I’ve gotten a lot of emails after the Leica X2 and M-Monochrom reviews asking about B&W conversion and processing; I guess the M-Monochrom announcement had a knock on effect on the way people started seeing things. It doesn’t make color cameras redundant for B&W work, though.
Let’s start by demystifying two things.
1. Certain cameras have certain particular B&W characteristics. True, but only if you use JPEG. If you are shooting RAW, they provide different starting points – this is from a tonal response point of view – but ultimately you can get a consistent look regardless of the camera. I know, because I do this all the time.
2. There are benefits to a monochrome-only camera. True. The Bayer filter and subsequent conversion is an interpolation of neighboring pixel image data to extract color information; luminance information is lifted from the photosite. Any sort of interpolation will reduce tonal accuracy and increase noise, because the luminance value you’ve got is now an approximation instead of a true value. However, it’s fairly easy to see that whilst there are benefits to shooting monochrome-only, you can actually convert a color RAW file into a monochrome one, and lower the perceived amount of noise – though not to as low a level as a monochrome-only camera. If you have a poor interpolation method, then the luminance values can be affected too – once again, increasing the perception of pixel-level image noise in a color image. Bottom line: yes, lower noise, and yes, better detail.
Also one of the images available in my print offer.
However, what you lose from a monochrome-camera is the ability to do control the relative luminance level of individual color channels. Why is this important? Suppose your color scene has a relatively small range of background tonal values, but your subject is a very different color. Its luminance may be the same as the background, but it stands out because of the difference in color. As we concluded in a previous article, this kind of image is a very bad candidate for B&W conversion off the bat, because you’d land up with something very flat-looking. (Real life translation: running out and buying an M-Monochrom isn’t going to solve your B&W conversion woes, but it will give you an interesting starting base – especially when it comes to noise and dynamic range. Those of you who don’t mind doing a bit of work, hold on to your normal cameras. And in fact, these techniques apply to the M-Monochrom too.)
Actually, if you’re prepared to do some work, this not necessarily the case. It’s still possible to separate the subject from the background on the basis of luminance only; you just need to work a bit harder. You’ve even got a few options here. Park that thought for a moment, we have to introduce the basics of B&W conversion first.
The simplest method is to desaturate. All this does is throw out color information, and leave luminance information only. You are then free to do whatever you wish to complete processing of the file. After much investigation and experimentation, this is actually the method I use, coupled with another trick or two. Desaturation can be done in ACR (saturation slider, first tab) or in Photoshop (Hue/Saturation tool, then desaturate the master)
Slightly more complicated is the gradient map. You can use the standard linear black to white transition (press D in photoshop first, then add a new gradient map adjustment layer) – which gives very similar, but not quite the same, results as desaturation. Gradient maps with a straight gradient tend to be a bit more contrasty than desaturation. If you want to experiment a bit, it’s actually possible to put in intermediate control points into the gradient and bias it towards a high key (mostly white, black fades out faster) or low key (black stays for longer) look. What actually works here will depend on your image, however, so be prepared to do some fiddling. The good news is that if you use a new adjustment layer, the gradient is easily modifiable without having to redo your entire conversion.
Finally, we’ve got the channel mixer. Best used on the RAW file in ACR, this lets you decide how much of each individual color channel goes into making the final image. Note that the tool only uses the luminance components of each channel, and it’s additive; this means that color (and perceptual color) information is discarded. To make things even more complicated, there’s a separate B&W conversion adjustment layer in Photoshop itself that effectively does the same thing as the ACR conversion, but it only has six channels for you to play with instead of the eight in ACR.
Remember the conundrum of how to isolate a different colored, but similarly luminous, subject from the background from earlier? The solution to this is the channel mixer. You can increase the luminance of the primary color of your subject, and decrease that of the predominant background color; the converse also works. The problem comes when you’ve got a mixture of colors in both subject and background, and some of those are common colors. (Don’t get carried away though: remember that some images just don’t work in black and white).
This isn’t, the entire toolkit, of course. You’ll find that after this kind of conversion, things look rather flat. That’s because a lot of how the human eye perceives contrast and separation is dependent on differences in hue; obviously we have removed that, so we have to artificially put it back in again. Two of Photoshop’s tools will be your best friends here: the dodge and burn brush, and the curves tool. Understand how both of these things work, what the dos and don’ts are, and you can work magic with any B&W conversion. A tablet is also extremely helpful for these things, as it gives you precision control and feathering over your brush application. It lets you avoid hard edges, odd abrupt transitions, and permits highly precise editing.
At this point, it’s probably worth talking about plugins and filters. The former are either a set of Photoshop actions, or a separate program, that controls the conversion – specifically the luminance translation of each cool channel into a luminance value – and the tonal map of the final file. Whilst they are extremely popular and used by many ‘internet street photographers’ either to save time or because they are unable to get their desired results from a nuts and bolts conversion, I personally avoid them because they do not give you enough fine control, and even worse, everybody’s images that were run through that filter look the same. There is no personality or skill in that.
Photography is arguably art and very much down to personal taste. If you are 100% happy with the way those results look, great; I’m jealous of the amount of time you’ve saved in your workflow. However, claiming this is art is disingenuous; it’s like finding out Ansel Adams shot BW400CN (a B&W film designed to be run through a C41 color processing machine) and developed it at the local pharmacy – instead of Tri-X or Plus-X, controlling his development time and chemical composition, and then cutting precision masks to dodge and burn portions of his subjects.
There’s a second type of filer that’s useful, and in either form, it performs a similar function to the channel mixer – it either admits or cuts out light that’s of a certain range of wavelengths. The most common example of this is a physical red filter that goes over the end of your lens; the effect is dark skies, because very little of the blue spectrum passes through the red filter and onto the recording medium. It works with digital too, but you have to remember to adjust exposure accordingly, and obviously not use it in color mode. You can also replicate this effect digitally. Add in a new layer, make it one color, and then select the appropriate blending mode; then only do your B&W conversion. There are interesting results obtainable through this method.
If you pull back the B&W conversion layer slightly – assuming you didn’t directly apply the conversion to the image – then it’s also possible to use a color layer to create a toning effect; sepia or platinum is probably the most common. You can even use a graduated fill layer to provide a variable effect; this is especially useful for increasing the density of skies, for instance.
Personally, I prefer to shoot color and then convert to B&W; not because I can’t decide upfront how a scene should be presented, but because there’s a lot of flexibility in how I want to handle the conversion later to highlight certain aspects of my subject, or achieve certain tonal looks.
I’ll go into detail on my personal B&W workflow with an end to end example in a future article. MT
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