Originally Posted by
Mike Buckley
When you convert to monochrome, whatever tonal variations in the sky were displayed in the color version should also generally be displayed in the monochrome version without having to do anything special. The overall tone of the sky will look very different in the monochrome version depending on the color filter and the strength of that filter that you use to convert. As an example, when I convert your image using a yellow filter at full strength, the entire sky is pure black as in your first attempt. However, if I reduce the strength of the filter to 50%, the overall tone becomes more like charcoal grey and the tonal variation begins to become apparent. If I reduce the strength further to 25%, the overall tone has a luminosity value of about 40 and the lighter tones become about 55. When I reduce the strength to 0%, the overall value is about 60 and the lighter tones about 75.
If I want the sky to look its brightest, I will use a blue filter at 100% strength. However, my experience is that the rest of the landscape scene generally suffers using that filter compared to using the yellow filter.
I generally determine the color filter I want to use and I then adjust the strength of the filter as needed.
Everyone has their own way of thinking about converting to monochrome and, indeed, there is no right or wrong way.