Curvemeister's LabMeter

LabMeter is a specially designed Lab image that is compatible with Photoshop version 6.0 and later. LabMeter uses Photoshop's soft preview feature to generate a precise, real time modifiable view of the color space associated with any of your installed profiles.

The uses for LabMeter are almost unlimited. Use LabMeter to precisely compare gamuts with one another, or see whether a particular color or set of colors fits into sRGB, or can be printed on your printer. You may quickly see whether a profile contains obvious errors, such as disjoint patches of color in the middle of the gamut, or ragged edges.

LabMeter is compatible with both Macintosh and Windows. It consists of a specially created Lab image. And best of all LabMeter is a free download from Curvemeister.com!

PhotoShop's curves interface is used to specify LabMeter color gamut values for L = 50 %

Instructions:

1. Download and extract LabMeter and open it in PhotoShop.
2. Turn on Gamut Warning - most of the LabMeter image will turn gray at this point. If this is the first time you have used LabMeter, you will see an outline or cross-section of the color gamut for 50 % Luminance.
3. Click on the View>Proof Setup>Custom menu item to bring up the Proof Setup dialog.
4. Make sure the Preview box is checked, and that you have selected Perceptual or Relative Colorimetric intent..
5. Click on the various profiles in the Profile List and note that the shape of the profile changes.
6. Double click the layer named "Click to Set" to open up the Curves adjustment layer.
7. Move the white end of the curve up and down, and watch the gamut change shape according to the brightness.

Questons and Comments:

1. Each location on the graph represents a single color or hue value. The beauty of the Lab color space is that the color's a and b values are independent of brightness.
2. You may use PhotoShop's eyedropper sample points to mark locations on the graph. For example, in the image above, the four eyedropper points are set to the corners of the SWOP coated gamut at L = 50%. Once the markers are in place, you may easily rotate through the various profiles and see which ones contain your colors.
3. To locate a particular color that you want to use in an image, for example an intense blue sky:
   • Use the info palette to get the Lab values for your color.
   • Double click the LabMeter adjustment layer and set the white end of the curve to match the L value of your color.
   • Click on PhotoShop's eyedropper sample tool, and drop a sample point on the LabMeter image so that the a and b values match those of your desired color.
   • Now you may select your gamut and locate your color.
4. You may view as many profiles at one time as you wish. Use PhotoShop's View>New View menu item to create another view of LabMeter, and set it's Proof Setup to view the desired profile. Use this technique to view several profiles side by side. They will even change simultaneously as you change the Lightness value.
5. Check out LabMeter's less-precise brother, the Curvemeister Gamut Viewer. The Gamut Viewer displays an approximate view of a profile at several different Lightness values simultaneously.
6. I have two windows open - one for the workingspace and one for the profile. 50-20-20 is at the same location on both maps. This does not tell me what values the profile is converting 50-20-20 to. Am I using this tool correctly?
   The location and Lab values will be the same. You can set the eyedropper to show the color values for your RGB and CMYK working spaces. Note that the eyedropper values are for your working spaces, and do not reflect the Custom settings of your soft proof.

Please with your own questions and comments.

Links to related items:

• Gernot Hoffmann has created a Lab image that uses the same principle as LabMeter, which shows 100 slices of the gamut volume CIELab.
  Read Gernot's document. Download image.

• For best viewing, adjust your monitor until you can see all the squares. Site designed by Paradox Media