# Questions tagged [calculations]

Photographic math — equations, formulas, algorithms related to making or processing images.

45 questions
Filter by
Sorted by
Tagged with
7answers
188k views

### Is there a general formula for image size vs. print size?

What size images do I need for common print sizes, such as wallet size, 8x10, and 16x20? Is there a general formula? How could that size change if, for example, a 16x20 was printed on canvas rather ...
9answers
7k views

### Can a smaller sensor's “crop factor” be used to calculate the exact increase in depth of field?

If APS-C and similar crop-sensor digital cameras have a focal length multiplying effect such that a 50mm lens has an apparent focal length closer to the field of view of an 80mm on a full frame camera,...
5answers
180k views

### How do I calculate the distance of an object in a photo?

If I took a picture of a windmill on the horizon — given that I know the sensor size and the focal length of the lens and other factors to do with the shot — could I calculate how far away an object ...
3answers
4k views

### What is the formula for percent of frame filled at a specific distance and focal length?

I am thinking about buying a new lens specifically to take photos of distant targets (birds, bears, etc). I currently own the Canon 70-300 IS USM, which is a nice lens, but I find that if I want to ...
3answers
881 views

### Why I am getting different values for depth of field from calculators vs in-camera DoF preview?

When using depth of field and hyperfocal calculators, I get very different result versus the in-camera DoF preview of my Fujifilm X-M1. For example: With DOFMaster (or any other online calculator), ...
3answers
5k views

### 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 ...
7answers
20k views

### Do I use the crop factor in calculating aperture size and area?

How do I calculate the aperture size and area, considering an 35mm equivalent focal length value and non-equivalent aperture f-number (in terms of exposure, no multiplication of the crop factor of the ...
3answers
2k views

### How can I calculate the effect of a supplementary close-up lens (a.k.a macro filter)?

If I have a +1, +2, +4, or +10 close-up lens which attaches to the front of my regular lens, how can I calculate its effect on close focusing distance, figure out how much magnification I can get from ...
6answers
41k views

### Is there a formula to calculate DOF?

I am pretty clear about that DOF depends on: Focal length Aperture or f-stop Distance from subject Sensor size and more (as pointed out in this comment). But my question is: Is there any formula ...
5answers
44k views

### What is the relationship between size of object with distance?

How does the size/length of an object vary with distance? Is it a logarithmic relationship? exponential? linear? I plotted a curve of the size/length of an object for different distances from the ...
3answers
15k views

### Calculate object size when I have physical pixel size

How do I calculate the object size when I have focal length = 25mm distance to object = 700mm CCDs pixel size = 4,4µm ? My camera is this one. Appreciated! Edit: Could this work: real height = (...
2answers
4k views

### How do I calculate the number of stops between two shutter speeds?

What is the math equation to calculate the difference between two different shutter speeds in stops?
5answers
5k views

### Is it exactly true that doubling the focal length makes everything look twice as big?

I had come to the conclusion that if one lens has twice the focal length of another, that means it makes everything look twice as big. Conversely, if a lens has half the focal length, you see twice as ...
2answers
10k views

### How to calculate the optimal pinhole size?

As far as I've understood, optimal diameter for pinhole size is calculated by formula where d - the optimal diameter for pinhole c - constant f - focal length (distance between pinhole and ...
5answers
17k 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 *...
6answers
1k views

### Why don't cameras provide you with DOF information?

The viewfinder is usually not 100% accurate in representing the final image you will get and I've lost a few shots while using a too narrow DOF. I would imagine that cameras, knowing the focal length, ...
1answer
1k views

### How can I calculate sensor size (width and height) from focus length, vertical, and horizontal angle of view?

How to calculate sensor size (width/height) when knowing focus length, vertical & horizontal angle view (FOV)?
3answers
5k views

### How to determine camera location from an existing photograph?

I have old photos of a town and landscape around it. I'd like to take these photos again, from the same locations. In some cases I am struggling with finding the original location of the camera. I ...
1answer
2k views

### How can I calculate the change an extension tube makes to the maximum magnification of a lens? [duplicate]

Possible Duplicate: How can I calculate what the effect of an extension tube will be? My understanding is that extension tubes increase the magnification of lenses by reducing their minimum ...
3answers
1k views

### Can I calculate sensor size from pixel dimensions and number (to find angle of view)?

I read up an equation on Wikipedia i.e. a camera's angle of view can be found from the following equation angle of view = 2 arctan ( d / 2f ) where f = focal length and d = size of film or sensor. ...
3answers
2k views

### How much distance should one move so that a shot that can be framed at xx mm be framed at yy mm?

Is there a website / app that will tell you approximately how much distance a person should move so that they are able to frame the same shot at different focal lengths? Say for example, I'm using ...
1answer
1k views

### How to calculate the correct focal length needed for a subject of a given size and distance?

I need to purchase my first ever lens. So far I've only used lenses that were built into a camera. This specific lens is for the BlackMagic Deign Pocket Cinema Camera (a video only camera, but one ...
3answers
953 views

### Why are my pictures blurry even though a DOF calculator shows everything should be in focus?

In theory, according to the DOF calculator, I can achieve infinity focus with my Sigma 10-20 at f/3.5 when focusing at a subject that's 2m away but when I put it to the test my pictures come out super ...
1answer
18k views

### How do I calculate the ground footprint of an aerial camera?

I have a very simple math problem, but I cannot seem to figure it out. I need to calculate what portion of the ground will be visible when viewed from a UAV mounted camera. I believe I have it solved ...
5answers
3k views

### 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 ...
2answers
20k views

### How can I calculate focal length from a photograph?

I posted this question over on Stack Overflow, but someone suggested this site might be of more help to me. I'm doing a college project where I'm trying to calculate the focal length of a camera ...
3answers
1k views

### Why isn't my computation of the actual size of an object in a photograph matching the expected value?

Let's say I have a full frame camera (Sony A7) with a 50 mm lens (Canon FDn 50mm f/1.4) mounted on it. At a given object (a plane) distance I should be able to compute the size of the image in real ...
1answer
111 views

### DoF app: should I round the image format/width up or down?

The DoF app I have calls for the sensor width to be set. The specs for my Sony α33 say the image format is 23.4 x 15.6mm. Do I dial-in the 23.4 or the closest to it? If I must go slightly over/...
2answers
45k views

### How to calculate the FOV in degrees from focal length or distance?

How does one to calculate the field of view (or angle of view) in degrees from the following details: sensor size (for example, 1") distance to target (for example, 7 feet) focal length (for example,...
1answer
8k views

### 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 ...
8answers
3k views

### If viewers don't respond to the rule of thirds, why do some photographers still emphasize it?

Previous posts (1, 2) explain the concept of the Rule of Thirds and the Golden Ratio. Some previous answers state that the Rule of Thirds is the Golden Ratio, but that is not true. The two are ...
2answers
4k views

### What is the image size of the Sun / Moon in the frame with a given focal length?

I'm interested in taking a picture of the Sun / Moon using a telephoto lens. For example like this. It would be very helpful for me to know what the approximate image size of the sun / moon would ...
5answers
2k views

### Is rotation an intrinsic lossy operation (for angles not multiple of 90 degrees)?

mattdm's statement "that blur is largely reversible if you do the exact same thing in reverse" raised the question in my mind. The rotation is a geometric transformation of the image that consist of a ...
2answers
7k views

### How can I get the image/sensor dimensions in mm to get Circle of Confusion from EXIF?

I need to get calculate some formulas based on Circle of Confusion and/or image dimensions (diagonal) in millimeters based on EXIF data only. IOW, I cannot say "this photo was shot with Canon 5D3 ...
5answers
9k views

### is the Nikon 35mm f/1.8 worth it after i have the kit lenses? [duplicate]

I have a Nikon DX (D5100) camera with the two most basic kit lenses: 18-55mm f/3.5-5.6 VR and 55-200mm f/4-5.6 VR. These two lenses cover lots of scenarios, but I'm starting to believe there is more ...
4answers
762 views

### Does the crop factor affect the field of view (FOV)? [duplicate]

I'm working on smartphone cameras. I want calculate Field Of View of different smartphone cameras using the formula : FOV = 2 arctan(SensorSize/2f) where: f is the focal length sensor size is the ...
3answers
5k views

### How do I convert focal length to maximum distance?

I would like to know whether there is any relation between focal length and distance. For example, what is the max distance I can shoot from a 55mm-300mm lens?
3answers
2k views

### How do I know how much light will be needed for a given film speed, shutter speed, and aperture?

For a given film type, shutter speed and aperture, how do I calculate the light needed to get a good exposure? For example, if I use a f/8 aperture, an exposure time of 100 ms and a ISO 800-film (...
3answers
2k views

### Why do depth of field calculators show *more* DOF for larger formats with the same lens parameters?

I thought I had a pretty good seat of the pants understand of DOF. But I've been playing with DOF calculators and it's giving me results that don't line up with my practical experience, so I'm ...
3answers
192 views

### How to scale between two white balance settings for perceptually equal increments?

If I have two white balance settings (say, one for direct noon sunlight, and one for full shade) and I want to create a series of interpolated settings that span between the two, what would be the ...
1answer
521 views

### Lens f-number and speed on adapted lenses

A lens has a focal length, and its entrance pupil has a diameter. The ratio of these is an f-number. The size of the entrance pupil is limited by the size of the front element, and we describe lenses ...
2answers
1k views

### Calculate camera tilt angle from 2D image [closed]

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): ...
1answer
486 views

### How much does extending affect range of focusing distances?

It's well known that moving a lens away from imaging surface will decrease both minimum and maximum focusing distance. There are times when it would be good to know how much those distances will ...
2answers
831 views

### Why are the area of aperture, focal length, and amount of light specified in these terms?

So I'm looking at the wikipedia article on Aperture, and I'm a bit confused. I understand aperture to be the diameter of the hole that lets light in. In the article, someone states that The ...
3answers
1k views

### How to get focal length from a camera specification which gives a value like “4.5-22.5”?

I am using a Sony W520 camera. The specifications mention Focal Length (f= mm) 4.5-22.5. What number should I take? The lower value or the higher? And if not both of them, then how to calculate actual ...