Infinity focus

K

KevinP

Well-known member
For documenatry use are there any negatives with using the infinity option of focus on HPX170??

Rather than use manual focus and risk it hunting for focus when you didn't want it to.
 
I assume you mean autofocus hunting for focus, not manual focus. There are a few threads here dealing with a disadvantage of focusing to infinity with the HVX200--don't know if they would apply to the HPX170 or not. If I am recalling correctly, the issue had something to do with the need to use a long focus distance rather than infinity to keep distant objects in focus, although I don't remember the particulars of the discussion.

Kevin
 
Thanks - I'm filming a few people sitting around just slightly different distances from the camera and I want them all in focus. So if I use autofocus or manual there's a possibility the furthest/nearest may be in soft focus. So I wondered about infinite - it doesn't have to be a long way off in focus they are all within 20 foot.

Would infinity focus handle that OK?
 
Depends on what f-stop you used and what focal length you're at. Infinity Focus is designed to bring objects at infinite distances into focus -- it doesn't make everything in focus. You use "infinity" focus when you want to shoot the mountains, or the moon.

There is a concept known as the hyperfocal distance, which is a focus distance you set where everything from infinity on down to half the hyperfocal distance would be in focus. For example, if the hyperfocal distance for your particular lens/aperture combination was 20 feet, and you set your lens focus position at 20 feet, then everything from 10 feet to infinity would be in focus.

So the rule to get the deepest depth of field is to set your lens as wide-angle as you possibly can, move the camera as far away as you possibly can, and set the iris as deep as you possibly can (i.e., as close to f/11 as you can get it.)
 
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