Digital Photography 101, Part 5

Difficult Exposure Problems, Sharpness, Saturation and Contrast


In this last article of the Digital Photography 101 series, I discuss difficult exposure problems and also explain setting the sharpness, saturation and contrast functions of digital cameras. This is the fifth article in a series of five that deals with setting the more important functions on a digital camera. As usual, the article goes a bit beyond camera setup to a discussion of the basics of using a digital camera. If you haven't read the first four installments of this article you might want to do so before beginning this article. Part I, Part II, Part III, Part IV.

Difficult exposure problems: In the last article I discussed how to use exposure compensation to to resolve difficult lighting situations. However, there are times when even exposure compensation will not solve the problem. These are the times when there is simply too much contrast in the scene for the camera to capture; the shadows and highlights are too far apart to capture detail in both. This is the kind of situation when the overexposure warning on the LCD screen will usually blink to tell you that something in the picture has been overexposed. If you don't solve the problem, the sky will be pure white or the shadows will be pure black in the picture. And this is a problem that cannot be fixed during editing. You have irrevocably lost essential detail in the image.

The usual scenario is that you are shooting a landscape and trying to include both close up foreground which is often quite dark and far off mountains and sky which are very bright. The picture looks fine to your eyes since they can see much more contrast than a camera can, but the camera will capture the picture with either the foreground completely black or the sky and mountains completely white. Cameras, even very good digital cameras, simply cannot see nearly as much contrast as the human eye can. Cameras can see at most five stops of contrast and the human eye can see twenty or more stops of light.

The way of fixing this problem in the old days of film, was to use a square piece of glass about 4"x5" in size that is called a graduated neutral density filter. This filter is very dark at the top and gradually gets lighter and lighter until it is completely clear at the bottom. The photographer would hold the filter in front of the lens, or use a filter holder to hold it in place, so that the top part of the filter darkened the sky and the bottom part let all the light into the lens. This evened out the light and, if you were very lucky, resulted in a perfect exposure. Unfortunately, this process was time consuming and inaccurate and generally didn't work very well; usually the skies ended up too dark and the foreground was still underexposed.

There are much better solutions available to the digital shooter. One solution is to shoot two shots of the scene, one shot should be a stop or two overexposed and the other a stop or two underexposed. In the first shot the shadows will the perfectly exposed and in the other shot the sky and mountains will be perfectly exposed. Then the two shots can be seamlessly combined in Photoshop for a perfect picture in which everything is correctly exposed.

Another solution that works when the contrast is not too difficult, is to capture the scene in one shot this isn't perfect yet; the foreground will be a little underexposed and the sky will be a little overexposed. RAW format should be used when taking the picture. Then open the picture twice in the Camera Raw part of Photoshop. Adjust the first picture in Camera Raw so that the foreground has a perfect exposure and then adjust the second picture in Camera Raw so that the sky and mountains have a perfect exposure. Then it is a simple matter to combine the two pictures using an imaging program like Photoshop to create a perfect picture where both foreground and sky are perfectly exposed. Since you were shooting in Camera Raw, these adjustments can be made losslessly for one stop up and one stop down and maybe two stops either way. The result is a picture just like the one you saw with your eyes.

When I write the series of articles describing how to use Photoshop, I'll tell you how to do these two tricks in exact detail. Editing is so important that I'll try to get to this soon.

Setting Sharpness, Saturation and Contrast: Almost all digital cameras have a provision for setting image sharpness, saturation and contrast. Of course if you are shooting in RAW Format, (see Part II of How To Set Up Your Digital Camera for information on RAW) there is no need to set these functions in any special way since the camera adds no saturation or contrast or sharpening to images at all. You have to add these adjustments later using a imaging program like Photoshop where it is possible to do a far better job than the camera can do.

However, if you are shooting Jpg images, which are what most people shoot most of the time, you have the option of having the camera add various degrees of sharpening, saturation and contrast. The default setting of most cameras is to add a lot of each of these adjustments. If you plan to have your pictures printed as 5x7's at the local processing lab or someplace like WalMart, you should probably leave the camera with the original default settings. However, if you plan to ever enlarge these pictures at all, even to 8x10 or 11x14, I recommend that you turn off all these in-camera adjustments. This is definitely true if you plan to print the pictures yourself.

Not turning off these settings, along with not using a tripod, are the major reasons most people think you can't enlarge digital pictures much. If these settings are turned off and the camera is a decent one, and if you use a tripod, and you did a good job taking the pictures, it is amazing how big digital pictures can be enlarged.

I want to use my Olympus C8080, (an 8 megapixal prosumer camera that I paid $800.00 for three years ago) for backpacking because it is so light: it weighs ten pounds less than my professional Canon digital camera outfit. So the other day I was testing just how big I could print an image taken by this camera. I was totally amazed when I found I could enlarge this image to 33x50 with very little image degradation. Of course, the camera was a pretty decent one (even though it is far from being a professional camera), I was using a tripod, and I was lucky. I couldn't enlarge all the images I shoot with this camera this much, but the point is, if I don't screw up, the camera is perfectly capable of taking this kind of a superb image. If I hadn't completely turned off the sharpening, contrast and saturation, I wouldn't have had a chance.

In-camera sharpening is particularly bad; it can absolutely ruin images for enlargement. In-camera sharpening will mutilate and even delete the delicate pieces of an image like small tree limbs and leaves making it impossible to make even a small enlargement. Contrast is just as bad. If the camera automatically increases the image contrast all the detail in both the highlights and shadows could be deleted leaving you with a picture with blown out skies and plugged shadows. Blown out skies are pure white and there is nothing you can do to bring back the blue sky or the clouds. Plugged shadows are pure black and again, nothing you can do will bring back the detail that gives life to shadows. The picture will be ruined forever. Sometimes too much contrast can be fixed if there is still detail left, but still, it is much better to have too little contrast rather than too much, why take the chance that you may lose irretrievable image data.

Over-saturation isn't quite as bad as too much sharpening and contrast. But again, why dork pixels around when you don't have to? Too much pixel dorking always ends up in image degradation. And it is especially bad if the camera gets the color balance a little bit wrong, which it often does. If this happens the camera pumps up the saturation of false colors that you don't even want and this will definitely cause problems during editing. You may never get rid of all those wrong colors that the camera pumped up to such high levels of saturation.

Just because you are turning off sharpening, saturation and contrast in the camera doesn't mean you have to forgo these options forever. You can always add exactly the right amount back to the picture once you are editing it in Photoshop. In Photoshop you can be very precise in adding exactly the right amount of saturation and contrast to specific parts of the picture using tools that are far,far better than those in the camera. Sharpening can also be added very delicately with special tools to sharpen just those parts of the pictures you want to sharpen and not to other parts that would be injured by sharpening.

A note of caution when turning off the in-camera sharpening, saturation and contrast. Many cameras have a scale for these adjustments that runs from something like +10 to -5. Don't think you can set these adjustments to 0, and they will be all gone. It is necessary to take the adjustments all the way to the bottom of the scale, like minus 5, if necessary. I don't know why camera manufacturers set their cameras up this way, but they do.

After all the adjustments are shut off, the pictures the camera takes may look a little flat and dull but don't worry about this, this can all be fixed perfectly when you edit the picture in Photoshop later. This is a basic rule of digital photograph, do all your picture editing in Photoshop, not in the camera.

This is the final Digital Photography 101article in a series of five . Give me an email. if you have comments or questions about this article.

Fred Hanselmann
November 15, 2007