Firefox 3 has support for color management, but it’s turned off by default and the only way to turn it on is to use about:config

Type about:config into the address bar
Type gfx.color_management.enabled into the find bar of the about:config screen.

Doubleclick the word false so it turns into True, and close the about:config page and restart Firefox.

Now Firefox will display photos with embedded color profiles properly and use color management. Photos without embedded color profiles will default correctly to sRGB and display as they would without color management.

First, always always shoot in RAW. That way the white balance is just a parameter attached to the RAW sensor data and not hardcoded into a jpeg that you will have to white balance and destroy image data. Shooting in RAW also gives you about half a stop more leverage in case you get your exposure wrong.

One of the most important things you can buy is what is called a greycard. The best is Gretag Macbeth, pricey but well worth it. There’s also a cheaper one called QPCard that also works great, either way… get one.

When you shoot your images, turn of auto white balance, shoot RAW and start each new location with a couple snaps of your grey card.

When you get home load up the images in photoshop, and add a curves adjustment layer. Now locate the button with the little eyedropper icon in the curves dialog and set the white, black and grey points by clicking on the corrosponding paches on the greycard and voila, perfect color balance.

If you don’t have a greycard you’t not completely screwed though.

Have a look at my Color Correction by the Numbers article.

Here’s a simple way to defringe colored edges, whatever the cause.

Add a new layer on top of your original image. Set this layer to the color blending mode. Zoom into your image so the colored edge is easy to see. Hit I to select your color picker and pick a color right next to where the colored edge you want to remove, don’t click the colored edge itself. Switch to your brush tool, set opacity real low, like 20 and make sure the brush edge is real soft. Adjust the brush size so it’s around the same size as the edge you want to remove.

Now simply paint over the edge and watch it disappear like magic, it will take on the color of the underlying layer eliminating the colored edge.

If the edge continues and the color next to the edge changes, make sure to pick up the color with the color picker again so the color you paint over the edge matches.

In LAB however we have luminance (The L channel) split from the color channels (A and B) and LAB is device independant so you can have an image with an L value of 100 (Max) AND have positive values in the A and B channels which in RGB would mean values above 255. This is not possible to show on a RGB device such as your monitor, but photoshop tries anyway to map these impossible colors to something that looks alright, and that’s a great thing.

One thing you can use impossible colors in LAB to do, is to fix blown highlights.

First load an image with some moderate areas of blown highlights, like a portrait shot with blown highlights on the forehead or shoulders for example and switch the color mode to LAB.

Duplicate the background layer so we are not working on the original. Now select the duplicate layer and set the blend mode to Color, use the color picker to select a color near the blown highlight and simply paint over the blown areas, don’t worry if this looks horrid and don’t try to be to presize, just make sure you painted over the blown areas. What you are doing is telling photoshop to leave the luminance alone (It’s maxed at 100) and ADD color to the area only. Well that’s not possible since that means more than 255 on your monitor, but photoshop tries anyway.

Now add a curves layer clipped to the color blend mode layer and fiddle with the color to get it to match the surrounding area as best you can. If you don’t know, you clip an adjustment layer to the underlying layer by holding down ALT and clicking right between the layers. Clipping adjustment layers to the underlying layer means the adjustment layer will ONLY affect the layer below.

Now comes the reason I said don’t worry about being presize. Doubleclick beside the color mode layer to bring up the layer adjustments dialog. See the sliders labelled Blend If Make sure you are using the Lightness channel and select the Underlying layer slider and grab the white arrow and pull it to the middle. This allows us to affect ONLY the impossible color we created and blend it out. Just pulling the white slider creates harsh transitions but if you hold down the ALT key and grab either side of that little arrow you can split it in two and create feathered edges that blends much better.

If there’s colors you can’t blend out properly using the lightness channel you may need to select the A or B channel and play around until you find the correct color to blend the impossible color out of.

You can deal with chromatic aberration in Camera RAW, but the best way is to deal with it inside photoshop where we have a much more powerfull environment to help us.

Chromatic aberration is caused by channels not aligning properly at places in the image. We can fix this by using the lens correction filter.

First convert your image to a smart object from the filters menu, and then select the Lens Correction filter from the filters/Distort submenu. When the filter dialog is open, turn of the grid by unchecking the tickbox in the lower part of the dialog as we don’t need it, it’s used to fix things like barrel distortion or pincusion distortion.

What we are interested in here is the Chromatic Aberration sliders labelled Fix Red/Cyan and Fix Blue/Yellow fringe. Adjust the sliders according to the color of chromatic aberration you have in the image. Watch other parts of the image as you adjust as fixing Red/Cyan may bring out Blue/Yellow fringe. You probably will not be able to fix everything, but don’t worry, the best is yet to come.

Done? Good, OK out of the lens correction dialog.

Any chromatic aberration left in the image is useually just color noise so lets fix that. From the filters/Noise menu select Median.

Whoa this can’t be good, it’s blurred my image so it looks like ass? Yes, that’s what we want. Adjust the amount slider so the chromatic aberrations you have left is blurred nicely, somewhere around 10-20 should do. Ok out of the median dialog box.

Right now we are applying the median filter to both color and luminance and that blurs the whole image like applying gausian blur or something.

Locate your median smart filter layer, see that little icon that looks like a couple sliders right beside the filter layer?

Doubleclick that and bring up the blending modes for the median smart filter.

Ready? Set the blending mode to Color and watch the remaining chromatic aberration being wiped out like magic.

By the way If you are A/B’ing your changes and get an annoying progress bar taking forever each time you turn a smart filter on/off, just turn it off once, then use undo/redo (Control+z) instead and A/B’ing will be instant.

To correct a color cast, you need to find the white, black and gray areas of your image and make sure the RGB values line up, for example if you have a white area and the histogram tells you that the values are 245,240,253 at the whitest area of your image then you know you have a color cast, the problem lies in finding these areas, just hunting around your image and pecking at the colors by looking at them is a tedious and error prone process.

Fortunately photoshop can help us here. First go to your layers palette and select ‘threshold’

Once the threshold dialog comes up, pull the slider all the way to the left, this will turn your image white, now *slowly* move it towards the middle, the first colors you see come back is your darkest areas, so click OK to add the adjustment layer.

Now go to your toolbox or hit ‘I’ a couple times until you get the color sampler tool, place a marker at a splotch of black, you have now located the black point that we need for later.

Now double click on the threshold adjustment layer to bring up the dialog again, this time move the slider all the way to the right, then slowly move it back towards the middle, the first colors that comes back now will be the whites areas, click OK.

Now place a color marker again at a white splotch of color, you have now located the white point in your image.

Now comes the tricky part, locating the gray area of your image, the threshold layer won’t be able to help us here unless we give it a little help ourselves.

Make sure you delete the old threshold adjustment layer since we are done with that.

Add a new blank layer above the image, fill it with 50% gray and set this layers blending mode to Difference.

Now we can add a threshold adjustment layer above the gray layer, move the slider all the way to the left, then pull it towards the middle, the first colors that comes back now will be our grays. Note that some images will not have a gray area, so if you find you need to pull all the way to the middle there is probably not any good gray area in your image.

Add a color marker at the gray area, and we are ready to neutralize our white, black and gray (If any) points, make sure you delete the gray and threshold layer before you continue.

You probably noticed an annoying window popping up every time you added a color marker, this window is very important so move it to the side so it won’t be obscured by other windows and have a look at it.

You will notice your color markers are displayed here, numbered #1, #2, #3, which corresponds to the black, white and gray markers you placed. These colors needs to be neutral, the RBG values needs to be the same or else there is a cast in your image, this is where the Curves dialog comes in handy.

Add a Curves adjustment layer. Let’s start with the blacks, look at the RGB values, we have a cast here in the reds, you can see it says 7 and the green and blue values are at 1, so wee need to bump down the reds, select the red channel from the drop down at the top of the curves dialog.

Move your mouse cursor out into the image area, now press and hold the control key down while also pressing the left mouse button and move exactly to the color marker labeled #1, you will notice while you move the cursor around a little bouncing ball flails around in the curves dialog box, and soon as you let go of the control key, a point will be placed in the curves dialog. Now that you have placed a point in the reds curve we need to ‘lock’ the affected area down so we don’t touch other colors near the reds, you do that by placing another point in the grid above the point you placed.

Now you can press tab and shift-tab to select the first point, then move the point downwards by pressing the down arrow key, watch the red level in the info palette for the black marker, and stop when it’s a 1 like the 2 others. Note than sometimes you will need to place more than 1 lock down point a little higher or lower in the curves grid, if you find that the slope affects to much of the image, watch the other color markers while you change the values, if the others are changing to you need more lock down points.

From here on it’s simply a matter of repeating the above process for the white and gray values, I suggest you allways start with the grays, as fixing the grays usually brings the blacks and white closer together and takes a lot of the work out.

But how do you find out which value is the correct if all 3 (RBG) values are different? Well, that’s where you need to use your eyes, does the image look to blue (Cold) or to warm (Red) or is there a tint to the image that looks wrong? This is why I suggest that you always fix your grays first as that will usually fix a weird cast and bring the blacks and whites closer together.

Be aware that this is a very mathematical approach, it is a ‘by the numbers’ technique after all, 100% correctness (Is that a word?) is not always flattering, but it is a very good starting point for adding back warmness or other curves corrections like the standard S curve and L*A*B steepening of colors.

Color Correction must always be done before you try to boost colors and contrast. If you have a cast and you try to boost colors you will make the cast even worse. My workflow is fix image dimensions, then crop if needed. You always want to crop before you do any color correction.