Understanding Digital Black and White Photography: Image Data

Part 2: Image Data

Tim Savage is a photographer, artist, teacher and author. He works for the University for the Creative Arts in Farnham and also teaches at West Dean College. He has put together a series of blogs for us on his understandings of digital black and white photography, this being the second of three. For further information and technical advice visit the guides section of the Calumet website or pop into one of our stores for expert advice on taking black and white photos.

Following my last blog post that described camera considerations for shooting black and white this next entry is dedicated to sculpting and shaping the resulting sensor data in to an optimal monochrome image. It is at this stage that things become a little more technical. Although not the most glamorous of concepts, the act of exposing the camera sensor to light can be thought of as a luminance data harvest.

All equipment, settings and conditions should be targeted towards attaining the highest quality and cleanest data possible to take forward into the software stage of the workflow. Learning to read the cameras histogram (which unambiguously displays the frequency and distribution of tone that will make up the final image) is an important aid, even more so when working in colour. You cannot trust your eyes, but you can trust your cameras histogram!

Having created an exposure in camera, the next stage is to process it. It is helpful to understand that sensor data is converted from light energy (photons) into electrical energy (electrons). These electrical signals are interpreted by the camera’s processor and then saved as data. More data is captured when shooting RAW than JPEG, which yields greater potential for the rest of the workflow.

Although somewhat counter intuitive, understanding how cameras work in colour informs the route towards great black and white photographs. This is because cameras sensors record three separate channels of red, green and blue (RGB) light. Software processing is used to convert each pixel to become either black, white or a shade of grey in between. There are plenty of ways of converting colour images to black and white, at a basic level Photoshop>Image Adjustments>Desaturate creates a black and white image version of a colour photograph though this usually appears flat and lifeless.

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A much better technique for converting the image data into black and white is to utilise the information contained within the RGB channels. This process allows the photographer to determine the colour response curve for individual channels to control their tonal separation in granular detail. For example, by assigning different luminance values to the primary and secondary primary colours the tonal distinction and separation of the subject may be varied to create very different versions.

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Understanding of how RGB values can translate though tone was a real epiphany for me and went a long way towards providing a digital equivalent of the response curve of film. It also became clear that workflow and photo software choices can be the making of a black and white photograph. Although I experimented with a wide range of tools, I found the most effective to be a combination of Lightroom, Photoshop, Silver Efex Pro2 with further specialist additions useful for sharpening, resizing or simulating grain. The importance of pixel-level detail management is emphasised in mono. Chroma and luminance noise impact upon the sharpness and clarity in black and white more than colour. The coin below demonstrates uncorrected noise on left (corrected on the right) Notice how much cleaner the black and white version appears when the appearance of noise is controlled optimally.

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For photographers seeking non-destructive techniques that may be used to finish an image beyond Lightroom, or to simulate a range of traditional darkroom effects such as dodging, burning, toning, tinting, solarisation, and other analogue effects such as pre-flashing the paper Adobe Photoshop remains the tool of choice. My next blog post will describe how HDR can be an effective tool when working in black and white, and taking the concept of increased dynamic range further how a digital version of Ansel Adams’ zone system workflow can be utilised using exposure modes and processing software.

Much more detail on image processing and the monochrome specific features of Lightroom, Photoshop and Silver Efex Pro2 are continued in greater depth in my book ‘Understanding Black and White Digital Photography’.

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