Smallest aperture & focus

SnappingShark · Jun 28, 2014

Simply questioning: if I choose the smallest aperture and focus to infinity - it doesn't really matter about where the focal point is through the viewfinder, does it?

480sparky · Jun 29, 2014

Yes it does. The focal point might well be still outside the DOF.

You can do better by setting the lens to the hyperfocal distance (instead of infinity) and increase the DOF. But that's still no guarantee the subject will be in focus.

Ido · Jun 30, 2014

Doing so will get you a lot of depth of field, but you will be

wasting most of it; and
using your lens's weakest aperture.

This video explains it pretty well: Creating Dynamic Landscape Photographs - YouTube
I've skipped it to around the point when focus becomes the topic, but if you like shooting landscapes, I highly recommend that you watch the entire presentation. I've watched it twice already.

tirediron · Jun 30, 2014

A great deal depends on the focal length of the lens; if you're using an 8mm, you're likely correct; if you're using an 800mm, maybe not so much.

ronlane · Jun 30, 2014

480sparky said:
Yes it does. The focal point might well be still outside the DOF.

You can do better by setting the lens to the hyperfocal distance (instead of infinity) and increase the DOF. But that's still no guarantee the subject will be in focus.

First off, good question Bright.

Second, Ken, do you prefer using hyper focus over just setting the focus to infinity or just short of there? Even when using something like f/8?

KmH · Jun 30, 2014

Using the smallest lens aperture offers focus sharpness issues similar to, but for different reasons, as using a fast lens wide open.

Diffraction Limited Photography: Pixel Size, Aperture and Airy Disks

WayneF · Jul 6, 2014

BrightByNature said:
Simply questioning: if I choose the smallest aperture and focus to infinity - it doesn't really matter about where the focal point is through the viewfinder, does it?

Someone ought to actually answer the question.

Yes, it could matter, if focused at infinity. The depth of field extends behind, and also in front of the focused distance. The distance beyond infinity is wasted, so focusing at infinity is not necessarily the theoretical best choice.

The concept you seek is called the hyperfocal distance. This is the distance, when focused there, the depth of field extends behind to infinity, and also extends in front closer too.

Hyperfocal distance places the focused distance within the depth of field, so depth extends both ways. The value depends on focal length of the lens.

For example (making up ballpark numbers), maybe at f/16, you focus at 40 feet. The depth of field might then extend from about 20 feet to infinity.

It is not necessarily a huge difference, more subtle. If focused at infinity, the depth of field might extend from about 30 feet, but 20 is less than 30.

Hyperfocal distance - Wikipedia, the free encyclopedia