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4
votes
2answers
149 views

How do zoom, magnification, and focal length relate?

Zoom lenses and cameras with superzooms are often sold with an × zoom number — like a 12x zoom or 30x zoom. The question How do I convert lens focal length (mm) to x-times optical zoom? explains how ...
0
votes
0answers
67 views

How to get width and height of an image based on distance

I have an app to overlay the images on the camera overlay. But I need to set the width and height of the image based on the user distance. If the distance is, say 8 feet, how can I calculate the width ...
1
vote
3answers
977 views

Is the formula for object image size given focal length, etc. independent of sensor size?

I am trying to figure out how big an object of, say, 50cm height at 100m distance and 600mm focal length would appear on a camera's sensor. The ubiquitous formula object size in image = focal length ...
0
votes
1answer
124 views

What focal length and quality of lens do I need to read 15cm high text at 500m away? [duplicate]

I have to photograph 15cm high printed text from 500 meters away. The text has to be human readable in the result. What kind of focal length do I need? Can i compromise, and get a camera with less ...
24
votes
4answers
4k views

Does my crop sensor camera actually turn my lenses into a longer focal length?

So, I mount a 200mm lens on my Canon 450D. It effectively becomes a 320mm lens. Is this the equivalent of 320mm on a full frame camera? That is, from what I've figured out I get an equivalent field of ...