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10 February 2007 @ 07:55 pm
Tutorial: Lightening images  
First off, I'm sorry it's been so long since I last posted a tutorial! I was doing tech support for another graphics app, so I naturally didn't want to do any more tutorials on my off time. But I've switched jobs, so here it goes.

wandersfound asked for assistance lightening an image. I have combined suggestions on that post with some of my favorites for the following tutorial.

If you have a dark image, there are a few things you can try to bring out the highlights. Of course, not every image can be rescued from underexposure or bad lighting, but we can sure try.

Here's the image we're starting with:


If you want to see any of the screenshots larger, just click.

The Addition Method:
1. Duplicate the background layer
2. Set the layer mode of the duplicate (Background Copy) to "addition"
3. If you want to make future modifications, merge the two layers (Layer > Merge Down)


With Curves:
1. Bring up the Curves tool under Layer > Colors > Curves
Notice the histogram (bar graph) underneath the straight diagonal line. The histogram reflects the proportion of pixels that are x level of grey, but we can change all that.
At this point, you could hit "auto" and be done, but here's the manual method
2. Start by creating the mid grey, light grey and dark grey points:

This helps you keep the middle grey static, otherwise any adjustment to the curve will affect the rest of the curve.
3. Make the dark points lighter by grabbing the dark grey point (the one closer to the dark part of the axis gradient) and dragging it upwards:

You can see in the preview that our image looks muddy. We can change that.
4. Brighten middle grey by grabbing the center point and dragging that upwards as well:

Don't be afraid to move these points horizontally as well!

With Levels:
1. Get the Levels tool under Layer > Colors > Levels
You want to concentrate on the Input Levels section of the window. The histogram again shows the proportion of pixels with that value of grey. The three triangles show you where "black," "white" and "middle grey" sit. Moving the triangles will change the brightness of the image.

2. Moving middle grey to a darker value will brighten the image because more of the pixels will now be lighter than middle grey. So grab that middle triangle and pull it to the left:

3. You may also want to move the white slider to make more pixels on the screen as "pure white." Be warned that moving the white or black sliders will move middle grey as well.

4. You could also try changing the Output Levels section: Move the black (leftmost) slider towards the right, and set the darkest pixel possible:

I don't recommend it, as it hasn't worked well for me, but you may find a use.
5. Don't forget about the eyedroppers! See a point in your image that is a perfect black? Click on the black eyedropper and then the perfect black on your image. Do the same for a perfect white spot with the white eyedropper, if appropriate.
Good black points: pupils, deep shadows
Good white points: light sources, reflections off of super-shiny surfaces
Keep in mind that the hue of the image may change to reflect the hue of the source point. Here's what happens when my middle grey is from a point that is yellow in hue:

To compensate for the yellow, the image has become greenish blue.
And when the middle grey is a blue of the same value:

The image is decidedly reddish orange.

Brightness-Contrast:
Probably the most straightforward of the brightening methods.
1. Bring up the Brightness/Contrast under Layer > Colors > Brightness-Contrast
2. Moving the Brightness slider to the right will make the entire image lighter:

3. So move the Contrast slider to the right and make the image less muddy:


Other Ideas:
1. Make a white layer on top and set it to "overlay" or "soft light":
(thanks, divergent!) Play with other colors for interesting effects.
2. Duplicate the background, desaturate it (Layer > Colors > Desaturate) and set the desaturated copy to "dodge" or "addition":

3. Use the dodge tool (type=dodge, mode=shadow or midtone) for troublesome spots:


Results:
Original Addition Curves Levels
B-C White Overlay Desat Addition Dodge



Things to keep in mind:
- Every image is different. I can't stress that enough.
- Combine methods! If one doesn't get it light enough, duplicate the layer and try another method on top.
- You could always mix layers, too: change the opacity or mode of another lightened layer and see if that gets the effect you want.
- Sometimes the image is just too low quality: if the resolution isn't high enough, there isn't enough data to turn shadows into midtones, and the result is grainy or otherwise unpleasant. Try finding another cap with a higher resolution, or brighten the image before scaling it down.
 
 
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(Deleted comment)
a DJ who lived in seclusion: sunny grinknittinggoddess on February 11th, 2007 07:13 pm (UTC)
You're welcome!