Can I apply colour tone curves before black and white processing in Lightroom?

Question

I realise the answer to this is probably "no", but it seems worth asking. Is there a way to affect the order in which the various processing steps are applied in Lightroom? And specifically, is there a way to apply separate red, green and blue tone curves *before* the black and white processing?What I mean by this is that if I select black and white processing, and then, in the tone curves module, apply a curve to only (say) the blue component, what I get is a tinted black and white image. In my case what I want is that the tone curve will be applied before converting to monochrome, so that I'll get a non-tinted black and white image with a different contribution from the blue channel. Of course I can export as a tiff and re-import, but I'm wondering if it can be done non-destructively.(The reason I want to do this is not important for the question, but in case anyone's interested, it's because I'm shooting in infra-red with a 720nm filter, which results in a "false colour" image. I'm finding I can get a much better white balance by using the colour curves to line up the peaks in the three channel's histograms. Having got the white balance right I then want to process into black and white, but because the monochrome conversion happens before the colour curves it doesn't produce the result I want.)

Answer 1

Hi! This is a good question. You're right in that it cannot be done directly. However, if you keep the file in RGB and desaturate in the HSL panel (move the S to 0 for all colors), you can then go back to the Tone Curve and apply a curve to each channel, R, G, and B separately. I find the Lightroom Tone Curve very sensitive, so you need to take care when applying the curves. It's an interesting way to get unusual tones for a monotone image.

By the way, I never convert to black and white by clicking on Black & White in the Basic Panel of the Develop module . I always use the HSL panel with 0% saturation. This allows me to affect the luminance (brightness) of each color in the original separately. Gives me much more control over the black and white 'look'. Lowering the luminance of blue, for instance, would darken the sky. If you have reds and greens that don't 'separate' as grays, the luminance slider can handle that quite nicely as well.

Good luck!