I use Nik Software’s Silver Efex Pro to do my black and white conversions, and I have to say that I continue to be impressed with using the blue filter when editing landscape images.
Allow me to backtrack a little. I’ve always been very taken with drama in landscape photography, particularly of the kind where a blue sky goes to black or very nearly so, and any white clouds in the sky end up really standing out. In film photography, this kind of effect often could be achieved by placing a red filter over the lens. Colored filters tend to pass their own colors and block complementary colors, so a red filter tends to lighten up things that are red and, importantly, darken things on the other side of the color wheel from red, such as the blue in blue skies. As a result, with black and white film a darkened blue sky tends to show up as dark grey or black.
In the digital world, most black and white images are made starting with a color capture (because the color capture contains more information – three channels, one red, one green, and one blue – as opposed to a black and white capture, which contains just one channel of information – greyscale). Because there is color information in the capture, when converting to black and white, you can digitally apply a “blue filter,” which will tend to lighten things that are blue and darken things that are, for example, red.
Using the blue filter in Silver Efex Pro is really easy. There’s a button you can push, and then a couple of sliders to control how strong the filter is and what hue of blue it is. Pretty cool, really.
In any case, in the past I routinely would use a red filter to really darken a blue sky. The image in this post, “Bristlecone Pine, Bare Branches,” would have been a prime candidate for this treatment in the past, because it has nice white clouds in the sky that probably would look really striking if the cloudless blue portions of the sky were dark grey or black.
But, of course, I didn’t use a red filter, I used a blue one. This had the effect of lightening the cloudless blue portions of the sky, making them light grey in the converted black and white image, and in fact reducing the overall contrast with those white clouds. It’s just the opposite of how I used to do things, but I’ve come to really like it. Putting the clouded and cloudless portions of the sky in the same value range – in this case, light greys to whites – creates a nice, delicate feel to the sky, at least in my opinion. Plus, it simplifies the overall composition, because the more unified values of the sky – again, all tending toward light grey or white – make the sky as a whole contrast more with the black needles of the pine tree, which is where I want the viewer’s eye to be drawn to.
I still like dark skies and am sure I will continue to use the red filter effect in the future. But it’s nice to have another tool in the toolbox, and an alternate way of interpreting blue skies in landscape photographs.