Part 2 of a 2 part series.
In part 1, we learned multiple ways to convert a color digital photo to black and white. But frequently that result isn’t good enough.
Images frequently, such as our sample, have a very flat contrast. That is, there are not a lot of black blacks and not a lot of white whites. This is actually a good thing. Most pro photographers want to shoot flat image in camera and will set their camera to produce the flattest images possible because its easier to add contrast in post (production) than it is to take it out.
Looking at the histogram for the image (the Levels tool or CTRL-L or Apple-L on Macs will display the histogram). You can see the curve of tones does not reach the 0 black point or the 255 white point.
You can perform an operation called equalization where you use the black and white tear-drop shaped drag controls and slide them inward until it meets the point where the histogram curve bottoms out. This in effect takes the image tones and stretches them so that they span the range of 0 to 255 giving us a white point and a black point. This is an easy way to add pop to images (including color). Be aware stretching the color or tone range causes Photoshop to insert gaps into the tones to spread what might be packed over 220 total tone value and stretch to 255. This is a little destructive to your image. Many people prefer to use “Adjustment Layers” to leave the original layer alone.
If you get too aggressive with your equalization, you will begin “clipping” your image. In the example shown here, I was too aggressive on the white point and you can see areas of the photo starting to blow out and become unattractive. Likewise on the black side, if you clip too much, you start loosing shadow detail and get large areas of solid black. If thats the effect your going for, then great, but most of the times, you want to avoid this and just bring the drag points in to meet the histogram.
That said, frequently images will have really bright spots, such as the sun shining off of a chrome bumper. These are generally small areas that are called “specular highlights”. They are expected to be blown out. You will recognize them in the histogram curve as the tones drop to the bottom then suddenly spike as you near the 255 value.
If you have specular highlights, its okay to slide the dropper left until it meets the real bottoming out of the tone histogram since the spike has no detail anyway.
The next step is adjust the contrast to get the effect your looking for. For this, I recommend the curves tool (or a Curves adjustment layer!!). With curves you can selectivally adjust the shadows, midtones and highlights as necessary. Applying a simple and subtle “S” curve, pulling the shadows a bit darker and pushing the highlights up is an easy way for you to add contrast and do it with control.
There would be a strong templation to use this tool or levels to brighten the over all image but you risk blowing out highlights too much.
We see a lot of photos where the subject has a milky white skin, yet the darks are nice and rich. One way to accomplish this is to duplicate your source layer, so that you have two copies stacked on top of each other. The set the layer blending mode for the new layer to “Screen”. This will lighten the photo and it may very well lighten it too much. You can adjust the opacity to taste. Then if your black areas lightened up too much you can use the erase and erase the blacks on the top layer to let the darker bottom layer show through.
Now from this point, depending on the eyes, you might need an eye lightening technique or if you want a vignette you might want to burn
the edges of the photo or add some textures to finish the shot.