Here's an extreme B&W conversion I chanced upon for Photoshop. Don't know whether it can be adapted for other programs. It works well on blue skies and white clouds, but the is a enough control for many effects, just experiment a bit.
Anyway, here you go.
For those that don't know, here is a run through of the Dual Sat method plus Channel mixer. A nice landscape pic with blue sky and white clouds will give the best results.
1. With the Background layer highlighted, click the Create New Fill or Adjustment Layer icon and choose Hue and Saturation. Set the saturation slider to -100%. The image will change to a B&W. Double click on the Hue and Saturation layer and rename the layer ‘Sat -100%’.
2. Again, with the Background layer highlighted, click the Create New Fill or Adjustment Layer icon and again choose Hue and Saturation. Don’t move any sliders, and click OK. Double click on the new Hue and Saturation layer and rename the layer ‘Sat Colour Adjust’. Below the Layer Tab in the Layers Palette is the Layer Blending Mode. This is usually says ‘Normal’, but we are going to change the Layer Blending Mode of the ‘Sat Colour Adjust’ layer to ‘Color’.
3. Double clicking on the Layer Thumbnail icon of the ‘Sat Colour Adjust’ adjustment layer. The Hue and Saturation menu with the sliders will appear. Move the Hue slider, and notice the changes happening to the image, not just the sky, but also the other elements of the picture. Make the blue area of the sky as dark as you can.
4. Now highlight the ‘Sat -100%’ layer and make a new Channel Mixer adjustment layer. If there is a 'Monochrome' box tick it, and then set the Red Channel to 100% and the Blue and Green to '0%'.
I like this method over just the Channel Mixer method, as there is only 1 slider to adjust in the ‘Sat Colour Adjust’ layer, as opposed to the Red, Green and Blue sliders in the Channel Mixer.
Now because I had the Dual Sat method, and a Channel Mixer layer up at the same time, I played about with how the Channel Mixer interacted with the Hue & Saturation layers. With the Channel Mixer layer above the other layers, I found that if I set the Channel Mixer to 100% Blue, and the Red and Green sliders to 0% and turned off the -100 Saturation layer, blue skies went a lot darker, and gave me the look that I have been striving for in my B&W landscapes. It can make pictures a bit noisy, but I haven't got as far as noise reduction yet.
You can also play will masking areas of the image off on the adjustment layers that you don't want to be affected as much, but that can get a lot more complicated.
I had not heard of anyone doing this anywhere else, but apparently Russell Brown, the Senior Creative Director of the Adobe Photoshop team did it before me.
Here's a picture with the effect. Not great picture, but it shows how it can darken blue skies
The is also the free
Virtual Photographer plugin that can give some very good effects, and not just for B&W. Try the 'Dramatic B&W setting for something similar to all that above.
Picassa's "Filtered B&W' can give good results has has been mentioned, and is good for seeing the effect of different simulated coloured filters on a B&w image.
