Questions tagged [focal-length]

Focal length is the distance (measured in mm) between the surface of a lens and the focal point, when the lens is focussed at infinity. Smaller focal lengths indicate wide-angle lenses, larger focal lengths indicate a telephoto lens.

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What does pixel width mean in the context of calculating camera placement distance?

I am setting up cameras for an experiment filming animals. In a experimental protocol paper that I'm following, it states that: Based on a pinhole camera model, the bound x_min on the pixel span of ...
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Equivalent lens to periscope camera?

I am trying to figure out an equivalent telephoto lens to the newer periscope cameras that report focal lengths in 35 mm equivalents. There are some similar threads such as How do I convert lens focal ...
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Are most (if not all) lenses' focal length described as the 35mm equivalent? [duplicate]

2 thoughts made me ask this question: Different lens looks different on the different-sized sensor and has a different 35mm equivalent Many normal and wide-angle lenses' optical center is not ...
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What does the focal length of a fisheye lens mean?

Say an ordinary lens, Sigma 30mm f1.4 for example, is designed for APS-C and thus produces images that have a 35mm-equivalence of 48mm. But what about the fisheye lens? From Wikipedia, it is said that ...
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How to calculate extension tube length when the focal length is unknown

A 16mm objective has a minimum focus distance of 1m. When an extension tube is used to decrease the minimum distance to 0.1m, how long is this extension tube? If b_1 is the distance between the lens ...
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Capturing License Plates From 50-100 ft (And Night)?

I'm attempting to build something with a Raspberry Pi that can hopefully capture moving vehicle's license plates 50-100 ft away (and at night). I understand very little about photography, but through ...
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Focal length, zoom-x, magnification, and their relationship to image size projected on sensor

I have been doing remedial research on zoom and magnification. Here are some of my conclusions ("sensor" here assumes a digital camera): The zoom-x number of a zoom lens is the maximum ...
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Is it possible to calculate field of view and aperture given focal length, k1 and k2?

I have some data coming from an API that looks like this: "camera_parameters": [0.785028, 0.032519, -0.053622] and the data structure that I would like to obtain should look something like ...
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Does the focal length on cropped lenses include a crop factor? [duplicate]

I'd like to be certain about the focal length written on the cropped lenses, e.g. I have a Sony NEX-5N with the original OSS 18-55mm kit lens. Is it actually an 18 to 55mm focal length with no "...
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Does focal length correlate to the required ND filter in sun photography?

I got my hands on an M42 500mm lens and want to try sun photography. I also have a 2x and a 3x converter, thus I'm able to get a focal length range of 500-3000mm. Back in the day I bought a Baader ...
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What is the relation between aperture number and exposure, keeping all other parameters fixed?

My language is German, so forgive my lack in English words, especially with regard to photography. I tried to understand at a very basic level the relation between aperture number and exposure and ...
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Motion tracking/VFX: How to get needed info for iPhone camera?

Basically, I want to do VFX with my iPhone SE 2nd Generation front-facing camera. The software being used is Blender up-to-date. I'm not sure what to set Blender for in the track camera settings field,...
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Distance marking on a lens - flange distance or film plane?

Some lenses have distance/ hyperfocal markings - is that with reference to the flange (outer mount point of the lens where it meets the camera body) or the film/sensor plane?
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Can I use a 127.5mm focal length on a crop camera to see what the view would be like using an 85mm full frame lens?

I have a Nikon D7500 which is a DX format camera. I am thinking of getting a Nikon 85mm lens but I only see one that is in FX format. I have a 70-300 lens in DX format and was wondering if I set the ...
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APS-C + speedbooster vs full frame

I own a Nikon in DX-format (Nikon name for APS-C sensor, crop factor ~1.5) and I'm considering buying a 50mm prime lens soon for it. (To be complete, my camera is a D5200, although I don't think the ...
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Is maximum focal length of P1000 similar to 300mm kit lens provided with APS-C cameras?

Is maximum focal length of P1000 similar to 300mm kit lens provided with APS-C cameras? Either in terms of 35mm or 1/2.3(sensor size found in P1000) format.
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How can I get more magnification when shooting wading birds?

I have a Canon EF 70-300mm 1:4-5.6 IS USM lens. Will all 300mm zoom/telephoto lenses give the same magnification of the subject as mine does or, to get more magnification do I need to get a zoom or ...
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3 answers
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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 ...
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1 answer
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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 ...
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2 votes
1 answer
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matching field of view between apsc and full frame

I'm sure this is a dumb question. I'm upgrading from a sony a6 aps-c to a sony a7Rii full frame and trying to determine which focal length of FE primes I want. I'm using my aps-c a6 as a reference to ...
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Focal length for a specific distance?

I have the following information: s: Image sensors dimensions: 6.00mm, 4.80mm, 3.60mm (diagonal, horizontal, and vertical) f: focal length range: 5.1mm - 51mm f = (s * WD / FOV), where WD is the ...
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How can I calculate a camera sensor's width and height?

I'm trying to compute the focal length for different field of views of a camera. Therefore I need the sensor size horizontally and vertically, but in the datasheet I only have the following ...
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Photogrammetry - use nodal point or entrance pupil for distance calculation? [closed]

I'm trying to accurately measure the size of objects via photogrammetry. The objects are 1 to 2 feet from the front of the camera lens, so where I start measuring from makes a difference. I think the ...
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2 votes
3 answers
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focal length to aperture relation while zooming - is my russian lens lying to me?

I have this old soviet/russian "Granit" 80-200mm lens, connected to my Canon 550d DSLR through M42 adapter. I also have "modern" kit 18-55mm lens. What I don't get is how aperture ...
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Photography tricks for widening objects or reducing narrowness?

I have a narrow face and feel this may negatively affect my streaming captures, especially with poor quality cameras, low lenses, poor sensors, etc. Are there any givens in getting a robust, wider-...
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3 votes
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Would an MFT to EF speedbooster on an MFT camera help me photograph and record backyard wildlife?

Upon learning that an Olympus 12-200mm with a 16.6x zoom will not be produce an equivalent or better zoom range as a Canon 70-300mm (see my previous question), I now pose the question: Would it make ...
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2 votes
1 answer
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Why does my Nikon DX AF-S Nikkor 55-200mm seem to be more zoomed in at 200mm than my AF-S Nikkor 18-200mm? [duplicate]

Looking for some input experience here. I have a Nikon D3300 and the following lenses: 18-55 VR kit 55-200 VR 18-200 VR 35mm fixed I primarily use the 18-200 lens out of convenience but was doing ...
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Actual Focal Length of the Tamron 70-300mm f/4-5.6 lens for Sony a7iii [duplicate]

I have a Sony RX10 iv and now realize that the 600mm lens is actually just 220mm. I am looking at the Tamron 70-300mm lens for my Sony a7iii and wondering if the Tamron shoots a full 300mm.
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Can a ratio/function be created to calculate focal length vs size-in-frame if I have two focal length shots from the same sensor and position?

I am trying to figure out what focal length lens I would need to get a specific object to completely fill the image from a camera. Assuming I have two RAW files from the same camera body, shot from ...
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3 answers
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Physics/Optics vs Photography definition of focal length

I've been searching for some confirmation regarding the difference in DEFINITION of Focal length between: Physics/Optics(Which in the simplest case uses a classical thin lens to define the focal ...
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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 ...
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1 vote
3 answers
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Comparing images of full frame against APS-C at same (large) focal length

About me As an enthusiast photographer, I am currently working with a Canon 80D with the following lenses: Canon EF-S 15-85 mm f3.5-5.6 IS USM Canon EF 70-300 mm f4-5.6L IS USM Only a small fraction ...
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How does having a large diameter make the SEL85F1.4 a premium lens?

I have been reading about Focal length and Fast lenses when I came across this lens which has 85mm focal length and F1.4 as FStop. https://www.sony.co.in/electronics/camera-lenses/sel85f14gm Generally ...
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4 answers
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Seeming contradiction on wikipedia about rear nodal points and how the principal plane is related to focal length

There are two lines on the wikipedia pages for "cardinal points" and "focal length" that seem to contradict each other, and I would be extremely grateful if someone could explain ...
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2 answers
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Telephoto lens for a cropped sensor

I have a nikon 3500 as my first camera, and I am starting to buy some lenses for basically travel and landscape photography. I bought so far a tokina 11-20 f2.8 DX to have a wide angle lenses, and now ...
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Computing the Focal Length

I have a course problem that asks to calculate the focal length of a camera with the following specifications: Field of view along the horizontal axis (X): 60 deg. Field of view along the vertical ...
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4 answers
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Is the focus point a variable or absolute size?

In illustrations of the focus point of a sense, it looks to me to be infinitely small and as a result the resulting convergence of light would not yield an image. If the focus point is NOT infinitely ...
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7 votes
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focal length and sensor width of a phone

I am trying some 3D scene reconstruction in blender using my phone camera but in order for the program to do its math it needs to know the sensor width and focal length of my camera in millimeters but ...
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Calculation of the heigth of the camera

I am trying to find the height of a drone using the camera only. I can calculate the distance of the object top and bottom. Object is a square platform with width=0.2m. I used the equation provided by ...
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Does reducing the focal-length using a telecompressor on a lens increase the image quality?

I am hoping that by adding a telecompressor, I will be able to reduce the focal length, thus increasing the image resolution/quality captured by the camera. 1) Is it correct to assume that by using ...
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What are the focal lengths required for aerial photography in alt range 400-1200m?

first i am new in the field: If i have a UAV fly in alt range between 400-1200m, and i want to capture photos like Google Satellite maps, and specifically i want the photos to have the same (or close ...
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Différence between a long lens design and a telephoto

I was looking at the Leitz Hektor and Ken Rockwell says "This is a conventional long lens design, not a telephoto. Its diaphragm sits right at 135mm from the image plane. The Nikkor lens shown ...
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2 votes
2 answers
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Would a Canon EF 800 f/5.6 with a 2x extender on a Raspberry Pi camera work? (9024mm focal length, f/90.24)

The new raspberry pi high quality camera has a sensor size of 1/2.3", with a C-mount. If I attach a C-mount to Canon EF lens adapter, then a 2x extender, then the Canon EF 800mm f/5.6 L IS USM, from ...
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4 answers
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Apparent size of subject in two different cameras with the same resolution and focal length (or FOV)

Consider two cameras with the same resolution (let's say 640x480) and focal length (or FOV) looking at the same subject. Let's assume that the subject is in focus in both cameras. Will the image of ...
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MFD equals 4x focal length? But published specs contradict that

I spent the better part of this evening perusing the series of equations behind this popular magnification calculator. Equation F10 states d ≥ 4f, where d is focus distance and f is focal length. I ...
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Help with flatness and compression understanding

Hello I am trying to understand the technical parameters needed to achieve this flat look. What I understand is that higher focal length affects your image because you have to move further away from ...
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8 votes
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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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Given the provided Image taken at 50mm, what focal length would I need to get the 80% fo the rabbit to fill the frame?

Given the provided Image taken at 50mm, what focal length would I need to get the 80% fo the rabbit to fill the frame?
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3 answers
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My 50mm lens isn’t focally fixed anymore?

I’m relatively new to photography and had recently purchased a Canon Rebel T7i. I had also purchased the Canon 50mm 1.8 lens to have at my disposal. When I first used the lens it was very “zoomed in” ...
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4 votes
3 answers
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What does normal focal length really mean?

First off, I wanna say that I have a qualification in photo-/videography and of course I do know the principles of normal focal length, how the angle of view relates with the focal length and sensor/...
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