Stephen Ingraham (who?)

the unofficial site for birders and digiscopers using Zeiss equipment.

Basic Adjustments:

Exposure: The exposure routines on modern digital cameras, and the sophisticated sensors that drive them, are nothing short of miraculous. They handle everything from patchy shade and bright sun (in the same image) to pure white birds against a dark green background. They do amazingly well with mixed light sources, and even handle back light fairly well (provided you remember to switch to spot metering). And, while some complain of a limited exposure range, of whites that burn out too fast and blacks that creep up over the darkest shades of color, my own impression is that the dynamic range of the most recent crop of  digital sensors is at least equal to print film, and may approach that of slide film.

Still, no matter how sophisticated the exposure systems are, they were not made to work through a spotting scope, and most digiscoped images will benefit from at least a little exposure compensation. True, you could do it all "in camera"...switch off the auto exposure control or programmed modes, or use the "exposure compensation" button or menu option...or even switch on the histogram and tweak the exposure using manual settings. You could do that, but I find that I am generally too busy trying to find, track, and compose the bird. Even with particularly cooperative birds I am too busy looking for that particular pose or behavior that will tell the viewer something interesting about the nature of this particular bird. I don't have time to spend more than minimal attention on exposure. I rely on the camera to get it "about right", and then, if necessary, I tweak it in an image editor.

There are a lot of ways to adjust exposure values in software. PSP seems to have retained/added every way known to man. The selections in PhE have been pared down in the most recent version but still get the job done. MPM has only basic Brightness and Contrast controls (with an added mid-point slider...see below). Picasa has a somewhat unique set of methods that is somewhere between the two extremes.

I have been through different phases in how I adjust exposure myself. I did a lot of work with Brightness and Contrast controls, and learned to appreciate the mid-point adjustment. I learned to use the level dialog in PhE. The three methods I will show you are what I use now, based on overall effectiveness and ease of use.

First, though, lets understand Brightness, Contrast, Mid-point, Shadow, Mid-tone, Highlight, and Saturation

Beyond Brightness and Contrast.

The Brightness and Contrast values are often linked : They generally appear in the same menus, dialogs, and routines in image editing software.

Brightness, refers to how much energy each pixel of the image is giving off. That's a strange way of saying it, but it is the only accurate way of thinking about it. Think of each pixel as tiny light bulb on a dimmer switch. You can turn the dimmer so that the lightbulb is giving off no light, or you can turn the dimmer up to full so that the light bulb is as bright as it can get, and you can set it anywhere in between. When you download your image file from the camera, it contains the brightness setting (dimmer position) for each pixel in the image on a scale of 0 (no light) to 256 (full bright). To complicate matters, of course, the file actually contains brightness settings for three colors, or channels, per pixel: red, green, and blue, and the relative brightness of each color determines the color of the pixel. For now though let's just think of each pixel having a single brightness setting (which is the sum of the three colors). If your exposure system is working right, the image should reflect the brightness values of the portion of the image that fell on each sensor pixel, adjusted for the curve of sensitivity of the sensor, to fit within the 256 brightness steps available. If your computer and image editing/display software is working right, that information should be accurately replicated in the brightness of each pixel of the display, and you should get an image that is pleasing overall, not to dark and not too light.

At the most basic level the brightness control simply turns up, or down, the brightness settings for all the pixels in the image, across the board, at the same time. It turns each pixel up or down by the same amount. Think of it as the master dimmer that controls the brightness of all the pixels. If your image is too dark, you can pump it up by turning up the brightness. If it is too bright, you can dim it down.

Contrast refers to the difference between the brightest values and the darkest values in the image. Ideally that is also 256 steps. Contrast moves around a center point...the pixels that are exactly half way between the brightest and darkest. When you increase contrast, the contrast control works by darkening the dark pixels (those on the dark side of the center point) and lightening the light pixels (those on the light side of the center point). When you decrease contrast, the control brightens the dark pixels and darkens the light ones.

The Brigtness control, however is only really useful for very small adjustments in brightness, a few steps (say 10) on either side of what the image file already contains. In the same way, if you alter the contrast with the basic Contrast control more than about 10% either way, the results are rarely acceptable. Part of the reason is the all or nothing approach both these controls implement. You only have 256 brightness values to work with. When you start changing values en-mass, then dark areas of the image are going to "go black"...they will be pushed down to 0 brightness (be extinguished) or light areas of the image will "max out"...they will be pushed up to 256 (burn-out). The more you alter brightness and contrast, the more pixels will be pushed to extinction or burn-out and the more information and image detail you will lose.

Normal, unadjusted image as it came from the camera	With 50% brightening: it's a wash
	I rarely use the Brightness and Contrast controls any more. There are better tools in most image editing programs for adjusting exposure.
With 50% contrast: note the wing gone black and the highlight going white.

Midpoint:

Adjusting the midpoint in PSP's levels dialog increases brightness only in the mid-range.	A similar result using the levels control in PhE.
	Mid-Point: as mentioned above, Brightness and Contrast are computed around a mid-point...the brightness value that is half way between no light and full light. Some programs allow you to shift the mid-point. This is a more subtle way of adjusting brightness than the raw Brightness or Contrast controls. It is one of the attractions of using the "levels" control dialog in PhE or PSP. Shifting the mid-point toward the dark side has the effect of lightening only the light tones without pushing any pixels to burn-out. Shifting the mid-point toward the light side has the effect of darkening the image, primarily the dark tones, without pushing any pixels to extinction.
Using an actual midtones control in MPM, see below.

Shadow, Mid-tone, and Highlight:

Figuring brightness and contrast around a mid-point, dividing the whole image into darker and lighter, as we said above, is not very effective. Both PhE and PSP, and Picasa to a certain extent, will adjust brightness using three "zones" of brightness within the image: shadow, mid-tones, and highlights. As you can imagine, shadow refers to the darkest portions of the image, and some routines are even "smart" enough to take contrast within small areas of the image into account. For instance, take a leaf that is darker on one side than the other because one side is in the shadow of the other. The darker side will qualify as "shadow "in some routines, even though its raw brightness value might place it relatively near the mid-point. Mid-tones, again, not surprisingly, are the brightness and color values clustered around the mid-point...but more than that they are the areas of relatively uniform brightness anywhere in the image that is not black or white. Highlights are the areas of image that stand out due to their relative brightness, no matter what their absolute brightness is. Using well crafted Shadow, Mid-tone, and Highlight controls, it is possible to adjust both the brightness and the apparent contrast of an image without pushing pixels to extinction or burn-out. This is my preferred method of adjusting exposure. It is quicker and more intuitive than the levels control (with which you can do about the same thing) and produces much more subtle and, to my mind, satisfactory results than the Brightness/Contrast and Mid-point controls. The exposure adjustment tools I now use are all variations of the Shadow, Mid-tone, and Highlight controls.

Saturation: otherwise known as color intensity.  Each pixel in the image is, as we mentioned above, made up of the brightness settings that correspond to the amounts of red light, green light, and blue light which were falling on the sensor pixel when the image was captured. When you turn up the saturation of the image, energy (brightness) is taken away from the weaker values in the mix and given to the strongest. Thus, when you turn up the saturation, in a pixel that is predominately red in the image, brightness is subtracted from the green and blue channels and added to the red...so the pixel becomes redder. When you turn down the saturation, in that same red pixel, brightness would be subtracted from the red channel and added to the blue and green, bringing the pixel somewhat close to an even mix of the three colors, making it grayer (since a perfectly even mix would be neutral gray). Sometimes, when the brightness of the overall image is changed, you can recapture some of the color detail by adjusting the Saturation (generally by increasing it).

Which brings us, at last, to the methods and tools that I do use.

Photoshop Elements:

Until recently, I did 90% of my postprocessing in PhE. PhE has excellent shadow, mid-tone, and highlight controls, but you have to look to find them.

There is a Shadows/Highlights dialog accessed via the Enhancements menu: (Enhancements: Lighting: Shadows/Highlights). Unfortunately it works just backwards from what I want to do. You can only lighten the shadows, and darken the highlights, bringing everything to a nice even  gray in the middle. That is not what digiscoped images generally require.

On the other hand, hidden in the Color Variations dialog (Enhancements: Color: Color Variations) is one of the best Shadow/Mid-tone/Highlight controls going. Using the options on the left (singe red arrow) you can select just one zone to work on at a time, and then, using the Lighten and Darken selections (on the right, double arrows) you can make very deliberate adjustments. If the initial changes are too dramatic, simply turn down the Adjust Color: Amount slider. For most digiscoped images I find that, with the Amount slider one click to the left of center, darkening the shadows by two clicks and lightening the mid-tones by one adds just that little bit of punch, and picks up the details in the lighter tones. And, since it is right there, I often punch up the Saturation of the Mid-tones by one adjusted click as well.

Paint Shop Pro:

The more I use Paint Shop Pro the more I like it. It has two options for Shadow/Mid-tone/Highlight control.

The Highlights/Mid-tones/Shadows dialog in PSP (Adjust: Brightness/Contrast: Highlights/Mid-tones/Shadows) provides direct control over the three zones. You can adjust each by entering numerical values, by clicking the little blue arrows to change the numerical value, or by clicking on the blue and white bar below the control to change the length of the blue bar. As in PhE, most digiscoped images, in my experience, benefit from a slight darkening of the shadows, and a slight lightening of the mid-tones.

On the other hand, PSP also has an interesting set of controls which are accessed through the Smart Photo Fix dialog (Adjust menu). Here you have overall brightness controls, shadow, and highlight. Once more, pick up overall brightness, and darken the shadows. This is one of the few Highlight controls that seems to work. It will reduce the brightness of an egret's plumage without turning it gray, often bringing out more subtle detail in the feathers. This control also has Saturation. A slight boost, especially when you have raised the brightness, can be effective. Finally, the PSP sharpening filter used in this dialog is one of the most effective I have used...it is very clean, and produces very few artifacts. This is my tool of first resort these days.

Picasa and Fill-light:/flash

Picasa does everything just a little differently. The Shadow/Highlight controls are in the Tuning tab on the left side of the screen. Instead of a mid-tones control, or the Overall Brightness slider in PSP, there is a Fill Light slider. (PhE used to have a Fill-flash dialog that works the same way, but it is gone in v4.x.) When you adjust the slider, it increases the brightness of the reflective portions of the image (which correspond, roughly, to the mid-tones) just as a fill-light or fill-flash would do if you used it on your camera, without changing the brightness of the deep shadows or the highlights. Picasa also includes a Shadow control that deepens the shadows, and a Highlight control that brightens the highlights. For most digiscoped images I find that just a bit of fill-light, and a bit of deepening in the shadows is effective. The Color Intensity slider is basically a Saturation slider and I do use it to punch up the color just slightly after using the fill-light.

Like I said somewhere previously, PSP still has every method of adjusting exposure known to man. The Fill Flash dialog provides the same functionality as Picasa's Fill Light and as the old Fill Flash dialog in the PhE, though it seems to work better than either. Fill Flash all by itself is a tool you would only use on a badly underexposed image...or, more likely, on a bird that is silhouetted against a bright background (you forgot to switch to spot metering didn't you!). On may files, the fill flash function will save an otherwise unacceptable image. You might be surprised at what a lot of detail is hidden in the dark silhoutette.

Again, these are all methods for making slight adjustments in the exposure of an image. They are not intended (with the exception of Fill-flash perhaps) to save a really bad exposure. On the other hand, these are the controls you would want to try when attempting such a save. Your adjustments would just be more drastic, and your chances of success a good deal less.

Let's look at a challenging image in several different image editing programs.

	The original image: heavily backlit and underexposed for the subject.
Paint Shop Pro: Cropping, then using the suggested settings in PSP's Smart Photo Fix dialog, but pumping up the saturation just slightly...	Yields this much more pleasing image.
Using the Fill Flash function in PSP...	Then the Smart Photo Fix, with some added saturation...
yields this...even better!	Moving on to Photoshop Elements: PhE Auto Smart Fix menu option, with the factory defaults...
yields this. Less than acceptable.	However, applying three clicks of lighten mid-tones, one click of darken shadows, and one click of saturation...
then Sharpening...	gives somewhat more satisfying results, but still not up to the Fill Flash/ Smart Photo Fix combination in PSP
Finally, giving Picasa a chance, using fill light to brighten, and darkening the shadows somewhat...	and then clicking sharpening once and saturation once..
	In the end, none of these images may be something you would want to keep in your portfolio...but if a record depended on an identifiable image, or if you just didn't have a Black-chinned Hummingbird at all yet...it might just do!
gives a very similar result to PSPs Fill-flash/Smart Photo Fix combination.