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Thread started 25 Sep 2011 (Sunday) 19:52

# Lens MM vs actual distance

Sep 25, 2011 19:52 |  #1

On a ff camera, how many feet closer would I be standing to a subject if I compared a 35mm to a 100mm to 200mm to 300mm to 400mm if each was like looking through only my eyes?

In other words, how many feet would I have to walk to make up the distance between each lens?

I am trying to decide what lens to get that is longer than my 70-300..... 400? 500? This is how I will figure it out. Thanks.

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Sep 25, 2011 19:59 |  #2

Changing the focal length will not make the subject appear closer, it will make the subject appear larger. Those are two differenct concepts.

If you double the focal length, the subject will appear twice as large on the sensor. So going from a 300mm lens to a 600mm lens (for example) would make a subject that filled half the frame now fill the entire frame.

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Sep 25, 2011 20:08 |  #3

What I am trying to gauge is if a subject fills the frame of 100mm lens at 10 yards, what focal length would I need to fill it at 300 yards? Approx 500mm?

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Sep 25, 2011 20:08 |  #4

Another useful guide is knowing that if you want an object that is covering the short side of your sensor to cover the long side of it, you need 1.4x.
In the case of your 70-300 at 300mm, that would be 420mm.

Juan

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Sep 25, 2011 20:14 |  #5

Higgs Boson wrote in post #13161968
What I am trying to gauge is if a subject fills the frame of 100mm lens at 10 yards, what focal length would I need to fill it at 300 yards? Approx 500mm?

100mm lens, 10 yards fills the frame.

300 yards is 30 times the initial distance to the subject, so to fill the frame with the same subject at 300 yards would require a 3000mm lens (100mm x 30).

Another way to think of this, starting again from 100mm lens and 10 yards, if you changed to a 500mm lens (5X the focal length) you would get the subject to appear the same size by moving back 5X the distance. So a 500mm lens would show the subject the same size at 50 yards (10 yards x 5).

My personal stuff:http://www.flickr.com/​photos/jngirbach/sets/
I use a Canon 5DIII and a Sony A7rIII

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Sep 25, 2011 20:20 |  #6

This is a good tool to make this type of calculations:
http://www.giangrandi.​ch/optics/lenses/focal​calc.html

Juan

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Sep 25, 2011 20:22 |  #7

Higgs Boson wrote in post #13161968
What I am trying to gauge is if a subject fills the frame of 100mm lens at 10 yards, what focal length would I need to fill it at 300 yards? Approx 500mm?

Are you aware of how distance between the camera (or your own eyes) and the various elements in the scene in front of it/you affects perspective?

There's a lot more to composing good photographs than just filling the frame with "the subject".

Skip Douglas
A few cameras and over 50 years behind them .....
..... but still learning all the time.

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Sep 25, 2011 20:24 |  #8

JeffreyG wrote in post #13162008
100mm lens, 10 yards fills the frame.

300 yards is 30 times the initial distance to the subject, so to fill the frame with the same subject at 300 yards would require a 3000mm lens (100mm x 30).

Another way to think of this, starting again from 100mm lens and 10 yards, if you changed to a 500mm lens (5X the focal length) you would get the subject to appear the same size by moving back 5X the distance. So a 500mm lens would show the subject the same size at 50 yards (10 yards x 5).

Ok so it isn't a doubling rule like stops, lol. It only works once, not exponentially. I guess I can't take pictures of stuff that far away.

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Sep 25, 2011 20:27 |  #9

SkipD wrote in post #13162041
Are you aware of how distance between the camera (or your own eyes) and the various elements in the scene in front of it/you affects perspective?

There's a lot more to composing good photographs than just filling the frame with "the subject".

Yes yes, you throw down the perspective concept in all of my threads, lol. There is more involved than just composition when you are taking pics of stuff really really far away and want subject isolation. If I am in a deer blind 50 feet off the ground and a deer is 250 yards away and I want to see the whites of his eyes, perspective of the tree behind it is not my main concern.

Game management is not about trees as much as antlers....

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Sep 25, 2011 20:29 |  #10

http://www.juzaphoto.c​om …al_length_compa​risons.htm

at the bottom there's a calculator so you can plug in the dimensions of your shot at 300mm, and it'll show you how much to crop to give an example of what 400/500mm would give you

Andre or Dre
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Sep 25, 2011 22:14 |  #11

Higgs Boson wrote in post #13162053
If I am in a deer blind 50 feet off the ground and a deer is 250 yards away and I want to see the whites of his eyes, perspective of the tree behind it is not my main concern.

Game management is not about trees as much as antlers....

I fully understand. Your questions, though, didn't really steer our thinking in this direction.

Skip Douglas
A few cameras and over 50 years behind them .....
..... but still learning all the time.

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Sep 26, 2011 05:42 |  #12

Fair enough. I appreciate your help as always.

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Sep 26, 2011 15:28 as a reply to  @ Higgs Boson's post |  #13

Higgs Boson wrote in post #13162053
Game management is not about trees as much as antlers....

SkipD wrote in post #13162532
I fully understand. Your questions, though, didn't really steer our thinking in this direction.

As long as we're being technical, steers don't have antlers. They have horns.

You're welcome.

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Sep 26, 2011 16:03 |  #14

Oh dear

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Sep 26, 2011 19:08 |  #15

number six wrote in post #13166375
As long as we're being technical, steers don't have antlers. They have horns.

You're welcome.

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Lens MM vs actual distance
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