- [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
in case you decide you want to print it out.
And I've gone ahead and mapped out
all the hue values on a circle,
starting at zero degrees for red
and then going back all the way around to 360 degrees
which would once again be red.
And so the visible color spectrum,
at least where hue values are concerned,
ultimately forms a continuous circle.
And so notice we have the industry standard colors of red
at zero degrees, yellow at 60 degrees,
green at 120 degrees, cyan at 180,
blue at 240, and magenta at 300 degrees.
And again, these are industry standard colors
which is why I've set them in the largest type.
In between, we have subjective colors.
Now I think we can all agree that 30 degrees is orange
but I'm calling 90 degrees lime,
150 degrees turquoise, and so forth.
Now around the outside,
we're seeing the 100% saturated versions of the colors.
Toward the inside, we're seeing 0% saturation.
So everything ultimately goes to gray.
Our color cast is 172 degrees
which means we need to send it from this point over here.
Probably right about here actually.
I'll just go ahead and drag around.
And you can see the hue values changing over there.
So right about there is our color,
and so we need to take it
in absolutely the opposite direction.
So we'll start by trying to correct
the color cast automatically
using two familiar commands, Auto Tone and Auto Color,
both of which correct the image
on a channel-by-channel basis.
And so notice if I switch over to the Channels panel,
we have a darkish red channel,
we've got a bright cheerful green channel,
and then we have a blue channel that's somewhere in between.
And so in other words, we have plenty for Auto Tone
and Auto Color to work with.
All right, I'll go ahead
and switch back to the Layers panel.
Now even though we've seen these commands before,
they are a little bit hard to predict, as you'll see.
And they'll help us to understand two other functions
that allow us to correct color cast inside Photoshop.
All right, so for the sake of demonstration here
I've got a control layer.
I'm going to go ahead and turn on the auto tone layer
and click on it to select it
and also make sure that neutral layer is turned on.
So I can click right there in the center of it
in order to lift what should be a neutral color.
And by the way, couple things to note here.
You can move your cursor around on the fly if you like
and you'll see those HSB values changing
there in the Color panel
in the upper right corner of the screen.
As things stand now, I'm sampling all layers.
So the composite view of the image,
which is going to work out just fine,
and my sample size is set to Point Sample.
In other words, I'm just lifting the point under my cursor.
And again, if you want a more precise cursor,
you can press the Caps Lock key.
So in other words,
you're lifting a single screen pixel of color.
If you want your sample size to be bigger,
then you can set it to something like
11 by 11 Average if you want,
which means 11 pixels wide by 11 pixels tall.
I wouldn't do that in this case
because we're going to start encroaching
on the color of the ring right there.
So I'll go with five by five Average,
and then I'll go ahead and click once again
in order to lift a color.
And so there it is.
We've got a huge value of 170 degrees, in my case.
A high saturation value, 39%.
We want it to be below 10%.
And then the brightness value doesn't really matter.
All right, so let's see what Photoshop's got.
I'll go up to the Image menu and choose Auto Tone.
It's pretty disappointing.
It's actually kind of hard to tell the difference.
This is the control image,
it's a little bit greener.
And this is the auto tone image.
And so now if I go ahead
and click at that center point once again,
then notice that I do have a reduced saturation value.
It's down to 25%.
It used to be more than 10% higher,
so that's a really good thing.
Problem is the image doesn't really look all that different.
All right, so now let's try auto color.
I'll go ahead and click on that layer
to select it and turn it on as well.
And then I'll go up to the Image menu
and choose the Auto Color command.
And so notice now if I click in the center of that circle,
I'm just trying to make sure I click
at that same point,
that I have a totally different hue value.
This time around now.
We're at 200 degrees.
So if you take a look at the big color wheel,
notice that we flip to the other side of cyan.
We're on the bluish side of cyan
instead of the greenish side.
But more importantly,
we've taken that saturation value down to 20%,
and the image looks a heck of a lot better as well.
And so just to review, here's the original unmodified image,
here is the auto tone adjustment, and here is auto color.
(light upbeat music)