does color space selection matter for working in black and white?

[bwana]

My thought would be absolutely not but raw images are demosaicized to color at the outset so it would be advantageous to be in prophoto for that step. But moving on from there I would turn down saturation to 0 and make basic adjustments in LR. However, I've been reading about the more elegant processing available in PS such as selecting not only 'geographic areas' of the image but selections based on luminance as well. Although finer changes might be achieved by staying in the color workspace and converting to black and at the last step, the actual visual impact of black and white requires me to SEE the black and white image. So I dont really know if I should convert to black and white as the last step or if it matters in reality. I am a novice and to my eyes, cannot really see a difference.

[Alan Klein]

In Lightroom, I click to BW then change the luminance of each of the major colors.  THis way I can see the changes to the BW tones in real time as I move the sliders.  If you wait to the end to switch to BW, then you won't know what effect you;re having as you're making the adjustments.

[bwana]

I realize the LR first demosaicizes to a prophoto-like workspace (melissaRGB). But as I was alluding to above, it seems that I should get and use PS to take advantage of luminosity masks. My quandary is whether it is necessary to work in prophoto in PS or another colorspace IF I am ONLY working in black and white. I guess I've never heard of highlights getting clipped in a black and white photo by down converting to a lesser colorspace - sRGB?

[Mark D Segal]

Why bother with Luminosity masks when you may not need them? Most of the advice on B&W conversion in LR, and Martin Evening has a whole chapter on this in his Lightroom 6 book, is to first optimize the colour photo, then flip it to B&W and see whether further adjustments are needed. As he explains in that Chapter, Lightroom offers several methods for doing B&W conversions and lots of control over luminance. As well, and I'm not sure of the current support situation, but what used to be Nik's/Google "SilverEfex Pro2" plugin was excellent for both general and localized B&W white work.

[Jeremy Roussak]

As well, and I'm not sure of the current support situation, but what used to be Nik's/Google "SilverEfex Pro2" plugin was excellent for both general and localized B&W white work.

It still is.

Jeremy

[TonyW]

In Lightroom, I click to BW then change the luminance of each of the major colors.  THis way I can see the changes to the BW tones in real time as I move the sliders.  If you wait to the end to switch to BW, then you won't know what effect you;re having as you're making the adjustments.

↑↑  This is a nice method where changes can be seen in real time B&W.  PS should offer more control using Image>Adjustments>Black and White, where you will get a dialogue box allowing you to adjust the luminosity of R, G, B, Y, M, C values.  This alone may be enough to achieve your aims.  If not then the addition of luminosity masks should help refine selections.

If you are working from raw then why not stay in Prophoto during conversion and manipulation and then if required to spawn a derivative for print etc then convert to whatever colour space you need?  Otherwise you are just throwing data away that may be useful

[Aram Hăvărneanu]

If you plan to use Photoshop, work in color and put a B&W adjustment layer on top that you can turn on and off. That way you can have a reference on how the B&W image will turn out, but you still have all the information for working with color when doing your Photoshop adjustments (for example masks are very often better created from only one color channel, even if the end result is B&W).

[Alan Goldhammer]

Most of the advice on B&W conversion in LR, and Martin Evening has a whole chapter on this in his Lightroom 6 book, is to first optimize the colour photo, then flip it to B&W and see whether further adjustments are needed.

I have also listed three other very good books on B/W conversion HERE on the 'Resources of Interest' tab (some or all may be out of print these days, I haven't checked lately but used copies are usually available).

[Mark D Segal]

In Lightroom, I click to BW then change the luminance of each of the major colors.  THis way I can see the changes to the BW tones in real time as I move the sliders.  If you wait to the end to switch to BW, then you won't know what effect you;re having as you're making the adjustments.

This is not correct. Any time you switch to B&W by selecting that option in the colour made control you can use those individual colour channel sliders and see the effect in real time. Moving them alters the luminance of the colour group wherever it is represented in the photograph, whether you make the conversion before or after adjusting the full RGB image.

[bwana]

thank you for your replies. the PS desaturation layer technique sounds good. And yes, i enjoy fiddling with the color sliders  in my desaturated image to simulate the use of color filters with black and white film. I guess I could implement that in PS with a color adjustment layer (if that exists).

@MarkSegal Is clicking the B&W button in LR identical algorithmically (under the hood) to simply pulling down the saturation?

[howardm]

I don’t think so.  the BW 'button' has some built-in non-linear recipe of how much % to tweak/reduce each color *group*, it's not just a simple de-saturation (which often looks like cr*p or no where near as 'interesting' as other methods.

[Mark D Segal]

thank you for your replies. the PS desaturation layer technique sounds good. And yes, i enjoy fiddling with the color sliders  in my desaturated image to simulate the use of color filters with black and white film. I guess I could implement that in PS with a color adjustment layer (if that exists).

@MarkSegal Is clicking the B&W button in LR identical algorithmically (under the hood) to simply pulling down the saturation?

No, it's not. All explained in Martin Evening's Lightroom book, and also see my article titled "Blending Berlin" for some insight on this.

For example, you can add a global mask to the photo, desaturate, and then erase the mask in areas you wish to retain in colour (for a "mixed media" outcome), as all the colour information is still available. As well, when you desaturate, the colour channels are not changed to luminance channels for each colour group. When you use the convert to B&W mode, the colour channels become colour-group specific luminance channels.

[Alan Klein]

This is not correct. Any time you switch to B&W by selecting that option in the colour made control you can use those individual colour channel sliders and see the effect in real time. Moving them alters the luminance of the colour group wherever it is represented in the photograph, whether you make the conversion before or after adjusting the full RGB image.

Mark, my point was it doesn't make sense to change luminance while you're still in color mode because you can't see what it's doing to the black tones until you switch to black white. You're better off being in black white while you make the adjustment to the luminance slider so you can see the effect in real time.   I don't see the point of constantly switching back to color mode as you adjust each total luminance.

[Mark D Segal]

I don't see the point of constantly switching back to color mode as you adjust each total luminance.

Neither would I. That's not what you do. What you do is optimize the photo for RGB JUST ONCE, then switch to B&W and make any further adjustments you need there. You will find most of the time that once the photo is well optimized for RGB, the amount of fiddling in B&W is minimal - icing on the cake really for emphasizing certain effects in one or more colour groups, which you do in B&W mode without switching back to RGB.

[Aram Hăvărneanu]

This is not correct. Any time you switch to B&W by selecting that option in the colour made control you can use those individual colour channel sliders and see the effect in real time. Moving them alters the luminance of the colour group wherever it is represented in the photograph, whether you make the conversion before or after adjusting the full RGB image.

Yes, I was talking about Photoshop, not Lightroom. In Lightroom, you can switch to B&W, and the underlying operations still happen in color under the hood (and you have access to channel mixing, etc).

However, I was assuming the OP wanted to edit photos in Photoshop (since he mentioned luminosity masks, etc). It's better to bring the full color image into Photoshop and convert to B&W there, rather than bring a B&W photo in Photoshop. The color image is simply more flexible. For example, in Photoshop you can create masks based on color (even though the final image will be B&W). If you bring a B&W image into Photoshop, you can't do that any more, as you threw the color information away.

Note that if you "open as a smart object" in Photoshop, you can still view the image as B&W in ACR/Lightroom, but still have the color information later on in Photoshop.

[Mark D Segal]

Why bother doing this in Photoshop when Lightroom does it so well and makes it all so easy?

[David Sutton]

thank you for your replies. the PS desaturation layer technique sounds good. And yes, i enjoy fiddling with the color sliders  in my desaturated image to simulate the use of color filters with black and white film. I guess I could implement that in PS with a color adjustment layer (if that exists).

@MarkSegal Is clicking the B&W button in LR identical algorithmically (under the hood) to simply pulling down the saturation?

Because any colour can be made light or dark by using the sliders in the B&W tabs of Lightroom or Photoshop, that gives you the most flexibility in your initial B&W conversion. Pastel shades will not go pure black or white, but anything a little more saturated will.
IMHO, desaturating a file for a B&W conversion is the worst of all options.
If you would like to see why, open the image below in Photoshop (leave it in sRGB). Add a hue/saturation layer and run the saturation down to zero.
David

[luxborealis]

Once the colour temperature of the colour image is optimized then converted to B&W (as Mark recommends), I recommend NOT using the individual sliders in the B&W panel. Instead, click on the Targeted Adjustment Tool, hover over the tone you want to lighten/darken, click and drag. Most tones are a blend of individual colours. Dragging just one slider can result in a grainy-looking effect within the tone as some pixels within what you see as a single tone are altered more than others.

As Mark pointed out, dragging in one location will change the values of the same colours in the whole image, so, beware! Using a colour range mask in LR CC may allow to further refine specific tones, but I’m not a CC user, so cannot comment.

Using the B&W panel well, plus a few other adjustments - all within LR - has meant, for me, no trips to PS and no use for Silver Effex, despite the hype about both.

[Mark D Segal]

Using the B&W panel well, plus a few other adjustments - all within LR - has meant, for me, no trips to PS and no use for Silver Effex, despite the hype about both.

Likewise - I find LR is usually more than adequate. I agree with your point about using the TAT on the areas one wants to re-tone, as more than one colour group can be implicated, but it remains useful to observe what happens when one implements movements of channel tones one by one. I have not noticed any graininess, except for very excessive reliance on adjustments of the Blue channel - in prior versions of LR it could cause artifacts; haven't tried/needed to push it yet in the latest version. 

[David Sutton]

Because B&W is more abstract it allows changes in luminosity without any reference to the original image. In fact, many B&W files would look odd if rendered back to colour.
And in general since it's all about the grey tones, and they can be controlled easiest by lightening  or darkening the underlying colours, ironically most B&W is all about colour contrast.
There is no right or wrong method to achieve good tonal separation in a B&W image. Usually I will optimise the file for colour separation and white balance it to remove colour casts. Mostly I will white balance the shadows, midtones and highlights separately, as the single click white balance in LR is too far off for many of my photos.
Then I'll use the sliders in a B&W tab to get me into the ballpark.
If that is not doing it, I'll grab that temperature slider in Lightroom and move it across its entire range. That makes for an interesting few minutes.
Then off to Photoshop for luminosity masking.
I finally convert the RGB file to QTR – Gray Lab colour space for printing. That allows softproofing in LR and gives a near perfect screen to print match with monochrome on a Canon printer.
I've nothing against Silver FX and similar if someone is in a hurry or they don't know where the are heading with an image, but as always there is the risk of ending up with the generic.