Hi All,
I am thinking of getting  a zoom lens and I remember there is a way of working out how much bigger the image would be relevant to the size if the lens as opposed to a primary lens.
I currently have a 24 - 85 and I am thinking of something like a 300 mm.
So guys can some one tell me how much bigger the image would be.
I am thining of shooting wildlife - birds etc.
I know the bigger the lens the better but constrictions are budget ( isnt it always ) and the fact that my wife and I like to walk a lot and alread I am carrying - camera - two lens's - tripod etc etc and before anyone says give the wife some of the load she carries the sandwiches and coffee - plus we aint getting any youger as we are both on the 60 mark.
Thanks for any help.
Eddie
ejn

Which camera do you have??

Nikon D100

Well i would think that no matter what lense you have....your image will still remain the same size. :tt2: And now for some more constructive help....you can always take a look at this site:

http://www.tamroneurope.com/flc.htm

For some reason the page is down at the moment. But keep trying and if i´m not mistaking, you will get an interactive window where you can literally try out different lenses millimeter for millimeter on different subjects and then you´ll see how much more a 300mm for instance would zoom compared to the one you currently have.

With a 300mm zoom compared to a 300mm prime, IN THEORY the manufacturers would make their degrees/field of view the same (somewhere in the vicinity of 8 degrees - give or take about .5 degrees) so there should be no visible difference between a cheap one and an expensive one. Feel free to get a less expensive one which will be lighter - but like you said, not as good construction and not as wide an aperture.  Always a tradeoff - funfunfunf!

If you're asking about the "magnification" factor, with the D100 it will be x1.5 meaning you will be using the equivelant of a 450mm lens.
Hope that helps-
-Lew ;-)

As for magnification of the subject, 50mm is generally considered 1:1, or same size about like the eye sees.  With a 1.5 crop, remember 50mm crops the image as a 75 mm field of view but the size is the same.

Zoom factors are not the same as magnification.  300mm  magnification is approximately 300/50= 6x magnification(like with 6x binoculars).  Too often lenses are sold(mostly in the non-dslr cams with one lens) with a "zoom factor", like somethng of 10x zoom factor.       If the lens goes from 18mm to 180mm that is a 10x zoom but is not a 10x magnification.  The magnification of the 180 would be about 3.6x, as with binoculars specs.

If I missed it here, someone please correct my blunder.       TomDart.

Hi All,

I am sorry I have not thanked you all for the replies.

Some bug took over my browser and I couldn't connect to the net.

Well that's not exactly true,I could connect but the browser was being diverted to the most unsavoury sites imaginable.It has taken me days to get rid of the problem but some how I did.Yes I have Norton and it didnt prevent it.

Anyway thanks to you all.

In hindsight I should have phrased the question better.

What I meant was "what would the magnification be,but you guys worked that out so thanks for the help.

A special thanks to Zacko,the Tamron site certainly helped.

Have a good day all.

Eddie

I´m glad i could help. I like that site...it´s probably the only time i´ll get to play with lenses with a focal lenght beyond 300mm, LOL.