Commentary

Photography: Reflections on Tonal Separation

What is Tonal Separation? The Geeky Version
Before beginning the discussion on tonal separation proper – it might perhaps be useful to first propose a working definition. The most straightforward definition may, perhaps, be that tonal separation how one describes the transition between the dark and light parts of a photograph (as well as the transitions between these areas inter se, e.g. the transition from deep shadows to medium shadows). If you’re wondering what I’m talking about, here’s a link to what is commonly referred to as the Zone System.
However, it is important (in theory at least) to appreciate that the definition is not without its difficulties since, if we really wanted to be pedantic, there is no such a thing as darkness – only the absence of light (along the visual spectrum at least, since light may travel in many wavelengths, the vast majority of which cannot be seen by the naked eye). In the same vein, simply because an object appears darker in an image doesn’t necessarily indicate the absence of light per se, it simply reflects (no pun intended) on that object’s ability to reflect (or absorb) light (or the different wavelengths thereof).
This is actually how our eyes perceive colour since colour is interpreted by our brains based on the available wavelengths of light which hit our optical nerve which is in turn dependent on any given object’s ability to reflect or absorb differing values of light (or the wavelengths thereof). What does this really mean? A red car appears red because this is the value least absorbed by the object in question – and thus the value most reflected to our eye.
*I’m not perfectly sound on the scientific principles – but this is roughly what I believe to be the correct position. Comments and criticisms are welcome.
Practicum
Putting aside the science for a moment and returning to the definition I posited earlier, tonal separation to the naked eye is about transition. Transition between – to borrow wording from the Lantern Oath – brightest day and darkest night. In photography terms, this would be the transition between and within shadows and highlights. That’s right – it’s not just about the transition between light and dark, but within the shadows and/or highlights inter se as well.
(perhaps a more technical definition would be the transition between the portions of the image with higher reflective value and those without – since what our eyes see is merely a reflection of light (along the visual spectrum) off objects which have differing abilities to reflect or absorb light
it is more accurate to speak of the degrees of light
Tonal separation is not unique to black and white photography – since
I’ve realised that over the past 6 months, I’ve gravitated towards shooting mostly in black and white. That’s not something I could have foreseen when I first picked up my camera with intent. I say mostly black and white because unlike some photographers I know – I’m not exclusive. I still like to photograph in colour from time to time – but mostly I’ve taken to shooting in monochrome.
When you think about it, black and white isn’t really an apt description for the medium – since the primary colour the photos are represented in is grey (or shades of it, and certainly more than 50). And if you really think about it – grey isn’t a colour either – it’s simply a measure of luminance, or the amount of light reflected off a given object. If that is the starting point, then a black and white photo is truly only black in the deepest shadows, where no light whatsoever is reflected, and white in the blown, irrecoverable highlights.  So in speaking about black and white photography, perhaps it is more accurate to speak of recording luminance values. That being said, and for ease of convenience, I think it would be somewhat silly to refer to black and white photography as anything other than what it is well known as (Candelagraphy doesn’t have quite the same ring to it).
This would be true of the Leica M Monochrom, which is sans Bayer filter and still true, although somewhat less so, about cameras with. Cameras with Bayer sensors capture luminance values but break them down into their constituent wavelengths, i.e. red, green and blue, and re-stitch (or demosaic) the image to present the photo in colour.
In any event, we’ve perhaps strayed a bit far from the actual subject matter of this post – which is really about tonal separation. Apart from composition, tonal separation is probably the next most important element in any black and white image. What does tonal separation really mean? Well to me is the contrast (or perhaps, more accurately, the transition) between areas of differing luminance values.

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