B&W Conversion Using The Channel Mixer
Submitted by mitch on Sat, 11/15/2008 - 14:56.
A quick and easy way to convert an image from color to B&W is to use the Channel Mixer dialog. You can blend information from the individual RGB channels into a B&W image.
If you look at the individual channels in an RGB image, you will see that each can be split into a new image. Each channel reacts to colored light differently. You can test this quickly in the Channel Mixer by selecting the Monochrome checkbox and then pulling the slider for each channel to 100 in turn, leaving the other two channels at 0.
For example, here's a color image from Scotland (who would have guessed?)
Just click the Monochrome checkbox and this is what you get . . .
I don't know who was the first person to demonstrate how to use the Channel Mixer to make a B&W image. I do know it is a common tip. What is not so common is how to siumulate B&W film filters to selectively boost the contrast of B&W conversions.
I found a few examples around the Web. Like the action set from Fred Miranda. Some recommendations in tips and tutorials. I found most of the filter effects to be lacking. So, I sat down with a corrected image of Macbeth ColorChecker Card and worked out some better settings.
| Filter |
Red
|
Green
|
Blue
|
Constant
|
| None |
45
|
35
|
20
|
0
|
| Red |
100
|
15
|
0
|
-15
|
| Green |
35
|
55
|
20
|
-10
|
| Blue |
15
|
15
|
80
|
-10
|
| Yellow |
60
|
30
|
10
|
0
|
| Orange |
75
|
20
|
20
|
-15
|
| Yellow Green |
25
|
65
|
15
|
-5
|
| High Contrast |
85
|
65
|
15
|
-40
|
To make it easy for you, I added a set of actions to my TLR B&W Conversion action set to automatically create Channel Mixer adjustment layers for these settings.
Let's look at a couple of examples. First, B&W conversion without a filter.
Now, B&W conversion with a red filter effect. Red filters lighten reds, make greens darker, and especially darkens blues.
Notice how the kilt darkened and the red border behind the stones lightened?
Here's a quick reference to B&W filters and the actions in my action set.
| Filter | Effect |
| Red | Lightens reds. Darkens greens and especially blues. |
| Green | Lightens greens. Darkens reds and blues. |
| Blue | Lightens blues. Darkens yellows. |
| Yellow | Lightens yellows. Darkens blues. |
| Orange | Lightens yellows, oranges, reds. |
| Yellow Green | Darkens reds, lightens greens. Good for skintones. |
| High Contrast | Not a filter, per se. Use to create high contrast image. |
I hope this technique helps with your digital B&W photography.
Don't forget to download my TLR B&W Conversion action set!
Technorati Tags: 
B&W conversion
How do channel mixer and other B&W conversions compare with the B&W adjustment layer offered in CS? And how does doing conversion in PhotoShop compere with doing in the Adobe RAW Converter 4.x?
Les
Re. B&W conversion
Channel Mixer was the preferred method by lots of Photoshop users before the B&W Adjustment Layer came along. The tip here is more relevant to users with older versions of Photoshop, since the Channel Mixer has been a part of Photoshop for a long time.
I love the B&W conversion abilities in Lightroom and ACR. I love being able to use the cursor to stroke the image and affect the underlying B&W conversion. (I really do need to make a video tutorial on this soon.)
You do need to be careful. If you whack the B&W conversion around a lot, you can make noise from one or more of the underlying channels more visible. I've seen a few threads on forums like Photography-on-the.net and DPReview.com about this.
The benefit of tools like the B&W Adjustment Layer is that they allow you to have selective conversions. It's like using a layer mask to apply separate settings to different features of a photo. Great stuff!
Advanced Digital Black & White Photography by John Beardsworth (A lark Photography Book) is a great reference and inspiration. I greatly respect his book Digital Black & White Photography, too. In some ways, it's the more advanced book. Especially when it comes to printing.
Have you tried the B&W Adjustment Layer? Had good results with it?
B&W Conversion
I used to use channel mixer and almost every other B&W conversion except image/mode/grayscale with CS, but have been using B&W adjustment layer since I got CS3. I've had pretty good luck with it. (Or at least that what my daughter tells me.)
How about reviewing the two books you mentioned for us?
I've tried the B&W conversion in ACR 4.x but didn't really like it for some reason.
Just wondered what others' felt.
Les
Beardsworth Book Reviews
Sure. I'll be glad to review both books. I might be able to get them done tonight. ;)