Quote Originally Posted by Marin
This is a bit confusing. Is there any way of comparing lens lenght in mm with optical magnification (like in binoculars)?

How would I know what lens lenght is enough? Shoul I buy a telephoto then?

What is the difference in 100 mm in focal lenght in real world?

Ok, I see that 80-400 mm is 5 times zoom, but 80 mm is not like human eye, what can we compare it to?

Thanks for answer anyhow .
What you need to know is the crop factor of the D-SLR you want, for ease let say it's 1.5.

This means the 80-400mm becomes a 120-600mm effective size, thats sort of 5 times zoom but only across the range of that lens. A "normal lens is aound 50mm "effective" size or about a 34mm, to be the equivalent of the "standard" wide angle of say a 28mm you need to drop the size to around 18mm.

So if you follow all the stuff above to compare with a camera that has one lens that does all your zooming it will give you the equivalent of around 28-600 using a 18-50 and a 80-400 and that is a zoom from wide angle to very zoomy, you do the math. Of course depending how far away your subject is that may still not be big enough and you may need a 300-800mm or the likes.

Cheers.

Pete