This post on enhancing contrast in digital photos was submitted by Leeroy Gribbon whose photoblog (www.decoy.co.nz) we recently featured here at DPS as Photoblog of the Week.
I’m a sucker for good contrast in a photo. Since I mainly like to dabble in monochrome work, contrast for me is the gravy train – second only to composition. Regardless of whether you take black and white photographs or colour ones, take them of your cat or of war zones, I feel a little bit of contrast goes a long way to making a photo come alive. So, let’s investigate together just what contrast is, and how we can bring it out in our work.
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What is Contrast?
Contrast is simply the amount of difference between tones in an image. To see this concept in action for yourself, fire up Photoshop and open an image. Open the ‘Channels’ palette (View -> Channels) and click on the Red, Green or Blue Channel. You will now see a black and white representation of your image. Open Levels, and pull the black slider to the right a little, and the white slider to the left a little. The image will change in tone. Effectively, what your levels adjustment has just done is push dark grey pixels towards black, and light grey pixels toward white, i.e., the difference (or gap) between the tone of a dark grey pixel and a light grey pixel has increased – Congratulations, you’ve just increased the contrast….
As you pull the black slider more and more to the right, and the white slider to the left, you will notice that more of the light tones will get blown to pure white, and the darker tones to pure black – shadow and highlight detail in your images begins to be sacrificed in favor increasing contrast. The ‘ideal’ balance between contrast and detail depends on the type of subject photographed, the lighting used, and also the mood and feeling you wish to convey in your image: What might be a good application of contrast to one image, may be disastrous for another. A creative eye and experience are necessary for deciding this, and the best way to gain these is to practice!
It is not the aim of this article to help you with this subjective part of the process. Rather, I would like to present several methods and techniques for enhancing contrast that I personally use on a regular basis.
Before we begin, a caveat:
First Things First
As wonderful as Photoshop or any image editing software is, the output you get is only as good as the input you give it. It may make an ugly photo look better, but it’ll never make it look good. This is as true for contrast as for any other aspect of a photo. You should view post-processing as bringing out the goodness already inherent in your captured images – much like polishing enhances the latent beauty of a diamond. Take special care to try and get everything right in-camera, and your processed images will be that much more impressive, I guarantee!
And one last thing, ensure you are editing all your images in 16-bit color depth.
1. Curves and Masks are Your Best Friends
Curves are perhaps the most powerful and useful image editing tool we have at our disposal. When you combine curves with masks, it’s like mixing peanut butter and honey together on toast – you get some sort of crazy super goodness greater than the sum of it’s parts. If you master only two aspects of image editing, it should be curves and masking. I do not want to go into how curves and masks work, as there are hundreds of articles on the net that explain them much better than I ever could. So, if you have yet to come to grips with curves and masks do yourself a favour and hole up with your good friend Google for a few hours. Or, if you’re feeling lazy, check these links I found for you:
Curves: http://www.cambridgeincolour.com/tutorials/photoshop-curves.htm
Masks: http://www.lunacore.com/photoshop/tutorials/tut003.htm
Once you know how to make a mean curve and paint a righteous mask, how do you bring the two concepts together? Let’s look at an example:
The first image (above) shows a basic B&W conversion of a photo I took.
The second image (above) shows the effect of applying a single curve to the image.
I’ve tried my best to accommodate all the tones present, but because the sky is so light and the water much darker, even with the separating power of curves if I try to push for a darker sky, I end up making the water too murky and dark, and the sky not as dark as I’d like it. The shore also leaves a little to be desired.
The solution is to make one curve for the sky, another for the water, and maybe another for the shore, then mask them in appropriately.
Although this sounds complicated and laborious, it usually only takes me about two minutes. The gradient tool certainly comes in handy for masking skies, and If you have a pen tablet masking becomes almost pleasant.
You can see the results of curves and masking together in the third image (above).
To my eye, this is much better than the second: The clouds have become more pronounced and dramatic. yet the water retains it’s texture and you can see the differentiation in the shore between the lighter sand and the darker pebbles.
You can see the finished image here.
This is a very powerful method, and may be all you ever need to make your contrast adjustments. It may take you a little while to get comfortable with the process, but putting the time in to learn the ropes will pay dividends on your images.
2. Dodging and Burning Like a Fox
Dodging and burning is a technique carried over from darkroom days. Unlike it’s darkroom counterpart, digital dodging and burning is a less frustrating and more accommodating process. You may have read about the technique before, but for completeness sake I will reiterate:
1. Hold Alt and click the ‘New Layer’ button on the Layers palette.
2. Change the blending mode to ‘Overlay’ and click the box ‘Fill with Overlay-neutral color’.
3. Duplicate this layer, and name one of them ‘Burn’ and the other ‘Dodge’.
Using a low opacity brush (5-15%) paint with black onto the ‘Burn’ layer to darken things, and with white on the ‘Dodge layer’ to lighten things – effectively increasing contrast. As we’re painting on layers, this effect is non-destructive to the original image. If you make a mistake, you can use 50% grey to paint out your error.
The above may be old news to you, but here is the key point: Dodging and burning will only help to exaggerate tonal differences already present in the image, it can’t make something out of nothing. I.e., You can’t dodge a black cat white, and you can’t burn the sun black. The trick is to examine your image, identify the lighter and darker part of your image and where they meet, then dodge and burn intelligently to bring these differences out.
Let’s look at another example.
The first image has some basic adjustments made to it, but I really want to bring out the play of light on those rocks. I make my dodge/burn layers, then using a soft 10% opacity brush, I paint black onto the dark crevices and nooks of the rocks, and white onto the peaks and edges exposed to the light. I want quite an exaggerated effect, so I give it maybe five or six passes with the brush.
The second image shows the dodging and the third the burning.
The fourth (below) shows the two together. You can see a marked difference in contrast compared to the first image.
You can see the finished image here.
3. Unsharp That Contrast
The following method has been around for a long time, and you’ll hear it being called various names like haze cutting, HIRALOAM, or local contrast enhancement. This technique involves using the Unsharp Mask filter at a low amount and high radius to increase tonal transitions between adjacent pixels. Here is my preferred way of doing it:
1. Merge all your visible layers into a new layer (Mac: Shift-Alt-Apple-E, PC: Ctrl-Shift-Alt-E (I think))
2. Select the new layer and open the Unsharp Mask filter.
3. Set the Amount to 20, the Radius to 50 and the Threshold to 0.
4. Change the layer style to “Luminosity’ to prevent any colour shifts.
5. Pull the layer opacity down to suit and/or add a mask to localise the effect.
You can experiment with the filter settings if you like, but I find it much easier to leave them as is and change the strength by layer opacity and/or masking. Make sure you view the changes at 25%, 50% or 100% magnification. At odd percentages like 33% or 66%, Photoshop applies weird interpolation that will hide distort the effect.
Be sure to use this technique sparingly, as it’s strength makes it easy to create an overly dramatic look. Also, because we are using the Unsharp Mask, watch out for haloing on ‘sharp’ transition edges, e.g., from a dark mountain to a bright sky.
It’s also an excellent technique to use on portraits for bringing out ‘snap’ in eyes and facial features. Just make to use a mask as otherwise it will exaggerate wrinkles and other imperfections. You can see the difference this technique makes by comparing the two images below. The first is the original, and the second has the above settings applied. I would later mask this effect to keep it isolated to the face and hands of the subject.
You can see the finished image here.
4. Applying Apply Image
‘Apply Image’ is a little known but powerful function that we can use to adjust contrast. Basically, Apply Image will take a layer or layers, and apply it back onto the main image with your choice of blending mode. It’s worth experimenting with. One of my favourite ways of using it is:
1. Flatten your image.
2. Go to Edit –> Convert to Profile –> LAB color.
3. Duplicate the background layer.
4. Go to Image –> Apply Image.
5. Select the Lightness Channel, Soft Light, 100% Opacity, and leave the two checkboxes alone. You’ll get a funky pink and blue like image.
6. Change the layer’s blending mode to Luminosity to remove these wacky colors but preserve the tonal changes.
7. Adjust the layer opacity to taste and/or use a mask to localise effect.
8. Don’t forget to convert back to RGB colour when you’re done.
You can also use this method to enhance color, by following the steps above but replacing the ‘Lightness’ channel with either the a or b LAB colour channel. The default setting will give rather garish results, so be sure to tone down the opacity.
The following two images show the result of using the Apply Image command with the LAB ‘Lightness’ channel:
You can see the finished image here.
5. Selective Color is the Icing On the Cake
This last method is ideal for doing any last fine-tuning of contrast after any of the above methods have been applied. It’s especially useful for black and white images, but don’t be afraid to give it a try on your colour work too.
The instructions are simple:
1. Click the ‘New Adjustment Layer’ icon on the Layers palette.
2. Select ‘Selective Color’.
3. In the Color drop-down box, select ‘Whites’.
4. Move the black slider to suit.
5. Repeat with ‘Neutrals’ and ‘Blacks’.
I’ll often bump the ‘Blacks’ up +1-5% to get some punch in the shadows. The ‘Neutrals’ can be pushed +5-20% to get rid of any murky tones. The ‘Whites’ are useful for recovering small blown white areas such as sunlit sky, by pushing it +30-40%. Alternatively, you can push any off-white tones up by pulling the slider to -20-40%.
Additionally, it’s possible to separate the ‘Blacks’, ‘Neutrals’ and ‘Whites into separate adjustment layers if you find them interfering with each other, i.e., have three ‘Selective Color’ adjustment layers stacked on top of each other.
That’s All, Folks
I hope this article has provided you with some ideas on how to go about adjusting contrast for your own work. As a final word, perhaps some of these techniques do not provide results as dramatic as you would have hoped. Unfortunately, like most things in life there is no ‘magic bullet’ when it comes to contrast enhancement in post-processing. Rarely will I use only one of these methods – the beauty lies in their ability to be stacked one on top of another, building up contrast and ‘snap’ gradually. Experiment with each of them, learn the advantages and limitations of each. and make them your own. Practice and experimentation are the best ways to learn any new skill.
If you have any questions about this article or anything photography related, please feel free to email me. You can find the contact email address at my site.
Lee Gribbon
http://www.decoy.co.nz
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