Understanding Exposure

Carrying on with my beginners landscape photography series, this post aims to help you understand the 'exposure triangle' so you can start feeling more confident using your camera and it's manual settings to really get the most out of it.

The 3 sides of the 'exposure triangle' are ISO, aperture and shutter speed. Photographers usually make their choices on settings based around either a specific aperture or shutter speed then figure out the other 2 based on this decision.  Below I will explain what the result on a photo would be by changing one side of the exposure triangle.


The ISO setting determines how sensitive the cameras sensor is to the light that has passed through the lens aperture and cameras shutter. The higher the number is, the more sensitive the sensor is which leads to a brighter exposure. The down side is that higher a higher ISO means more noise (grain) in the photo which is undesirable to landscape photographers. I always keep my ISO as low as I possibly can.


Higher ISO without changing aperture or shutter speed:

Brigher exposure, more noise/grain

Lower ISO without changing aperture or shutter speed:

darker exposure, less noise/grain.


The lens aperture is the small hole you see when you look down the lens through the glass elements. Aperture is measured in a series of numbers beginning with an 'f/', known as an 'f stop'. The smaller the number that follows the 'f/' the larger the hole is which will in turn let in more light leading to a brighter exposure (when ISO and shutter speed remain constant). However a larger aperture also means less of the photo in focus, or what we call a 'shallow depth of field'. This is sometimes a desirable effect for artistic intent, especially when shooting portraits. I'd say that 90% of the time, landscape photographers want good depth of field.

Full stop increments:

f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22

I recommend shooting between f/8 and f/16 for good depth of field. Higher than f/16 and you will begin to see diffraction. The sweet spot is usually around f/11 but this can depend on your focal length. Longer focal lengths require higher f/stops than wide angles for good depth of field.


Decreasing f/stop without changing ISO or shutter speed:

brighter exposure, shallower depth of field

Increasing f/stop without changing ISO or shutter speed:

darker exposure, better depth of field, can cause diffraction above f/16


This was shot at Eyebridge on the River Stour.  I used an aperture of f/2 to give the scene some depth.  As you can see, the foreground and background elements are soft (out of focus) drawing your attention to the subject, the bridge strut.

The iconic Kimmeridge Bay.  Shot at f/11 to achieve maximum sharpness from the stones in the foreground all the way to Clavell's Tower, the furthest element in the scene.


Shoot in 'aperture priority'. Change the aperture size (check how to do this in your cameras manual) and notice how the camera will automatically adjust the shutter speed to compensate based on the in camera light meter reading. I'm a Nikon shooter and tend to find that if I shoot in aperture priority, the camera often under exposes by a stop (1 full exposure value or 'EV'). If you find that your camera is under or over exposing them you can adjust for this using the 'exposure compensation' in your camera. Again, check your cameras manual to find out how to properly use this feature as it differs from one camera to the next.

In aperture priority you are also in control of the ISO setting. Adjusting this will also cause the camera to compensate on shutter speed.

Shutter Speed

This refers to the amount of time that the cameras shutter is open for to determine how much of the light that has already passed through the lens aperture that falls on the cameras sensor. The longer the shutter is open for, the brighter the exposure will be and vice versa (when aperture and ISO are constant).

Faster speeds will freeze motion, longer (or slower) shutter speeds will blur movement. The latter is a popular tool for creating artistic effects in landscape photography, particularly with scenes involving water or moving clouds. However to achieve these effects you will need a sturdy tripod to place your camera on and ideally a cable release to trigger the shutter so your hand doesn't move the camera just as the exposure begins. A cable release isn't essential as you can use the cameras built in self timer. A tripod however is essential to prevent camera shake which means parts of the scene are unintentionally blurred due to the nature of an unsteady handheld camera.


The range of full shutter stop increments is theoretically infinite.  Below is an example of some more commonly used in landscape photography.

1/60s1/30s1/15s1/8s1/4s,1/2s, 1s, 2s, 4s, 8s, 16s, 30s

The slowest shutter speeds for most DSLRs is 30 seconds.  Anything slower will require use of the 'bulb' or 'time' function.  To operate the bulb function you simply hold the trigger down for as long as you want the exposure time to be then let go.  A cable release is essential for this to avoid moving the camera during the exposure resulting in a blurry photo (camera shake).  Not all DSLRs have a 'time' function but I find this easier to use than bulb.  You simply press the trigger and let go to begin the exposure then press the trigger again to finish.


Fast shutter speeds without changing ISO or aperture:

darker exposure, freeze movement

Longer/slower shutter speeds without changing ISO or aperture:

Brighter exposure, blur movement.


The shutter speed for this image was 1/8 sec.  If you focus your attention on the water (click to enlarge) you will see this shutter speed was fast enough to freeze the motion of the water and the grass in the foreground.

Using filters I was able to slow the shutter speed down to 59 secs.  This long exposure time has created a nice smooth effect on the water and blurred the motion of the grass, portraying to the viewer that there was a breeze on that day.

Something I like to do is demonstrate movement in a scene, it gives the viewer a real sense of feeling they are there in the moment.  To do this you need to find a suitable shutter speed between the two demonstrated above.  This was taken at 0.8 sec.  Remember that art is subjective so there's no right or wrong answers.  Just have a play with your settings until you achieve a look that you like. 


Shoot in 'shutter priority'. The same rules apply as in aperture priority except you are now in control of the camera's shutter speed, the camera will adjust the aperture. Your camera will not be able to operate the bulb or time shutter functions in shutter priority mode as the shutter speed is unknown to the camera at the time you begin the exposure and therefore your camera can't calculate the required aperture.