Is there a calculator for subject size, distance, focal length, for size in frame?

[george013]

With a bit of luck it's doing the walking for me.
George

[travelfinn]

There is an app www.lenstutorial.com might help you.

[xpatUSA]

This is an odd question, but...

Is there a calculator or app that you can type in: Subject size, distance to subject, focal length, sensor (crop etc), and then have it tell you how much of the frame it will fill? I suppose I could do some tests to determine this, and also, experience would give me a second-nature instinct for it, but I thought there might be a tool to calculate it as well.

Thanks for any suggestions

Perhaps a slight problem with the inputs as stated?

Ignoring the 'sensor' for now; subject size (it's projection toward the camera of course) and distance (to the mid-point of the projection perhaps) are OK and calculation of the angle of view for that is trivial as has already been said.

But what 'focal length' is to be typed in? What's stamped on the lens will only do if the focus is near infinity. Is it possible to calculate the focal length + extension from the lens nominal focal length and the angle of view, for example?

I don't know off the top my head but someone will, I hope.

[george013]

Perhaps a slight problem with the inputs as stated?

Ignoring the 'sensor' for now; subject size (it's projection toward the camera of course) and distance (to the mid-point of the projection perhaps) are OK and calculation of the angle of view for that is trivial as has already been said.

But what 'focal length' is to be typed in? What's stamped on the lens will only do if the focus is near infinity. Is it possible to calculate the focal length + extension from the lens nominal focal length and the angle of view, for example?

I don't know off the top my head but someone will, I hope.

Let's stick to primes.
Your focal length doesn't change. A 50mm lens will be 50mm at infinity and nearby. What you do when you focus at a nearby subject, you move the lens away from the film/sensor. Maybe that's what you mean with extension.
I'm not sure if I understand you, but if you want to know that extension, you must know the subject-distance.
George

[xpatUSA]

Let's stick to primes.
Your focal length doesn't change. A 50mm lens will be 50mm at infinity and nearby. What you do when you focus at a nearby subject, you move the lens away from the film/sensor. Maybe that's what you mean with extension.
I'm not sure if I understand you, but if you want to know that extension, you must know the subject-distance.
George

Thank you, George.

Yes, I was referring to primes or a zoom at a fixed setting. Yes, by 'extension', I meant the amount by which the effective focal length increases when focusing on subjects closer than infinity. Like, for a macro lens at 1:1, the total length is doubled (simple lens).

What I don't know is how to calculate that length from just the 'size' of the subject, the distance to the subject and the nominal focal length.

Do you?

Without that effective length, the subject size in the image plane can not be calculated.

[george013]

Thank you, George.

Yes, I was referring to primes or a zoom at a fixed setting. Yes, by 'extension', I meant the amount by which the effective focal length increases when focusing on subjects closer than infinity. Like, for a macro lens at 1:1, the total length is doubled (simple lens).

What I don't know is how to calculate that length from just the 'size' of the subject, the distance to the subject and the nominal focal length.

Do you?

Without that effective length, the subject size in the image plane can not be calculated.

Theoretical that should be done withe the lens-formula.
1/focus distance=1/subject distance + 1/image distance.

When the subject is at infinity, then 1/infinity=0, thus 1/focus distance = 1/image distance.
I don't know the practical use of this calculation for macro. Those formulas are based on the optical center of the lens and that is hard to tell where it is. Maybe the summation of the subject and the image distance could be something to play with. There is a mark on the camera telling the place of the sensor. Then you don't have to worry about the optical center. Just loud thinking.
Be aware that if you want to play with it, use the same units, all mm or all meters or whatever you want. As long as it is decimal.
I assume you mean with focal length the length of the lens.

You know the size of your subject, and you know the size of your image you want to have. Than you know the magnification. From the calculator you can calculate the distance, that will be the subject distance. You know the focal value of the lens, so you can calculate the image distance. Image-distance + subject-distance is the distance from that mark on your camera till your subject.

George

[xpatUSA]

Theoretical that should be done withe the lens-formula.
1/focus distance=1/subject distance + 1/image distance.

Thanks again. Yes, I just went to the Wiki page and was surprised how simple that was. Seen it before but forgot about it. https://en.wikipedia.org/wiki/Lens_%28optics%29

,snip>
Be aware that if you want to play with it, use the same units, all mm or all meters or whatever you want. As long as it is decimal.

George

Durn, I wanted to use yards for the distance, feet for the size and mm for f

I'm going to do a spreadsheet for the OP now, for what it's worth . .

[xpatUSA]

This is an odd question, but...

Is there a calculator or app that you can type in: Subject size, distance to subject, focal length, sensor (crop etc), and then have it tell you how much of the frame it will fill?

Thanks for any suggestions

OK, here it is:



I have left the output as size as it appears in the image plane. The reason for that is 'size' is actually what is called a vector and that means we would need to know whether it is height or width or anywhere in between for any image. I leave that to you and also I leave it to you to know your sensor dimensions so as to be able to figure out the framing.

Yellows are inputs, greens are calculated values.

[george013]

OK, here it is:



I have left the output as size as it appears in the image plane. The reason for that is 'size' is actually what is called a vector and that means we would need to know whether it is height or width or anywhere in between for any image. I leave that to you and also I leave it to you know your sensor dimensions so as to be able to figure out the framing.

Yellows are inputs, greens are calculated values.

You can save the link Graham gave,http://www.tawbaware.com/maxlyons/calc.htm, it's a standalone javascript page. You can add the stuff you want.
George

[lukaswerth]

Matt,

why on earth would you need this? You realize most cameras have some sort of viewfinder device in order to frame the subject?

Lukas

[xpatUSA]

You can save the link Graham gave,http://www.tawbaware.com/maxlyons/calc.htm, it's a standalone javascript page. You can add the stuff you want.
George

George, there may be a misunderstanding. I am trying to satisfy the requirements of the original post, not what various members (including myself) thought that the original poster might find useful. None of the calculators shown in Grahame's link satisfy those requirements, unless I missed one.

My stuff would be posted on my website as a spreadsheet for the original poster to download and use/modify as he thinks fit.