by Julieanne Kost
Difference, Exclusion and Subtract have a neutral color of black. This means that black as a blend color will have no effect on the result color. The Divide blend mode has a Neutral color of white.
• Difference – Looks at the color information in each channel and subtracts either the blend color from the base color or the base color from the blend color, depending on which has the greater brightness value. Blending with white inverts the base color values.
• Exclusion – Creates an effect similar to but lower in contrast than the Difference mode. Blending with white inverts the base color values. Blending with black produces no change. The effect is a bit like using one image to solarize the other.
• Divide and Subtract – Both are intended for us with calibrated imaging however interesting creative effects are also possible. For astronomy and microscopy: you want to subtract background values (dark frames, factoring out hot pixels, etc.), and divide by a flat field image (removing vignetting and other lens defects, bringing insensitive pixels back up to normal range, etc.). You can remove lens falloff even if you have something that Lens Correction can’t handle (like mirror lenses, dust on the lens, etc.). Of course you can also use them for HDR toning tricks (or experimentation). Martin Evening has posted an excellent tutorial on these two new blend modes. Click here to read more…