depth of focus point, the sweet spot?

I've been doing some reading, and I do feel that I am making some headway and starting to develop a better understanding of photography basics. I need some help wrapping my head around a few things though:

1. First, I have a landscape scene that I want to shoot with a very deep DOF, so I'm going to stop down my lens as far as it will go. Where should my focus point be? Should I a) "aim" the focus point for 1/3 into the shot, or b) manually set the focus ring to "infinity" and ignore the viewfinder, or c) manually set the focus ring to lets say 2 feet and ignore the viewfinder? Which is the correct approach for maximum DOF in the shot? Since the viewfinder is only showing you what the shot looks like wide open, is it just a matter of practice and experience to get this right?

2. I understand that there is a "sweet spot" for sharpness and clarity. Is this a known value that can be determined by the lens you are using, or this something you have to find on your own for each lens you use? Does changing the focal length of your lens change this value? It seems to me that you would want to keep your aperture as close to this value as possible for sharp pictures, and then compromise as needed when DOF control is a major element of the shot you are taking. Am I on the right track here, or completely confused?

thanks for your input!

Your camera should have a little button for depth of field preview...which will stop down the lens temporarily. On Canons it's on the left front (as you hold the camera) just below the lens release button. For maximum depth of field in a landscape you should focus to infinity. Your lens should have markings for just how far away from the camera "infinity" focus begins since this varies a lot. Anything in frame short of that point will be blurry. If you focus at two feet you will have a portion of the frame in focus (depending on the length of your lens) and some before and after will be in focus. There is a great DOF calculator to help you understand depth of field at www.dofmaster.com

Amazing Grace wrote: Should I a) "aim" the focus point for 1/3 into the shot

This is an old photographer's tale, although sometimes it can work. Where the limits of DOF fall depends on focusing distance. At the hyperfocal distance the rear DOF limit is at infinity which of course is infinitely larger than whatever amount of DOF you've got before the subject. As you focus closer the DOF begins to even out front and back. At some point it becomes the same front and back.

Amazing Grace wrote: Which is the correct approach for maximum DOF in the shot?

Maximum DOF is always the hyperfocal distance. Hyperfocal distance is the closest distance you can focus in which the rear DOF limit is at infinity. It is not the same focusing distance as the infinity mark on your lens, and changes depending on aperture.

Depending on how bright your viewfinder is and if your camera has the feature you can try the DOF preview button. I've never used A-Dep mode, but that's what it's for too. Read about it in your camera manual. You can also google "DOF calculator" for lots of online DOF calculation sites. There are cell phone/PDA apps for it too.

Amazing Grace wrote: It seems to me that you would want to keep your aperture as close to this value as possible for sharp pictures

IMO if your lens shows a significant sharpness difference at different settings it's a lemon. Send it back. As old HCB famously said "Sharpness is a bourgeois concept." IMO getting the right DOF for the particular photograph you are creating is probably more important than minute sharpness differences.

"I’m always amused by the idea that certain people have about technique, which translate into an immoderate taste for the sharpness of the image. It is a passion for detail, for perfection, or do they hope to get closer to reality with this trompe I’oeil? They are, by the way, as far away from the real issues as other generations of photographers were when they obscured their subject in soft-focus effects." -Henri Cartier-Bresson

Henry Peach wrote:

Amazing Grace wrote: Should I a) "aim" the focus point for 1/3 into the shot

This is an old photographer's tale, although sometimes it can work. Where the limits of DOF fall depends on focusing distance. At the hyperfocal distance the rear DOF limit is at infinity which of course is infinitely larger than whatever amount of DOF you've got before the subject. As you focus closer the DOF begins to even out front and back. At some point it becomes the same front and back.

Amazing Grace wrote: Which is the correct approach for maximum DOF in the shot?

Maximum DOF is always the hyperfocal distance. Hyperfocal distance is the closest distance you can focus in which the rear DOF limit is at infinity. It is not the same focusing distance as the infinity mark on your lens, and changes depending on aperture.

Depending on how bright your viewfinder is and if your camera has the feature you can try the DOF preview button. I've never used A-Dep mode, but that's what it's for too. Read about it in your camera manual. You can also google "DOF calculator" for lots of online DOF calculation sites. There are cell phone/PDA apps for it too.

Amazing Grace wrote: It seems to me that you would want to keep your aperture as close to this value as possible for sharp pictures

IMO if your lens shows a significant sharpness difference at different settings it's a lemon. Send it back. As old HCB famously said "Sharpness is a bourgeois concept." IMO getting the right DOF for the particular photograph you are creating is probably more important than minute sharpness differences.

"I’m always amused by the idea that certain people have about technique, which translate into an immoderate taste for the sharpness of the image. It is a passion for detail, for perfection, or do they hope to get closer to reality with this trompe I’oeil? They are, by the way, as far away from the real issues as other generations of photographers were when they obscured their subject in soft-focus effects." -Henri Cartier-Bresson

But the easy answer is for lanscapes with a main subject i.e house, barn, tree, then focus on the subject. On landscapes that are strictly land then I like to focsu somewhere in the first third of the field. Then what was written above applies. Also stopping down all the way is not always right, as always you use the settings that get the best from the scene.