Topic: Flower vendor using the Jacob's Ladder

[Greg Groess]

Jacob...

Attached is a image from the class that I have tried to use the JL process on.
Some comments and questions....if you don't mind...

I find myself feeling like I hit this with a very large hammer and then pounded it into shape slowly.  What I guess I mean is I had to make grand changes to see some of the effect and then tweak it back problem by problem to get it somewhere near what I thought it should look like.  Is that because of the "zoom" layer or am I missing some other part of the process that makes the changes easier to see.

I did open a hue clock on the image but I found it really difficult to hit the skin tones.  Without the PS info pallet it was very dicey to get anywhere near what I thought a correct value was.  Is there any way you can see to allow the info pallet to sample the original without the overlaying filters?  I could not divine one; but I certainly am not the PS expert I have my pattern of use and I keep pushing myself into new areas.

Here are my curves and the images...
Any additional information anyone could add would help me get a better understanding of this interesting technique.
The last image is a screen cap of the original image found in the CM class work I can post a better version if needed.
Greg

[themightyzog]

Greg, you do not say what 'controlling' channel you used.

Here is a very quick attempt (less than 2 mins) using the L channel (with my action "Manual by Lch") with no curving of the L channel before using the Jacob's layers - not much change to the contrast, but I could have dialed in more.  I left the zoom opacity at 80%.

What I don't see how to do is add saturation, but I'm happy to do that as a separate step.

Does this simple curving help at all?

Chris

[Greg Groess]

Zog are you using CM as a smart filter in place of one of the Layers??

Interesting...I though about that but was unsure how to implement it.  If by controlling layer you mean which layer did I do my adjustments in I used the LAB version of the ladder action.  I then adjusted L in the L channel adjustment layer colored red and the other channels in each of the other red highlighted layers.  I made sure I changed the channels when I went into each one so i was not just adjusting the L channel always.

Your question leads me to believe that I am missing the boat totally here...

Greg

[themightyzog]

I think you are missing something - I certainly got confused when I started.

I do not think it is possible to use CM, I just used its curves for a quick screen grab.  I did everything in PS. 

If you have downloaded my actions (http://www.broadhurst-family.co.uk/lefteye/MainPages/jacob's_actions.htm), then just run the "Manual by Lch" on the rgb image - answer yes to both dialogs and then play with the single "Curves 1" layer - that should get you going.

Does that help? - if so then you can 'progress' on to Jacobs action (2nd image) and his more complete layers.  But I'm simple minded and rarely use all three.

I'm off to bed now - have fun and if I can help leave a message and I'll answer tomorrow
Chris
 

[Greg Groess]

Ok I tried it your way...
Much easier at least for now...


But there is trouble in paradise...In shot 1 I have a reasonable correction unitl......

In shot2.. I zoom into the face to see whats going on...

I tried to kill this off but was unsuccessful.  any thoughts??

Greg

[themightyzog]

Hi Greg,

You still do not say what controlling channel you are using - the selection of that is effectively the mask and if you go for the Auto ones, then it equalizes the channel before starting - this most likely introduces banding, so one then needs to blur.

I just used the L channel without any pre-curving.

One of the problems in using Masks in CM is curving it correctly - the same is true of JL (I think).

Remember I'm only a beginner in colour correction.  I certainly do not understand the maths behind this technique and to do it properly it really needs Jacob's input (when he has finished his exams).  One of the things I can not work out is why when curving in say the A channel, the B values also change (it could be my crude Colour Watcher reading screen colours, not the actual ones) - however when I play with the L channel, the colours do not change. 'Tis a bit of a mystery that may well be tied to the Linear Light blend and the maths. No doubt when more people start to play with this technique, all will be revealed.

If you go slightly mad and over the top, when making colour changes, then playing with the Zoom opacity may help you understand what is going on and how one can play with the correction curve.

I should try some other images - take the CM course car/fire engine colour change ones and see if that help to reveal more of the way this technique works.  You can also change the blend mode to any of the Overlay ones (not pin light) and have the same sort of control, but in differing degrees.

The main downside to me, is that the info palette will not work and that CM can not be used to curve (I no long enjoy curving in plain PS).  Also one begins to feel lost without the superb hue clocks.

[Greg Groess]

Within the context of masking this makes more sense.  It seems like this is very similar to the "CM version of Man from Mars" where you take the K channel and make it a saturation slider.  The curve is flat, Horizontal, and when you adjust the vertical position you reduce or enhance the effect. 

I think what might be going on as far as my image is that the mask is made in the A channel and then the color has more of a role in the correction.  It would also explain the banding since the channel data for A and B is coarse.  < Color Noise >.

See shot1 below.  It is the CM A channel mask adjusted so you can see the face.
BTW The Manual L channel part of your action does not leave the image with a curve layer unless I am applying it wrong.

Greg

[themightyzog]

Ah - re the Manual Lch action - it uses one of my standard subroutine actions and I expect that is upsetting it.

The action is as follows (if it is of any help)
Action: Manual By Lch
      Duplicate first document
      Convert Mode
         To: Lab color mode
         With Flatten
      Play action “ColourByLch” of set “CBsActions-JacobsLadder”
      Select layer “Curves 1”

Action: ColourByLch
      Play action “CurrentImage” of set “CBsActions”
      Set current layer
         To: layer
         Name:  “Toned channels”
      Select lightness channel
      Curves
      Gaussian Blur
         Radius: 0.1 pixels
      Set Selection
         To: all
      Copy
      Select a channel
      Paste
         Anti-alias: none
      Select b channel
      Paste
         Anti-alias: none
      Show lightness channel, a channel
      Select Lab channel
      Set Selection
         To: none
      Set current layer
         To: layer
         Mode: linear light
      Play action “Flat Curve” of set “CBsActions-JacobsLadder”
      Play action “Zoom” of set “CBsActions-JacobsLadder”

Action: CurrentImage
      Make layer
         Without Below
      Set current layer
         To: layer
         Name:  “CurrentImage”
      Merge Visible
         With Duplicate

Action: Flat Curve
      Make adjustment layer
         Using: adjustment layer
         Type: curves
         Adjustment: curves adjustment list
         curves adjustment
         Channel: lightness channel
         Curve: point list
         point: 0, 127
         point: 255, 127
         curves adjustment
         Channel: a channel
         Curve: point list
         point: 0, 128
         point: 255, 128
         curves adjustment
         Channel: b channel
         Curve: point list
         point: 0, 128
         point: 255, 128
      Group

   Action: Zoom
      Make adjustment layer
         Using: adjustment layer
         Type: curves
         Adjustment: curves adjustment list
         curves adjustment
         Channel: lightness channel
         Curve: point list
         point: 0, 63
         point: 128, 128
         point: 255, 192
         curves adjustment
         Channel: a channel
         Curve: point list
         point: 0, 103
         point: 128, 128
         point: 255, 153
         curves adjustment
         Channel: b channel
         Curve: point list
         point: 0, 103
         point: 128, 128
         point: 255, 153
      Group
      Set current layer
         To: layer
         Name:  “(zoom)”
      Set current layer
         To: layer
         Opacity: 80%

My! never realized there were so many steps - I just think of it as applying the L channel to the other two and changing the blend !

[Greg Groess]

Hmmm.. I have those actions as well..More playing needed here...


Greg

[themightyzog]

Strange - you should be just able to hit the action from an rgb image and everything should work out after you accept the curve & blur dialogs

[Greg Groess]

I'll play some more..but here is some food for thought...

I took this into the CM masking world and took a hack at it.  I used the K channel mask and limited my adjustment to the B channel as shown. This has to be close to what is happening under the hood of JL.  I adjusted the mask vertically first by Pivoting the K channel to a horizontal line then adding the curve.  It is over the top a bit but the results are pretty similar.  I Can control the B channel colors using the mask created in K.  If I set up 3 layers L, A And B as smart filters and apply the K channel mask in this mode It might give similar results...

Again...More testing...

Greg

[themightyzog]

Jacob will say whether this is similar - I believe not because the Linear Light blend is a violent overlay mode, when gray (ie the flat curve) does nothing and one then dials in colour as one likes by adding or subtracting over the 'mask'.  The other interesting points are
a) the point on all curves is the same for any pixel on the image, regardless of the individual channel values
b) it is possible to set multiple (neutral) points in Lab

If you take the red curves Jag and try changing that colour (using the A channel) - and then play with the zoom, you will probably find that the result is completely different from CM.  You can go from pink-ish to blue, just by changing the Zoom opacity!  (There is a small problem with the fence colour that one doesn't get using Lab normally)

[jacobolus]

Greg: first, what were you using as an input channel? Second, those a* & b* curves in your original post look pretty extreme to me. What part of the image are they hitting?

The real key for me to color correction using the ladder or any other method is approaching the image with the right mindset. I think these steps as described below generally happen anyway, but it's good to be explicit about it:

1. Clearly state the goal of your adjustment(s).  For instance, (1) "I want this sky to be darker and bluer" or (2) "I want to increase the contrast between leaves and branches" or (3) "I want to separate the pink parts of this flower from the red parts, making pink more neutral and red more colorful", or whatever.

2. Figure out how to use the tools you have to meet your goals... Which means figuring out how to map the model of the world assumed by the toolmakers onto the model in your head. I find the ladder much closer to my goals than tools baked into Photoshop.  For instance, in the examples above: (1) Using the b* channel as input, bump lightness down at the left end of the curve, and then do the same for b*.  Possibly push a* up or down for that region too, to adjust hue towards purple or cyan. (2) Probably use a* as input, or perhaps L*, then click some points onto the curve for branches and leaves, and push them apart in L*, and maybe a bit in a* too. (3) Use a* as input, and make the curve slope upward between pink and red regions, maybe by dropping the pink parts below 0, then push L* up for pinks and down for reds.  Etc. Etc.

I'm actually writing some these days, with screenshots, but other tasks keep popping up.

[jacobolus]

Using a mask has a completely different effect.  It can be useful, to be sure, but it's not the same concept.

* * *

As for noisy channels: Try using a Gaussian blur or surface blur on the ladder inputs, if they're otherwise creating excessive noise or banding.

* * *

Finally: Yeah, (a) it doesn't seem to be possible to use Photoshop's info palette to get info about the global values until the curve has been put away, and (b) the whole color-shift-in-sub-100%-zooms issue is really obnoxious, a straight-up bug as far as I'm concerned.  Possible ways to deal with this include: working on a down-rezzed version of the file and then copying the curves over when finished; working at 100%, or at least keeping a few views of the image open at 100%; Making sure to merge visible layers into a new layer from time to time, to make sure you're doing what you want.

Photoshop CS4 may help with one or both of these, but I haven't tried it.

[Greg Groess]

Jacob,
Thanks for the response.  As usual I will have to absorb the response and try out the suggestions...

Greg