Originally posted by gut1kor
Hi
I searched on net but did not find the answers. I am stuck with a doubt regarding focal length and zoom capabilities. To say exactly, if I have two lenses 18-250mm, and 70-300mm which lens can bring a given subject more closer from a given point at the highest focal lengths?
How to calculate this reachability with any given lens and also in fixed focal length lenses? Does getting the zoom by diving the focal range numbers (250/18 = 14x and 300/70 = 4X) has any explanation in finding out which brings the subject more closer?
Please clarify.
Cheers
Gunasekhar
Gunasekhar, the higher the focal length number for a lens the greater the magnification of the subject you see though the viewfinder,just like looking through binoculars or a telescope.
As the magnification gets bigger the total area you see gets smaller, so when you look through your viewfinder with the lens set at 18 you will see from side to side [and up and down] more than if you set it to 55, however at 55 the subject in the middle of the frame will be bigger,
so to answer your question the 300 will give you the largest view of your subject.but you will see less of the total area you see with your eye.
try this .what you see with your eye is approximately the same size as what you see through the viewfinder with 55 mm lens on a Pentax DSLR but what you see with your eye from side to side is approximately what you see with a 18mm
lens.
so now you run into the problem of trying to balance what you see width wise against magnification!! which is why we stitch images together sometimes to give the viewer what they would have seen if they were there.
get complicated doesn't it?,
welcome to the wonderful world of photography!
regrad
Alistair