Levels and Curves when Editing
Use levels and curves to adjust the overall tone and contrast in your digital image
What Are Levels and Curves?
Levels and curves are two options in Adobe Photoshop and other editing software that allow you to adjust and fine tune the contrast and overall tone of a digital image or photo. The Levels adjustment basically changes ALL of the tonal range whereas Curves gives you the option of choosing which section of the tonal curve to change.
Introduction
If you are shooting digitally, with a Digital SLR in particular, these are two of the tools that you should be finding yourself using a lot. Levels and curves. Especially if you shoot RAW. Digital SLR's, as I have mentioned elsewhere, produce a flatter image than your original film SLR or digital point and shoot.
With film, these kinds of corrections were done for you at the processing lab. Because "point and shoot" cameras are aimed at the mainstream market (who want nothing to do with the processing), they produce instant, bright and bold images straight from the camera. When you get into the realms of the Digital SLR, you are heading towards a more professional style of photography. Therefore, more of the post processing is left to you.
Dull as Dishwater
Many people complain of images looking bland and lifeless or colourless when they first buy a DSLR and this is why. By manipulating the levels and curves of an image, you can quickly and easily replace the brightness and colour to your images with great effect. Let me illustrate this for you.
On a recent trip into town (Weymouth), I noticed the bridge was opening (Fig.1). I took quite a few shots with my Canon EOS 5D Mark IV and the images were ok. If not a little bland. For those of you interested, the exif data is
Here is the image opened in Photoshop CC:
Levels and Curves Fig 1 - Click for Larger Version
As you can see I have chosen a subject for this section with lots of contrast and a fine, sharp detail. This is to enhance the importance of levels and curves. Once you have opened your image in Photoshop, go to:
Image - Adjustments - Levels
A box will appear as in Fig.2.
Levels and Curves Fig 2 - Click for Larger Version
As you can see, a histogram will appear that looks like a mountain range. In this case there is a small gap to the left and a slightly larger gap to the right. The left part of the histogram is the dark side and the right, the light side.
The larger gap on the right means that the image was slightly underexposed. This is rectified by moving the white slider on the right, back to the base of the "mountain range" or histogram as in Fig.3. Don't overdo it or you will blow out some of the detail in the lighter areas of your image.
Levels and Curves Fig 3 - Click for Larger Version
When you move the slider, you will instantly see the image brighten up. As a test, I always click the preview button on and off a few times to see the effect. "Before and after"!
Choices
With the black slider on the left, you have a choice. You can either bring this also to the base of the "mountain range" or histogram to the right. Alternatively, if you bring it to the centre of the first peak as I have in Fig.3, the blacks will turn pure black for a real "punchy" and contrasty image. This is personal preference and you will know what works by using the preview button and having a play. Again, don't overdo it.
Another "quick fix" way of adjusting the levels is to use the 3 eyedropper tools. These appear in the levels box just above the preview button. Select the left eyedropper, or black one and then use this to click on a black part of the image.
Then select the white eyedropper and do the same on a white part of the image. You can use the centre or grey tool but you have to be fairly accurate with part of the image you choose. Otherwise you may get some colour cast appearing.
Note: This is similar to using a grey card when taking a light exposure reading at the point of exposure.
Ok, that is levels covered to a degree, now for curves.
I won't go into full detail of adjusting each individual colour separately, as this is meant for beginners and general workflow. We will make minor adjustment to the full RGB spectrum.
I personally use the curves tool quite sparingly as overuse can lose a lot of the detail in an image. As I do a lot of sunny, bright and colourful work, the curves tool enables me to add some extra punch and boldness to the colours of my images.
Go to;
Image - Adjustments - Curves
The box that appears is very similar to the levels box. Similar except that the histogram is replaced by a straight line from bottom left to the top right. This is the curves line. See Fig. 4.
Levels and Curves Fig 4 - Click for Larger Version
Quick note while I remember
If at any point you get to the stage where you dislike your adjustments, press Ctrl and Alt together and the "cancel" button in either the levels or curves box becomes a "reset" button. Click on it and you will revert back to the image before you started to play.
If you look at the very minor adjustments that I have made in fig.4, that is almost the extent of how much I personally use the curves tool. It is a kind of "S" shape with the top adjustment adding brightness to the image and the bottom adjustment darkening the shaded areas. This, or near to it, is normally enough to add a bit of contrast to your images.
Hover cursor over image to see the before and after. On mobile? Tap inside and outside the image.
Obviously as each image differs, the adjustments will also differ. Don't use this tool all the time such as with "misty" looking shots as you will lose that pastel effect by adding too much contrast. Experiment with fine adjustments to each of your shots but remember, again, not to overdo it.
If you are feeling really adventurous and are looking to make some weird and wonderful effects, they can be done using the curves tool to the extremes. Try it and see what happens. It is a good way to begin to learn how light and pixels work together.
