Distance to fill the frame

Hey folks! I have a math problem that I cant seem to answer for myself and search button is not working for me since I dont know the keywords to search for.

How would I compute the distance I have to be, using ff sensor, 50mm fl, and subject if 6ft tall, if i want to capture the whole body using landscape orientation? How about if its portrait orientation? If anybody can give me the answer as well as the formula to get to the answer so I can save it.

Thanks!

In landscape orientation, 50mm on FF produces 27 degrees of vertical angular FOV and 39.6 degrees of horizontal angular FOV. I did a quick drawing in autocad. So you'll need ~12.5ft in landscape and ~8.4ft in portrait orientation.

Al

From the splendid table of lenses in the sticky we find that the AOV of a 50 mm lens on FF is about 27° in the vertical direction (I assume your subject is standing) when in landscape orientation.
We then apply some trigonometry.
Assuming that your camera position is about 3' above ground to make life easier, we find that the cotangent of half the AOV = the distance to the subject divided by 3'.

cot(13.5°) = d/3'
=> 4.17 = d/3'
=> d = 3' x 4.17
=> d = 12.50'

Anything easier to memorize other than this? Lol.

If it matters, im 5'9", so im guessing camera height from the ground is 67-68".

I was hoping to use this as base information and get similar info I need if I were to switch to different fl.

musashi wrote in post #14288764
Anything easier to memorize other than this? Lol.

If it matters, im 5'9", so im guessing camera height from the ground is 67-68".

I was hoping to use this as base information and get similar info I need if I were to switch to different fl.

The easier method is looking through the view finder with the lens on the camera. I also noticed your lenses are zoom lenses...

themadman wrote in post #14288852
The easier method is looking through the view finder with the lens on the camera. I also noticed your lenses are zoom lenses...

Im considering on getting primes thats why im researching. I know i can just use the camera but I dont have anything 6ft to shoot at the moment. Thanks for your reply even though it didnt help or answer the question.

I dont really know why, but It just hit me know that I wanted to know. To make a long story short, im moving overseas and I dont have anything, and I mean ANYTHING, that I could use. Im living out of a suitcase waiting for my flight. So I guess I got bored and needed something to keep my mind occupied. My main goal really is to find out if I were to get primes, will using them wide open yield enough dof. The question was for 50mm, thinking I could just extrapolate from the answer if I were to change the variable to a 24mm or 85mm fl, or if changed the 6ft subject to 4 1/2 to 5 1/2 ft subjects.

But if theres really no simple formula for the question im asking, then I thank those who have tried to help.

musashi wrote in post #14289077
The question was for 50mm, thinking I could just extrapolate from the answer if I were to change the variable to a 24mm or 85mm fl, or if changed the 6ft subject to 4 1/2 to 5 1/2 ft subjects.

Easily done.
With the frame-filling answer for 50 mm as a base, if you change the focal length by a factor of x you must change the distance by a factor of x.

With the frame-filling answer for 6' as a base, if you change the subject height by a factor of x you must also change the distance by a factor of x.

Mix as required and serve.

I guess it depends on what you mean by simple.

How about "f/5.6".

xarqi wrote in post #14289128
Easily done.
With the frame-filling answer for 50 mm as a base, if you change the focal length by a factor of x you must change the distance by a factor of x.

With the frame-filling answer for 6' as a base, if you change the subject height by a factor of x you must also change the distance by a factor of x.

Mix as required and serve.


I guess it depends on what you mean by simple.

How about "f/5.6".

Lol. Thanks for that. I guess from the answers before and with your answers now, I can adjust some numbers accordingly and get the value I needed.

While im at it, if im understanding this all correctly, from the data given before, I needed 12.5ft working distance while in landscape mode. With everything staying constant, but I changed my fl to 85mm or 24mm, my calculations is as follows;

85/50=1.7
1.7*12.5ft=21.25ft new working distance to fill the frame while in landscape orientation

24/50=.48
.48*12.5ft=6ft new working distance to fill the frame while in landscape orientation

Are my calculations correct? All assuming of course that the other info didnt changed. (6ft subject, using ff)

musashi wrote in post #14289208
Are my calculations correct?

That's certainly how I see it, but I could have it wrong, so wait on someone else for confirmation I think.

kjonnnn wrote in post #14289146
Well you have to time to figure all that out .. it probably has something to do with angle of view...

http://en.wikipedia.or​g/wiki/Angle_of_view

Thanks for that link. I saved it for future reading, I think I got a headache just browsing thru it!

Go here: http://www.tawbaware.c​om/maxlyons/calc.htm
Scroll down to the Dimensional Field of View calculator
Input the appropriate info
Hit "calculate"

It will tell you how high and how wide your frame is, at a given distance, with a given focal length.

@snydremark thanks for that. I bookmarked it.

Thanks also for everybody that helped me out on my curiosity/dilemma. Once again, POTN members comes through and helped me out, like you guys always have since I started. This is why I never get tired of visiting this place everyday, Now I can say I learn something new again!