Just say NO to F22

Actually, avoid F16 and smaller (F22 etc) if at all possible.

This is an article about hyperfocal distance, which is related to depth of field. Depth of field is an incredibly complicated subject. Much that you will find online about it is inaccurate, sometimes absolute rubbish. For a truly accurate discussion see this article: Tom Hill discusses Depth of Field

The Landscaper's obsession with Depth of Field

In a landscape photograph, what is normally needed is for the entire image to be sharp - from the foreground all the way to infinity. So Landscapers are by definition very interested in getting sufficient depth of field. To achieve this, the lens must be focussed at the hyperfocal distance for the aperture it is set to.

The hyperfocal distance is the optimum focus distance for the lens at that aperture and depth of field is guaranteed to measure from 1/2 of that distance to infinity. The smaller the aperture, the closer the hyperfocal distance. For example, a 20MM lens, on a 35MM camera has a hyperfocal distance of 15 feet at F2.8, 5 feet at F8 and just 2 feet at F22.

That means at F22, the 20MM lens if focussed at 2 feet will get everything in sharp focus from 1 foot to infinity.

Armed with this knowledge, many landscapers automatically set the aperture to F22 and focus at 2 feet. They reason "I'm getting maximum depth of field, so this must be good". In addition, many, if not all, of the images they see in Landscape Photography books by top professionals all have an aperture of F22 or smaller. So why not copy them?

Reasons to avoid F22 when using a 35MM (or smaller) camera system (digital or film).

This also applies to the current crop of digital slr's that use 35MM lenses but have a smaller than 35MM imaging chip. If you own a digital slr this advice applies to you. If you own a digicam, this also applies to you!

Traditionally, professional landscape photographers such as Charlie Waite and Joe Cornish, use medium or large format cameras. These make a massive difference to their choice of apertures to achieve a decent depth of field. Why? Because a wide angle lens for these formats is typically a 50MM or greater in focal length. On a medium format camera, a 50MM lens has a hyperfocal distance of 17 feet at F8 and 6 feet at F22. This means, on the larger format cameras, there is very little choice but to stop down to F22 or smaller to get the needed depth of field, especially if there are close foreground elements, which often feature in Joe Cornish's images. (This doesn't mean that users of larger format cameras should automatically stop down to F22 - the question should always be 'what aperture do I need for this image?')

	Lower image quality due to diffraction
	Slower shutter speeds*
	Increased chance of seeing sensor dust**

*Sometimes this is an advantage, such as photographing waterfalls
**Digital SLRs only

 Diffraction occurs when the aperture becomes so small that it affects the light quality.

 Slower shutter speeds are a problem on windy days - branches and foliage move, often spoiling the image. Additionally, handheld shots become impossible at long shutter speeds, eliminating the chance of a 'grab shot'.

 Sensor dust is often a problem with digital SLRs - when the lenses are changed (or a zoom lenses suck air into the camera) dust gets into the camera and some of this can stick on the image sensor. This shows up as nasty spots on the images, needing work in an image editor to remove. However, at larger apertures (such as F8 and F5.6) the effect of the dust is minimized. At F16 or smaller you will see it.

Of these disadvantages, the first is the most important as it reduces the image quality and there is no way to compensate for it. Sure, it won't show up that much in a small print or web image, but an A4 print is another matter.

Medium and Large formats compensate for diffraction because the final image (on film or digital) is so much larger than 35MM that less enlarging is needed for printing. With 35MM (and the current crop of APS-C sized sensors in many digital SLRs and the tiny sensors in digicams) the captured image size is small and it needs all the quality it can get.

There's another factor here: most lenses have a 'sweet spot' at around F8/F11, where its image quality is at its highest. Image quality at larger and smaller apertures is often less.

So here's my advice: when taking a landscape photograph, examine the scene and identify how close the nearest part of the image is to the camera. Unless it is too close, set the lens to F8/F11 and focus at the hyperfocal point. The result is going to be an image with everything in focus at maximum quality. If you need a slower shutter speed, consider using neutral density filters.

Calculating Hyperfocal Distance:

This is just maths. Use the calculator below to determine the hyperfocal distance: