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I bet this sounds odd question but will ask anyway =)
When making lens to focus to infinity, how close i can actually have the point where i focus?
Currently when i make my af lens to focus infinity i usually make it from sunset, focus on it->lens to MF and tape it there.
Was just wondering, that could i do it more closer object?
It would depend on the aperture and associated depth of field (DOF). The smaller the aperture (larger f-stop number) the larger the depth of field. The DOF will also be affected by the lens focal length. So depending on the focal length and aperture you can have a DOF which would range up to infinity but still have closer objects in focus as well. Some people will also focus to a hyperfocal distance - which is basically the focal distance which gives the largest DOF from close up to infinity. Lots of reading and opinions on hyperfocal distance usage.
But the short answer is to just check a DOF calculator and input your lens and aperture, etc to find the DOF and subject distance which gives focus to infinity.
Stephen
Setting the lens to the hyperfocal distance (which varies with focal length and aperture) is the best approach. There are ample online calculators and smartphone apps which will give you the appropriate hyperfocal distance, and those same calculators/apps will tell you the closest point that's in the DoF with that focus distance setting.
It depends also on your sensor size (cellphone \ compact cameras have more depth of field)
With a Full Frame 24mm F/8 at 8'
With a 100mm F/8 at 136'
Check out the calculator
http://www.dofmaster.com/dofjs.html
I suspect you are asking for landscapes with a wide lens. It is good to know hyperfocal distance and such but if you are working at narrower apertures (f/8-f/16) and a wide lens (24mm) if you are over 10' you should be ok.
Currently have 24mm lens and mainly using infinity with northern lights
In that case, before you go out focus on something about 6 m / 20 ft away, then tape your lens and you're good to go.