Level: Increasing from Basic to Advanced
Offhand I would say to know at least a dozen of different techniques for converting color photos into black and white images, and there are even more plugins doing the job for you. For a hands-on approach with full control here are three of the most important conversion methods in Lightroom and Photoshop.
Which is the best method? None, it always depends on your image. They all can lead to a good starting point before giving the images the perfect look.
The Gradient Map is probably simplest useful method of converting a color image into a greyscale image. Open a color photo in Photoshop, make sure in the tools panel the foreground color is black and the background color white, from the adjustment panel add a Gradient Map layer.
Though not having any influence on the conversion this method can save your life if the other two don’t work well for any reason. If the bw conversion you created with the Gradient Map layer looks like a negative slide, the background colors in the tools panel were in the wrong order.
Pro: Converting your your images to black and white with a Gradient Map is extremely fast. Compared to the standard greyscale conversion in the image mode menu on top it is non-destructive. The layer can be deleted anytime.
Con: You have zero influence on the results: take it or leave it.
Conversion with Color Sliders
The conversion with sliders is kind of most people’s standard. You can do in the RAW converter already, like in Lightroom or Capture One, before translating the RAW image into pixels. If working with jpeg files it does not matter whether you work in Lightroom or Photoshop for this conversion.
In Lightroom navigate to the development page, click on “Black and White” (in the “Basic” tab on the right), and scroll down to the “HSL/Color/B&W”. For the preferred Black &White Mix we can move the sliders left and right. Each slider will darken and brighten a color in the underlying original color image.
In Photoshop more or less the same conversion method can be found in the adjustments panel. Add a “Black and White” layer and you will see the sliders show up in the properties pop-up window. Same here, move them left and right until you reach your desired black and white image as a starting point for further improvements.
Pro: Lots of control on the conversion details though still being a very fast technique
Con: Not much, just take care if sliding to the far right and far left. Sometimes you might see some undesirable side effects.
BW conversion with Channels
This technique is clearly in Photoshop’s playground. It is a little bit more work but can bring fantastic crisp and clear results. Open a color image and switch from the “Layers” tab to the “Channels” tab (as we did in the most recent masking tutorial).
Click on the red channel, then on the green channel, and as last on the blue channel and choose which of the black and white conversions is you favorite starting point.
When you are sure, press Ctrl+a for selecting all (marching ants show up around the image frame), click on the RGB channel once (brings your color image back), switch back from the Channels tab to the Layers tab, press Ctrl+v for inserting your selection.
If things went well, a new layer with your black and white selection was created, which now can be further improved non-destructive with the curves tool (see earlier tutorial) and other adjustment layers. At best give the new layer the name “red channel bw conversion” or something similar.
Pro: Very precise and highest flexibility (red the extension below), often very crisp and clear conversions.
Con: None, well, it is going to be more work than the other techniques.
Going Pro: Extension of the Channels Conversion
Sometimes the favored channel of bw conversion in this technique shows more noise in the darks. Or sometimes parts or the image are better in one channel, other parts of the image are better in another channel. Good news, there is a way to merge these things – thanks to the layer masks wew were practicing on in past weeks’ tutorials.
Let us assume we had added the red channel as our favored black and white conversion to the layers tab. But if zooming into the image we had discovered in the blue channel there is much less noise in the darks. Why not apply the blue channel conversion to the dark parts and the red channel conversion to all the rest?
One channel we already have chosen and copied to the layers. Let’s say it was the red channel. For adding another channel on top we first have to deactivate the new layer “red channel bw conversion” by clicking on the eye icon next to the channel, making the conversion effect disappear. We are back to the color image again. Now activate the base “Background” Layer by once clicking on it.
Ok, same procedure as before. Switch to the channels tab, click the blue channel, Ctrl+a for selecting all, click on the RGB channel once to make the color image show up again, switch back to the layers tab, Ctrl+v for inserting the blue channel black and white conversion. Rename the new layer to something like “blue channel bw conversion”.
We now should have a base “Background layer” and two newly created differing versions of black and white layers on top. For our purposes we probably have to change the order a bit, putting the blue channel bw conversion layer on top of the red one (simply drag and drop the layer with the mouse). Then we can also reactivate the red channel bw conversion layer by clicking on the eye icon again.
Let’s recall, we want to apply our assumed low noise blue channel bw conversion layer on the dark parts of the image. Presentl y the blue channel conversion layer is on top and 100 percent dominant. The red channel conversion underneath has zero effect.
Well, having followed past postings you already know what to do for limiting the effect of the blue channel on top to just specific areas of the image: create a mask, blocking out the effect of the top layer, and painting in only the areas where the top layer should be applied.
Activate the top blue channel conversion layer with one click. A basic black mask for blocking the layer effect totally you might remember can be created by Alt+Click on the rectangle with hole icon in the bottom (all described in more detail past tutorials). Activate the mask with a clicking on the new black rectangle in the layer (which actually is the mask).
Pick the brush from the tools panel and paint with white into the dark areas in your image and wherever you painted the low noise conversion from the blue channel bw conversion layer will shine through wherever you want. Noise is more prominent in darks, so you might want to paint the dark areas.
What, painting all dark areas in the image by hand? I agree, it’s not the way I would do it, too much work. A way more sophisticated mask especially for this task, created automatically by Photoshop, would be a Luminosity Mask. This is going to be explained in the next tutorial.