What focal length lens to match 15X 50 Binoculars ?

[Mark Grant]

I have some fantastic binoculars, canon 15x50 IS , there not actually mine, I bought them for my wife for a present although I do use them

http://www.warehouseexpress.com/buy-canon-15x50-is-aw-binoculars/p1001567

http://www.amazon.co.uk/Canon-Image...EE9B/ref=sr_1_1?ie=UTF8&qid=1305837728&sr=8-1

They are 15 x magnification with 50mm diameter lenses.

What focal length 35mm camera lens would I need to get near the same field of view/ magnification ?

I really dont know, hence the question.

I want a long lens, but dont know how long.

 

[Larry Bolch]

If one assumes that a 50mm lens is "normal" then it would take a 750mm (15×50) lens to equal the binoculars in theory. However, binoculars can both have considerable magnification and also be wide-field or narrow-field, plus the lens in your eye and its retina become part of the total optical system. While cameras and binoculars are both optical devices, they operate quite differently.

 

[Pete Askew]

Hi Mark, as Larry says it is a tricky thing to work out as the two optical systems sort of work in different ways but I understand what you are trying to get to. Probably the easiest way would be to estimate the angle of view you are getting with the binoculars (it might even say) and then use a table / calculation like http://en.wikipedia.org/wiki/Angle_of_view to identify a lens that would give a similar field of view.

 

[Mark Grant]

Thanks guys

I think I am getting nearer.

The canon specs are here:
http://www.canon.co.uk/For_Home/Pro...age_Stabilisation/15x50_IS/index.aspx?specs=1
says ' Real field of view 4.5 degrees'

looking at the chart here:
http://en.wikipedia.org/wiki/Angle_of_view#Common_lens_angles_of_view

4.5 degrees looks to be about the 500mm or 600mm length.

I could be way off but a Canon 500mm f4 is a possibility for my wildlife shots.
I will see if I can borrow one or hire etc.

I almost bought a used canon 400mm f2.8 from a shop near me last week, my wife was with me though, so I was encouraged not to

 

[Larry Bolch]

I looked at the specifications for both lenses. 500mm = 5°, 600mm = 4° so the binoculars are in between.

 

[Mark Grant]

Thanks Larry,

I am using a Canon 60D at the moment so it is 1.6X mulitiplier, so a 400 mm lens should be the equivalent of 640 mm.

500mm f4 should be good.

 

[Chris Dodkin]

Mark - make sure you have a strong monopod or tripod handy, you're going to need it!

Also you will probably want to look at a gimbal head if you're shooting any moving wildlife.

Your 60D is going to look amazing hanging off of a great white