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Re: [blondgecko] Yuji and Hans reposted with changes:
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kriso9tails
Nov 20, 2008, 3:05 AM
Views: 4876
Registered: Jul 1, 2001
Posts: 7772
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Short Explanation: Duplicate layer + multiply mode is good for darkening an image that looks overblown, but not necessarily for flat images or adding contrast in general. Conversely, if the image looks underexposed you can use the same trick only it'd be duplicate layer + screen mode. If you just want to adjust contrast overall, then curves is the best tool. If you have a bunch of similar colours in a scene and you want to bring out some colour contrast then curves in Lab mode is the best way to go. Less Short Explanation: No real revelation here, but blend modes create new values based on the interaction of the values in a base layer and a blend layer. With multiply mode it multiplies the the values of each colour channel (as a percent) to produce a new value. So, going channel by channel Photoshop will do the following (in RGB): (base layer x blend layer)/255 as an example, if you had a solid colour, r:118 g:65 b: 33 and you created a duplicate layer and switched the blend mode to multiply on the top layer, you'd get the following result; r: (118 x 118)/255 = 55 g: (65 x 65)/255 = 17 b: (33 x 33)/255 = 4 r:55 g:17 b:4 1) if either layer's channel has a value of 0 then the result will be 0 2) If either layer's channel has 255 as a value then the result will be the other layer's channel value Because of this, multiply will create contrast with a duplicate layer, but unless you're using pure white, it will always darken the image as well. By reducing the opacity of the blend layer, you also reduce the amount of contrast added. Overall, you have very little control this way. Screen mode is similar only with the inverse effect: 255 - ((255- base layer)(255-blend layer))/255 Curves is the best option for overall contrast. It just maps out densities along a gradient and allows you to manipulate them. In RGB and CMYK you can alter the master curve, or the curve of each channel individually; it is the single most fluid tool for this in Photoshop. LAB mode, however, is unique. It is comprised of three channels: one for luminance and two that contain colour data. The channel structuring is a little odd, but the important thing to understand is that lightness and darkness in the image are determined by the luminance channel. The a and b channels control colour. Because of this you can control the overall contrast of the image by adjusting the curve for the luminance channel and you can control the colour contrast separately by adjusting the curves for the a and b channels. Actually, that's a really bad explanation, but halfway through I realized that it wasn't as simple as it all seemed in my head. Well, there are some very simple and practical applications of these things, but they make more sense when you see them done.
(This post was edited by kriso9tails on Nov 20, 2008, 5:51 AM)
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Edit Log:
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Post edited by kriso9tails
() on Nov 20, 2008, 3:10 AM
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Post edited by kriso9tails
() on Nov 20, 2008, 3:18 AM
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Post edited by kriso9tails
() on Nov 20, 2008, 3:19 AM
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Post edited by kriso9tails
() on Nov 20, 2008, 3:21 AM
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Post edited by kriso9tails
() on Nov 20, 2008, 4:03 AM
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Post edited by kriso9tails
() on Nov 20, 2008, 4:56 AM
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Post edited by kriso9tails
() on Nov 20, 2008, 5:51 AM
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