Color Correction with Photoshop in 7 Easy Steps
One of the most difficult things to do when you’re starting out in digital photography is to recognize and remove a color cast from an image. Not only do you need to work out that you’ve got a color cast, but you also need to find a means of fixing it.
One method of color correction that I like to use is one that I learnt from Photoshop gurus, Dan Margulis and Taz Tally - any errors in this process are mine and not theirs.
The process relies on reading data from the image and then adjusting the numbers that the image provides. It’s a way to remove a color cast that is relatively simple and which involves reading and setting RGB values rather than making objective decisions about an image. I’ll show you how to do this using an image shot in the early morning and which is hazy, underexposed and which has very poor color.
Step 1
To get started, open an image that you think has a color cast. Choose Window > Info to display the Info palette. This gives you information about the pixels in your image and, if you’re working with a standard photo, you’ll have RGB mode displayed in the upper left corner of the dialog.
Step 2
To make the color correction I’ll use the Info palette to display information about the image. To do this I’ll need to make some color sample points on the image and I’ll do this using the Color Sampler tool which shares a toolbar position with the Eyedropper. Click the Color Sampler tool and, from the toolbar, select the 3 x 3 Average Sample. This is important as you’ll want to sample a larger area than just a single pixel.
Step 3
Now locate a place on the image which should be white or a light neutral gray in color. Click on it with the color sampler tool and you’ll see a marker appear on the image with the number 1 beside it. Make sure the point you select is one which should be white or light gray and don’t select an area of the image which is blown out such as a light spot.
Repeat the process, this time clicking on another point which should be either white, black or a neutral gray. This gives you a second sample point. You can continue and add a total of four markers if desired. Each should be placed in an area of the image which should be white, black or a neutral gray.
Step 4
Check back in the Info palette to read the color information for each of these points. For the lightest points you should see values of around 245 for the R, G and B channels. For the darkest points the value should be around 15 for each of the channels. For gray points you should have equivalent values of R, G and B, although they can be any value, they just need to be roughly the same for each.
Step 5
If your image has a color problem you’ll find that the numbers at each point are not within a range of 2 or 3 values of each other. To color correct the image what you’ll do is adjust the curves for each of these channels to bring them closer to each other. Choose Layer > New Adjustment Layer > Curves and click Ok. You’ll be correcting individual channels so from the Channel dropdown list select Red and then Ctrl + Click on the first point that you marked in your image. This adds a small marker on the curve line which shows you where this point in the image appears on the curve.
Identify whether you need to increase or decrease the value at this point. To increase it, drag upwards and to decrease the value drag downwards. You’ll see that you’re not making subjective judgments here; you’re simply adjusting the curve to bring the numbers closer together and closer to the desirable value of 245 for a white point and 15 for a black one.
Step 6
Repeat this last step for all the sample points that you created on the image and then repeat it for the Green and Blue channels so that you end up with all the sample points containing values that are within 2 to 3 values of each other.
Step 7
When you’re done, click Ok to close the Curves dialog. You can now apply other fixes such as adding contrast to the image with a further Curves adjustment or use the new Brightness/Contrast tool in Photoshop CS3.
Using the Info palette combined with sample points on the image makes it easier to remove color casts by reading and adjusting numbers.
20 Responses to “Color Correction with Photoshop in 7 Easy Steps”
January 14th, 2009 at 2:21 am
There are times when colour correction whether global or local would be better performed in LAB mode. This is because in RGB you can only directly affect the Red, Green and Blue colours and other colours indirectly by their combinations.
In LAB mode you can directly affect Yellow/Blue and the Red/Green which can give new variants on changes.
For images with multiple light sources do set measuring points with the eye dropper and then hand tune the curves for each of the measuring set points.
Niels Henriksen
January 14th, 2009 at 3:36 am
This seems like it could be quite helpful, but It would be really helpful to me to see a before and after.
January 14th, 2009 at 6:05 am
To make this a little simpler, you can define those points in the Curves dialog box itself.
January 14th, 2009 at 9:18 am
Good article. I would also like to share a genious tip on how to find neutral grey (50% grey) in a picture:
1) Make a new layer.
2) Fill with 50% grey
3) Set blending mode to DIFFERENCE on the grey layer.
4) Add a THRESHOLD adjusment layer. Drag the slider all the way to the left and start dragging it to the right. The first black areas that first appear on the image are 50% grey in your image. Add a marker with the Eyedropper tool as explained in the article above on one of these black spots.
January 14th, 2009 at 10:42 am
i would like to agree with deirdre, before and after would be good
January 14th, 2009 at 7:03 pm
Thanks a lot for this. I realise this may seem odd to some people, but have you tried using Picasa for basic colour correction? Apologies if I’m preaching to the converted here, but I do know some people who have tunnel vision and regard Photoshop as the best and/or only solution to every photographic problem. :)
I’m obviously not trying to suggest Picasa is superior to Photoshop, but I use it for sorting my images and doing some of the basic work that can take a lot longer in other programs. If you click on a photo and use the ‘tuning’ tab on the menu you get a nice little pipette icon with which you can click on a white or light grey area and it automatically adjusts the image for you. I’d be interested to see how this compares to Photoshop’s results, but it seems to be the same process, simply automated.
January 14th, 2009 at 9:55 pm
Nice tutorial, I’m never one for getting colours right straight away so this helps!
January 15th, 2009 at 12:51 am
@zetson Awesome tip. Tried it out and it worked great. Thanks!
January 15th, 2009 at 2:32 am
Interesting, thanks :-)
January 15th, 2009 at 4:08 am
Great process! That made color correction very easy. Thanks for sharing - you saved me a lot of time fiddling with “Color Balance.”
@zetson - also a great tip! Thanks
January 15th, 2009 at 3:41 pm
interesting I will have to give this a try!
January 15th, 2009 at 10:26 pm
This works! Thanks for the detailed tuorial.
January 16th, 2009 at 12:06 am
for someone who is just new in photoshop can someone direct me to a site for beginners. I am hearing about RAW and all these scare me
January 16th, 2009 at 2:09 am
Hi Bode, You should, err, try this one :) Have a look around in the forums, there are many people that can help you in there.
Best,
Sime
January 16th, 2009 at 8:19 am
Yes, this procedure will find neutral gray in the UNcorrected photo. But that isn’t what you want …. you want what SHOULD be neutral gray once the photo has been corrected. Scott, Dave and the rest of the Photoshop guys are flat out wrong on this one. They have backed off in version two of their color correction using gray dropper …. saying to the effect “this method will often get you close.” When you click on gray eye dropper, you are telling PS to “make this color neutral because it should be neutral …. that is, it should be gray. Gray is an equal mix of R, G, and B.
Anyway, this is something that got started … and wasn’t thought through all the way. While it may get you close, it’s logical is wrong. Think through it yourself to understand the flawed logic. Anyway, …… good day. :-)
Jeff
Good article. I would also like to share a genious tip on how to find neutral grey (50% grey) in a picture:
1) Make a new layer.
2) Fill with 50% grey
3) Set blending mode to DIFFERENCE on the grey layer.
4) Add a THRESHOLD adjusment layer. Drag the slider all the way to the left and start dragging it to the right. The first black areas that first appear on the image are 50% grey in your image. Add a marker with the Eyedropper tool as explained in the article above on one of these black spots.
January 17th, 2009 at 1:49 am
I am apparently Doin’ It Rong, because mine came out really weirdly colored.
January 18th, 2009 at 4:27 am
When you do a custom white balance, use a polarizer or set the camera to cloudy, you will get a better, less blue cast, picture outdoors to begin with, so you won’t have to mess with the color balance. Do it correctly when you capture the image and save a lot of post processing time. Another alternative is to change the camera settings using different white balance pre-set modes on the camera and select the best color and best exposure for the desired effect for the image from several shots when you upload them. Be sure your monitor is calibrated properly as well as your printer.
January 19th, 2009 at 2:43 am
Didn’t work for me either.
when I move the curve for one sample the other one moves as well.
It’s easier to jsut type inthe corrct ‘output’ number such as 245 rather than move the curve but still this causes the other samples to move. would be nice to see a youtube video on it should anyone want to create one.
I am trying the instructions from another tutorial - it it works I’ll post the link.
January 19th, 2009 at 3:26 am
yep–this link has a more fool proof method:
http://www.flickr.com/groups/photoshopsupport/discuss/72057594125375245
January 22nd, 2009 at 7:49 pm
A great method to use for accurate results, thank you. But for newbies - remember photography is an art form and use your eyes to get images YOU are happy with…….
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