BW Conversion: Desaturation vs. Monochrome Mixer

Question

BW Conversion: Desaturation vs. Monochrome Mixer

Hey all,

I wanted to ask what others' experiences have been when doing conversion from color to black and white. What I seem to be finding is that straight desaturation (moving the Saturation adjustment slider all the way to the left) produces a better quality conversion than using the Monochrome Mixer (I am generally using RGB values somewhere in the neighborhood of 75%-15%-10%). The Monochrome Mixer approach seems to produce a grainy result with less contrast. Desaturation seems to produce a smoother, more pleasing result.

Questions:

1. Has anyone else had the same experience?

2. What is everyone else finding to be the most effective way to convert color images to black and white (best control of contrast, aesthetically pleasing, etc.).

3. Is there any reason why the Monochrome Mixer should give drastically different results than desaturation?

Thanks in advance.

Brad

G5 dual-2.3Ghz, 4.5GB RAM, Nvidia 7800GT, Mac OS X (10.4.8), Powerbook G4-1.33GHz-17", 1GB RAM, Radeon 9600-64MB

Posted on Oct 12, 2006 12:21 PM

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Answer 1

kgelner

Level 4

1,205 points

Oct 12, 2006 1:44 PM in response to Bradley O'Hearne

1. Has anyone else had the same experience?

2. What is everyone else finding to be the most
effective way to convert color images to black and
white (best control of contrast, aesthetically
pleasing, etc.).

3. Is there any reason why the Monochrome Mixer
should give drastically different results than
desaturation?

I personally prefer the monochome mixer - it should have absolutley no effect on quality, and in fact a monochrome mixer set to around 33% for all channels should be identical in all respects to a simply desaturated image (untested).

What could be leading to your observation though is that generally there will be more noise in some color channels than others, and so if you aleter the channel mix you may also be increasing the visible noise in an image. I would expiriment with the presets in that tool to see what other mixes look like, and if they seem to have the same issues.

There's nothing wrong with desaturating to get B&W, I just prefer being able to fine tune the channel mix.

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Answer 2

Oct 12, 2006 4:30 PM in response to Bradley O'Hearne

Bradley,

3. Is there any reason why the Monochrome Mixer
should give drastically different results than
desaturation?

Yes, for the same reason that folks use colored filters when shooting B&W film. A red filter or yellow filter is commonly used when shooting landscapes, as it darkens the sky, which makes the clouds more visible.

Here are some examples:
http://kenrockwell.com/tech/photoshop/b-w.htm

But don't take my or anybody else's word for it—try it yourself and see which results you like!

FWIW, Lightroom's channel mixer beats the pants of Aperture's functionality in this regard.

Cheers,

Andreas

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Answer 3

Oct 12, 2006 4:48 PM in response to Andreas Yankopolus

Thanks for the reply kgelner and Andreas. Yes, I am hung consistently over the LR - AP barrel. I like virtually the entire range of LR adjustment functionality over AP. In fact, I just did some direct comparison of RAW images converted in LR vs. AP. I am using a Canon 20D, very common. But it appears the AP still hasn't gotten RAW conversion right for the 20D. I have noise and posterization, and even bizarrely, a photo with a big orange streak through it, and I have none of that in LR. So if it were a function of just adjustments, I'd be using LR, and I still may be. I just decided to take a 250 image shoot through both LR and AP to compare LR Beta 4 to AP 1.5.

And moving past initial adjustments, I can deal with either rating / selection functionality. Where LR botches my workflow is where I need to create multiple renderings of the same image (one bw, one color, one sepia). While in AP, it of course is enabled by terrific versioning capability, in LR, while oddly you can create a new copy by opening in Photoshop, you can't for some mystical reason simply duplicate an image. This means misery for having to show 10 images to a client each with 3 different looks. And what's more, exporting an entire shoot from LR to import in AP is quite time consuming.

So getting back to the topic at hand, I'll tool around with the BW options, and see what I can find.

Brad

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Answer 4

Oct 13, 2006 12:23 AM in response to Bradley O'Hearne

Hi Brad,

there's a wealth of information out there on how to do B&W conversions from an RGB file. Using the monochrome (channel) mixer is just one of them.

Many Photoshop wizards are working with a conversion from RGB to Lab before further processing their image, removing the a and b channels during the conversion. In this way only the Lightness information is used for the image (as it would on the perfect b/w film). Some then do heavy post-processing on the converted image, applying mask layers, duo- or triple tone splits, and yet more edits. All this probably works well, and I've tried many of these methods in Photoshop.

These days I'm sticking with the channel mixer (in Aperture) - using a variety of pre-set filter settings (deep red, orange, yellow-green, blue-green)I can quickly switch between my pre-sets which can dramatically change my image, certainly affecting contrast (and thus the visibility of grain).

Try using a) 80% red, 15% green, 5% blue on a face, and then change that to 10% red, 70% green, and 20% blue.

As a finishing touch, I'm normally applying a little bit of sepia (0.5) which gives me that "warm" touch.

Take a look at my b&w's on flickr:

http://flickr.com/photos/41457884@N00/

Cheers,
Karl

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Answer 5

jkw38

Level 1

5 points

Oct 13, 2006 7:21 AM in response to Karl Geiger

Karl,

Some nice tones you have in your images. I'm just wondering, were the pix of Stefan made in Aperture?

jeff.

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Answer 6

Oct 13, 2006 7:44 AM in response to Karl Geiger

Karl,

Those B&W's are fantastic. Thanks for sharing!

Brad

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