Home Edizioneed. 8 256 Shades of grey

Written by Simone Angarano

In order to explain how to handle Black and White photography in the digital age, it is necessary to understand some simple basics starting with how colour is formed.

The colour in a digital image is captured by photoreceptors, sensitive to one of the primary colours – red, green or blue. Depending on the mixed quantity of these three colours, a different response and consequently a different colour is determined.

In the RAW file, the brightness level of each RGB channel is indicated on a scale from 0 (no light) to 255 (maximum light intensity). This means that each pixel can appear of up to 16.7 million different colours (256 levels per channel raised to the cube, as there are three colour channels).

Why then are we only talking about 256 shades of grey in black and white?

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In a black-and-white photo, everything is simplistically reduced to a single channel that goes from white to black in 256 shades of grey; therefore, the risk is that different colours will appear identical once converted, as there will no longer be hue and saturation but simply their brightness.

The secret to get a better result in the BN is to have a wide variety of brightness in the various areas of the photo.

For example, a photo containing many tonal variations will create interesting shapes and textures that will make the image look rich even without colour. In any case, in order to achieve the best results, it is not enough to simply ‘convert to black and white’ but you will have to work on the original colours with post-production programmes such as Photoshop.

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When a colour photo is converted to black and white, its tones are transformed into shades of grey.

When we are in a B/W environment, if all three colour channels of a pixel have a value of 0 we get black; if they are all 255 we get white. Intermediate values such as 110,110 or 12,12 give neutral greys.

So it is crucial to create contrasts to emphasise shapes and textures, don’t forget that this is 256 shades compared to 16.7 million in colour photos.

When converting to B/W you will immediately realise that there will be a very good contrast between Blue and Yellow, Red will be very similar to Magenta and Green to Cyan. Therefore, having many colours does not determine an impactful image in BN, but the key lies in the brightness that these colours have, so you have to play on the various colour channels by varying their intensity on a scale from 0 to 100.

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Beyond these technical notions, my advice is to look at and study the work of the great masters of photographic history and how they made Black and White photography incredible, such as  Ansel AdamsJeanloup SieffEdward Weston,  Bill Brandt Henri Cartier-Bresson.

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