LAB and LAB Actions By Mike Watson, based on publications by Harold Davis The goal was to improve my Star Trails images by: 1. Creating more contrast between the stars and the sky 2. Selectively adding more texture and color 3. Selectively sharpening to increase the effect Harold Davis discusses LAB color at length in many of his books. For the purposes of this exercise I relied on the techniques described in The Photoshop Darkroom, (TPD) and The Way of the Digital Photographer, (The Way) by Harold Davis, and a one-on one session with Harold to bring it all together for my star trails image. During this process it occurred to me that there are a lot of important details to be remembered and that the best way to learn the LAB technique and make sure I was doing the right things in the right sequence was to record the repeatable Actions in Photoshop. This has the added advantage of speeding me to the creative processes. LAB Color is an alternative color model which provides a wider range of colors than any other color space and presents creative opportunities not available in other color spaces. Following is a description of the Workflow. There are five Actions, four of which I recorded and one of which was recorded by Harold Davis and which he has made publicly available (2). An Action is a series of steps recorded in Photoshop which are used to capture repetitive tasks and automate processes. Actions are stored as.atn files (1). Actions do not make creative decisions and I do not describe the creative considerations - the why and how to fine tune particular tools those are brilliantly described in detail and with beautiful graphics in Harold s books using a variety of different subjects, and where possible I provide the page reference numbers. However, one of the big lessons learned is to use LAB with a light touch - it is easy to go over the top and create garish effects. Before going into LAB mode it is acceptable to do normal post processing. This may include working on original RAW files in the post processing tool of choice, be it Lightroom, ACR, Photoshop or Aperture, and then add LAB processing to the workflow to tease out additional contrast, texture and color. Mike Watson Page 1
First Time: The first time you change the mode of an image to LAB, perform the following steps to set your LAB Profile. Note: You only need to do this once. Open an image Convert image to LAB: Image > Mode > LAB Color Convert the profile: Edit > Convert to Profile Source: LAB Color Destination Space: LAB Color Engine: Adobe (ACE) Intent: Relative Colorimetric Use Black Point Compensation OK Action Steps Nothing described below should be interpreted as implying any part of this process is formulaic. There are steps in this process where creative decisions need to be made and some settings are included. These suggested settings are good guidelines and a good starting point. Experiment with these settings in the context of the image, and the creative effect being sought. 5 Action Steps: There are five Action Steps listed in sequence which include menu selections, navigation, and various settings included in the Action. It should be noted that the Actions were recorded as a complete process. However, each Action may be run stand-alone such as when post processing takes place over several sessions and you want to pick up where you left off, or alternatively, you may want to achieve just that one effect. To complete any of the steps below the image should be in the LAB mode, (Image > Mode > LAB). Each Action is recorded so that it first converts an image to LAB Mode. When you have completed the Action and achieved the effect you want, the Action converts the image back from LAB to RGB, (Image > Mode > RGB), and you can re-save the result. Step 1 - LAB Equalizations. To extend the contrast range of an image by spreading out the black and white values thereby creating more contrast between the elements of an image. In this case I wanted to increase the contrast between the stars and the sky, (TPD pg. 162-167). Open the image you want to work with and convert to LAB (Image > Mode > Duplicate the image (TPD pg. 156) Equalize the duplicate image, (Image > Adjustment > Equalize) Move the duplicate image to the original where it will appear as a layer, and rename this layer Click on the duplicate copy to make it active then click Select > All, and then Edit > Copy Click on the Original to make it active and Edit > Paste Mike Watson Page 2
Rename the layer LAB EQ Change the blending mode of the layer to Soft Light to gently increase the contrast range, (TPD pg. 70-71). Decrease the layer opacity to something in the 10% - 15% range to create a subtle effect. WIP Checkpoint: Save-As your layers image Flatten the image Convert the image from LAB to RGB, (Image > Mode > RGB) WIP Checkpoint: Save-As your flattened image Step 2 - Lightness Channel Adjustments. Using the Lightness (L) channel Adjustment Curve to create more subtle contrast and texture in an image, (TPD pg.194-196) Select the Eyedropper tool and set sample size to 3 x 3 or 5 x 5 In the right hand panel select Channels. By default, all four channels are selected. Select the Lightness channel by clicking on the word Lightness and then make sure all channels are visible by clicking on the LAB eyeball, (for playing with eyeballs see TPD pg. 155) Select Image > Adjustment > Curves. Note that only the Lightness Channel is now visible. Select Options and set target clipping for shadows and highlights to.20% Select the small grid view to assist with fine tuning the curve Move points on the curve to create a very subtle S shaped curve effect. By way of example, on a lighter image move the left hand slider pointer so that the number 25 appears in the Output box and 28 appears in the Input box. Likewise, move the right hand slider pointer so that the number 75 appears in the Output box and 72 appears in the input box. The will give one form of a very subtle S shaped curve Make sure the center of the curve goes through center of the grid (50/50) Convert the image from LAB to RGB, (Image > Mode > RGB) WIP Checkpoint: Save-As your image Step 3 - a & b Channels Adjustment Curves. To selectively add more color, or increase the intensity of color using the a and b channel adjustment curves. For discussion of LAB channel adjustment curves refer to The Way (pg. 156-163) and TPD pg. 194-197). Duplicate the layer Click on the Channels tab and confirm all Channels are selected Select Image > Adjustment > Curves which brings up the Curves dialogue box we saw above but this time the Channel selections, initially shown by default as Lightness, now includes Channels a and b Select the small grid Mike Watson Page 3
Click on the Channel box arrow and select Channel a. The a Channel goes from Green to Magenta, and each color has its own curve. Refer to The Way, pg. 156. Symmetrically bringing in the ends of the two straight curve lines changes these colors in the image. Slowly move the end points until you get the desired effect for the a Channel. Rather than using the mouse, for finesse I prefer to click on one of the slider pointer on the bottom axis of the box and use the up and down arrows on the keyboard ( and ) to carefully move the curve for in small increments, and then repeat this for the pointer on the other side of the graph box for the other color To download the Lab Inversion or Cross Processing Action go to http://www.taylorandfrancis.com/cw/davis-9780240815312/p/volume_1/ Repeat this step for the b Channel. The b Channel goes from Yellow to Blue Cycle through these two steps until you achieve the color effect you want Convert the image from LAB to RGB, (Image > Mode > RGB) WIP Checkpoint: Save-As your image Step 4 LAB Inversions or Cross Processing. To selectively add even more color to an image. This Action was written by Harold Davis, is publicly available (2) and its application is thoroughly described in TPD pg. 157-180. Duplicate the layer Run the Action. This Action creates 7 transformed image files. The best way to see and use these files is to change the arrangement of your Photoshop windows to Float All in Windows, (Window > Arrange > Float All in Windows) From the 7 images select the first one which you want to use to selectively add additional color to the original, and move this selection into the original as a layer Rename this layer (e.g. a Channel) if it is the a Channel inversion you are using Make sure the selected layer is highlighted and add a hide all layer mask to it, (Layer > Layer Mask > Hide All) Change the Bending Mode for this layer to Color Blending Mode. You may use different blending modes to achieve different effects. For blending mode treatments refer to The Way pg. 156 and TPD pg. 168-169) Make sure the Hide All Layer Mask for the Layer is selected and paint on it using a low (e.g. 10%) brush opacity to very selectively, and very subtly, reveal the more intense colors of the layer Repeat these steps for the other images from which you want to add some color or texture WIP Checkpoint: Save-As your layered image Mike Watson Page 4
Flatten the image WIP Checkpoint: Reverts to RGB (Image > Mode > RGB Color) and Save-As your image Step 5 Selective Sharpening. To selectively draw the viewer s attention to particular areas of an image using the Lightness Channel and Unsharp Mask, (See TPD pg. 198-200). Duplicate the layer you want to sharpen (Layer > Duplicate Layer) and rename it to Sharpen In the Channel panel select the Lightness channel and then select the eyeball in the Lab Channel Go back to the Layers tab to confirm the layer Sharpen is selected and choose Filter > Sharpen > Unsharp Mask Use the Amount Slider and experiment to sharpen the layer Add a Hide-All layer mask and paint in the areas you want to sharpen Use Layer Opacity to reduce the effect as necessary Convert the image from LAB to RGB, (Image > Mode > RGB) WIP Checkpoint: Save-As your image Mike Watson Page 5
Running an Action Open an image If you do not see the Action tool icon or the available Actions, click on Window > Actions Click on the Actions pointer to open the Actions Panel. This will list all Actions currently loaded Select the LAB Actions set and click on the pointer to the left of that title to see a list of titles for the 5 Action Steps Select a Step (e.g. Step 1 Lab Equalization). With this step highlighted, click on the triangular Play Selection pointer at the bottom of the Actions panel. Each selection shows its function if you hover over it. Follow the guidelines provided. When you reach a guideline box containing instructions and a Stop button, click on the Stop button and perform that step. This will either be a creative step or a WIP Save-As step. When you have completed that step click on the same Play Selection pointer at the bottom of the Action panel to continue the action Keep running the Action until you reach the end of it. As you go through an Action each step will be highlighted, and if you are still within the Action, keep going. When you have completed an action the Highlight will revert back to the top to the title of the Step you just completed You may discontinue using an Action and not save your changes at any point Notes: (1) (2) On Windows.atn files are located in Desktop > [User Name] (System Folder) > AppData > Roaming > Adobe > Adobe Photoshop CC > Presets > Actions On Mac.atn files are located in [User Home Directory] > Library > Application Support > Adobe > Adobe Photoshop CC > Presets > Actions (Assumes the CC version of Photoshop replace with your version). LAB Action by Harold Davis is available from http://www.taylorandfrancis.com/cw/davis- 9780240815312/p/volume_1/ Mike Watson Page 6