Using the Levels adjustments in Photoshop
At the end of my tutorial about cropping in respect to bird photography I said I’d look into the possibility of doing a short tutorial about levels, again in respect to bird images, although it obviously has relevance to all images.
Well here it is, Levels.
In Photoshop CC2015 we will be using the levels dialog box which can be found like this
I’m not sure where to find it in any other editing program but I’m sure it will be easy to find.
Here is an image that I recently took
Now the first thing we should do is crop it to the size, shape and composition that we want the final image to be. This was covered in the Tutorial on Cropping that can be found here.
(The original RAW image wasn’t quite like this as I’ve adjusted some of the values so that I can show what I mean about levels)
Here is the cropped image, cropped in the size, shape and composition that I want for the final image.
So what do we mean when we say Levels. First of all we really need to understand the histogram of the image. Now before you go all glazy eyed and switch off, please bear with me. It really isn’t that scary and will really make a great difference to your images if you get it right. If you take each pixel in an image and give it a value from 0 to 255 that relates to the brightness of the pixel then place the pixels on a horizontal line depending on their values, with 0 on the left and 255 on the right, you will end up with a Histogram that will look like this (for this image)
In this example we are seeing the sum of all three colour channels, namely Red, Green and Blue.
0 is black, or no Red, Green or Blue, and 255 is white, or maximum amount of Red, Green and Blue, so the histogram shows the number of pixels in the image ranging from the darkest black on the left to the whitest white on the right. In this example most of the pixels are in the mid range. If you look at the ends of the black area that represents the pixels in the image you will see that they don’t reach either end, but fall short.This is because we haven’t got any whites or any blacks in the image which gives a smaller dynamic range and results in an images that looks washed out. It’s very easy to improve this by moving the start and end points for the histogram and this is done by moving the little pointers at either end in towards the dark area that represents the pixels in the image. Here is what I did to this Histogram
You can see I moved the end points to where the pixels start to rise at the black end and fall off at the white end. This results in an image like this
You can hopefully see the difference where the image has more POP and looks less washed out.
I will mention the pointer in the centre of the histogram although I rarely use it. If you move it to the left you will move the mid point and the number of pixels to the right will increase and so the image becomes lighter.In the same manner, if you move it to the right you will move the mid point and the number of pixels to the left will increase and so the image becomes darker. Here’s an example of moving the centre point to the right
This makes more of the pixels in the image darker
One point of note, this doesn’t change the black point or white point of the image
This is what you need to do to improve the dynamic range and to get the most out of the image.
To show the differences in the histogram here are 2 further examples, one over exposed by 2 stops and the other under exposed.
2 stops over exposed image
2 stops over exposed histogram. You can see most of the pixels are above the mid point resulting in a very bright image, to the point that some of the whites are blown, meaning they no longer have any detail in them.
2 stops under exposed image
2 stops under exposed histogram. You can see most of the pixels are below the mid point resulting in a very dark image, to the point that some of the blacks are completely black, meaning they no longer have any detail in them.
It is possible to get some of the detail back using the histogram and levels but it never looks as good as if you got it right when you took the shot. One way to improve getting information back if you got it wrong during shooting is to shoot in RAW and change the exposure in Lightroom or whatever your RAW converter of preference is.
I hope this is of some use to someone and although it wasn’t meant to be the definitive Levels description it should help explain it to the novice or someone starting out on Post Processing.