# Foo - Wanted: Camera experts

Bikeforums.net is a forum about nothing but bikes. Our community can help you find information about hard-to-find and localized information like bicycle tours, specialties like where in your area to have your recumbent bike serviced, or what are the best bicycle tires and seats for the activities you use your bike for.

View Full Version : Wanted: Camera experts

markhr
02-15-09, 02:21 PM
Please could anyone be so kind as to point me in the direction of either a list of slr lenses by length that achieve two thirds subject picture and at what distance to the subject this is achieved or equivalent math formula based on distance to the subject.

Assume the subject is a 1.80m (~5'10") person.

Allen
02-15-09, 05:37 PM
Sorry, I've lost your trail there.
Am I right to assume you are trying to calculate the size of objects in the frame using a person as the reference standard?

linux_author
02-15-09, 05:42 PM
http://www.reflectiveimages.com/depthoffield.htm

bikebuddha
02-15-09, 06:08 PM
I don't think he's looking for a DOF calculation, rather I think he wants a lens that will frame 2/3 a person for a portrait. Well the answer is almost any lens will do this, it's just a question of how close (or far) you want to be. Consider, with a wide angled lens say 24mm you could frame 2/3 of a person while standing relatively close. However because aspect ration of the 24mm lens it might not be a very flattering portrait. Back in the film days almost everyone had a fast 85mm for head and shoulders portraits with a shallow depth of field. I still say the fast 85's were some of the best lenses ever made, get one and take two steps back.

Allen
02-15-09, 06:14 PM
I don't think he's looking for a DOF calculation, rather I think he wants a lens that will frame 2/3 a person for a portrait. Well the answer is almost any lens will do this, it's just a question of how close (or far) you want to be. Consider, with a wide angled lens say 24mm you could frame 2/3 of a person while standing relatively close. However because aspect ration of the 24mm lens it might not be a very flattering portrait. Back in the film days almost everyone had a fast 85mm for head and shoulders portraits with a shallow depth of field. I still say the fast 85's were some of the best lenses ever made, get one and take two steps back.

Ah. Yes to all buddha says then.

markhr
02-15-09, 08:24 PM
thanks for the replies folks - sorry for the rather crap question.

Subject is a person and I'd like to know which lens lengths would give me a full figure in at least 2/3 of the framed shot at different distances. Either a table by lens length and distance to subject or a formula that I can just plug in distance to subject (for a fixed height subject) that returns lens length.

e.g.

edit: assume 35mm slr if that helps :(

avmanansala
02-15-09, 08:41 PM
From what I recall, a 6' tall subject will be reproduced full length on the long side of a 35mm frame, on a camera 6' from the subject with a 35mm lens. So at 9 feet, you should get a subject 2/3 the long side of the frame (assuming a portrait orientation).

Learned it from a candid street shooter, Al Smith (f8bthere) at Nikonians.org:

A lot of this depends of the lens focal length or the angle of view and how much of the background you want, I would think.

avmanansala
02-15-09, 08:52 PM
I found this Dimensional Field of View Calculator (scroll down):

http://www.tawbaware.com/maxlyons/calc.htm

This should get you you where you want to go, play with the numbers.

If you plug in the 35mm focal length, focal length multiplier of 1 (assuming 35mm film), 6' subject distance, you can see that the horizontal (long side) dimension is just over 6'...

Plug in a value of 9' for subject distance, a 6' subject will cover 2/3 the frame.

With a 50mm lens, you'll want 13' camera to subject distance, and with an 80mm lens, you'll need to be about 20' away from a 6' tall subject to achieve the same result (assuming a 6' subject...so much easier than 5'-10") in a portrait orientation.

markhr
02-15-09, 09:01 PM
Those camera calculators look nice.

However, I'm trying to work backwards from distance to subject without knowing what lens length (the table or formula should tell me this).

That is, for a 1.80m subject 25m (or 50m or 121m or 564.3m or...) away, what length lens would I need to achieve a picture similar to this ( http://cache.gettyimages.com/xc/1784878.jpg?v=1&c=ViewImages&k=2&d=17A4AD9FDB9CF1939057D9939C83F106CE3CE935EF6724F65A5397277B4DC33E ) with the subject filling 2/3 of the frame?

edit: avmanansala thanks - just spotted your edit

avmanansala
02-15-09, 09:18 PM
If you plug and chug the numbers, you should be able to get to where you want to be. :)

Personally, i would probably go for a 50mm or an 80mm.

markhr
02-15-09, 11:45 PM
If you plug and chug the numbers, you should be able to get to where you want to be. :)

Personally, i would probably go for a 50mm or an 80mm.

I was thinking more of these point and shoot cameras.

24* optical zoom

Nikon coolpix p90
Kodak EasyShare Z980

26* optical zoom

olympus SP-590UZ

Not quite what I asked about but I'm assuming that any difference would be good enough for guv'mint work.