# Questions tagged [calculations]

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

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1 vote
86 views

### For a lens with multiple elements, does the nodal points coincide with the principal points?

(Please note by "nodal point" I am referring to the cardinal points and am by no means referring to the kind of nodal point commonly seen in tilt-shift discussions) The (object) principal ...
• 551
86 views

### How can I calculate the focal length, sensor size, and resolution for a machine vision camera given angle and field of view and working distance?

I´m looking for a high-image quality machine vision camera with suitable lenses. The specifications are a working distance of 600 mm, a Field of view of the smallest side of the sensor is 400 mm (...
1 vote
187 views

### How to calculate average gamma from gray scale?

I need to calculate average gamma from 9-step grayscale. I have a grayscale measurement export from HCFR. I can calculate gamma for every gray step like this: Row A is the grayscale measurement ...
• 141
69 views

### Calculating FOV for mismatched lens/sensor size

I have this 50mm lens that gives the FOV for a 2/3" sensor in its spec sheet: Diagonal: 12.6° Horizontal: 10.1° Vertical: 7.6° I have this camera, which, according to its spec sheet, has a 1/2....
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1 vote
58 views

### 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 ...
• 141
275 views

### How can I measure the flicker frequency of a light source with my phone?

I have a Hue light and want to measure the flicker frequency (due to the PWM) without buying an expensive photometer. Is it possible, to calculate it with such an Image, by counting the bars from the ...
• 155
1 vote
239 views

### How do I determine distance to an object when I know the object's size and the camera's angle of view?

I'm trying to find the distance of an object, where the original size of the object is known. Unfortunately, I cannot seem to find either focal length or sensor size online, but I know that the camera ...
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### DOF formula vs the simplified DOF formula

I was calculating the theoretical difference in the change of the DOF (depth of field), between a frame achieved on a 25mm signature prime and an "identical frame" achieved by using a 75mm ...
• 343
1 vote
3k views

### Calculating the size of an object from a single image, given the distance from the camera

I was looking at other questions on here and I'm pretty sure it's not a duplicate so here it goes. I'm working on a problem where I need to calculate the size of a particular object in an image. The ...
1 vote
147 views

### How does an afocal lens produce an image on a screen?

I'm really confused about it. If such a lens is necessarily focused at infinity and does not have a plan of focus, then, does it mean it can produce a clear picture on a screen, no matter how close it ...
2k views

### How to count the amount of pixels an object in a photograph takes up

I have been trying to find out the distance of an of object from an image using this calculator https://www.scantips.com/lights/subjectdistance.html But I need to know how many pixels long the object ...
102 views

### Step-by-step description of the preparations, gear, apps, settings, ... needed to take image of a plane before the moon

I recently saw the following photograph on Facebook by ePixel Aerospace: with the following caption: Mission accomplished! Just about a year ago, I was commissioned to capture a special Qantas/Lunar ...
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### How to calculate the Aperture and Focal length needed for depth of field

I have a virtual camera in a game engine. The camera has an DOF setting where you can set the : Distance to object Aperture Focal length I would like to set a depth of field (lets say about 5m) ...
638 views

### How to determine via a math formula when a lens is wide angle or macro

Lets say I have a device with 3 separate lenses. One will be the main reference lens, and then the two others may be a wide angle lens or a macro lens, or also even a replica of the main reference ...
• 121
628 views

### Is x50 zoom camera able to zoom 500 meter target area from a 6 km distance?

I have a x50 zoom camera and here is some specs of the camera and lens: Focal length: 6 mm ~ 300 mm Field of view: 58.4° ~ 1.4° Resolution: 2 MP I drew a scheme to explain my question properly, you ...
696 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 ...
1 vote
71 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 ...
868 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. ...
• 207
1k 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 ...
1 vote
400 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 ...
• 1,633
249 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 ...
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1 vote
760 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 ...
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1 vote
994 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 ...
• 123
1k 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's depth of field article, as ...
2k 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 ...
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861 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/...
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1 vote
127 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 ...
• 1,633
136 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 ...
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320 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 ...
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131 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,...
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1k 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 ...
1 vote
354 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 ...
• 263
6k 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: ...
• 127
2k 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 ...
• 133
5k 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) ...
• 203
521 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....
906 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 ...
• 241
677 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 ...
• 109
369 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 ...
• 219
4k 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 ...
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1 vote
4k 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: ...
1 vote
242 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 ...
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1 vote
536 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 - ...
444 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 ...
131 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, ...
4k 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 ...
1 vote
685 views

### What does the value of 'exit pupil' represent on a lens datasheet?

On this datasheet of the Kowa LM25HC lens I have access to, there is a number called exit pupil, which equals -57.9 mm. What does this number represent? This is not a question about what the exit ...
949 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 ...
1 vote
10k views

### How to calculate stops of light lost from a teleconverter?

How would I be able to take the multiplication value of a teleconverter (1.7, 1.4, 2, etc) and find out how many stops of light are lost when using it just based on that number?
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