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Understanding a few things...


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There are a few features that I'm not entirely sure how to use, what it can be used for, etc.. I have checked all of these throroughly in the in-program help option (F1), however still am confused on them a bit.

Layers>Adjustments>Curves...

I under stand how to change the line, but I have no idea where to put the points and why. I understand that the one section brightens up the picture and the other darknes it slightly. How does it know what its brightening? Or is it the entire layer? And how does this differ from brightness?

Layers>Adjustments>Autolevel

I have absolutely no clue what this is for. The help thing states:

This can be used to equalize the colors of an image so that overly dark or bright images are brought back to a normal range. This is equivalent to using the Levels adjustment and then clicking the "Auto" button.

Layers>Adjustments>Levels

Same thing as above, I don't understand it entirely.

And just real quick, what is "alpha blending?"

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Layers>Adjustments>Curves...

How does it know what its brightening? Or is it the entire layer? And how does this differ from brightness?

Layers>Adjustments>Autolevel

Layers>Adjustments>Levels

And just real quick, what is "alpha blending?"

Layers->Adjustments->Curves is a way to change the brightness values of a layer. The horizontal axis is the "current" value and the vertical axis is the value that the current one will become after you click "OK." For example, if I wanted to brighten up the parts of my image that are 50% gray, I would make a control point in the middle and move it up. If I wanted to make the values that are 75% bright a bit darker, I'd put a control point on the diagonal line 75% of the way to the right and move it down. Playing around with it really helps figure out how it works. A tip: only play around with it with 2 or 3 control points at first...otherwise it can be hard to understand what's going on.

The Levels and Autolevels are similar...they're for controlling the brightness settings for a layer. The sliders on the left sort of limit max/min values from the original image. For example, if I had a photo of a piece of paper that was a bit dark (but I wanted it white), I would move the top slider on the left down until the paper turned white. If the letters on the page were grey and I wanted them black, I would move the bottom slider up. The sliders on the right control the output levels. The middle slider makes the image brighter/darker. The top and bottom sliders select which brightness values will be the whole images' new max/min values. Usually, you want the top right and bottom right sliders to be at the top/bottom of the slide. The middle one is the one you want to play with most often. Autolevel is an algorithm that picks positions for the slider that are probably pretty good for a normal image.

Alpha blending determines whether or not when you paint (or do anything else with transparent colors) the new color is added to anything below it or simply replaces it entirely. Play around with it to see. You'll usually want it turned on.

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