Questions tagged [calculations]

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

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2 answers
42 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 ...
0 votes
1 answer
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
2 answers
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
2 answers
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 ...
0 votes
1 answer
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 ...
4 votes
2 answers
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
1 answer
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 ...
0 votes
3 answers
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 ...
5 votes
3 answers
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 ...
6 votes
1 answer
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 ...
0 votes
1 answer
294 views

How to obtain a subject's measurement from image [duplicate]

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]\...
3 votes
3 answers
18k views

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?...
7 votes
3 answers
6k 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 ...
0 votes
2 answers
2k views

How do I correctly convert from aperture diameter into f-stops?

I'd like to know whether it's possible to convert the radius of the focal point into f-stops properly. The following equation illustrates that the diameter is dependent on the f-stop: $$ \text{...
2 votes
1 answer
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 \$\...
6 votes
7 answers
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 ...
3 votes
3 answers
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
2 answers
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 ...
25 votes
9 answers
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
3 answers
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 ...
0 votes
2 answers
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 ...
0 votes
1 answer
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 ...
2 votes
1 answer
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/...
4 votes
4 answers
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. ...
54 votes
7 answers
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 ...
2 votes
2 answers
2k views

I'm hoping to prove this distance to camera equation:

$$ D = \frac{f\times H}{h} $$ where $$ \begin{align} D &= \textrm{distance from lens to object} \\ (d &= \textrm{distance from lens to 35mm film}) \\ f &= \textrm{focal length} \\ H &= ...
4 votes
5 answers
20k 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 600 mm focal length would appear on a camera's sensor. The ubiquitous formula $$ \textrm{object size in image} = \...
47 votes
5 answers
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
2 answers
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
3 answers
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 ...
14 votes
3 answers
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 ...
0 votes
2 answers
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 ...
-2 votes
1 answer
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 ...
0 votes
3 answers
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) ...
-2 votes
1 answer
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 ...
8 votes
3 answers
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 ...
2 votes
3 answers
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 ...
3 votes
1 answer
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 ...
2 votes
3 answers
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
2 answers
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
2 answers
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 ...
7 votes
5 answers
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 ...
0 votes
1 answer
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
0 answers
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 ...
0 votes
1 answer
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
2 answers
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 ...
0 votes
2 answers
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 ...
20 votes
6 answers
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 ...
18 votes
5 answers
66k 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 ...
9 votes
1 answer
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 ...