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 that I have never heard mentioned is order-of-operattions when it comes to masking. Being aware of order-of-operations can make a tremendous difference. This can easily lead to a phenomenom that I call Doubling Back. You can do this easily with Curves by getting a little bit crazy with the curve. You can even do this with Displace. In Curves, imagine you have anchors that are at 64 and 128. To see the Double Back phenom, just move the 64 anchor above 128. It will cause, I don't know... solarization? I call it Double Back. This can also be seen in Displace, but I'm not in the mood to show that. Another place where this occurs is when masking adjustments. When you mask an adjustment, you are moving certain values, and it is easy to move those values beyond values that you are not moving in the mask. - start with a photograph with decent contrast - Colour Range > Midtones (even though I hate Colour Range for this, it illustrates very nicely) - use that as a mask for Levels Adjustment Layer How far can you move the Gamma (midtone) slider before you get solarization or Double Back? This means that you have to get the masks and the adjustments to play nice. Getting the adjustments to play nice isn't too hard, but getting the masks to play nice can be a bit of a pickle. To get the masks to play nice, I use the 100% rule. Let's switch to a bit of a sloppy Curves view. Horizontal is Lum and the veritical is mask values. Let's say that you want to divide a photograph into highs and lows in a straight-up manner. That is, no major tweaking. Easy enough, and it looks something like this: [img]http://tech-slop.serveit.org/wiki/images/lumxmask_HL.gif[/img] Notice that high + low = 255/100%. This is good, and the masks will play nice. Now let's divide a photograph up into high, mid, and low. If we use the above high/low and just toss in mids, we get something like this: [img]http://tech-slop.serveit.org/wiki/images/lumxmask_HMLoverlap.gif[/img] As you can see, high + mid + low != 255/100% at all points along the Lum line. In this manner, it can be very easy to overly double-adjust values and cause solarization. In order to divide a photograph into high, mid, and low with masks that play nice, you have to use something more like: [img]http://tech-slop.serveit.org/wiki/images/lumxmask_HML.gif[/img] If you go back and look at the Gradient Map settings that I posted earlier, you should see that they are consistant with the last graphic. That is, the highs and lows are cut-off at the 50% mark. Order of operations, eh? Yes, can make a big difference. Let's say that you divide a photograph into highs and lows and use those as masks. This is largely what I've been talking about. Let's say we change the order a little bit. - extract Lum - generate a mask for highs - using the tweaked photograph, extract Lum again and mask lows Because some of the values got tweaked after tweaking highs, the lows will be changed a tad. This means that the mask for lows can very well be very different. Largely I consider this bad. But not always. Consider Shadow/Highlight for a moment. It will divide a photograph into highs and lows, then - and only then - get the midtones. Get HML in one swoop, or adjust HL and then get midtones... ? [b]Big[/b] difference. The paradigms of masking and order of operations holds true for many things in Photoshop. What happens if you use Levels and Hue/Sat in different order? What happens if you use Levels and Hue/Sat in different order with masks? Hmm... food for thought. This whole thing is one of the reasons whey I adore using Equalize for masking purposes. However, the whole thing does fall apart with the addition of one simple concept. And yet it still kind of holds true. Pretty funny, actually. Loading...
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