# Questions tagged [calculations]

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

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### 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 ...
41 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....
1 vote
52 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 ...
1 vote
108 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 ...
219 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 ...
6k 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?
1 vote
2k views

### How do I calculate the depth of field of cameras on mobile phones with auto focus?

I just hope to learn the relationship between depth of field (DOF) with the distance on my mobile phone. When I capture one cup with the distance about 20 cm from my phone, what 's the DoF? When I ...
2k 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 $$\text{angle of view} = 2\arctan \left({d\over2f}\right)$$ where $f$ is the lens's focal ...
4k 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 ...
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 ...
294 views

604 views

### How to understand the definition of dynamic range?

From "The ISO Definition of the Dynamic Range of a Digital Still Camera", I have the following formula: $$\mathrm{DR} = \frac{1.4L_\mathrm{sat}G_\mathrm{i}}{N_\mathrm{D}}$$ where \\$\...
24k 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 ...
2k views

### Why does EV increase as ISO increases?

From what I understand, the lower the EV value, the more exposed (bright) the image is. EV decreases as aperture decreases. More light gets in with lower apertures. EV decreases as shutter speed ...
1 vote
14k views

### How to calculate the Horizontal and Vertical FOV (in mm)

I am having some trouble finding a standard way to calculate the horizontal and vertical field of view of an image based on a set of initial input parameters. I do have values for the following ...
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,...
1 vote
964 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 ...
676 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 ...
46 views

### 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 ...
746 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/...
810 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. ...
192k 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 ...
2k views

212k 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 ...
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
131 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 ...
15k 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 ...
1k 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 ...
91 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 ...
731 views

### 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) ...
386 views

### Pixels per inch relation

I have a Nikon DSLR D5500 and a 18-55mm lens and a 50 mm lens. I was calibrating the camera to get the pixels per inch using each of the lenses and all other factors like the distance from the object ...
25k 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 ...
537 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 ...
569 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 ...
300 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 ...
1 vote
683 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 ...
1 vote
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, as shown in the figure below: My ...
8k 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 ...
534 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
60 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 ...
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
388 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 ...
244 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 ...
43k 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 ...