focus at infinity?

[Pro Image]

Guys this may help.

It's a little long but I think it's good reading material.

http://www.sweethaven.com/academic/lessons/021500/110/?unNum=1&lesNum=6

 

[kex]

Doubt that. Depends completely on what lens and what aperture you're using. With a 400mm lens at f2.8 for instance, your DOF at 30m is only from 29.5m to 30.5m. Easy to see that if you just focus at infinity, something just 32m away won't be in focus. Stopping down to f5.6 changes that to 29.1m to 31m in focus, still not sharp enough.

I've explained this already before on this forum when some time ago at national day someone suggested shooting planes in flight just by focusing at infinity. Not going to work.

u mean it is impossible to shoot planes by focusing at infinity ?i didn't know about dat..

 

[sehsuan]

u mean it is impossible to shoot planes by focusing at infinity ?i didn't know about dat..

simply because the object isn't that far to be consider infinity (eg, sun).

 

[kex]

a flying plane is definitely far enuff for any lens to be set at infinity,i have yet to see any lens with focusing up to 500m range.