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Using the colour wheel to select filters for black and white

Posted by Merco_61, 09 August 2022 · 1,200 views

Filters are subtractive, so they lighten their own colour and darken the reciprocal. To guesstimate the effect of a filter, you can look at the colour wheel and a sector of about 60˚ either side of the main colours for the filter will get the most pronounced effect.
This means that a red filter will lighten colours that span between magenta and yellow and darken colours from green to blue. A yellow one will make red to green lighter and magenta to cyan darker etc.

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Using a good monochrome conversion app, you can set the exact position on the wheel you want, often with a slider so you see the effect in real time. Remember to choose your spectral response curve first as the filter will react differently depending on what film you are trying to emulate.

I actually hadn't noticed it until now, I've been logged on all day, but was busy with other things most of the day.  It looks like it would go hand in hand with my chart on Affinity Photo and work well with it, though the chart in Affinity is nowhere near that explainitave, it would be a good tool.


As for choosing a filter to use on a lens, it's excellent!  Perhaps a few examples would help though of the same subject taken with various filters attached?


Here's how I do it in affinity.  I snapped a shot with a D700 and 20-35mm f2.8 lens @35mm.  Just a random color shot from my files converted to B&W and adjusted to my liking.  I couldn't manage a screen shot in Affinity. 



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This is about as far as I've gone with Digital B&W conversions.  I was never an expert on the ''Gray Scale'' however I do have a set of cards.  In film I dodged and burned when printing with small paddles as I suspect we all did. 


I should probably dig out my old books and study up on a few of the finer points for this challenge. 

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That pane in Affinity controls the spectral response. I don’t think it has any filter emulations.


I have another blog about using these channel mixers, though.Black and white conversions using the channel mixers in Lightroom - NikonForums.com


I just hope Affinity is similar to Lightroom in how it works. The only curve I see that would be completely useless is Tri-X as Affinity doesn’t have a slider for purple.

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All I can say is Affinity is very expansive and can do much more than I understand, what you see in the above picture is just one persona, there are many more!  I have a paper manual of several hundred pages and I've barely scratched the surface of what it can do.  The picture is just the basic photo editor persona.

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I have now shot a series of similar still life shots.


First, a colour version. Shot with my D700 and the same 105/2.5 as the others. Portrait preset in Photo Ninja is the only edit.



Here comes a series of shots on Ilford PAN F, developed in ID 11 and scanned.


No filter:



B+W 090 Light red



B+W 040 Medium yellow orange



B+W 022 Medium yellow



B+W 060 Medium yellow green



I had no slow film stock in 120 and delivery seems to be at least 6 weeks, so I had to use my good old F4 instead of the Rollei. This meant that I only had a partial set of filters available.

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