Oct 3, 2010

Turning Color to Black & White in Photoshop


So, have you noticed that the process to turning a photograph into black and white is not always as simple as many may make it seem. I'm especially directing this to the users of "Hue/Saturation", because I made an interesting discovery that'll make you reconsider your Color to B&W processing in Photoshop!!

Okay, what's the big idea?
See now there's 2 ways to turn an image black and white in Photoshop, one is using the Black & White adjustment by creating an Adjustment Layer or by going through Image > Adjustments. It works but I only mess with the sliders about 20% of the time when I use this.
The other way is to apply Hue/Saturation adjustment and just set the saturation to 0%, and there you have it. BUT I'm going to show you why that process isn't going to give you the same look you were probably expecting!

So, I'll tell you!
First off, Black & White photography does not mean "no colours", which is exactly why I'm against using Hue/Saturation alone. BnW images tend to have high contrast, so you'd have to throw in something like Curves or Levels to create this, and I'll show you why in a few. Also, I'd like to point out one flaw to Hue/Saturation: It actually REMOVES contrast... okay I dunno if that's what I mean but I shall show you.

Go into Photoshop and create a new document, preferably rectangular, like 500 x 200 pixels. Now, get the gradient tool and after picking the rainbow gradient, draw it out from left to right so we have the full spectrum in our image.

Okay, cool. Now create a Hue/Saturation adjustment layer and set the saturation to 0...
...see what I see...


Well if you don't, let me draw your attention to something else. Have you ever tried to print out something in color on a black and white printer, or photocopy something coloured into black and white? Notice exactly what happens? Red tends to become really dark and colors like green and blue tone grey, while magenta turns nearly white!

... See it now?

Our Hue and Saturation just turned the image into... 50% gray!!! So that's the problem with Hue/Sat, it levels out the luminosity to 50% gray and, in turn, we would lose detail in various areas.

 Before you get all defensive (if you plan to), just undo/hide the Hue/Sat adjustment and apply a Black&White adjustment (CS4 and above), what do you see? Yes, the contrast is still intact and you can see exactly where the colors should be!

There's a significant difference here. Basically, Hue and Saturation has lost a lot of information. If I had an image of relatively uniform luminosity (though impossible), I'd lose everything. This problem would mostly affect designers.

Anyway, there's an easy way to solve this: How? Well just set the Blending Mode of the layer to Color!

Cool, problem solved. In fact, Hue/Sat has more contrast.

One thing you may also want to do is add another Hue/Saturation adjustment below this black and white-ify layer and messing around with the hue and see what it does (in a color image, preferably). Basically, it'll affect how bright each color will become. Say I was wearing a blue shirt and it came out to dark (as above), messing around with the hue to make my shirt yellow BEFORE it reaches the Hue/Saturation layer (remember, they process upwards), my shirt will become white in black and white, and so on with various cases:

Click to view larger. (CC) Attribution Share-Alike

In this example, I have taken a photo I had (adjusted a bit with curves) and set as this ORIGINAL. Next, I applied a Hue/Sat set to color and I got a fair BnW image, but I noticed that my skin looked rather dark, so instead of brightening, I simply shifted the Hue/Sat and got something I liked (+120) as the image on the right. (My skin was GREEN without the adjustment :-S)

Basically, using the experiment we had done earlier comparing the spectrum to hue/sat, I've created something with lighter areas on what I want and darker on what I want... which can be done by tweaking individual colors in the hue and saturation adjustments pallet. Actually, this is pretty much what the colored sliders in the Black & White adjustment do!

Okay, so we've sorted out the color issue, but what about the contrast issue?

Well, that's simple enough: Levels or Curves!

Here's how it's gonna work, just throw in a Levels or Curves adjustment and do your thing. Note that in Levels, you want to bring the black slider (shadows) to the left and white slider (highlights) to the right, then play around with the grey slider (midtone)!
For Curves, create an S shape, but don't overdo it. The degree of this S determines how much contrast you gain.
Don't exactly do like this image, but that's basically how it works. Depending on your image, adjust as required.

Also consider applying a BROWN photo filter, or rather a VERY subtle brownish color to the image (like even 3% opacity or something), it adds an interesting feel to the image, especially when people look at it, then look the second time and go "is this like.... brown... ish...??"

There's a much better explanation of how B&W works (especially straight off camera stuff) here:

(The very site I spoke of in the previous post)

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