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3) Curves method

Experiments in colour

I’ve been watching and reflecting on colour; how are the subdued, complementary colours obtained in movies or television dramas? Or in the cinematic style of some photographers. There is something more happening in post-processing than fine tuning of colours and exposure adjustments. This post records my online research and an experiment in ‘colour grading’.

RGB

RGB is the colour-model mostly used in digital photography and video. It is an additive model (so compound colours are formed by adding primary – red, green, blue) based on light rays, not mixes of ink or paint. In contrast, artists (painters) recognise red, yellow, blue as primary colours – as we learn in school; and the print industry CMYK Color System (Cyan – Magenta – Yellow – Black), which reflects the base colour of inks used in printing. In a nutshell, there is more than one type of colour system and at first this can be confusing. Here is a useful RGB colour wheel from Bluelobsterart.com. Some things to note about this colour wheel and the information it shows.

  • rgb-color-wheel-lgThe primary colours of red, green, blue split the 360 degree spectrum in thirds. The wheel starts and finishes with red; one notices the same with the colour picker in LR and Photoshop.
  • The numbers show the amount of the primary colours contained within each colour on the wheel. They work on a scale of 0-255 (not a percentage). For example, the colour red comprises 255 red, zero green and zero blue. These same numbers are the ones shown in LR and Photoshop when one hovers over an image with the colour picker; the software is telling you how the colour is made up in the RGB system. 255 represent a fully saturated colour, 0 represents a fully desaturated (or no colour).
  • Without delving too much in to the theory of colour combining, colours on the opposite side of the wheel are complementary, meaning that they provide the strongest contrast when placed next to one another. For those with Adobe Creative Cloud membership, the colour.adobe website provides an RGB colour wheel that allows one to experiment with different colour schemes and save the results. The same capability is provided directly within Photoshop (windows/extensions/adobe colour themes).

Photoshop tools

Brief reminders from review of YouTube instructional videos referenced below. Basic methods are using curves adjustments (most control); selective colour adjustment layer; or a colour look-up adjustment layer (PS built-in preset).

  • Starting point should be to remove colour cast before applying colour grading (black / white points /
  • Colour balance – allows for adjustment of colour in each of the tonal ranges: highlights, mids, shadows etc.
  • Curves adjustments with layers – using luminosity blend mode for only lightness values (ie not affecting colour saturation) and using colour blend mode for colour only adjustments (ie not affecting brightness values).
  • Note that when adjusting curves of individual colour channels each channel is used to affect its own colour and it’s opposite (eg Red stripped out gives cyan).
  • Use of channels for selections / mask creation relating to specific colours (eg reds for skins).
  • Colour cast removal through layer filled with 50% opacity of opposite colour (invert colour selection on layer) – principle that opposite colours cancel one another out, making neutral colour. Level of opacity changes degree of adjustment.
  • Channel mixer – includes presets: find one that creates high contrast in the image and then reduce opacity if necessary to bring through adjusted colours.

Lightroom tools

Fewer options and flexibility in LR than PS, but effect can be added by using individual RGB channels, split toning, and selective adjustments.

Worked example

My starting point was this RAW file and my aim was to create image with a sinister gang-land feel to the colours (these young men were actually perfectly friendly!) :

Morocco raw

Below is a LR edit, cropped to 16:9. Key adjustments were adding blues to the shadows (curves channel adjustment); split toning to add more blue to shadows, and green tint (sickly) to the highlights. It was trick to control the application of adjustments precisely within LR but the colder shadows and brighter highlights (skin) successfully add contrast.

Finally the PS attempt (or three).

Click to view as gallery

Of the three approaches, the colour lookup method was the least successful – #2 – (an automated approach, rather than crafted). The curves approach – #3 – created the most colour contrast between the skin-tones and the background tones, reflecting the greater degree of control. All three of the PS attempts create a more cinematic, desaturated look than I achieved in the LR example.

Overall, there is a fair degree of craft in this work and, with practice and experience, one would expect improved results. What I take from this is that the practice of post-processing is as almost as importance to the practice of camera-work to creating a final vision.

References

Color.Adobe [website]. Available from: https://color.adobe.com/create/color-wheel/ [accessed 21.5.16]

Colormatters [website]. Color Systems. Available from: http://www.colormatters.com/color-and-design/color-systems-rgb-and-cmyk [accessed 21.5.16]

Phlearn [Youtube channel]. How To Apply Cinematic Color Grading To Your Photos. Available from: https://youtu.be/aaMfMZEFetc [accessed 21.5.16]

Photoshop Learning [Youtube channel]. Cinematic Color Grading (Movie Looke Effect) – Photoshop Tutorial. Available from: https://youtu.be/GFuenozbiE0 [accessed 21.5.16]

 

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