bottom to show through outside the end points. To me that sounds like reverse thinking.

    Whew!!! I think I need something to drink.
  • webwizardwebwizard Big grins Posts: 73Registered Users Big grins
    edited November 6, 2006
    I'm blown away. I just ordered the book after discovering its existence in anothewr thread about blown out sky fixes. Today, I discovered this thread. What a great resource! Thanks all of you who contributed to this effort.
  • asamuelasamuel sleazy grins Posts: 451Registered Users Major grins
    edited November 17, 2006
    I am bookless, so forgive my ignorance I try to get my finger in with the summaries.

    Does everyone always have to flatten their images before moving on to RGB again? To me this seems like a disadvantage? No?
    where's the cheese at?

    http://www.samuelbedford.com
  • cbcortezcbcortez Big grins Posts: 11Registered Users Big grins
    edited December 6, 2006
    converting to B&W
    hi guys, i have the book. can i ask a simple question. In chapter 6, Dan outlines a summary on how he created his B&W version of the buildings. This is where he apply imaged to the red channel and then made the green channel a bit lighter and then he said it converts to the b&w version.

    when he said it converts, what does he actually mean? what do you do to convert? do i just go to image -> grayscale?

    thanks
  • cbcortezcbcortez Big grins Posts: 11Registered Users Big grins
    edited December 7, 2006
    no one has any ideas regarding my question above?

    thanks.
  • ruttrutt Cave canem! Posts: 6,511Registered Users Major grins
    edited December 7, 2006
    cbcortez wrote:
    no one has any ideas regarding my question above?

    thanks.

    Yes, he just does Image->Mode->Grayscale
    If not now, when?
  • ginger_55ginger_55 Crazy Creek Babe Posts: 8,416Registered Users Major grins
    edited December 7, 2006
    Laughing.gif, it is those every day words used in a new context that can really confuse a person.

    Glad to have read someone else with problems. I think my biggest problem in this stuff is learning the vocabulary. If I had it all down, I could zip thru a book or a tutorial.

    ginger
    After all is said and done, it is the sweet tea.
  • cbcortezcbcortez Big grins Posts: 11Registered Users Big grins
    edited December 7, 2006
    thanks so much for the answer :)

    Ive gone back to chapter one....Laughing.gif.
  • I SimoniusI Simonius WeatherSealedPhotographer Posts: 1,034Registered Users Major grins
    edited January 12, 2007
    Late to the `party
    Had borrowed the book fro te library but decided to get my own copy.

    Late to the aprtty but hope I can still join inthumb.gif
    Veni-Vidi-Snappii
    ...pics..
  • jfriendjfriend Scripting dude-volunteer Posts: 24,828Registered Users Major grins
    edited January 12, 2007
    A perfect LAB example...
    If anyone wants a classic example of an image begging for a LAB retouch, go check out this thread. The image isn't mine or I'd post it here, though I offered a classic LAB retouch on it in the thread.

    Grab the original from that thread and try it yourself. You only need to know chapter 1 of Dan's LAB book to do really nice things to punch up this image.

    The image starts out with low contrast and pretty dull colors, exactly what LAB is really good at punching up.
    --John
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  • QuitaritaQuitarita Loving Life Posts: 126Registered Users Major grins
    edited January 14, 2007
    Simon King wrote:
    Had borrowed the book fro te library but decided to get my own copy.

    Late to the aprtty but hope I can still join inthumb.gif

    Me too! I just read the first 2 chapters and my head is spinning. :) Just practicing and trying to get the hang of it. How are you doing?
  • QuitaritaQuitarita Loving Life Posts: 126Registered Users Major grins
    edited January 14, 2007
    jfriend wrote:
    If anyone wants a classic example of an image begging for a LAB retouch, go check out this thread. The image isn't mine or I'd post it here, though I offered a classic LAB retouch on it in the thread.

    Grab the original from that thread and try it yourself. You only need to know chapter 1 of Dan's LAB book to do really nice things to punch up this image.

    The image starts out with low contrast and pretty dull colors, exactly what LAB is really good at punching up.

    Hi John,

    I'm playing around with this image and also saw your take on this image in that thread you posted above. My colors are not as bright as yours. I was wondering by how much you brought in your A & B channels. Did you do it symetrically? I'd post my take here but I don't think that is a kosher thing to do since it is not my image, right? I brought them in by 10, then 15 then 20.

    Gracias,
  • jfriendjfriend Scripting dude-volunteer Posts: 24,828Registered Users Major grins
    edited January 14, 2007
    LAB questions
    Quitarita wrote:
    Hi John,

    I'm playing around with this image and also saw your take on this image in that thread you posted above. My colors are not as bright as yours. I was wondering by how much you brought in your A & B channels. Did you do it symetrically? I'd post my take here but I don't think that is a kosher thing to do since it is not my image, right? I brought them in by 10, then 15 then 20.

    Gracias,

    I brought them in quite a bit on that image, more than I usually do because of the character of the image. I don't remember exactly, but I suspect it was probably around 30% on each end, perhaps even more. You just have to use your own eyes to judge how far to go. What you need to avoid is unrealistic colors that either look like an artificial color or look too brilliant to fit in the scene. I usually start with 20 in on each end and then back off if that creates something unrealistic or go more if that's not enough.

    For images that do not have a color cast and you want to keep them that way, you will want to keep the middle of the curve fixed in the middle because that keeps neutral things neutral. The easiest way to do that is to just bring the two ends in evenly and that's what I did on that image.

    The reason this image is so perfect for LAB is that the colors in the original are very dull and there are no bright colors anywhere in the image. If you look at the histograms for the A and B channels in LAB mode, you can see how all the pixels are concentrated right near the middle of the range. The symmetrically steep A and B curves just spread those colors out across a wider color range. When you combine this color enhancement with a bit more contrast on the L-channel, you can make a startling difference.

    A more common case than this image is that there are some bright colors and some dull colors in the image. In that case, it's a little more difficult to keep from overdoing the bright colors while still enhancing the dull ones, while still keeping everything realistic. That typically requires some more than symmetric curves and is the subject of many of the more advanced chapters in Dan's LAB book. I mentioned this image because the simple techiques work so well on it.

    I think you're probably right that we shouldn't post derivatives of that image here without the author's permission. In my experience non-pros are usually pretty good about granting permission for this type of educational use when asked if you ever want to do that.
    --John
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  • QuitaritaQuitarita Loving Life Posts: 126Registered Users Major grins
    edited January 14, 2007
    jfriend wrote:
    I brought them in quite a bit on that image, more than I usually do because of the character of the image. I don't remember exactly, but I suspect it was probably around 30% on each end, perhaps even more. You just have to use your own eyes to judge how far to go. What you need to avoid is unrealistic colors that either look like an artificial color or look too brilliant to fit in the scene. I usually start with 20 in on each end and then back off if that creates something unrealistic or go more if that's not enough.

    For images that do not have a color cast and you want to keep them that way, you will want to keep the middle of the curve fixed in the middle because that keeps neutral things neutral. The easiest way to do that is to just bring the two ends in evenly and that's what I did on that image.
    ...

    Hi,

    Ok - I increase the steepness and it worked better. I guess I thought I was going too far but in reality I wasn't going far enough. So much to learn...

    Thanks for the help!
  • Duffy PrattDuffy Pratt Major grins Posts: 260Registered Users Major grins
    edited January 14, 2007
    Try going overboard on the A and B curves, way beyond what you think would be any good. Then dial it back using the opacity slider for the layer. This is a simple way to get a feel for how far you can go. Dan says that he is using this technique more and more in his actual work.

    Duffy
  • QuitaritaQuitarita Loving Life Posts: 126Registered Users Major grins
    edited January 14, 2007
    Try going overboard on the A and B curves, way beyond what you think would be any good. Then dial it back using the opacity slider for the layer. This is a simple way to get a feel for how far you can go. Dan says that he is using this technique more and more in his actual work.

    Duffy

    Cool! I hadn't thought of that. I'm going to try that from now on.

    Gracias,
  • MyerMyer Big grins Posts: 25Registered Users Big grins
    edited July 5, 2007
    Is Anybody Still Here
    I'm not sure anybody is still here but I'll go ahead anyway.

    Following reading the LAB canyon book, LAB has become my colorspace of choice for my standard corrections.

    My regular approach is to:

    Go into LAB

    Steepen appropriate portion of L if there is not already a great deal of contrast.

    Steepen A and B in the range of 10-15% (I find more usually results in over-saturated colors)

    Select the L channel and:
    Highlight/Shadows to bring back area that are very dark and reduce the highs. I find that reducing the highs is the most important part as it remoze haze and glare and add crispness to the end result.

    Add some sharpenning to the L channel.
    = = = = = =
    I now place a high degree of importance on the Highlight portion and am considering moving this to the first step.
    - - - - - - -
    Any comments and experiences would be much appreciated.
  • Manfr3dManfr3d Likes it bokehlicious! Posts: 2,008Registered Users Major grins
    edited August 30, 2007
    I just tried the LAB method and it works very well.
    But how can I export an image to say sRGB for the Web?
    When I try to do it all the color glory gets washed away.
    What am I doing wrong?
    “To consult the rules of composition before making a picture is a little like consulting the law of gravitation before going for a walk.”
    ― Edward Weston
  • GJMPhotoGJMPhoto Gary Posts: 372Registered Users Major grins
    edited August 30, 2007
    Convert or Assign?
    Manfr3d wrote:
    I just tried the LAB method and it works very well.
    But how can I export an image to say sRGB for the Web?
    When I try to do it all the color glory gets washed away.
    What am I doing wrong?

    Are you using Convert to Color Space or Assign Color Space????
  • Manfr3dManfr3d Likes it bokehlicious! Posts: 2,008Registered Users Major grins
    edited August 30, 2007
    I simply saved as jpg then tried to select sRGB colorspace
    (like LAB via menu). How can I convert to a colorspace like
    you mention?
    “To consult the rules of composition before making a picture is a little like consulting the law of gravitation before going for a walk.”
    ― Edward Weston
  • pathfinderpathfinder Drive By Digital Shooter western IndianaPosts: 14,325Super Moderators moderator
    edited August 30, 2007
    When you have an image in the LAB color space, you need to go to Image>Mode>RGB.

    Next, unless your working space is sRGB, you need to go to Edit>Convert to Profile> sRGB.

    Then you can save your image that is destined for the web.
    Pathfinder - www.pathfinder.smugmug.com

    Moderator of the Technique Forum and Finishing School on Dgrin
  • Manfr3dManfr3d Likes it bokehlicious! Posts: 2,008Registered Users Major grins
    edited August 31, 2007
    pathfinder wrote:
    When you have an image in the LAB color space, you need to go to Image>Mode>RGB.

    Next, unless your working space is sRGB, you need to go to Edit>Convert to Profile> sRGB.

    Then you can save your image that is destined for the web.

    Now it works. Thank you very much! thumb.gif
    “To consult the rules of composition before making a picture is a little like consulting the law of gravitation before going for a walk.”
    ― Edward Weston
  • LAB.ratLAB.rat Big grins Posts: 65Registered Users Big grins
    edited August 31, 2007
    Myer wrote:
    I now place a high degree of importance on the Highlight portion and am considering moving this to the first step.
    Which would be good, because I believe Dan said it works better in RGB (the highlight part only).
  • GJMPhotoGJMPhoto Gary Posts: 372Registered Users Major grins
    edited September 1, 2007
    Manfr3d wrote:
    Beer is proof that God loves us and wants us to be happy. - Benjamin Franklin
    Did Franklin REALLY say that? Is there no end to how smart that man was???
  • IcewayIceway Yatoo Posts: 7Registered Users Beginner grinner
    edited June 11, 2008
    I'm in!
    help each other
  • Manfr3dManfr3d Likes it bokehlicious! Posts: 2,008Registered Users Major grins
    edited June 11, 2008
    GJMPhoto wrote:
    Did Franklin REALLY say that? Is there no end to how smart that man was???

    :D

    Actualy I've never researched this question until now. But it seems that you can choose between two answers:

    a) Be a scientist (http://www.beerinfood.com/Franklin.html)
    b) Join the party (http://www.talkbacktees.com/NewFiles/06-003.html)
    beer.gif
    “To consult the rules of composition before making a picture is a little like consulting the law of gravitation before going for a walk.”
    ― Edward Weston
  • MyerMyer Big grins Posts: 25Registered Users Big grins
    edited March 2, 2010
    Is anybody here?

    I'd really like to see a thread on LAB get revived.

    I'll check in a few days to say if there are any signs of life.
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