Understanding Aperture and Landscape Photography – Why F16 Isn’t the Only Choice

Landscape photography is, in my opinion, one of the most difficult disciplines of outdoor photography, and perhaps one of the most challenging genres of photography in general. At first glance, the art seems straightforward. You find yourself a pretty piece of scenery, wait for some good light, and click the shutter. Easy, right?

And yet that’s not the end of the story. I have screwed up endless opportunities by making errors in composition, focus mistakes, unwanted motion blur, over and underexposures, and of course, by messing up the settings of my camera. I suspect anyone who has dedicated much time to the art of landscape photography can say the same.

Let’s Talk About Aperture

While entire articles, even books, have been written about each of those errors and frequent mistakes, there is only one I’m going to discuss here – aperture.

What aperture should you use in landscape photography, f/16 right? That’s what I’ve always heard. It’s the perfect combination of sharpness and depth of field. So set your aperture to f/16 and shoot away.

That’s it, article finished. I hope you enjoyed it. No, of course, that isn’t all. But I am surprised how many photographers assume that is the end of the story.

The real answer to the question of which aperture to us is – all of them – depending on the situation.

First, landscape photography is much more than just the classic composition that includes a foreground element in front of lovely background scenery. Rather there are detail shots, aerials, night photography, telephoto landscapes, and god knows how many other sub-genres within the category. For each of these, and for each situation within, a different aperture may be appropriate.

Before we get into that – first a warning.

Sharpness Issues

Wide Open

There are costs to different apertures. Wide open, most lenses will be soft because every part of each glass element in the lens is being put to work. Imperfection in the lenses, dirt, scratches, and the physics of light all combine to mess with your image sharpness. This is part of the reason that sharp, fast lenses cost so much. The glass has to be excellent to retain sharpness wide open.

Diffraction

Diffraction happens at the opposite end of the f-stop range. When the aperture is closed way down, images also show a reduction in sharpness, but not for the same reason. Rather, something called diffraction occurs. Diffraction is actually a term derived from physics of waves.

Take a look at the terrible hand-drawn illustrations I made below and you can see why I’m a photographer, not a painter. Hopefully, however, you’ll also learn something about diffraction. The lines on the left show waves moving across space. Think of them as light waves or ocean waves, it makes no difference.

As they approach a wall with a large opening, the gap allows the waves though largely intact causing only a slight dispersion and curving of the incoming wave.

But apply a smaller opening (below), and suddenly those waves are quickly curved and dispersed.

In photography, a large aperture will cause relatively little change in the light waves entering your camera, but a small aperture will force a small amount of light to spread, disperse, and curve before hitting the sensor unequally, and with less intensity. This results in a loss of sharpness.

While the physics of it all is interesting, when it comes to photography, what you really need to know is that very small apertures will be less sharp than mid-range apertures.

Attaining Sharpness

It’s probably clear to you by now that if you wish to achieve maximum sharpness then neither fully wide open nor closed down apertures are the best. Rather, sharpness can be found somewhere in between. For most lenses, 2-stops down from wide open is the sharpness sweet-spot.

Perhaps that is why f/16 is so popular in landscape photography, it’s a good compromise between sharpness and depth of field.

So What Now?

We are back where we started, right? Just shoot at f/16.

Well if tack-sharpness were the end all and be all of landscape photography, that would probably be the case.

However, sometimes you may wish to sacrifice some lens sharpness for shallow depth of field or suffer some diffraction blur for the sake of attaining a long shutter speed.

Detail Shots

Landscape details are those small parts of a landscape that catch your photographic interest. This may be a cluster of autumn leaves, a stone in a tundra meadow, or light upon snow-covered trees, among many other possibilities.

In such situations, you may want to isolate that interesting subject from a cluttered background.  You can do that by embracing the shallow depth of field, through the use of a fast (large) aperture.

I was photographing a couple of years back on a crisp autumn day. Frost covered the meadow I was walking around, and each stem of grass glittered in the early morning sun. Spotting one particular stem, rising from the rest, I paused. I wanted to isolate that single piece of grass.

So, using a 70-200mm f2.8 lens, I opened the aperture wide to create a shallow depth of field, composed, and shot.

I’ve used this strategy, again and again, with my landscape photography. Shooting autumn colors, I frequently wish to isolate a single leaf, or patch of foliage from a distracting backdrop. Fast apertures and shallow depth of field are the only way to do this.

In such cases, I’m happy to sacrifice a bit of sharpness.

Aerial shots

In aerial photography, you are always well separated from the landscape you are photographing (if you aren’t, you’d have much greater concerns than making photos). Thus, depth of field is not your top concern.

Meanwhile, the vibration of the airplane or helicopter’s engine is a much greater risk for lack of sharpness than setting your aperture too open.

When I’m shooting aerials, I open my aperture wide open to maximize shutter speed. When you need a shutter speed of around 1/1000th of a second, minimum, a wide open aperture is the only practical way to go.

Long Exposures

Purposefully dragging your shutter for multi-second (or even multi-minute) exposures requires you to greatly reduce the light hitting your sensor. Even with a low ISO and a neutral density filter, trying to get a long exposure on a bright day is impossible without stopping down your aperture.

I was shooting along a river in Alaska a couple of years back, on assignment for a conservation organization. It was a bright afternoon, but some clouds were breaking up the sky making for decent photography conditions.

I knew I would be unable to return there in the evening, so I needed to make the most of the situation. Despite the bright afternoon light, I still wanted a long exposure of the flowing water.

I lowered my ISO to its minimum setting (50), put on a 4-stop neutral density filter, and sacrificing a bit of sharpness, stopped my aperture down to f/22.

With that combination, I was able to get an 8-second exposure of the flowing river. The rippled water blurred pleasingly to a ghostly reflective surface, and I got the image I wanted.

Night Photography

Here in Alaska, I spend a lot of time shooting the Northern Lights and taking out visiting photographers to do the same. There is a myth about Aurora photography that you need a long exposure – you don’t. In fact, you really don’t want one.

One of the things that make the Aurora Borealis so spectacular is the details in the curtains, the shifting colors, and the near-constant motion. A long exposure, anything more than a few seconds, will cause all those details to blur away. Fast shutter speeds (or as fast as you can manage) are far, far better.

To get a fast shutter speed at night, you have to be willing to open your aperture all the way up, sharpness loss, be damned. High ISOs and fast lenses set wide open will allow shutter speeds fast enough to capture the details of a fast-moving aurora display.

Conclusion

So sure, in classic landscape photography, with a foreground element, and background scenery, you’ll want a deep depth of field and maximum sharpness. In those conditions, by all means, set your aperture to f/16 and forget about it. But such situations are not all there is to landscape photography.

Your cameras and lenses are equipped with many tools. To say there is only one that is “right” is like saying that the only tool a carpenter needs is a hammer. Sure a hammer is the perfect tool for a carpenter when he needs to bang in a nail, but it’s really lousy at cutting boards.

What is the lesson here? Set your aperture for what is needed for the scene, not how you’ve been told it should be by someone else. “They” say a lot of things. You don’t always have to listen to them. 

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