Ramble: Masking with Equalize — OZONE Asylum, home of the Mad Scientists

Ramble: Masking with Equalize

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Your Text: Insert Slimies » Insert UBB Code » Close Last Tag \| All Tags UBB Help	One thing I tend to do is run in circles. Sometimes I really hate this. I have a quandry, start exploring, and eventually end up right back where I started. Answers lead to more questions. Several answers down the road, I'm back to the original question. Ugh. But sometimes I really enjoy running in circles. This is like a satisfying game of Connect the Dots. Rather, Connect the Concepts. Check this out: [url=http://www.pages.drexel.edu/~weg22/edge.html]Edge Detection Tutorial[/url] In that tutorial there are three graphs. The first graph is a gradient. The second graph is the first derivative. As luck would have it, the original gradient gives the second graphic (first derivative) the appearance of the infamous Gauss bell curve. Coincidence? Hmm... Now, the third graph is the second derivative. Does it look familiar? Does it? I showed a sloppy offset wave that looks just like it. Not only that, but it happens to be High Pass. Did you know that High Pass does the second derivative of a gradient using the Gauss bell curve? Of course you did. And all that crap comes around full circle. I'm very satisfied with this round of Connect the Concepts. Bloody awesome. Now we are going to pull the contrast aspect out and play with that for a bit. Contrast, to set in opposition in order to show or emphasize differences. That's it. Pretty simple, really. Honest. I wouldn't lie to you. At least, not intentionally. But even then I'm prone to addendum to patch things up. Right? The sloppy contrast wave that I showed was for an image on the whole. Easily done with Curves. Or you can use Levels or Brightness/Contast for sloppy contrast. This is a popular way of stretching data to emphasize difference. The second derivative showed in the tutorial is High Pass. This will increase contrast using a specific frequency based on surrounding values of a given pixel. Ah, yeah. Even though this is a form on contrast, it is commonly known as sharpening. Ah, frequency and contrast. Lovely subject. A lot of people using various frequencies for various sharpening tasks. Consider sharpening eyes but not sharpening the acne on the forehead. Sharpen, then use a mask to keep the sharpening that you like. Masking a sharpening frequency is well known in most retouching circles. But there is still so much more to be explored and played with. Masking a frequency is only half of the story. I'm going to repeat that. Masking a frequency is only half of the story. Have you ever considered manipulating the frequency itself before using it to sharpen? This is the other half of the story. Even though clipping usually isn't a problem when it comes to sharpening, I'm going to use clipping as an excuse to show the basic technique. Where in an image can you add and subtract to cull detail without clipping the half of the detail in the highs and lows? In the middle, of course. (If you are working on midtones and clip under or above, you might want to re-examine your flow. And I thought I was crazy. Egads!) - some random photograph - favorite method to select midtones - use said selection to mask sharpening Using that, you should be able to keep everything legal, within bounds, or whatever. Now, this might not exactly make sense in a practical manner, but beer with me for a few. Why mask out the HL and keep only to M? Let's say you have a photograph of some sheer curtains over a bright window. Rather high lum with some subtle detail. You want to pull out some of the detail, but you don't want to blow out the highs because they are already pretty close to being blown out. If you sharpen the curtains, you are going to clip some noise right over 255 (or whatever number you use). In a case like this, prolly Levels, but might not be enough as you want to punch some detail as well stretch the curtains as a whole. Time to modify the frequency itself. Well, crap. Even though I just talked about using highs as an example, the graphic that I prepared uses lows. Heh, that's what I get for listening to Barry Manilow while flowing. Take everything I just said and flip it. So, our basic technique evolves a little bit by simply modifying the frequency to take the subtract parts out. Taking the subtract parts out for shadows, and my layer rig looks something like this: [img]http://tech-slop.serveit.org/wiki/images/tweakhighpass.gif[/img] I prefer Linear Light and flattening to 128. Why? Because wiggling the anchor that's at 128 can be fun. But feel free to mix it up. Blondie just started singing. I think I need more Korn in my diet. Meh, I'll switch to Queen for the next few minutes. [i]There goes my baby. She knows how to rock-n-roll. She drives me crazy...[/i] Ah, much better. What was I talking about? Well, shit. Levels and a modified High Pass wave. I have used this combo many times to get far more detail out of the shadows than either would allow solo. Can pull things out a great deal before the data stretching starts getting nasty. And he nails the dismount! The crowd goes crazy! Now get to playing before I get my chainsaw out and start breaking stuff. Ah, that's the Limp Bizkit talking. I think it might be time for some Tequila to mellow down. Loading...
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