# Questions tagged [calculations]

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

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2answers
428 views

### Why is the image plane at Z = f in pinhole camera models?

Can someone show me the mathematical interpretation of why the image plane is at Z = f in the pinhole camera model? I found a possibly useful formula in Wikipedia, as shown in the figure below: My ...
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 ...
1answer
129 views

### How to calculate height of camera and ground coverage via geometry?

I have a GoPro7 that I will mount on a pickup vehicle to capture ground images with video capture. The camera isn't top down but has about 20 (or 30) degrees inclination from the vertical axis. I want ...
4answers
171 views

### Calculate lens FOV difference between Full-frame and APS-C sensors?

According to manufacturer specs 20mm lens has Field of View 94 degrees on FF (35mm) sensor and 70 degrees on APS-C sensor. Another 35mm lens only has Field of View specified for FF (35mm) 63 degrees. ...
0answers
36 views

### How to calculate under or over exposure using these values TTL meter (Lux), Shutter speed and ISO/ASA

I would like to get into film photography as a hobby, I own two 35mm film Cameras which both have broken TTL meters, they are common Fujica bodies and I would like to replace the (battery damaged) TTL ...
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 ...
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 ...
1answer
75 views

### Finding real life width and height knowing camera properties and distance to object [duplicate]

I'm trying to basically find the width and height of someone's face I know the following: distance from face to camera in mm the sensor height in mm the focal distance in mm distance in pixels ...
2answers
231 views

### DOF comparison between two lenses

Someone told me: To compare the amount of DOF of two lenses I just would need to calculate the size of the entrance pupil. The lens with the bigger entrance pupil has less DOF thus creates nicer ...
2answers
219 views

### How are wide angle lenses able to project an image onto a sensor?

The Nikon F-mount has a flange distance of 46.5mm. A 14mm lens for example has an horizontal angle of view of about 104°. How is a lens able to project an image from the rear element onto the sensor ...
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 ...
1answer
150 views

### Holga 120 WPC exposure times

I'm struggling to reconcile the recommended exposure times of a Holga 120 Wide Pinhole Camera as suggested by Holga, vs the values I am getting via an app like Pinhole Assist (or even when computing ...
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 ...
4answers
378 views

### Calculating the “35mm equivalent” circle of confusion/DoF

I'm gonna introduce my concrete example, but I'd like to know how do do this calculation in general. Say I have a middle-format camera with film height 58mm and a 90mm/3.5 lens. What is the equivalent ...
3answers
138 views

### Is the hyperfocal distance calculation outdated?

The hyperfocal distance H is calculated by H = (f^2)/(N*c)+f where f is the focal length, N the f-stop and c the circle of confusion limit. Lets assume we use a fullframe sensor. All those calculators ...
1answer
924 views

### How to estimate pixels per degree for an image from a camera phone using EXIF data?

This is my first time to look at metadata and I'm confused by the focal length stated in this file that a friend e-mailed to me. It was taken with a cell phone. I'm trying to roughly estimate the ...
2answers
175 views

### How to calculate the precision/resolution of a camera

I know there are other questions about this but I couldn't find the answer I was looking for... I am developing a control system using a camera and I need to know theoretically the precision/...
1answer
105 views

### What aperture to use to get the same DOF as in a panoramic image

When I take a panorama with a 80mm lens at F/2.0 on a fullframe body such that the resulting image has a equivalent field of view of a 50mm lens on the same body, what would then be the equivalent ...
1answer
84 views

### What's causing my camera to slow down AFTER the image was saved?

I tested my Nikon D800 with a SanDisk Ultra 64 GB 80 MB/s SD card. I have a device which measures time and is triggered by the green LED light on the back of my camera which indicates that it's ...
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,...
2answers
106 views

### Generate a sequence of exposure time options mathematically [duplicate]

Is there a way to generate a sequence of usual/standard exposure time options mathematically? Something like 1/5000, 1/2500, 1/1500, 1/1000...1/500, 1/250/ 1/125...1/60...1/30...1/8, 1/4, 1/2, 1, 2, 3,...
1answer
629 views

### How can i calculate the direction vector of a pixel? [closed]

So if you take a pinhole camera and make it as the origin of our plane(3D) and a pixel from the image plane and connect the two with a straight line it should make a vector, which has direction and a ...
6answers
260 views

### Can we prove that the object is not tilted from photo(s)?

This is an image of Al-Masjid an-Nabawi. Can we from this image, or from combination of images available online say with a certain degree of confidence (prove?) that this red circled minaret is ...
4answers
2k views

### How to correctly calculate the Dynamic Range of an image

I'm trying to compare the dynamic range of a correctly exposed LDR picture with the dynamic range of the HDR image obtained with 3 LDR pictures. Right now I'm calculating the DR as: stops = log2(...
2answers
577 views

### angle of view and distance from subject calculation for a smartphone

I would like to calculate the angle of view of a photo taken by a smartphone, in order and estimate the distance from a subject of a specific size. Let's do calculation for a Samsung S7, which has a ...
5answers
2k views

### Why doesn't the focus distance at which my lens has magnification 1 match the formula?

From the Magnification Wikipedia page, I have the following equality: M = di/do = f/(do – f) = (di – f)/f with M the magnification, f the focal length, do the distance from the subject to the lens,...
3answers
954 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 ...
3answers
879 views

### How to calculate the max size of an image based on the canvas size?

How to calculate the maximum height or width of an image based on the canvas size or poster card size? example: image size is as below: height: 3648, width: 5472, and poster card size: 150 * 100 (W*...
2answers
2k views

### Shutter Speed from the Exif ShutterSpeedValue

Extracting Exif data from my photo (using python) among the other values I have: 'ShutterSpeedValue': (8643856, 1000000), 'ApertureValue': (1695994, 1000000) After some research, I found that the ...
4answers
3k views

### How to calculate focal reducer crop factor for APS-C to MFT?

As far as I can tell, the crop factor determines the size of the projected image circle and should match the ratio of sensor diameters (with standard mount forward / backward distance). My ...
1answer
276 views

### How do I calculate how high a camera needs to be to fit an object in the frame based on its field of view?

I'm doing a computer vision application related to snooker for my dissertation. In a section of my report, I’m talking about cameras and it would be good if I’m able to do the calculation stated above....
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?
2answers
572 views

### What is the formula to calculate aperture (“diaphragme” in French)?

Let's say I have these data for my camera: t : Exposure time in seconds ("temps de pose" in French) C : Incident-light meter calibration constant ("constante lumière incidente" in French) S : ISO ...
1answer
443 views

### How to calculate the new focal length when usng a lens mount adapter

I'd like to know how to calculate the new focal length when using a lens adapter. Is there any formula? To be more specific: I need to attach my old lens (four third) to new micro four third system ...
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 ...
3answers
1k views

### Is it possible to calculate focal length of a picture taken with a zoom lens if you know the aperture?

I need focal length (for my IA homework), but I didn't know that in real world I would only get the aperture. Ok, my camera is an Olympus X-21, and manual says: Olympus lens: 6.3 to 18.9 mm, f/3.1 ...
3answers
244 views

### Does field of view change for different lens model for the same focal length?

I am using two lenses - Tamron 75-250mm F/3.8-4.5 Model 104A and AF-P DX NIKKOR 70-300mm. When shot with lenses set to 250mm of focal length, the field of view for the Tamron lens is greater than the ...
3answers
884 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), ...
4answers
7k views

### How to calculate the size of the image circle at infinity focus?

How can I determine the diameter of the image circle (i.e. the diagonal size of CCD required to fully utilise a telescope's optics) at near-infinity focus? I have looked around online and found this ...
2answers
3k views

### Calculate the distance of an object in a picture? [duplicate]

I'd like to know the distance between the camera and the object, just by looking at the object height (pixels) or it's width and the real life dimensions. Here is a formula we can get on the internet: ...
2answers
203 views

### How can the focal length for shake reduction be determined when the lens is mounted using a reverse lens adapter?

My camera (Sony A7RII) offers image stabilisation (SteadyShoot). I shoot macros using a 50mm and a 28mm Olympus lens reverse mounted with anadapter. What values should I enter in the menu to ...
3answers
836 views

### How to measure distance of exit pupil to sensor plane

Is there an experimental way to determine the distance of the sensor plane to the exit pupil? (acuracy a few milimeters with distances between 10-70 mm) Why I want this In my lab I am working with a ...
2answers
481 views

### How can I use a non-TTL lightmeter beyond its built-in ISO range?

Some introductory information first: I got into photography a few months ago and I have very basic knowledge on the matter so be patient - the answers may be obvious for you. The camera is Zenit 11 - ...
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 ...
1answer
470 views

### Estimating Distance From An Image [duplicate]

Assuming that the person stands parallel to a wall. The person and the wall are at the same ground level. The person takes a picture of the wall (Considering that the person always captures the bottom ...
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 ...
1answer
289 views

### How do extension tubes affect the image circle? [duplicate]

If you abuse your lens by just stacking a bunch of extension rings one on top of the other, will this start to affect your image circle? For instance, you have a lens that can just about cover your ...
1answer
119 views

### a general account on parameters of a camera; which are innate, which are derived, which can be processed later, etc [duplicate]

So we all know there are 3 golden parameters in camera: aperture, iso, shutter speed. I could sense those 3 parameters are innate, which means they are directly related to the mechanics of the camera, ...
3answers
2k views

### What is 'sensor height?'

The accepted answer to the question, How do I calculate the distance of an object in a photo?, refers to sensor height. What is sensor height and how do find/calculate it in this context? I'm using a ...
1answer
560 views

### How does blur radius change with distance from the point of focus at macro distances?

In a macro situation, is there a known function that maps the blur radius as a function of the physical distance from the plane of focus? I'd expect this function to give near zero (in pixels) at ...