Photoshop Lab Color: Ch. 1

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  • gusgus Registered Users Posts: 16,209 Major grins
    edited September 11, 2005
    Before...

    35421385-M.jpg

    After....

    35527015-M.jpg
  • DavidTODavidTO Registered Users, Retired Mod Posts: 19,160 Major grins
    edited September 11, 2005
    Nice.
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  • DavidTODavidTO Registered Users, Retired Mod Posts: 19,160 Major grins
    edited September 11, 2005
    pathfinder wrote:
    Dave, the background shifted from a neutral grey to a greenish cast also behind the horse. The flesh tones seemed ok, but their def was a color shift.


    Well, I gotta figure out how to get the skin tones right without screwing up the background. The dirt may look neutral in the first, but the magenta is too high on the flesh tones. How do I remedy that without screwing everything else up?
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  • ginger_55ginger_55 Registered Users Posts: 8,416 Major grins
    edited September 11, 2005
    Thanks, David. Those colors, they are real, they just are exagerrated versions of what is there. They can be brought out by the manipulation. The problem comes that they can't be printed. They are too something. Saturated, strong, whatever.

    The same thing can happen in RGB only with over saturation and things, probably curves there, too. I am quite careful with curves, or anything I do. Less is better lots of times. I don't know how the gamut thing works either, but you can have a bit off, I did read that, just not a lot.

    The colors are real. Look in Rutt's first photo, the blue is there. I can see it before it is magnified. I think his yellows are magnified, too. Actually everything is. I, personally, don't like the colors, but............ they were there in the first place, just not as intense.

    I seriously doubt that the colors go back to being printable, or change, by going back to RGB. They can "exist" in RGB, too. For the calendar, I had one photo that was not really printable. The green was too saturated. Instead of working more on that photo, I went to a different one. Greens are not my favorite color to work with. That was an RGB issue.

    ginger

    re how to show my work flow, I don't know what I am going to do about it. I think it is obvious from what I said as to what I did. I was just working yesterday to keep my mind off of stuff here, so it really isn't important unless you all really want to know something.

    There are very few people whose directions I understand on the list, if the wrong person answered me, I would be worse off than before I started as everyone would just be more frustrated.
    After all is said and done, it is the sweet tea.
  • ginger_55ginger_55 Registered Users Posts: 8,416 Major grins
    edited September 11, 2005
    pathfinder wrote:
    Dave, the background shifted from a neutral grey to a greenish cast also behind the horse. The flesh tones seemed ok, but their def was a color shift.

    I tried John's recipe taken from chapter 1 on a wedding shot I did last weekend, just for grins to see what effect it would have on people rather than vegetation or canyon walls like Margulis talked about in chapter 1.

    John's post:
    "This technique is:

    1. Convert the image to LAB
    2. Curves
    3. Steepen A and B channels symetrically by bringing in the endpoints of each curve toward the center equally. After this, the curve (line actually) will still cross the center horizontal center at the vertical center.
    4. Steepen the L curve through the areas where the detail is of most interest.
    5. Apply the curves
    6. Activate only the L channel
    7. USM, trying the values 200, 1.0, 10 ""


    This is exactly the recipe I used for the second image I am posting here. I did use a slightly different amount of USM as I was shooting 16 Mb files - so I used 200, 2.0 10 for sharpening




    And the shot with the increase in the a and b curves - straight lines through the center, but one block steeper along the top and bottom row, minimal changes in the L channel.



    Definitely more color in the flowers, the vegetation, and the skin tones. I was surprised by how much more I liked the second shot. The first seems to have a faint grey cast to it by comparison.

    PF, there is definitely more pop in the second one.

    You, also did not show your workflow, and I am sure you know how, don't you?

    The only thing I would be interested in knowing, except as to how aggressively you did the a and b curves, I was not aggressive about it. I went about 3/4 of the way to the first "line", at the most. I know that I was not completely symmetrical about it, in other words, the top was not necessarily the same as the bottom as to how far over I went, as my mind had not grasped that in Rutt's recipe.

    Also, I think the lighten curve is more subjective. Rutt's look strange to me from what I have been doing in RGB, and it would drive me nuts to have to keep the center point all the time. I don't quite understand the words "flatten", "steepen", though I did try. I thought it was interesting that you could find your area of interest by using the cursor. I was not quite certain what to do about it, but I did try to do what I thought was "steepening" at around those points.

    One, PF, did you start working on your wedding photo right out of RAW? Did you do much in RAW? Your shots, like mine, only look like a matter of "degree", I do like the second one better, but it just looks like a bit more pop than the first one.

    ginger
    After all is said and done, it is the sweet tea.
  • ruttrutt Registered Users Posts: 6,511 Major grins
    edited September 11, 2005
    ginger_55 wrote:
    how did you get percentages????

    Click on the bar at the bottom of the curves dialog. It will reverse the scale of darkness to lightness (or warm to cool in A or B). At the same time it will show percentages instead of absolute numbers.

    Dan likes the curves with darkness on the right and I've gotten used to that as well. PS doesn't have consistent defaults. RGB defaults to lightness on the left and LAB and CMYK are the opposite. Dan always has lightness on the left.
    If not now, when?
  • ruttrutt Registered Users Posts: 6,511 Major grins
    edited September 11, 2005
    ginger_55 wrote:
    Rutt, I have no idea how to show what I did. I never have known how to show my work space, and I have commented about that in the past and asked for help.

    I don't have a windows box at hand but I did a google search for "windows screen snapshot" and found this:

    http://www.google.com/url?sa=t&ct=res&cd=4&url=http%3A//www.softpedia.com/get/Multimedia/Graphic/Graphic-Capture/MWSnap.shtml&ei=ahQkQ7ONGsbSaPjwuMAD

    It also seems that there is a builtin function to copy a particular window to the clipboard:

    http://www.cardbox.co.uk/tech_screen.htm

    Once you do this, you should be able to past it into a PS window and then save.

    In either case, once you have a graphics file just upload to smugmug and then use in you posts just like a smugmug photo.
    If not now, when?
  • ginger_55ginger_55 Registered Users Posts: 8,416 Major grins
    edited September 11, 2005
    I am awake, .......this is just messing, you can delete
    35558606-L.jpg


    I took your version, the first one, David and uploaded it. Then I applied the a curve, symmetrically. The B curve is where the sweetlight and color shift comes in, IMO. I have not changed from numbers to percentages, so when I talk top and bottom, it might confuse you. But, in essence, I decided to put some sweet light in (I can't actually put it in, I balanced the curve so that the warmer colors, or the yellow, was more pronounced). I moved the "top" part of the curve in, it was in moving the "bottom" part of the curve that I realized that was where the yellow was. I did not move it symmetrically to the top part. (In other words, it is not moved over as far as the top, I don't think. They were not the same) I eyeballed it. I am just messing around, so that is what I did. I made it so a bit of sweet light showed up, but not a lot.

    I loved your first photo, David, so I think it is a matter of taste as to which one prefers. I don't really care much about "truth" in colors, I care about "preference" in colors.

    On the L curve, I moved them in pretty symmetrically, but I don't like too much contrast, particularly since I already liked the contrast that was there. I ran the cursor over it, the skin tones are always my area of interest with a shot of a person. They were towards the top. I moved that a bit to the left, I think.

    No pictures of the work flow, but it was slightly eyeballed. I don't know what was true. I think there is more green in the background in my version, but that is just how I see it.

    I forgot to sharpen it.
    After all is said and done, it is the sweet tea.
  • ruttrutt Registered Users Posts: 6,511 Major grins
    edited September 11, 2005
    DavidTO wrote:
    The flesh tones definitely had too much magenta in relation to the yellow, that's why I did that. This shot was taken just after the sun had set behind a hill, so it was very warm.

    When I steepened the L curve in her face, it got too contrasty and harsh.

    I guess the part that's getting ahead is exactly how to give her more yellow/less magenta in LAB.

    Once we get to chapters 3 and 4 you will start to learn a lot of differnet ways to address the imbalance of magenta and yellow in her face while retaining the neutrality of the horse. But for right now, there is a way of doing this WITH symetrical A and B curves. I gave you a huge hint already. I think it's a good exercise to figure that out. What symetric A&B curves increase yellow while decreasing magenta?
    If not now, when?
  • ruttrutt Registered Users Posts: 6,511 Major grins
    edited September 11, 2005
    DavidTO wrote:
    Well, I gotta figure out how to get the skin tones right without screwing up the background. The dirt may look neutral in the first, but the magenta is too high on the flesh tones. How do I remedy that without screwing everything else up?

    Patience. We'll get there soon enough. For now, concentrate on solving the puzzle of finding symetric curves which decrease magenta while increasing yellow. All the clues are here.
    If not now, when?
  • ginger_55ginger_55 Registered Users Posts: 8,416 Major grins
    edited September 11, 2005
    rutt wrote:
    I don't have a windows box at hand but I did a google search for "windows screen snapshot" and found this:

    http://www.google.com/url?sa=t&ct=res&cd=4&url=http%3A//www.softpedia.com/get/Multimedia/Graphic/Graphic-Capture/MWSnap.shtml&ei=ahQkQ7ONGsbSaPjwuMAD

    It also seems that there is a builtin function to copy a particular window to the clipboard:

    http://www.cardbox.co.uk/tech_screen.htm

    Once you do this, you should be able to past it into a PS window and then save.

    In either case, once you have a graphics file just upload to smugmug and then use in you posts just like a smugmug photo.

    Thanks, Rutt. You were posting as I was working on David's photo. I will work on showing the workflow for something later.

    g
    After all is said and done, it is the sweet tea.
  • ruttrutt Registered Users Posts: 6,511 Major grins
    edited September 11, 2005
    DavidTO wrote:
    Rutt,

    Another question I have is, how do you ensure that you aren't making colors that aren't real? I know that LAB can make colors that don't really exist. I've tried proofing with sRGB and CMYK, but I don't really understand how the Gamut check thing works. When I change the mode back to RGB do I automagically lose the colors that RGB can't represent? That would make sense, since that's my understanding of what happens if you go through CMYK; it's lossy.

    It just seems that I should be able to make colors in LAB that are so vibrant as to be beyond the gamut of RGB and, of course, CMYk.

    This is a good question and a big part of the topic of Ch 2. I'd like to reserve discussion for that thread.
    If not now, when?
  • ruttrutt Registered Users Posts: 6,511 Major grins
    edited September 11, 2005
    WOW, 'Gus. David accomplished what I never could with you. Great!

    'Gus, since you are a moderator, please would you mind moving the posts in this thread into the Ch 1 thread? They relate directly and I'd like to consolidate the discussion for later readers. Thanks.
    If not now, when?
  • ruttrutt Registered Users Posts: 6,511 Major grins
    edited September 11, 2005
    Humungus wrote:
    Before...

    35421385-M.jpg

    After....

    35527015-M.jpg

    'Gus, try steepening the B curve less. There is no rule that you have to steepen both A and B curves the same. The green of vegatation has both a green (A) and a yellow (B) component. Often you want to steepen the A cuve more than the B curve to make vegation more vibrant without making it more yellow.
    If not now, when?
  • ruttrutt Registered Users Posts: 6,511 Major grins
    edited September 11, 2005
    ginger_55 wrote:

    Also, I think the lighten curve is more subjective. Rutt's look strange to me from what I have been doing in RGB, and it would drive me nuts to have to keep the center point all the time. I don't quite understand the words "flatten", "steepen", though I did try. I thought it was interesting that you could find your area of interest by using the cursor. I was not quite certain what to do about it, but I did try to do what I thought was "steepening" at around those points.

    This recipe does not call for the L curve to be symetric or even linear. Look at my L curve for the lighthouse shot. Writing the L curve for this recipe is less mechanical than the symetric steepening of A and B curves. As I wrote in my initial post:
    With the curves dialog open, you can mouse over the immage with the (left) mouse button held down. A point will appear on the curve showing exactly the point on the curve of that point on the image. By moving the mouse accross an area of interenst in the image, you can figure out which part of the curve controls that area.

    First master this technique. Bring up the L curve and move the mouse over:
    1. The lightest points of the images
    2. The darkest points of the images
    3. The areas of greatest interest in your image.

    Now bring the light endpoint of the curve inward not quite as far as the lightest points of the image. Bring the dark endpoint of the curve inward not quite as far as the darkest point of the image. At this point you have accomplished approximately what "Auto Levels" would do, increased the contrast with a linear (but not symetric) steepening of the L curve. Now experiment with some interior points to further steepen the curve through the areas of interest. This last part takes practice and a light hand. But it can be very effectve; this was the lesson of LAB and the Turner sky In that shot, the whole goal was to make the curve steep through the highlights to bring out the subtle variations in the sky. Often, much more subtle curves are required. But take heart, this is a lot easier to do in LAB because brightness is given by a single curve L. Using the composite curve in RGB doesn't quite do the same thing as there are interactions between the channels.
    If not now, when?
  • ginger_55ginger_55 Registered Users Posts: 8,416 Major grins
    edited September 11, 2005
    David, David's A curve is not symmetrical. I have been sitting in the living room obsessing on that information. That is probably what threw the color off.

    I have also thought that bringing in the curves symmetrically should not cause a shift, but neither of us, David nor I, brought them in symmetrically. The A curve in David's case and the B curve in my case.

    One thing I wanted to say, and this might be what you do not want me to say, Rutt, but doing this, moving curves, IMO, takes a lot of faith. One end of the curve changes what the other end does. It is difficult for our minds to follow a "recipe" and do this. I have to have faith and move both ends before making a judgement.

    OK, now I can get my ten lashes.

    Also, what is a clipboard? People keep mentioning that. When you all write a book of definitions, you might want to include that word.

    g

    If it is going to be self evident, in the googled sites, I can find out the definition myself.

    I never knew what we were doing in Turner Sky. That is one reason it was so frustrating to me. I have learned a lot since then, but I have gaps in my learning, like fundamental definitions.
    After all is said and done, it is the sweet tea.
  • ruttrutt Registered Users Posts: 6,511 Major grins
    edited September 11, 2005
    ginger_55 wrote:
    David, David's A curve is not symmetrical. I have been sitting in the living room obsessing on that information. That is probably what threw the color off.

    Exactly. If you keep the curves symetrical, you will not introduce change neutral colors, though you might emphasize a cast which already exists.
    ginger_55 wrote:
    I have also thought that bringing in the curves symmetrically should not cause a shift, but neither of us, David nor I, brought them in symmetrically.

    Exactly.
    ginger_55 wrote:
    One thing I wanted to say, and this might be what you do not want me to say, Rutt, but doing this, moving curves, IMO, takes a lot of faith. One end of the curve changes what the other end does. It is difficult for our minds to follow a "recipe" and do this. I have to have faith and move both ends before making a judgement.

    Right now we are just trying to learn one thing at a time so that we really understand it at a deep level. This symetrical A+B curve recipe isn't the best thing for all shots, or even most shots. But understanding it completely is the point of this thread and will form the foundation which we will build on. Very soon, we'll branch out. But for now, tunnel vision and faith are required. If you need to skip ahead, buy the book. Else, hang in there.
    ginger_55 wrote:
    I never knew what we were doing in Turner Sky. That is one reason it was so frustrating to me. I have learned a lot since then, but I have gaps in my learning, like fundamental definitions.

    Instead of fretting about asymetric curves before we get there, go back and reread the Turner Sky thread until you understand it. Ask questions on this thread and I will answer them. The real point of that thread is learning to write an L curve which is well within the scope of this chapter.
    If not now, when?
  • NikolaiNikolai Registered Users Posts: 19,035 Major grins
    edited September 11, 2005
    Dan's Lab book
    I just got it last week, didn't have time to read through.
    I LOVE LAB, and find myself to use it more and more lately. As a fromer mathematician, I have no psychological problems with "theoretical" spaces in general, and this one is practical enough to be immediately useful.:-)
    Just wait till I get finished with "Canyon conundrum":-)
    Cheers!1drink.gif
    "May the f/stop be with you!"
  • DavidTODavidTO Registered Users, Retired Mod Posts: 19,160 Major grins
    edited September 11, 2005
    rutt wrote:
    Patience. We'll get there soon enough. For now, concentrate on solving the puzzle of finding symetric curves which decrease magenta while increasing yellow. All the clues are here.


    I'll have to try adjusting the curves symmetrically, but not necessarily the same, which is what I've been doing. Whatever the a curve gets, that's what I've been giving b. When I'm symmetrical, that is. When I have time I'll try handling them each separately, but symmetrically.
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  • ruttrutt Registered Users Posts: 6,511 Major grins
    edited September 11, 2005
    DavidTO wrote:
    I'll have to try adjusting the curves symmetrically, but not necessarily the same, which is what I've been doing. Whatever the a curve gets, that's what I've been giving b. When I'm symmetrical, that is. When I have time I'll try handling them each separately, but symmetrically.

    That's the right idea. Now I've started to reach Ch 3 and this is really the topic there. Still, this is a good puzzle which will help your understanding if you solve it. Symetric curves add yellow and subtract magenta.
    If not now, when?
  • ginger_55ginger_55 Registered Users Posts: 8,416 Major grins
    edited September 11, 2005
    AAAAAAAAAAAAGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGHHHHHHHHHHHHH!

    35601376-L.jpg


    35601381-M.jpg

    35601382-M.jpg"

    35601375-M.jpg


    That was a lot of work
    After all is said and done, it is the sweet tea.
  • ginger_55ginger_55 Registered Users Posts: 8,416 Major grins
    edited September 11, 2005
    The first time I did it, the lightness curve was a bit more complicated. By the third try, it had deteriorated to THIS above.

    g (And that was not the end of things, as you saw, Rutt) I think a clipboad would be nice.
    After all is said and done, it is the sweet tea.
  • ruttrutt Registered Users Posts: 6,511 Major grins
    edited September 11, 2005
    ginger_55 wrote:
    AAAAAAAAAAAAGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGHHHHHHHHHHHHH!

    Please translate into English. Is this good or bad? Are you frustrated with the result on this image?

    The basic recipe here won't be good for every image. What has gone wrong here in you opinion? Can you guess why?

    Consider more subtle curves and consider a non linear L curve to focus contrast on your subject instead of background.
    If not now, when?
  • ginger_55ginger_55 Registered Users Posts: 8,416 Major grins
    edited September 11, 2005
    rutt wrote:
    Please translate into English. Is this good or bad? Are you frustrated with the result on this image?

    The basic recipe here won't be good for every image. What has gone wrong here in you opinion? Can you guess why?

    Consider more subtle curves and consider a non linear L curve to focus contrast on your subject instead of background.
    1) A Lot of damn work

    2) I have no idea what went wrong, the colors are accurate as far as I can see.

    3) I had a non linear L curve until I had done it twice with things not coming down to upload smugmug. By that time, I just did it as easily as possible.

    to see if it would come down. However, I do not think that my non linear curves were that much different in the end results.

    ginger
    After all is said and done, it is the sweet tea.
  • gusgus Registered Users Posts: 16,209 Major grins
    edited September 11, 2005
    Thanks rutt...when you blokes talk about steepening, how much are you doing it ?

    Im just curling up the bit at the end...is that roughly what you all do ?

    Also is there an easy way to curl it up without the whole line going stupid ?
  • gusgus Registered Users Posts: 16,209 Major grins
    edited September 11, 2005
    rutt wrote:
    WOW, 'Gus. David accomplished what I never could with you. Great!

    'Gus, since you are a moderator, please would you mind moving the posts in this thread into the Ch 1 thread? They relate directly and I'd like to consolidate the discussion for later readers. Thanks.
    ok...onto it.
  • ruttrutt Registered Users Posts: 6,511 Major grins
    edited September 11, 2005
    Humungus wrote:
    Thanks rutt...when you blokes talk about steepening, how much are you doing it ?

    Im just curling up the bit at the end...is that roughly what you all do ?

    Also is there an easy way to curl it up without the whole line going stupid ?

    Go back and look at my initial post. The simplest form of this technique is just to move each endpoint of the curve inward exactly the same amount. That's what I've been calling "symetrical steepeining." It's symetrical, because the endpoints move inward the same amount which keeps the center of the curve (line really) crossing the 0,0 point. This is important because it preserves the color balance of the shot. It will never make a color that was yellow into a blue color or a color that was green into a magenta. It only makes things that are already green (for example) greener, enhancing the differences different greens. It's linear, because only the two endpoints move and the curve remains a line. There are lots of reasons for nonlinear curves, but you can do A LOT with linear A+B curves so learn how to use them first until you get comfortable with them. The L curve is different. Try to find a neighborhood of the curve which encompases the parts of your image where you want to enhance detail and try to make that steep by pulling the curve down at it's start and up at its end. Easy does it. You may also want to try linear L curves which work almost exactly like auto-levels except you get to pick the white and black points.

    The curve you posted isn't likely to do much. In the A and B channels, all the action tends to be near the middle of the curve. Small moves there will have a big impact on your image. The ends of the curve, where you have made your big change only impacts very very saturated colors. Very very very very saturated colors. (This is a big part of the subject of Dan's Chapter 2.)

    Play with the A and B curves and don't be afraid. You can always undo or just cancel. Try moving the endponts quite a lot, (40%) Try reversing the endpoints by pulling the endpoint that is on the top to the bottom and visa versa. Dan suggests trying experimenting with increments of 10, 15, and 20 to get the hang of symetrical steepening. I often use numbers between 15 and 5.
    If not now, when?
  • DavidTODavidTO Registered Users, Retired Mod Posts: 19,160 Major grins
    edited September 11, 2005
    OK, so I reworked the shot of my daughter and horse. I messed up (going too fast) and didn't save my L curves, but here's the A+B:

    35633264-L.jpg35633270-L.jpg


    Here's the result:
    35633350-L.jpg


    And after Lightness and L sharpening:
    35633445-L.jpg


    For reference, here's the original RAW conversion:
    35473524-L.jpg
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  • ruttrutt Registered Users Posts: 6,511 Major grins
    edited September 11, 2005
    DavidTO wrote:
    OK, so I reworked the shot of my daughter and horse.

    Perfect, given the constraints I set. And better than the previous effort which introduced a yellow cast.
    If not now, when?
  • gusgus Registered Users Posts: 16,209 Major grins
    edited September 11, 2005
    Didnt you blokes say to keep A & B the same ?
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