Blank and white conversion methods

[Garbz]

I'm interested in the various methods people use to convert a RGB image to black and white. There's several I have used in the past:

Desaturate - Lazy cop-out of a method, don't think I've ever done this to a serious photo.
Convert to LAB, and retain only the L channel - I don't do this much due to it being complex, clobbering layers, and the result is invariably too bright.
Add a grey layer and set the blending mode to saturation - I like this a lot as it approximates the lightness of visible colours.
Use the channel mixer and set RGB to 29% 60% 11% - Produces the same results as the above blending mode method.
Use channel mixer outright - Probably my number one technique due to its great flexibility.

So what do other people do to convert to black and white? Any methods I haven't mentioned here?

Other mentions in this thread:
Convert to greyscale - contrast seems weird to me. Blue appears to have an unnaturally low ranking in this case.
The gradient mixer - can be applied as an adjustment layer and looks very similar to the blending mode to saturation method.
The complicated gsgary method -

 

[ann]

Use channel mixer and adjust as needed. SOmeone where in my files i have a sheet that somone worked out long ago about which numbers to use for specific film types.

That of course was long before specific programs came along, which seem to have film types available .

Lately I have been using SIlver efex pro, but make adjustments rather than just a preset. THe software reminds me of darkroom work so that may be an influencing factor.

Years ago i tried LAB but found it too complex for my beginning efforts in the computer digital world.

 

[clanthar]

Channel Mixer by far and away to answer your question as asked. However most of my b&w conversions are accomplished in a RAW converter and never make it to the RGB photo stage.

Joe

 

[Helen B]

I used to use the channel mixer, but now I use the B&W conversion method (Image-Adjustments-B&W) more. It does much the same as the channel mixer, and is just as adjustable.

The numbers that ann referred to may be these. Those particular numbers were often quoted in various forms a few years ago. They are wrong on three counts, but it's not important unless you want accurate film emulations or film-film comparisons. Whoever calculated them originally did not understand how to read spectral sensitivity curves or the effect of light source. Note that Ilford and Agfa films appear to have maximum sensitivity in the green channel; Kodak films have maximum sensitivity in the blue channel. That's incorrect, but you need to know the difference between the way Agfa/Ilford prepared their curves (wedge spectrogram in tungsten light) and the way Kodak do it (radiant energy spectral sensitivity).

Best,
Helen

 

[unpopular]

The software I use has pretty accurate film models for a few b/w films. I usually set the "curve-type" setting to "L*" to maximize shadow detail without affecting hilights. Not sure what that does exactly.

I will often also make a straight color version and pass it through channel mixer to select any aspects of that I'd like.

On a very rare occasion I will pull the Lightness channel from LAB, place it in it's own document and then grab other channels from RGB and do the mix manually, or I will replace the least desired channel in RGB with the Lightness channel and use channel mixer.

 

[Rephargotohp]

The only way to consistently keep luminosity of tone constant is to use convert to grayscale (and then back to RGB to be able to use the max amount of tools and filters in PS) It may not be your artist vision of what you want,but it is the most accurate conversion

How to Get Your Colors Correct in Black & White | BH Insights

 

[Derrel]

I apply a Gradient Map, and select the black gradient. It is easy to do, fast, and best of all, it looks good! It's very useful when performed, and then the Highlight/Shadow function used a bit, not too much or unnaturally, and then a minor curves adjustment is done. My personal feeling is that one of the things "digital" does simply NOT do as well as film, is to show surface textures in B&W, and so I often do a pass of unusual unsharp masking at a high percentage(150 to 200%), an abnormally high radius value (10-15 pixels), and a zero threshold, which exaggerates local contrast, and adds a real feeling of "texture" to objects. I wil usually apply a FADE to that unusual USM, for nuance. That last idea, about texture and USM, is from master print maker Ctein, in a column he wrote for The Online Photographer blog about 3,4 months back.

 

[MLeeK]

I use the channels and I don't use any particular settings because each image is different. I adjust the colors I want to be bright/light to be that way and the ones I want dark to be dark.

 

[gsgary]

Channel mixer 68% 24% 8%
And the quick way
Image>mode>Lab color
Image>mode>greyscale
Hold down control key click on grey channel
Select>invert to shadows
image>mode>rgb color
Layer pallete.solid color
Change blending mode to multiply
Control-alt-shift-E
Change blending mode of new layer to overlay
set opacity 20%
Filter>other>high pass filter>radius 50%
Flatten

 

[Helen B]

The only way to consistently keep luminosity of tone constant is to use convert to grayscale (and then back to RGB to be able to use the max amount of tools and filters in PS) It may not be your artist vision of what you want,but it is the most accurate conversion

How to Get Your Colors Correct in Black & White | BH Insights

The author of that article doesn't seem to know much about the various methods available in Photoshop. 'Convert to greyscale' is not the only way of getting what he describes as 'correct' greyscale values, and it does mean that you have to convert back to RGB. Other methods will make the exact same conversion while staying in RGB. I'm not sure what the purpose of doing a 'correct' conversion is for anything other than scientific purposes, however - it's good to use a conversion method that allows some deliberate variation of the colour mix. B&W film does not do a 'correct' conversion.

As an aside, any method of conversion from RGB to greyscale is incorrect with respect to the original scene because the RGB image has already simplified the spectral information from the original scene too much for an accurate conversion.

Best,
Helen

 

[Garbz]

Channel Mixer by far and away to answer your question as asked. However most of my b&w conversions are accomplished in a RAW converter and never make it to the RGB photo stage.

Even your RAW converter has a method. For Lightroom it is effectively a glorified channel mixer.

The only way to consistently keep luminosity of tone constant is to use convert to grayscale (and then back to RGB to be able to use the max amount of tools and filters in PS) It may not be your artist vision of what you want,but it is the most accurate conversion

I'll dispute that. The typical RGB swatch does not look at all consistent with what I would describe as accurate luminosity. That can be seen in his example too, the red car looks noticeably brighter than the blue, yet converted takes on the same luminance value as the sky in either case. That's not really consistent (or maybe I'm anti-colourblind ). Anyway it's another to add to the list. I naturally assumed the convert to greyscale option did the same as desaturate so I never touched it. My other gripe is that it is destructive. I instantly put any method that asks "do you want to flatten the image" into the don't use pile, just like the conversion to LAB if I'm not already working in LAB.

I apply a Gradient Map, and select the black gradient. It is easy to do, fast, and best of all, it looks good!

Very neat. Never played with this before. You missed another big advantage though. It can be applied as an adjustment layer and tweaked to suit later in the processing stage.

I usually set the "curve-type" setting to "L*" to maximize shadow detail without affecting hilights. Not sure what that does exactly.

L* is a type of curve that approximates linear values to equal brightness steps (nearly logarithmic values) as our eyes see. Not sure how it is applied in the software. Probably a difference of the sRGB curve intrinsic to any normal looking image file and the L*. Since L* naturally weights shadows more this ends up brightening only the darker areas.

 

[Alpha]

Believe it or not I occasionally use Calculations.

 

[MTVision]

Believe it or not I occasionally use Calculations.

I've never used calculations for black and white before. I'll have to try it out. I do use calculations for other things though!
I use a gradient map, camera raw, the black and white adjustment.

 

[clanthar]

Channel Mixer by far and away to answer your question as asked. However most of my b&w conversions are accomplished in a RAW converter and never make it to the RGB photo stage.

Even your RAW converter has a method. For Lightroom it is effectively a glorified channel mixer.

Very true. One of the problems with using channel mixer or Photoshop's B&W conversion is rapid noise buildup. I get better noise control working from the RAW file than from an after the fact RGB conversion.

Joe

 

[ann]

Not sure if the chart Helen refers to is the same one buried in my files, I would have to check the numbers; but I am not sure that is important these days.

I do remember when I first started with digital ( which was screaming and dragging my h eels) I was clueless about so many things and found them a helpful starting point.

Am still clueless about so much, and will have to think about the gradient map option.