Questions tagged [calculations]

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

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1answer
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Calculate the distance of an object in a photo Android [duplicate]

https://photo.stackexchange.com/a/12437/61513 here is a formula for calculating distance if we know the size of the object. Can I use this method for photos/frames made by Android cameras? And if I ...
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6answers
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Is there a formula to calculate DOF?

I am pretty clear about that DOF depends on: Focal length Aperture Distance from subject Sensor size and more (as pointed in the comment). But what is the question here is: Is there any formula that ...
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3answers
183 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 ...
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3answers
978 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. ...
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1answer
132 views

Performing pixel- and channelwise division in PhotoShop

Every negative has certain base color, i.e. the color of unexposed areas. I want to know how to fraction this number out of my scans. In pure math, this is nothing particularly strange, I assume ...
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2answers
980 views

How can I estimate the magnification factor for a camera?

I am trying to estimate the magnification factor of a camera for research purposes and I am running into a few issues. It would be great if someone could help me understand what's going on here. I ...
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1answer
5k views

What's the difference between S LOG and V LOG [closed]

I know what logarithms are, what shooting RAW is, and how storing images logarithmically increases details in shadows. But what's the difference between "S log" and "V log"? I've also seen mention ...
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1answer
11k views

calculating aperture and shutter speed inversion [duplicate]

I'm taking a manual photography class, using my canon rebel t5. Any tips on how to calculate aperture and shutter speeds easily? (I know they have to be inverted). After I meter my photo (set at -0-)....
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2answers
997 views

Estimate object size [duplicate]

If I have a [digital] photograph of an object, can I estimate it's approximate size? I notice with interest that my camera (Nikon D3300) seems to record the approximate focal length of the lens in ...
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5answers
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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 *...
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2answers
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What is the power output from two speedlites combined?

When you have two speedlites in a softbox firing at the same time, let's say at 1/64 power, what is the total power output?
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1answer
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How do I calculate the coordinates for secondary colors on a CIE chromacity diagram?

Imagine a typical device gamut on CIE xy diagram: x and y coordinates for primary colors (red, green and blue) is defined and known, how to calculate secondary colors (cyan, magenta and yellow)?
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1answer
576 views

Calculating exposure when using ND Filter during/after the sunset or sunrise

It is very simple to calculate the exposure time when using ND Filters when the light is constant. Long exposures captured during changing lighting conditions make it much more difficult to calculate ...
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3answers
2k views

More megapixels to compensate for small zoom (Or: How good is Sony's Smart Zoom?)

Short version of my question: How can I compare cameras with different optical zooms and different megapixels (more megapixels can allow cropping for a fake zoom effect) in order to tell which camera ...
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3answers
3k 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 ...
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2answers
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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: aperture ...
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3answers
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How can I automatically get a (approximate) Lux value from overexposed and underexposed pictures?

As you will soon understand, I am not a photographer. For research in a completely different field, I am interested in estimating, even with a large approximation, the brightness of the environment in ...
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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 (...
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3answers
3k views

How do I get the right size image for a specific small photo frame?

I have a picture frame that is 2 1/2 x 3 1/2 inches. I would like to know what kind of dimensions, in pixels, I should use with my Nikon D3300 to make a photo for the frame?
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3answers
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Difference between focal point and distance away from object? [duplicate]

I have a macro lens for the camera on my phone. I want to calculate the magnification of the lens because the one i purchased does not state it. I've found this guide which states the mathematical ...
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3answers
272 views

Can I increase 35mm-equivalent focal length with both the crop factor and an extender?

I have a Canon EOS 7D Mark II (1.6x crop factor), and I have a Canon EF 100-400 IS USM. Working with just 400mm for the purposes of this question, my understanding is that my 35mm-equivalent focal ...
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4answers
2k views

White balance math for white, black, and grey color cards

This question got me very close to my answer, but I'm looking for more precision: What is the math behind white-balance, and how to choose it? I have an image with white, grey, and black color cards ...
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2answers
542 views

When to use the LV formula?

EV = log2(f^2/T) LV = EV + log2(ISO/100) Question is to those that this is already clear. It is not a math question, it is a photography question about using Light Value. My puzzlement is "what ...
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1answer
508 views

How can I tell what focal length a zoom lens was set to for a photo of the moon?

It appears that neither the Sony 55-210 mm f/4.5-6.3 nor the Canon EF-S 55–250mm f/4–5.6 reports the actual focal length to the camera: both cameras' metadata show the lens but report the focal length ...
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3answers
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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 ...
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2answers
5k views

How to automatically measure subject dimensions (width/height/distance) without physically measuring?

What methods are used for automatically measuring the dimensions (width/height/distance/etc.) of a subject without having to get in there with a measuring tape? I am just starting to get into ...
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1answer
159 views

How do I interpret flashlight specs for light painting at a distance?

Context So I've seen light painting shots and I'd like to try it out sometime. I'm more interested in painting say parts of the landscape so they stand out during a long exposure. Question Is there ...
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1answer
88 views

Proper method to measure the magnification of a reversed lens [duplicate]

I have a 50mm prime lens and a 18-55mm standard lens at my disposal. How do I measure the magnification of a reversed lens when used with a reverse mount. What are the factors that come into play to ...
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3answers
2k views

Which SS/F-stop table is the correct one?

While reading a book that was recognized as a good one by many readers, I found the following table: This means that any of these settings would each result in the same amount of light hitting the ...
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3answers
449 views

Why does my camera give a very different reading from my lightmeter?

I'm new to digital photography. I start shooting in aperture priority mode, unless some situation require some shutter speed attention. Both ISO and SS is calculated by camera. I am looking at some ...
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2answers
655 views

Can I use my camera to measure lens light transmission?

I want to compare and quantify the light transmission of various lenses (with some custom modifiers). So I have a target setup with constant illumination, and a camera body for them ready to shoot ...
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1answer
121 views

How can I determine the distance to a subject in a old photo with little other information?

My question is similar to this one, but I don't know how accurate the formula will work with old photos. If I assume that the runners would be 1m80 (5'11"), would it possible to estimate how far ...
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2answers
902 views

How do you calculate the focal multiplier of a non-full frame camera?

I'm currently using a Sony RX100 Mark 3 camera and want to buy a Canon 6D + 24-105 F4 L lens from an online retailer, which is not in my country. (before continuing I'd like to state that there are ...
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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 ...
2
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1answer
96 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/...
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1answer
15k 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 ...
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1answer
73 views

Choosing lens for a studio to record classes [duplicate]

I'm building a home studio to record Math classes: I have a blackboard (1,90m width by 1,20m height) and the distance from the camera to the blackboard would be around 1,80m (on a tripod, 1,70m from ...
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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 ...
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1answer
299 views

Where can I find photos taken by a calibrated camera to make a 360° panorama? [closed]

I am trying to write up an automatic 360° panorama stitching program for my final project, in order to do so, I need to accomplish four steps: Find the horizontal and vertical field of view for a ...
2
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2answers
368 views

Can I calculate my phone's sensor size from f-stop, focal length, max aperture, or other metadata? [duplicate]

Could I work out sensor size of my phone from these info: F-stop= f/2.6 , focal length = 3mm, max aperture = 2.8 and others info like: resolution unit, exposure time?
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1answer
374 views

Mathematical relation between aperture and DOF [duplicate]

I know that aperture and DOF are inversely proportional. But, can anybody explain to me the Physics/Optics behind that? What's the mathematical relation that relates aperture with DOF?
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1answer
175 views

How do I calculate the total exposure value of two light sources?

Assume that I'm taking the photo of a lamp in an outdoor cloudy day. The lamp itself has the luminance corresponding to 17EV. The environment has the illuminance corresponding to 14EV. What will be ...
4
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1answer
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 ...
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1answer
82 views

Should addition of RGB values be used when adding lens flare to an image?

From the physical theory of lens flare, it is the image of the light source after many times of light reflection between the optical lens surfaces. So it would sound reasonable to add lens flare ...
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2answers
18k 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 ...
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2answers
31k 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,...
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3answers
4k 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?
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1answer
158 views

How do I measure the distance from an object to fit it in the screen? [duplicate]

I'm curious if there is any math formula for this. Let's take a close-up of a human face for instance, given the human face is about 20cm/8 inches, how do I choose the right focal length and from ...
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2answers
530 views

How to accurately calculate size in image using relations and a reference

OK so the relation math is easy enough. If you know the size of an object, say a 12" ruler in the image, and you put the ruler flat against another object like a door. You take a picture of the door ...
2
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3answers
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 ...