Exercise: Colour into tones in black & white

by Suzy Walker-Toye

Colour

The exercise on p119 is about trying to explain the use of colour filters on the outcome of a black and white photo. The exercise gives you the option of using actual colours filters on your camera of you have them or faking it with software if you do not. As I do not I choose to fake it with software as directed and I discovered something interesting (if not wholly unexpected). The sliders in LR (and probably photoshop is the same) do NOT mimic traditional filters. They can, if you know what you are doing with the sliders, and if you already know how traditional filters work, but I think this will confuse many people taking the OCA course (I did me, until I had it properly explained by Mike, B&W extraordinaire).

So what is the difference? Well, a traditional colour filter will lighten the area of that colour and darken the area of the complimentary colour in the resulting black and white image. So an orange filter would be used to darken a blue sky for example. In contrast the sliders in LR only darken and lighten the colour of that slider and all the other colours remain untouched. To demonstrate this I have taken a colour photo with all the primary & secondary colours, Blue,Red,Yellow,Orange,Violet, and Green.

These first photos below were processed using the sliders in LR. I made virtual copies of the colour photo and then, as directed, converted to black and white and tinkered with the b&w mix sliders for each. However, I noticed that the default position of the sliders on the neutral were not all the same (not a great place from which to start a comparison so I created another “neutral” with all the slider at -35.

Neutral b&w conversion – and default sliders, and next to that the increased yellow slider as an example…

LR Neutral LR Neutral Sliders LR Increased Yellow slider

Below is the set of LR slider based conversions. Notice for that each conversion, only the colour of that slider has been affected..

A photoshop plug in called Silver Efex Pro actually does have the facility to correctly mimic the use of tradition filters and their effects so here are the results of the same photo being run through against different filters.

You can see from this that the green filter not only lightens the green background but also darkens the red chilli, and also noticeably darkens the pruple box (because of the red element making up the purple from blue). Hopefully you’ve found this post interesting.

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