Monday, June 24, 2013

Black and White Vs. Grey Scale

Photivo B&W Conversion (RAW File)

Black and White Conversion can be an enjoyable pursuit, and there are many different ways to accomplish it, giving widely varying results. Quite often, I see pictures in the Black and White section of Flickr that are not really B&W at all, but rather, just a dull mix of grey shades. There are a number of contributing factors to this error, the most common of which is to simply open a colour JPG and then either use the "Desaturation" or "Convert To Greyscale" functions in Photoshop. Here are examples of each:

JPG File Desaturation

JPG File Convert to Greyscale

As you can see, this simply doesn't work. There's nothing happening that causes the car to contrast with it's background, and also, there's really no true black or true white anywhere in the picture.

If all you have is a JPG (no RAW file), you'll get far better results using a Black and White Conversion Application, like DxO Labs or Silky-Pix. GIMP also has excellent B&W conversion plug-ins, as I've used in this example:

JPEG with GIMP Kodak T-Max 400 Simulation

Black and White Simulation Applications apply a "curve" that emulates proper B&W film, even down to specific characteristics of the brand and type. As you can see  things are starting to improve here, with shadow detail showing up,and a greater tone range from black to white. The car is starting to separate from it's background properly too. But my eyes are still not seeing much in the way of true black or true white here.

To get truly good results with Digital B&W, you need to use the RAW File. The first photo above is the RAW File processed to B&W using Photivo (similar to Lightroom). Here we see a great separation of the car from its background, a near perfect tonal range from black (the tire sidewalls) to white (the windshield frame). The grille has great contrast, and I even put in a soft Vignette to further highlight the car. I believe this one is the best of the lot, but there is still one more approach - that is using your RAW file conversion application to adjust the curves yourself:

RAW File, Using "UFRaw" to Adjust Greyscale Curve

This time, once I established the blacks and shadow regions, I was trying harder to lift the whites to a super-brilliance. One might argue I went too far with it, as there is a lot of gleaming here around the chrome, and in the car's metallic paint that's washing out some highlight detail. Others might say I "nailed it" because after all, isn't that what show cars are made to do - that is "gleam in the sunlight"? It's all a matter of personal preference at this point. On-screen, I personally prefer the Photivo rendering at the top, but for making a good print, I would guess the UFRaw version would look better. I should talk briefly about UFRaw - it is the most basic of all RAW Converters offered under Linux, and is not available for Windows or Mac. The amazing thing about UFRaw is that when it opens a RAW file, it uses an automatic algorithm that gets the exposure perfect within a +- 3 Stop range with very low noise (or even further with some noise). Usually there's nothing else you have to do but to export the picture directly out as a JPG! But it does have lots in the way of added features, most notably a great facility for customized B&W conversion, as I've demonstrated here. It also allows the most basic of adjustments to a colour picture, but is not nearly a versatile as Photivo is.

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