Black and White Photography, Part 4

Technique 6 – Twin Hue/Saturation Adjustment Layers

I said earlier that using a single hue/saturation adjustment layer is not a good way of making a black and white image because it doesn’t let you control the conversion.  But the simple addition of a second hue/saturation adjustment layer gives you an adjustment that works with just a single slider and a drop down box.

To start, create a hue/saturation adjustment layer, and then just leave it.  If you want, you can name it “Adjustment” for ease of use.  Then, create a second hue/saturation adjustment layer above the “Adjustment” layer.  This one can be called “Desaturate.”  Drag the saturation slider down to -100% and set the blend mode to colour.

This gives you the same black and white conversion that you get using a single hue/saturation adjustment layer.  But the “Adjustment” layer beneath it gives you the option to create different effects.  Open up the “Adjustment” layer and slide the hue slider along.  You’ll see the tones of the image change.  Skin tones will brighten until they are almost white, then plunge into dark shades of grey.  Leaves will also brighten and darken, as will skies and cloths and just about everything else.

The reason is because as you drag the hue slider, you are changing the colours in the underlying image (if you want to see this, click the eye icon to hide the “Desaturation” layer).  And this means that the luminosity of each colour changes, getting darker and lighter, depending on where the slider is.  So, you might be changing the sky to a shade of green, or skin tones to purple.  This doesn’t affect the final image, of course, since there is another hue/saturation adjustment layer which is pulling all the colour out.  But the changes in luminosity remain, and so different areas of the black and white image get brighter or darker.

This technique is starting to give us more control, since we are easily able to adjust the luminosity of pixels depending on their original colour.  We can get more control over the conversion because we can choose particular colours to adjust from the drop down box.  You can choose red, and then the hue slider will only adjust red tones in the image.  But this technique can be a bit clunky to use as there you have to keep changing between colours in the drop down box.  Later techniques will have separate sliders for each colour.

Technique 7 – Calculations

This technique is actually quite powerful, and was one of the earliest ways Photoshop had to create black and white images.  It was also used back in the early days of Photoshop as an advanced selection tool, because it is able to blend channels together.  But it is listed here, instead of among the best of the best, for one reason.  It’s not very intuitive.  There’s no easy way to predict what results you’ll get.  It’s a matter of trial and error, playing around with different settings until you find one that suits the image you are working on.

Start by going to the Image menu, then choosing Calculations.  This opens up the Calculations dialogue box.  In this box, you can choose two sources, which Photoshop will then merge together.  For each source, you can choose the layer you will use (if you haven’t done any editing on the image, you can just use the background layer, but if you have done skin smoothing, you may want to create a merged layer to use), and you can then pick which channel you want to take.

What’s a channel, you ask?  In Photoshop, a channel is just a kind of selection, and it works the same way as a layer mask.  On a layer mask, you can paint white to show the layer, and paint black to hide the layer.  A channel is basically the same thing, a selection of a colour in the image.  White shows where there is a lot of a particular colour, and black shows where the colour is not present.  So, if you open a portrait and select the red channel (the channels palette is usually a tab next to the layers palette), you will see white where there is a lot of red in the image, such as the model’s skin, and black where there is very little red, such as the blue of the sky.  Similar channels exist for green and blue.

In Calculations, you are taking two of the channels and blending them together to create a new channel.  In Source 1, you choose the first channel that you want to use, and in Source 2, choose the other channel you want.  It will usually be a different channel, but you can choose the same channel for each source.  Once you have chosen both of your sources, choose the blend mode.  These are the same blend modes you have for blending layers together. With this technique, Overlay, Soft Light and Multiply often work well, but feel free to play with the others.  For portraits, you can try blending the red and green channels with the blend mode set to Multiply (or try Overlay if it comes out too dark), but this really is a technique that you have to play around with.  It’s almost impossible to predict the end result of this technique until you actually do it.

Once you have got the effect you like, you aren’t finished.  Calculations has not converted your image to black and white yet.  It has simply created a new channel.  To make the image black and white, create a new layer and fill it with black.  Then go to the Select menu and choose “Load Selection.”  Choose the Alpha 1 channel in the Channel box and click OK.  Then go to the Edit menu, choose “Fill” and select “White.”  This will turn any selected pixels white, but because the channel has created shades of grey, it means that some pixels are only partially selected.  As a result, when you fill the selection with white, they will not turn all the way to white, and will instead become a shade of grey.  This will give you the black and white conversion on the new layer you created.

In the next and final post, I’ll look at the most powerful black and white conversion techniques – the Channel Mixer, the Black and White adjustment layer, and Camera Raw’s Black and white conversion.