Friday, August 14, 2009

It's Wabbit Season, We Got To Be Bery, Bery Quiet.

The first thing I noticed about today's image was the amount of noise it had in the shadows. A quick check of the metadata showed I had shot it on 800 ISO. That shouldn't have been too bad with a D300, but it was more than I wanted in an image with a whimsical feel to it. The first stop in the workflow was my "normal" "first stop" of neutralizing the color balance. I've gone through that exercise before, so I won't repeat myself here. With step one down I just had to deviate from the norm and get rid of the bulk of the noise. Now, being the cheap SOB I am, I don't have one of the noise reduction plugins that are out on the market. I'm also not crazy enough to think Photoshop's "Reduce Noise" filter works worth a damn. So, what's the "easy, cheap, effective" method of getting rid of noise and keeping edge detail? Hit the "read more" and I'll let you know.

And here is the rest of it. Becoming reasonable at Photoshop is a series of hand-me-downs of techniques that increase your knowledge. It's sort of like the old game of "telephone" where you line up a group of people and whisper something into person number one's ear. What comes out the other end (given enough players) typically sounds nothing like what was originally said. I've seen the same type of thing in "real life" when I was an engineer in a green sand foundry. (another story) The technique I used on today's image is one I heard from Felix Nelson of NAPP who heard it from Corey Barker (also of NAPP). If Corey came up with it originally I don't know, but it works pretty darn good.
Noise, in a color image capture is made up of Red, Green and Blue (RGB) random dots on the sensor. The higher the ISO setting the greater the noise. Well, if the noise is RGB and the image is made up of a Red Channel, a Green Channel and a Blue Channel it would appear we can isolate each source of noise. Typically the Blue Channel is most heavily effected by noise, with the Green Channel and Red Channel having lessor amounts. In more recent versions of PhotoShop we also have something called Surface Blur. Surface Blur's function is to blur surfaces and leave edges alone. The Wizards over at Adobe know "how" it works. I just care "that" it works. So, if we know where the noise comes from, and we have a method of smoothing out large "flat" areas we have something to work with. Just the same as my using individual Hue/Saturation Adjustment Layers to control the density of each color (Red, Yellow, Green, Cyan, Blue and Magenta), this method uses individual color channels to control the reduction of noise. The big difference is that we have to go with Image Adjustments rather than Adjustment Layers. That means everything is applied to a single layer. Not the worst thing in the world to happen, but not the best either. To "get" that single layer we can use what's known as "the left side of the keyboard" plus E. That's CTRL, ALT, Shift E. That'll preserve the underlying layers (just in case) and give us a composite of all the layers below. Think of it as basically your "new background" layer.
Here comes the easy part. Open your Channels Panel and select a channel (let's start with red, as it comes first in the stack). Select Filter/Blur/Surface Blur. I've never used the preview more than when I'm clearing up noise using this technique. From wherever you start, click off and on the preview to see what's going on at the current settings. Where we need to end up is at the lowest values that produce good edges and the least noise. Too much of either Radius or Threshold will destroy the edges. Too little won't remove enough noise. Experiment. (Use low numbers) Once the Red Channel looks good, move on to the Green Channel. When you like what you see in the Green Channel, head over to Blue. Once you have the noise under control, hit the RGB Channel and go back to your "normal" processing.
This is another one of those deals that takes longer to read the explanation than it does to do the work. Until I find an image that is so far out of whack on the noise scale that this method doesn't work, I'll keep using this freebie method. If you'd like to check out the lack of noise because of this method, click on the image. That'll open a larger view in another window. You should be able to use the CTRL and "+" keys to increase the apparent screen size. Look at the wood above the number eleven in the center of the shot. At 500% you can see the image starting to fall apart (it is a low resolution copy of the image), but it's tough to pick up any noise.


Kathy Marciante Photography said...

Can't wait to try it Tom!! Great explanation! Love the shot.