Advanced BW RGB processing

[slackercruster]

Read some Color to BW converions use RGB masks giving seperate control to each layers. Do you find this technique important to use? Compared to a quick Lightroom BW conversion with tone and contrast controls alone used.

 

[Garbz]

You'll need to elaborate on what you mean by masks and layers when it comes to converting to black and white. Do you mean the colour channels by chance?

If so yes. Black and white is all about tone control. In the old days we did that with a whole collection of expensive colour filters on the lens.
If not then still yes. Any tool that gives you custom control over the tone in the image is important to a black and white conversion.

 

[slackercruster]

Don't know much about it. But color channels sounds right.

Do you have examples of what a regualr BW conversion would look like as compared to a BW color channel conversion?

 

[KenC]

The current versions of PS (at least since CS5) give you not only R, G and B sliders to adjust during conversion, but also C, M and Y, so you can really fine-tune your tonal values arising from any particular color. It's even possible to mask multiple BW adjustment layers and use different settings for different parts of the image, although I've never gone that far. I never used LR, so I can't comment on what's possible there. I don't have any examples because I only use the BW adjustment layer to do conversions, and in the previous version of PS that I had (CS) I used only the channel mixer which allowed R, G and B adjustments.

 

[KmH]

ACR's (Lightroom/Camera Raw) HSL/Grayscale panel gives you 8 color sliders to use for making B&W conversions.

PsCS5's B&W Adjustment layer gives you 6 color sliders, or you can use a Channel Mixer Adjustment layer that gives you 3 color channel sliders.

 

[Garbz]

Don't know much about it. But color channels sounds right.

Do you have examples of what a regualr BW conversion would look like as compared to a BW color channel conversion?

Exactly the same, depending on how you do it. There's a few direct methods to convert a colour image to black and white:

Value based: Takes the RGB value adds them together and divides by 3. For a perfect set of red green and blue stripes they would all look 33% grey. A yellow, purple or cyan stripe would look 66% grey, and white looks white.
Lightness based: Takes the RGB values but weights them according to how our eye perceives colour intensity. I.e. A stripe of red green and blue, the blue looks very dark, the red medum, and the green bright.
Custom: The channel mixer allows you to select any arbitrary value of these: e.g. 100% Red, 0% Green, and 0% Blue is the same as a photo taken through a Wratten #25A Red Filter.

These are all colour based, There are other methods too such as changing the colour system to LAB and then dropping the A and B channel leaving only lightness as a result, or using a gradient map which in a very simplistic way could be explained as the curve tool used for black and white conversion.

The best way, is just grab a list of various methods from google: 7 Black and White Photoshop Conversion Techniques
And do some. Play around with a variety of images. There is no one way to do this conversion, it all depends on what looks good for a specific photo.