Short and to the point, this photography†tutorial†will†dispel some common confusion which involves the manual focusing of a lens to the ‘infinity’ setting. The ‘infinity’ setting is commonly used at night time for example when a photographer would like to shoot a night landscape photo maybe on a 15 to 30 second exposure they would use the manual ‘infinity’ setting on the camera’s lens because the auto focus will not operate.
What this tutorial clears up is the confusion regarding the sentence, ‘Take the lens setting all the way up to infinity and then back up a little’. Now what he rightfully explains is that not all lenses are the same so in his first example he uses the swivel focus ring on the lens and guides the marker lines to go all the way to the ‘infinity’ mark, but oh wait, the marker goes past. He then ‘backs up’ to re-align it with the ‘infinity’ sign, so it is by doing this which clears up the sentence in question. There is a however, and that is the other lens like for example some of the newer Nikon dslr ones†you cant physically go beyond the ‘infinity’ sign so if you were to ‘back up’ you would quite simply not be on ‘infinity’ but on a different setting all together!
So there you have it, hopefully the confusion is cleared and you can now understand that not all lenses are the same and that it is important to understand the kit you have or intend to buy.