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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120 views

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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135 views

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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80 views

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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169 views

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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3answers
547 views

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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152 views

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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1answer
160 views

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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186 views

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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460 views

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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1answer
76 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 ...
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434 views

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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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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274 views

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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138 views

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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4answers
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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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787 views

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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1answer
88 views

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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4answers
484 views

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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1answer
142 views

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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3answers
114 views

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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2answers
145 views

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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4answers
277 views

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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107 views

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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4answers
135 views

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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1answer
958 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 ...
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1answer
133 views

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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3answers
447 views

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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3answers
128 views

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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1answer
987 views

What focal length do I need to get the same field of view as an iPhone SE?

I have a FujiFilm camera (mirrorless crop) with a 35mm lens while iPhone SE has a 4mm lens. What focal length lens do I need for it to get the same field of view as on the iPhone SE?
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4answers
372 views

Bad photos (no focus). What are these photos called?

I'm creating an open Neural Network that could identify if the photo is blurred. This way I need to find many photos of objects at close range, and the focus should be upset. The same as you can see ...
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3answers
1k views

relationship between focal length, perspective projection and camera distance

This page here describes that the focal length does not result in perspective distortion, while this page here describes if you increase the focal length and camera distance to infinity then it ...
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2answers
78 views

Four-thirds (or any crop) sensor compared to full sensor camera: question about the meaning of “doubling the effective focus length.” [duplicate]

I can best ask this by setting up a situation: A friend and I are standing in the same place pointing our camera’s at, say, the same bird that is some distance away. I have a micro four-thirds crop ...
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1answer
376 views

Determining the CCD width of a camera [duplicate]

How can I determine the CCD (imaging area width) given image details such as focal length? I have images taken by cameras, but very little information about the cameras themselves (I have focal length ...
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4answers
292 views

Second lens after Nikon 16-80 mm: Nikon 50 mm f/1.8g or other? [closed]

I know that comparing lenses is a subjective and often futile effort, but I hope that if I convey my priorities and current understanding (as a relative beginner), I can still gain a lot of insight ...
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2answers
233 views

What's the best choice of lens from an optics surplus shop to get a Stanhope Lens-like magnifying function?

I am looking to do some experiments with my cellphone and a lens, holding the lens in contact with my cellphone lens. I'm looking for a lens that has the shortest back focal length length possible, so ...
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1answer
660 views

How can i calculate the direction vector of a pixel? [closed]

So if you take a pinhole camera and make it as the origin of our plane(3D) and a pixel from the image plane and connect the two with a straight line it should make a vector, which has direction and a ...
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3answers
270 views

Lens for 1/2“ sensors, installed on a 1/3” sensor

I want to install a lens built for sensors 1/x" (with 1 <= x <= 3), on a sensor 1/3". I need to have an horizontal field of view of "a cm", when my working distance is "b cm". What is the ...
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3answers
282 views

How to find out what part of image is less lens-distorted?

I'm developing an application which uses a Canon DSLR to sequentially shoot an object from different views. Often the object is too big to fit in frame so I have to make more than one series of photos....
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6answers
262 views

Can we prove that the object is not tilted from photo(s)?

This is an image of Al-Masjid an-Nabawi. Can we from this image, or from combination of images available online say with a certain degree of confidence (prove?) that this red circled minaret is ...
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1answer
46 views

Scripting s series of camera shooting with different aperture and focal length

Is there any software, app, or any way that I can script a series of photo shooting with Canon camera with different aperture and focal length? Something like Things I tried DSLR Controller App ...
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1answer
89 views

Ghosting artefacts in narrow DOF photographs

Snapping with a Canon EOS 600D in narrow DOF situations (for example with low f-stop numbers at long focal lenght), I get ghosting artefacts on the parts of the photograph which are out of focus. ...
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1answer
159 views

What lenses have the most human eyelike images [duplicate]

I have heard wide lenses make your head inflated which isnt good for portraits like the telephoto which deinflates your head. So If I use 35mm prime on full frame. Does it mean I will get perfect ...
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3answers
167 views

What lens would I need to photograph a very distant cathedral dome?

I want to be able to photograph the dome of St Paul's cathedral from King Henry's Mound in Richmond Park. Would a telephoto or zoom lens be the best, what focal length/zoom would be the best for ...
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6answers
2k views

How do I calculate the difference in lens reach between a superzoom compact and a DSLR zoom lens?

I know it's a beginner question, but I spent the last 3 days reading this forum and other resources on the Internet and I reached a breaking point. So decided to ask the question after all, as I ...
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3answers
1k views

Do medium format lenses have a crop factor?

When having a 50mm lens made for a APS-C camera its often the case that the lens has a focal length of 50mm on fullframe. However this means that you are getting something like a 75mm due to the crop ...
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1answer
54 views

Question on f-number and exposure [duplicate]

Is there any mathematical proof to show that the exposure in a camera is independent of the focal length used, if the f-number (ratio of focal length to lens diameter) remains constant?
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2answers
293 views

Relationship between f-number and amount of light being let into the lens system [duplicate]

Why does smaller f-number imply greater aperture diameter and consequently, greater amount of light entering the lens of a camera? As evidenced from my study across a number of resources, an absolute ...
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1answer
729 views

What's the real focal length for 18-55mm in my APS-C camera? [duplicate]

I want to buy a new lens (canon ef 50mm f/1.8 stm) that I know that the real focal length in my camera is around 80mm, but my question is if this happens in the same way whit my actual lens (18-55mm). ...

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