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    • The three colorspace which are most well-known are R.G.B., C.M.Y.K., and Grayscale. These three colorspaces are practical and real-world. Any changes made in intermediate steps immediately affect the item being edited, so that early steps place limitations on later steps. In addition to this in R.G.B. any change in lightness or darkness has an immediate affect upon color content as well.

      But what if no changes were made until the final step and what if changes in lightness and darkness had no affect upon color content until the final step.

      This is only possible in a colorspace that is theoretical and algorithmic based. Just as in algebra, there are imaginary numbers based on the square root of -1, so also in this theoretical colorspace there would be "colors" which were self-contradictory.

      This is the L.A.B. colorspace. In this colorspace, the L channel controls lightness and darkness, while the alpha and beta channels define color content. A picture is imported into the colorspace. Various changes are made to the mathematical definitions of the content of the photograph. Then the final step is exporting the product to a real world colorspace.

      In the picture below the original is from the Yellowstone National Park Service and is in the public domain. The picture on the right has been edited in the L.A.B. colorspace. The changes made to this photo were made throughout the photo. Any exclusions were defined by color and/or lightness value not by what area of the photo was affected.

    • In 2008 I participated in a book review, chapter by chapter, of Dan Margulis book "Photoshop LAB Color; The Canyon Conundrum and Other Adventures in the Most Powerful Colorspace" on the dgrin.com website - The links are not all still working, but there is still a lot of good information about LAB and what it can do for an image editor. More modern RAW engines can do so much more now, than they could back a decade ago, so that I rarely resort to LAB tricks - but they still can be useful at times and are worthwhile to know. Steepening the curve of the a and b channels is still a good trick to know, like in the image above.

      I'm not sure I can find all the chapter discussions any longer, but here are a few

      Chapter 1 is here - https://dgrin.com/discussion/18308/photoshop-lab-color-ch-1

      Chapter 2 - https://dgrin.com/discussion/18549/photoshop-lab-color-ch-2

      Chapter 3 - https://dgrin.com/discussion/18763/photoshop-lab-color-chap-3/p1

      Chapter 5 - https://dgrin.com/discussion/20907/photoshop-lab-color-chapter-5

      Chapter 7 - https://dgrin.com/discussion/20433/lab-color-discussion-chapter-7-workflow

      Chapter 12 - https://dgrin.com/discussion/21859/photoshop-lab-discussion-chapter-12

      Chapter 14 - https://dgrin.com/discussion/26724/photoshop-lab-color-chapter-14-once-for-color-once-for-contrast/p1

    • He has released a new edition of this book. There have been many changes between the two books. If one has not read the 2015 edition, I would recommend looking through it to see how much has changed.

    • Good to know, I will do that!

      Ooops!

      I see used versions on Amazon for $899.99 up to over $3K, and one new copy for $2673.42, so I may hold off on a purchase right now. There is substantial demand for a book published over three years ago, it seems.

      Interesting, I am sorry I missed it in 2015.

    • I was also a participant in the Dgrin reading group that @Pathfinder mentioned. At that time, I was new to photography and found it highly instructive. Quite apart from its power as a tool, I found it more intuitive to conceptualize color adjustments in LAB, which separates lightness from hue--it was just easier for me to look at LAB values and know what to expect than with RGB numbers. But as Jim said, raw processors have improved greatly in the last decade, and it has been years since I have needed to drop into LAB space in Photoshop. LR gives me all the color control I need. Today I generally use a simplified version of Margulis's Picture Postcard Workflow, in which I do the color adjustments in LR, then create a B&W version for brightness, contrast, structure and sharpening, then blend them in luminosity mode. Sounds complicated, I know, but with the right macros and scripts, it's a lot faster than what I used to do. It also automatically gives me both color and B&W versions, so I can choose which I prefer. Full disclosure: I am strictly an amateur and only rarely worry about printing so my problems are likely simpler than yours.

    • Could you give us a few hightlights of the changes? I'd be especially interested in how Margulis has adapted to improvements in raw processors. He used to be rather skeptical, but I imagine that has changed.

    • I am sure that I would be inadequate to such a task. The book is available through interlibrary loan if you are ever back in the states. I don't remember much discussion on RAW processors. He does have other books which deal with other aspects of photo editing which I have not read. I suspect that his views on RAW processors were reserved for those books. I suspect that "Modern Photoshop Color Workflow" deals with that topic. But, I have not read it.

    • I wandered through your LAB Colorspace Reconstructions on Google + - https://plus.google.com/collection/I016b

      and enjoyed seeing again the possibilities within some images.

      After some reflection I realized ( or remembered after being nudged ) that LAB color can be quite helpful in low color environments ( like the Canyon Conundrum in the title of the book discussed above ) and icebergs, photographed in Greenland under very, grey, overcast skies might benefit from a quick trip through the LAB color space.

      Nothing more than a jump out of Lightroom to PS to LAB with curves applied to the a and b channels - no blending needed, and the image I find more appealing than the image I sent over to Photoshop. Not a great image but a bit better. Even better woud have to returned under better atmospheric conditions, but that is not always possible with icebergs, or many things in the real world.

      So thank you for reminding me about the LAB colorspace. I really would like to find the new edition of the book, but not at current prices - I will check my local library, but I am not optimistic.

      I may make more use of wanders through LAB than I have been recently - especially for images shot under low flat grey light.

      Original image on the viewer's left, edited image via LAB on the viewer's right side of the pair of images below.

    You've been invited!