# Questions tagged [calculations]

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

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### 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 ...
5k 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?
4k views

### Is there a formula for calculating exposure when enlarging prints?

I'm curious if there is a formula to determine my exposure in the dark room. Suppose my print comes out perfectly with the following: 8 seconds f/11 height of 8 +3 contrast filter Is there a ...
1k views

### Calculate camera tilt angle from 2D image [closed]

I want to calculate the camera's tilt angle from a photograph, without knowing anything about the camera (or lens). Suppose I can extrapolate the vanishing points (one-point or two-point perspective): ...
246 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 ...
14k views

### How to calculate the real size of an object from two photos in different types of perspective, knowing the dimensions of one of the objects?

How to calculate the real size of an object from two photos in different types of perspective, knowing the dimensions of one of the objects in these pictures? When I was in college, we did such ...
183k 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 ...
1k views

### How to calculate the correct position for this inception style photo

I came across this post: How is this changing vertical perspective effect achieved? Let's say those pictures have been taken by a drone, how would you calculate the positions (latitude, longitude), ...
2k views

### Why do depth of field calculators show *more* DOF for larger formats with the same lens parameters?

I thought I had a pretty good seat of the pants understand of DOF. But I've been playing with DOF calculators and it's giving me results that don't line up with my practical experience, so I'm ...
8k views

### Calculate angle/field of view from 2D image

I want to calculate the angle of view (or field of view) from a photograph, without knowing anything about the camera (or lens). Please have a look at this example: It is assumed the angle between ...
4k views

### How do I calculate the “effective focal length” of a cropped photo?

Suppose I’ve taken a photo and then cropped it. If the crop is extreme enough then I might want to go back and take the same photo with a more telephoto lens so that I can take full advantage of my ...
1k views

### Is my distance/size math for macro photography correct?

I was comparing Panasonic lenses the other day, and I wanted to know about their macro capabilities. Obviously Panasonic lists the closest focusing distance, but this doesn't tell me much about the ...
2k views

### How do I calculate film ISO compensation for non–through-the-lens metering when using an ND filter?

I have a Yashica Electro 35 film rangefinder camera. I usually load some higher sensitivity film so I can easily take pictures indoors, but now in summer I ran into trouble shooting outside on several ...
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 20cm from my phone, what 's the DOF? When I ...
2k views

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

D = f*H/h where D = distance from lens to object (d = distance from lens to 35mm film) f = focal length H = height of object h = height of object's image on 35mm film I've seen some form of this ...
1k views

### How can I calculate sensor size (width and height) from focus length, vertical, and horizontal angle of view?

How to calculate sensor size (width/height) when knowing focus length, vertical & horizontal angle view (FOV)?
4k views

### 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 ...
194 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 ...
1k 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. ...
180 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 ...
1k 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 ...
6k 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 ...
13k 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-)....
1k 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 ...
18k 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 600mm focal length would appear on a camera's sensor. The ubiquitous formula object size in image = focal length *...
2k views

### 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?
1k views

### 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)?
597 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 ...
3k 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 ...
5k 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 ...
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: aperture ...
1k views

### 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 ...
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 (...
4k 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?
1k views

### 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 ...
292 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 ...
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 ...
631 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 ...
586 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 ...
5k 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 ...
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 ...
165 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 ...
95 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 ...
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 ...
579 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 ...
791 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 ...
125 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 ...
962 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 ...