Photographic math — equations, formulas, algorithms related to making or processing images.
Questions tagged [calculations]
164 questions
7
votes
3 answers
Can we measure size of an object using EXIF data from a photo?
A lot of people have asked if we can measure the distance of an object in photo. But I was wondering if we can measure the size of an object in photo. Of course assuming we know everything from sensor size to height of the photographer etc.
Example:…
Sudarshan Kadam
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6
votes
5 answers
How do I calculate the “effective focal length” of a cropped photo?
Suppose I’ve taken a photo and then cropped it. If the crop is extreme enough then I might want to go back and take the same photo with a more telephoto lens so that I can take full advantage of my camera’s sensor.
If I’ve taken a photo at a given…
bdesham
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5
votes
1 answer
Calculate angle/field of view from 2D image
I want to calculate the angle of view (or field of view) from a photograph, without knowing anything about the camera (or lens).
Please have a look at this example:
It is assumed the angle between the line CENTER-LEFT and CENTER-RIGHT is 90° in…
Dick
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4
votes
2 answers
Calculate camera tilt angle from 2D image
I want to calculate the camera's tilt angle from a photograph, without knowing anything about the camera (or lens). Suppose I can extrapolate the vanishing points (one-point or two-point perspective):
Is it possible to determine the tilt angle?…
John M.
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3
votes
3 answers
Calculate object size when I have physical pixel size
How do I calculate the object size when I have
focal length = 25 mm
distance to object = 700 mm
CCDs pixel size = 4.4 µm ?
My camera is this USB 1/1.8" CCD C-mount camera.
Edit: Could this work?
$$ \text{real height [mm]} = \frac{\text{object…
chwi
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2
votes
1 answer
How to calculate the real size of an object from two photos in different types of perspective, knowing the dimensions of one of the objects?
How to calculate the real size of an object from two photos in different types of perspective, knowing the dimensions of one of the objects in these pictures?
When I was in college, we did such calculations but it was a long time ago and I have no…
Mateusz Marzetz
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2
votes
1 answer
calculating aperture and shutter speed inversion
I'm taking a manual photography class, using my canon rebel t5.
Any tips on how to calculate aperture and shutter speeds easily? (I know they have to be inverted).
After I meter my photo (set at -0-).
And Set ISO at 200 (this is all set by the…
AngBrammer
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2
votes
1 answer
Using a set formula to measure distance in a photo but the answers are coming out much smaller than expected?
I am using the formula
distance to object (mm) =
focal length (mm) * real height of the object (mm) * image height (pixels)
---------------------------------------------------------------------------
object height…
user29836
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1
vote
1 answer
Calculate the coordinates for secondaries on CIE chromacity diagram?
I'm trying to use this solution to calculate the secondary coordinates from primaries: https://photo.stackexchange.com/a/75238/115749
But it won't work for any other primary than those in the solution (red and green).
The results are wrong.
Here is…
FLX
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0
votes
2 answers
Estimate object size
If I have a [digital] photograph of an object, can I estimate it's approximate size?
I notice with interest that my camera (Nikon D3300) seems to record the approximate focal length of the lens in the Exif data. (It seems to round it to the nearest…
MathematicalOrchid
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0
votes
1 answer
How to obtain a subject's measurement from image
I am trying measure real object height from an image. I'm using the below formula
$$ \text{real height [mm]} = \frac{\text{object height [px]}\times \text{pixel size }\left[\mathrm{mm\over px}\right]\times \text{distance [mm]}}{\text{focal length…
Arun
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