shooting distance?

[Kellyj69]

I am new to DSLR photography .. I have a Rebel XS. I'd like to get a telephoto lens. I'm looking at a 75-300mm lens ..

question :

How can I tell how far away an object (person) has to be before I can fill my lens with it? besides trial and error for example .. If I wanted to shoot a baseball game from the stands.. how do I know how close my seats need to be to be able to shoot the players clearly? is there some correlation between mm's and yards?

Thanks

KJ

[sk66]

There are online FOV calculators. HERE'S on of the better ones.
At 300mm the FOV is about 7 degrees across the horizontal...how much area that includes depends upon distance to subject.

[Kellyj69]

ok .. now I'm really confused lol .. distance to the subject is what I'm trying to figure out ..

basically .. if I have the ability to shoot at 75-300mm .. at a baseball game, how close/far away do I (or can I) be to fill my image with the batter? ex .. at an average MLB park , the distance from home plate to the center field wall is about 400ft (120 meters) at that distance .. how do I calculate what focal length to use to fill the image with the batter?

Or .. suppose I'm on a safari and want to take a picture of a lion .. how do I know how close I can get to him without looking through the viewfinder and walking closer til I get eaten

maybe I just don't have the knowledge to understand that calculator.

[sk66]

Using the calculator I linked to:
change the "multiplier factor" to 1.6 (for XSi) start with 300mm focal length and then change the distance until you get a vertical FOV of around 5ft to fill the image in portait layout (a bit more for player swinging bat).

Otherwise, use focal length and multiplier of 1.6 to get FOV in degrees (doesn't change w/ distance). At 300mm it comes up with 3* vertical and 4.5* horizontal (5* diagonal) and then you have to guesstimate...

[Kellyj69]

Thank you!

[Kellyj69]

[QUOTE=sk66;1026546]Using the calculator I linked to:
change the "multiplier factor" to 1.6 (for XSi) start w

how did you come up with the 1.6?

[candleman]

Originally Posted by Kellyj69

Using the calculator I linked to:
change the "multiplier factor" to 1.6 (for XSi) start w

how did you come up with the 1.6?

thats the "crop factor" of your sensor in relation to a standard Full Frame sensor.