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  • - [Deke] All right, now we're going to take a look

  • at all three of the auto commands

  • that reside here in the Image menu,

  • Auto Tone, Auto Contrast, and then Auto Color.

  • All three of which look at the luminance data

  • on a channel-by-channel basis

  • and make changes automatically

  • without even bringing up a dialogue box.

  • Now even though they sometimes work,

  • I am by no means suggesting

  • that they are the best ways

  • to adjust luminance data inside Photoshop,

  • but they might be the most popular.

  • Based on Adobe's analytics data,

  • they're click data from people who buy into the program.

  • Auto Tone, Auto Contrast, and Auto Color

  • together rank among the top 10 most commonly

  • used features in the software

  • in which case I want you to know how they work.

  • So here we are looking at some old school $100 bills.

  • And if you've seen my course before,

  • then you've seen this sample file.

  • It just happens to be the best demonstration

  • I've come up with.

  • And so we've got this top left bill,

  • which is our control image.

  • That is to say the one that we're not going to change.

  • And then we've got one layer each

  • for Auto Tone, Auto Contrast, and Auto Color.

  • I'm going to zoom in on the Auto Tone layer

  • by Alt or Option clicking on its thumbnail.

  • And then I'll just zoom out ever so slightly

  • by pressing Ctrl + minus or Command + minus.

  • And then with that layer selected,

  • I'll go up to the Image menu

  • and choose the Auto Tone command.

  • Now what this command does is it finds the darkest pixel

  • on a channel-by-channel basis

  • and changes it to black

  • and then it finds the brightest channel

  • on a channel-by-channel and changes it to white.

  • So in other words, it makes different modifications

  • for each of the red, green, and blue channels.

  • And as a result, not only do we increase the contrast.

  • So this is before and this is after.

  • But we also get rid of that green color cast

  • that is by nature associated

  • with an old school $100 bill

  • and we create a kind of reddish color cast in the shadows.

  • So Auto Tone can be really useful

  • if you're trying to get rid of a color cast.

  • But if you like the coloring of an image,

  • it's going to very likely mess it up.

  • All right, let's compare that to Auto Contrast.

  • I'll go ahead and Alt or Option click on that layer

  • and scoot it down just a little bit here.

  • Make sure the layer is selected.

  • And then I'll go up to the Image menu

  • and choose Auto Contrast.

  • Now this command also looks at the darkest pixel

  • and the brightest pixel in the image,

  • but it does so on a composite basis.

  • So in other words, it doesn't go channel-by-channel.

  • So it just finds the darkest pixel makes it darker,

  • the brightest pixel and makes it brighter.

  • And as a result, we maintain the green color cast.

  • So notice, this is the low contrast version of the bill

  • and this is a high contrast version.

  • We do have more contrast,

  • so darker shadows and brighter highlights

  • but we have the exact same greenish color cast

  • as we did in the past.

  • All right, compare this to the most complicated

  • of the auto functions, which is Auto Color.

  • Go ahead and Alt or Option,

  • click on that guy in order to zoom in on it.

  • Make sure it's selected as well.

  • And then go up to the Image menu and choose Auto Color.

  • Now before I choose it, let me explain how it works.

  • It's going to take the darkest pixel

  • on a channel-by-channel basis

  • and make it black and neutralize it as well

  • so that it doesn't have a color cast.

  • It's going to do the same thing to the brightest pixel

  • channel-by-channel and neutralize it.

  • And then it's going to try to find an exact midtone

  • and make it neutral as well.

  • And when I say neutral

  • I mean leach the color out of it, so that it's gray.

  • And so notice, as soon as I choose the command,

  • I am seeing dark neutral shadows

  • as well as bright neutral highlights.

  • And so the only colors that are surviving

  • even in the midtones are these very saturated greens.

  • And so if I were to zoom out

  • by pressing Ctrl + zero or Command + zero on the Mac

  • so that we can take in all of the bills,

  • you can see that Auto Contrast

  • is the one that's going to maintain the colors

  • inside of the image.

  • Auto Tone is going to remove any color cast,

  • but very likely replace it with a different color cast

  • in the case of these red shadows.

  • And Auto Color is going to do its best

  • to neutralize the shadows, highlights,

  • and midtones inside your images.

  • All right, so in the case of this $100 bill,

  • Auto Contrast probably does the best job.

  • In the case of an actual photographic image, you never know.

  • Now the first step in correcting the color cast

  • or if you prefer color bias of a photograph

  • is to identify what that color cast or color bias is.

  • And so here we are looking at an underwater GoPro photo.

  • No lights whatsoever.

  • Your photos don't have to be underwater.

  • I just happen to have a lot of them.

  • And so we can safely assume that this guy is too green.

  • After all, I'm about 30 to 40 feet deep

  • and so I've lost a lot of the color spectrum.

  • You lose the reds first, then the oranges, then yellows

  • and after a while, you're left with greens and blues.

  • But we are seeing a little orange here and there.

  • And even if we're pretty confident this is a greenish cast,

  • there's no sense in not checking for sure.

  • And you can check exactly what the color cast is

  • using the Eyedropper tool

  • which you can get by pressing the I key.

  • And one I've done is I've created

  • a bunch of copies of this layer

  • for comparative purposes later on.

  • But I also up here at the top have this shape layer,

  • which is a circle, which is identifying the region

  • that I think ought to be neutral.

  • And when I see neutral, it should be a lightish gray.

  • Whereas if I were to click inside there

  • and notice when I click and hold, I am seeing a color ring

  • which is showing me the old foreground color on the bottom

  • and the new foreground color at the top.

  • We can plainly see that that is a kind of green.

  • All right, but to confirm for sure

  • what we need to do is make sure

  • the color panel is on screen.

  • And if it's not, you can go to the Window menu

  • and choose the Color command.

  • Of course, do not choose the command

  • if it has a check mark in front of it,

  • and then click on the flyout menu icon

  • in the top right corner

  • and switch to HSB Sliders

  • is generally the easiest way to work.

  • And that way we can see our hue, saturation,

  • and brightness values.

  • Now all the brightness value is doing is telling us

  • that this is a pretty bright color,

  • so it's somewhere in the mid tone to highlight range.

  • That's just fine.

  • It's not anything we need to worry about.

  • The hue value is telling us the base color in degrees

  • and I'll show you what that looks like in just a moment.

  • And then the saturation value goes from gray at 0%

  • all the way to the most highly saturated version

  • of that specific color at 100%.

  • Now if this were a neutral image,

  • if it didn't have a color cast,

  • then this saturation value

  • would be somewhere in the zero to 10% range.

  • Instead, it's extremely high at 37%.

  • That means we have a pronounced color cast.

  • All right, let's take a look at the hue value, however.

  • 172 degrees is very close to cyan.

  • And so I'll go ahead and switch over

  • to this big color chart that I've created for you.

  • And by the way, it measures 32 by 22 inches