A Word on Luminosity

[Frank Piechorowski]

A technique for fixing a low contrast image.

Here is a simple technique for fixing a low contrast image like this

http://www.piechdesign.net/tutorial_img/luma_start.jpg

First we need a b&w layer of the image. We can get this a number of ways…

1) Desaturation
a) Click <layer><duplicate layer> - Give the new layer a name – I called my “Luminosity Layer”
b) Desaturate this new layer – Click <image><adjustments><desaturate> (or <shift><ctrl>+U)

2) Copy a Channel
a) Look through the channels RGB and see which channel makes the best b&w image
b) Click <image><apply image> and fill the new layer with that channel

3) Personal B&W converstion
If you're good at doing your own b&w conversion… use that as your new layer.

4) Set the blend mode of this new layer to “Luminosity”

Your layers pallet should now look like this:

http://www.piechdesign.net/tutorial_img/luma_layers_pallet.jpg

Now for the trick…

With your new layer highlighted in the layer pallet

5) Click <image><adjustments><levels> (or <ctrl>+L) to pull up the Levels box.
6) Drag the left hand arrow to the left edge of the histogram
7) Drag the right hand arrow to the right edge of the histogram
8) Fine tune the balance by dragging the center arrow to find what looks right to you

NOTE: For even finer control you could use a curve instead of levels.

Here are the values I picked for this image:

http://www.piechdesign.net/tutorial_img/luma_levels.jpg

Your final result will come out like this:

http://www.piechdesign.net/tutorial_img/luma_final.jpg

You can do farther fine tuning by adjusting the opacity of your luminosity layer.

This simple and fast technique can rescue many a flat, washed out image.

Give it a 'shot'... post your results.

[Tim Armes]

Hi Frank,

I'm not sure I see the advantages of this technique.

If I use your original image and simply use a levels layer to fix the black and white points, then I get a similar result...

Tim

[Frank Piechorowski]

Yes, but depending on your image you may get unwanted changes to your colors. This method allows manipulation of the lightness without worry of unwanted color change.

[JohanElzenga]

Another way of doing it is to convert the image to LAB mode, open up 'Curves' and steepen the Lightness curve.

[Nill Toulme]

I don't understand... why would setting the black and white points change the colors?

Nill
~~
www.toulme.net

[KrisCarnmarker]

If you create an adjustment layer and set its blending mode to luminosity you get the same effect, no? At least that's what I've been taught, but I'm no expert.

[Tim Armes]

Yes, but depending on your image you may get unwanted changes to your colors. This method allows manipulation of the lightness without worry of unwanted color change.

No problem.

Create a levels layer, alter the black and white points and then change the mode to luminosity. Same effect and a lot simpler.

In general I try to avoid any layers that involve copying a layer and making changes to it. In your example you lose both the B+W conversion and the levels settings. If you want to change your luminosity mask you have to start again.

75% of the time the same effect can be achieved by using adjustment layers, clipping masks and fusing modes, allowing you to find tune the settings at any future point.

Tim

[Frank Piechorowski]

Great stuff Tim.

The whole idea of these posts is to get people to add thier techniques. Photoshop is one of those great tools that gives you 1000 ways to do exactly the same thing.