Dynamic Range & Stops

Dynamic range is the difference between
this and this. If you've ever taken a picture and the
sky looks completely solid white even though you could see texture in the
clouds with your eyes, that's a dynamic range problem. If you're taking a picture and your
subjects faces were completely in shadow even though the background seemed properly
exposed, that's a dynamic range problem. So let's
talk about how to fix those problems and what dynamic range is.

To understand
dynamic range, you have to think about what black and white are. And that seems
obvious because our brain kind of takes care of black and white for us
automatically, and our cameras take care of it automatically, too. But our cameras
don't always make the right choice. White is the very brightest part of the
picture and anything in the scene that might have been brighter than what the
camera decides is absolute white is going to be completely lost.

Everything
just becomes solid white, even if there were shadows and textures
in there. Similarly, black is absolute black and
anything below that point gets completely lost. Detail, textures and the shadows
completely disappear. So here's the problem: your brain can see
about 12 to 14 stops of data between black and white.

It can see this massive
amount of range, but your camera can only see about eight
stops of data, or at least in the pictures that you typically look at there are about
eight stops of contrast from black to white. So the way your camera handles that is,
it looks at a scene and kind of picks middle gray. What it thinks should be right
in the middle between black and white. Four stops of light below that are the
shadows and four stops above that are the highlights.

That gives you that, about
eight stops of dynamic range, and when you look at the picture it looks nice
and contrasty, it looks very natural. But it's leaving out a lot of data above
that white and below black that your eye might have been able to see just fine. So you can control how those eight stops
are organized. You could use exposure compensation to
make the picture brighter, therefor bringing up the shadows but clipping
more the brightest parts of the picture.

You could use exposure compensation and
dial in negative stops, making the entire picture darker showing more of the
highlights but clipping some of the shadows. You'll use exposure compensation up or
down to decide what the most important parts of your picture are, choosing
whether to clip the highlights or to clip the shadows. Basically deciding
which part of your subject is the most important part. And in something like a
portrait, you would want the face to be nice and brightly exposed.

What if you actually want to show more
than that eight stop range? You have two options for that. You can
shoot raw. Raw images capture usually between 11 and 14 stops of data however when you look at the jpeg
generated by that raw file, you'll probably still just see eight stops.
Shooting the raw does allow you to adjust the exposure compensation after
the fact, however. You can also adjust the raw file to show less contrast to cram
in all those 11 or 14 stops into the final jpg file.

High dynamic range techniques take the
brightest parts of the picture and kind of shift them down, making them darker
and will take the shadows and raise them up. This shows those details in the most
extremely bright and extremely dark parts of the picture without making the
entire scene too low contrast. You should always think about the
dynamic range of your picture and how much of that dynamic range your camera is
capturing. One more factor is the noise.

The brightest parts of a picture with
eight stops of dynamic range are about 256 times brighter than the darkest
parts. Now, you might not think about that,
especially when you're looking at a scene. But gathering 256 times more light
means that part of the image will be much cleaner. In the shadows, gathering 1/256 of the same light as the highlights? You're going to be seeing a whole lot of
noise because the camera simply isn't gathering that much light.

That's why if you look closely into the
shadows or you raise the exposure of shadows, you'll often see little red blue
and green speckles in there. That's that digital noise and can be really annoying
and ugly especially in very contrasty scenes such as night photography where
everything is either a shadow or a highlight. So to minimize that noise, I urge you to
look at your histogram while you're shooting, do what they call shooting to
the right. Make sure that the right third of the
histogram has some data in it.

If you're shooting raw, you have about
two stops of highlights that you'll be able to recover later. You might even plan to shoot a little
bit to the right of your histogram, knowing that you have a little bit of
that data. I hope this video is useful, if you have any questions for me add a comment
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