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Midtone Selections using 50% gray layer or gradients

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Old 08-29-2005, 07:03 AM
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realaqu realaqu is offline
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Midtone Selections using 50% gray layer or gradients

this tutorial tells you how to use 50% gray layer to get much more accurate mid-tone area selection. [details]
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Old 09-01-2005, 06:15 AM
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Great tutorial, one suggestion I would make is it would be nice to see screenshots of a more realistic example of its usage as well as the images you have.
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Old 09-01-2005, 08:50 AM
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Ah, mid-tone selection. I've got boat loads of notes on this, but I'll keep it short with simple variation that uses Luminosity and can be custom defined.

- Adjustment Layer > Gradient Map
-- Stopper like so: Black on left, White in middle, Black on right
-- Move the stoppers around until happy
- Copy Merged and paste into Alpha, or something

You can keep the stoppers at 0%, 50%, and 100%, or you can eyeball the image, or you can use the Histogram to help eyeball things.
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Old 09-01-2005, 10:06 AM
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realaqu realaqu is offline
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That is really a great way, I forgot this method.
thank you

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Old 09-01-2005, 01:41 PM
cinderella cinderella is offline
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Examples please. I'm not sure what ya'll are talking about. Thanks
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Old 09-03-2005, 08:07 AM
mdavis mdavis is offline
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This is similar to the method Kelby gives in his latest CS2 book with credits to Dave Cross for the idea. He simply creates a new layer, fills it with 50% gray (Edit-Fill menu), sets blend to "Difference" and then uses the Threshold command and sliders to find the emerging pixels. This is quick and easy and can give you a feel for POTENTIAL neutral objects.

But there is a huge potential for error here, so be very careful. If you isolate channels and begin messing around with hi/lo points in individual channels, you are resetting color balance, because you assume by doing so that there exists a true neutral gray somewhere in the image and that the lightest and darkest points are true white/black and must be balanced relative to the other channels. By using the threshold slider method, you can see if there is neutral gray in the image at THAT stage of color (im)-balance by noting any pixels visible at zero slider position. The farther away from zero you must move the slider to find pixels appearing, the less likely they are to be truly neutral.

Consider the problems. If you use AWB in your camera or scanner, the algorithms in the capture device look to set the brightest area and darkest area as white/black, and base color balance on those endpoints. When you overlay 50% gray, you are finding neutral as defined by the white balance of the captured image, not necessarily true neutral. The same is true of always setting the white/black points with droppers. There may not BE a pure white or pure black in the image.

The best way to set color balance in most images is simply to look at them on a reasonably calibrated/adjusted color monitor and search for "unreasonable" colors. There are very, very few true neutral gray objects (most concrete, tires) to pin to balance midtones, so you have to use your own judgement to pick out colors that are "off" and then use the info pallet (or equivalent) to adjust them. Other common areas that can be used are sky and skin, once you learn the relative amounts of RGB or CMYK (or LAB) that are "reasonable".
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Old 09-20-2005, 05:33 PM
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realaqu realaqu is offline
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I use my method in this thread to increase the contrast of mid tone of this picture.

hope that helps

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Old 10-05-2006, 08:02 PM
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CJ Swartz CJ Swartz is offline
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Re: mid-tone selection


Thanks for giving me another tool for toolbox! Thanks also to Stroker and mdavis for additional thoughts and different strategies.
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Old 10-05-2006, 08:48 PM
drisley drisley is offline
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Re: mid-tone selection

Curious, why do you need to select the green channel for this?
Will this give different effect on different images (vs blue or red)?
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Old 10-05-2006, 09:44 PM
leuallen leuallen is offline
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Re: mid-tone selection

Hey Drisley,

What you doing here? Check out the effect to using Stokers gradiant mid tone over the base image. Set gradient layer to soft light. Add a hue/sat, curves, and
selective color adj. layer and play. The result below. Different than in the other thread.

Attached Images
File Type: jpg test-mid-tone-LL.jpg (92.9 KB, 39 views)
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