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

Not without leaving Lightroom. As you correctly noted, Lightroom does not currently offer any facility for re-ordering the Develop module's order of operations. If you have decided that Lightroom is the only program in which you will be editing images, you may have to resign yourself to the destructive (and somewhat naïve) method of exporting and re-importing.

However, Photoshop is built to do exactly what you require (any similar layer-oriented editor such as GIMP would likely suffice, but Photoshop has particular advantages mentioned below). By using a curves layer underneath a black-and-white layer, you could readily achieve the results you seek.

If you are particularly reluctant to leave the Lightroom interface, and require non-destructive editing without losing the ease of Lightroom's cataloging functions, the next-best option is using Photoshop itself. Adobe have made it very easy to edit your files in other applications, Photoshop being one of many such other editors.

The advantage to using Photoshop is that Lightroom is already programmed to read Photoshop documents, so your layers are preserved upstream of any edits you make in Lightroom thereafter. To return to the Photoshop file and alter your edits non-destructively, all you need to do is select the newly-imported image in your catalog and "Edit in…"

Note that, later on, you can only alter edits that were originally made in a non-destructive fashion!

The workflow will likely look something like this if you opt to use Photoshop:

1. Upload files from your camera/cards to your computer by your means of choice
2. Add one, some, or all of the files to your Lightroom catalog
3. Optionally, use Lightroom to make basic changes such as lens corrections and color profiling. (These edits will be rendered to a copy of your file before sending it off to Photoshop, so consider them to be destructive!)
4. Use "Edit in…" to edit the image in Photoshop to add curves, and decide whether you need a color or black-and-white image downstream in Lightroom's edit module — black-and-white conversion can be done either here or later with little to no difference in the results.
5. Save the file, whereupon Lightroom will automatically add the image to the catalog alongside the original.
6. Optionally, edit the image further in Lightroom, possibly including a black-and-white conversion, according to your ordinary workflow.

To see exactly how Lightroom handles the transfer of files into your application of choice (especially if colorspace and bit depth are of concern to you) check out the "External Editing" tab of Lightroom's preferences.

Answer 2

According to people that are very close to LR development, the sliders and other actions are applied in the order you applied them.

My workflow is as follows: go to B&W tab and in Black and white mix I adjust sliders to my liking. Then I go to Split toning and apply light toning if appropriate. Not sure how this would look with the multi channel IR, though...