Landscape shots, Focus 1/3rd into the shot

I always hear this phrase "focus 1/3rd into the shot" to make everything sharp and I don't understand how to achieve this. I usually focus on the "main" object, such as a church in the distance and choose F16 or so. I've read though that I should focus 1/3rd of the wya into the shot. I THINK I understand, but what if say 1/3rd into the shot is just water? Do I still focus on the water and everything else would be sharp?

Sorry for the noob question but I'm trying to improve my landscapes etc and this seems to come up often

It is a rule of thumb meant to give you more foreground focus and still keep your main subject in focus. This assumes you have something interesting in the foreground and you do not want it blurred. At f/16 it is less of an issue... that is, focusing near or far is only going to affect you near focus limit by about a 1/2 foot at 24 mm.

I believe the "focus 1/3 into the shot" rule was meant to appoximate the hyper focal distance at f/8 which would maximize near field focus and yet provide good focus at infinity.

If you are happy with your foreground focus, then do not worry about it. If you like a crisper foreground, then get an app that calculates hyper focal distance to see were your limits are. HFD is not the total answer, but it helps to understand the effects.

I also tend to set at f/16. Difractive distortion is very limited and yet I get good DOF. I tested all my lenses and wrote on them all the f stop that produced the sharpest shot, and for the most part they peaked a little below f/16, but the difference at f/16 was pretty imperceptible. But f/18 was my limit were the diffraction problem crossed the line for most lens I own. So I go with f/16 for a good combination of DOF and sharpness.

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I like f/11 for landscape type images. f/16 is starting to get into diffraction territory on the ~ 20 MP full frame sensors. Tripod + live view is great for checking critical focus near and far.

Dave

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Originally Posted by Squidy

I THINK I understand, but what if say 1/3rd into the shot is just water? Do I still focus on the water and everything else would be sharp?

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Yes, this is pretty much it. Really, you are trying to bracket the shot so you have sufficient depth of field so your entire shot appears to be in focus. Having a "story telling" or "landscape" aperture (f/8+ typically) is the first step and then the focusing ~1/3 into the shot the second.

You can play with online DOF calculators to see why. Focus too close, and you will have foreground and background blur. But start getting even a little bit out in the scene, and you will still have some level of foreground blur, but the point where background blur starts quick goes to "infinite."

For example: FF sensor, 24 mm, f/8 but focus at 3 ft the DOF limits are 2.19 ft foreground (so less than 2.19 ft, you have noticeable blur) and background blur starts at greater than 4.77 ft. Move out to 5 ft these go to 3 ft and 13.3 ft, then 8 ft and suddenly you have 3.99 ft for foreground and "infinite" for background. In otherwords, "noticeable" background blur has no starting point.

A good starting book for things like this is Bryan Peterson's "Understanding Exposure."

In theory, we focus on a plane that's parallel to the sensor, perfectly flat, and infinitely thin. However, in theory, theory and practice are the same, in practice they are not. You're always going to have SOME depth of field (measured in millimeters, perhaps, but non-zero nonetheless). That DoF is going to be thinner on the near side of the magic focus plane than it is on the far side of the magic focus plane. Focusing 1/3 of the way into your scene is a way to approximate that distribution of DoF.

Especially with landscapes, sometimes you might just need to manual focus, and you'd focus on this magic spot 1/3 of the way into your primary scene. When I say primary scene, I'm referring to the area you want in-focus.