When I’m asked how I get such intense landscape photographs I respond that it all begins with the fundamentals, the photographic foundation.  Given that you have the other elements of a great photograph – a terrific subject and fantastic light – you are still not guaranteed a compelling image if it doesn’t have a solid foundation.

What is the photographic foundation?  It’s two things – a proper exposure and the correct focus.  These are so basic we never talk about them very much but, if you’re like me, you’ve had to walk away from a potentially great image because one or both of these were not carefully attended to in the field.

So let’s talk about exposure.

Exposure

The Correct Exposure

A great photograph begins with the ‘correct’ exposure.  If the exposure is too far off it can’t be ‘fixed in Photoshop,’ regardless of what people may say.

But what is a correct exposure?  Well, to a large degree that depends on the photographer’s intent.  The photographer may intentionally over or under expose the image to create a particular mood.  However, this is a conscious decision.  So it’s difficult to come up with rules that define a correct exposure.  But there are a couple of things to avoid – highlight and shadow clipping.

Highlight clipping is when areas of the image are rendered as pure white without any detail.  Highlight clipping is to be avoided, especially in digital photography.  It usually cannot be recovered in post processing.  In fact, the camera manufacturers have recognized the severity of the highlight clipping problem and given us the option of having the LCD flash whenever it occurs.

Shadow clipping is the opposite; that is, areas of the image that are pure black and lacking in detail.  Shadow clipping is actually desirable if the intent is to create silhouettes.  But if the intent is to have detail in the shadow areas then shadow clipping is a problem.  You might be able to open them up in post processing but chances are that will produce noise.

Of the two, highlight clipping is by far the more grievous sin but most of the time the correct exposure is one that avoids both.

The Four Exposure Variables

There are four variables that come together to product a correct exposures – light, ISO, aperture and shutter speed.

Light

By light, we are referring to the light that is illuminating our scene.  Light has two properties that are important to exposure – intensity and dynamic range.

Light intensity is overall brightness of the scene.  The intensity falls off as we go from a clear sunny day to overcast, open shade, night or a cave.  A correct exposure will have to adapt to the intensity.

Dynamic range is the difference between the darkest and brightest parts of the image.  It is usually expressed in f/stops.  If the dynamic range is 2 or 3 stops it is considered a low contrast or flat image.  If the dynamic range is 10 or 12 stops it is considered a high contrast or high dynamic range image.

ISO

ISO is a measure of the light sensitivity of a digital camera’s sensor or of a film.  As the sensitivity increases it requires less light to produce a correct exposure.  ISO numbers in the 100 to 200 range have a low sensitivity.  High sensitivity would be ISOs in the 800 to 16oo range or even higher.

Aperture

The third exposure variable is aperture.  This is the size of the opening in the lens that controls the amount of light that is admitted.  The aperture is controlled by opening or closing a circular diaphragm inside the lens.  Aperture is measured in f/stops.  Wide apertures have f/stops of f/2.8, f/2 and f/1.4.  Small apertures have f/stops of f/11, f/16, f/22 and more.

A lens will be have a maximum aperture.  Many lenses have maximum apertures in the f/4 to f/5.6 range.  Fast lenses have maximum apertures of f/2.4 and below.  Faster lenses are a lot heavier and a lot more expensive.

Shutter Speed

The last exposure variable is shutter speed.  This is the length of time the shutter is open and is measured in seconds or fraction of seconds.  Most digital cameras cover a range of shutter speeds from as long as 30 seconds to as short as 1/1000 second or even shorter.

Setting the Exposure Variables

As outdoor photographers, we only have control of three of the four variables.  We generally don’t have control of the light.  But there are considerations we need to take into account when deciding how to set the other three.

Setting ISO

Landscape photographers generally prefer the lowest possible ISO.  That’s because it produces the highest quality images.  As the ISO is increased two things are generally compromised – noise and tonal gradations.  The current crop of digital cameras are excellent at minimizing noise at quite high ISOs but the best tonal gradations is still achieved at low ISOs.

Now, there are times when a high ISO is called for.  For example, photographing in very low light conditions like the night sky, or an hour or so before sunrise or after sunset.  In the sunrise situation I start with a high ISO, maybe 800 or 1600.  But as the sky brightens I reduce the ISO before making any other adjustments like f/stop.

Setting Aperture

Landscape photographers generally prefer smaller apertures.  This is because so many landscape compositions require depth of field which increases as the aperture gets smaller.  So it’s not uncommon to use f/stops of f/8, f/11 or even higher.

Again, there are conditions where wider apertures are called for.  This is especially true when you intentionally want a shallow depth of field as in when doing macro photography.  This is referred to as ‘Selective focus.’

Because depth of field is such a primary concern, landscape photographers usually shoot in aperture priority mode.

It is worth mentioning however, that very small apertures produce a phenomenon called diffraction.  This is when the light passing through the small opening in the diaphragm interacts with its edges and is scattered.  This produces a softening of the image.  The effect may not be huge but can be noticeable.  Each lens has a sharpness sweet spot that is generally 2 to 3 stops above the maximum aperture.  So, if you have a f/2.8 lens the sweet spot would be f/5.6 or f/8.  This would produce the maximum sharpness.  If you’re concerned about this it’s a good idea to test your lenses at different focal lengths and f/stops to determine the sharpness sweet spot.

However, when it comes to a choice between depth of field and sharpness, depth of field wins every time.

Setting Shutter Speed

When shooting in aperture priority mode the shutter speed falls wherever it falls.  In other words, shutter speed is less a consideration for landscape photographers than aperture.  It doesn’t matter if the exposure time is 2 seconds or 1/200 seconds.  As long as the camera is on a tripod you get a good image.

As with the previous two variables, there are exceptions.  There are times when shutter speed becomes important.  If a breeze is blowing nearby leaves then you’ll need a shorter shutter speed.  You may need to adjust the ISO or the aperture to get the shutter speed down.

In the opposite direction, you may want a long shutter speed if you’re photographing moving water.  Again, you may need to adjust aperture and ISO to lengthen the exposure time.  And if that doesn’t give you the exposure length you want you may need to add a neutral density or polarizing filter.

Evaluating Exposure

Digital photographers are really fortunate.  We get to evaluate our exposures immediately after we capture the image.  And that’s because our cameras can display a histogram.

A histogram is simply a graph that shows the amount of each shade of gray in an image from pure black to pure white.  The left side of the histogram is the blacks and the right side, the whites.  The histogram can tell us a lot about an exposures:

• Is it over or under exposed
• Did the dynamic range of the sensor capture the entire dynamic range of the scene

A good habit to get into is checking the histogram after every shot.  That way if you see a problem you can compensate for it and retake the shot.  It’s actually not that hard to fool the camera’s built in light meter and some exposure compensation is  often called for.  I’ve noticed that even making a seemingly insignificant change like zooming in our out a little can change the exposure enough to require a different exposure compensation.

Over and Under Exposed Images

The ideal exposure is one in which the histogram fits nicely between the left and right edges.  It’s best when there is a little bit of room at either end.  This indicates an image whose dynamic range is a little less than the dynamic range of the sensor.

An overexposed image would show the histogram pushing up against the right side of the graph.  Most likely there would be highlight clipping.  An under exposed image would push up against the left side with likely shadow clipping.  A glace at the histogram after each shot will tell you very quickly if you have any problems.  If you have over or under exposure problems you need to adjust the exposure and retake the shot.

Low Contrast Images

Sometimes you run into situations where the contrast of your scene is very low.  This produces a histogram that looks like a narrow hill with steep sides.  Generally if you’ve used the exposure set by the camera the hill will be to the left of center.  This looks good on the LCD but is not the best image to work with in post processing.

A better histogram would be one that was slightly to the right of center but not so far to the right that you get highlight clipping.  The reason is that this image will have more information than the darker one and more information means you have more flexibility in post processing and can produce a higher quality image.  This practice is referred to as, “Expose to the  right.”  So when you encounter this situation, capture one image at the exposure determined by your camera and then overexpose slightly for the image you will work on.

High Contrast Images

Quite often we encounter situations where the image’s histogram completely fills the graph and then some.  It’s pushed up against both the left and right sides.  This is a situation in which the dynamic range of the scene has exceeded the dynamic range of your sensor.  When this happens you have a couple of options.

You can expose for the highlights and let the shadows fall where they may.  Get a good exposure on the highlights that eliminates any clopping. You will end up with lots of shadow clipping but this will create a strong silhouette effect.  There are many situations where this is highly desirable.

For those situations where silhouettes are not desirable you can use a graduated neutral density filter to hold back the bright area.  This works very well in landscape photographs where you have a bright sky but a dark foreground.  With the graduated neutral density filter you can hold back the sky two or three stops and thus give the foreground a full exposure.  This was a hallmark of Galen Rowell’s photography, so much so that one major filter manufacturer named a whole series of graduated neutral density filters after him.

Graduated neutral density filters work best when there is a line that is pretty much straight separating the bright and dark parts of the image.  If that’s not the case then this next technique works well.

The third option is to use the HDR technique.  This is when you take multiple shots at different exposures and blend them together on the computer with a software utility like Photomatix Pro.  The overexposed image captures the shadows without clipping and the under exposed captures the highlights.  There are anywhere from zero to three or more exposures in between that capture the mid tones.

RGB Histogram

There’s one more thing that should be said about histograms.  So far we’ve been talking about the luminance histogram.  That’s the histogram that displays the amounts of each shade of gray.  And while this is usually a good indicator, there are times when you can have clipping in one of the color channels – red, green or blue – that does not show up on the luminance histogram.  The problem is not so much with clipping on the shadow end as clipping in the highlights.  A situation that I find most problematical is clipping in the red channel, particularly when photographing the red rocks of the American Southwest or brilliant sunrises and sunsets.

To address this problem, may cameras are capable of displaying an RGB histogram.  That’s three graphs superimposed on one another – red, green and blue.  This is the most helpful histogram because you can detect clipping in a single channel.  So if your camera supports an RGB histogram, use it.

Exposure Summary

In summary, landscape photographers prefer to shoot with the lowest ISO possible, usually 100 or 200.  They also prefer small apertures and shoot in aperture priority  mode.  Finally, they check their histogram after nearly every shot, making compensations to the exposure as necessary.  Follow these guidelines and your photographs will have a strong foundation.

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