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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187 views

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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245 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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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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83 views

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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743 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
81 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
436 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
134 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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96 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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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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244 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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103 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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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
770 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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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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115 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
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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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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
944 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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77 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
236 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
227 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
201 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
344 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
199 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
230 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
225 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
44 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
73 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
90 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
148 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
53 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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177 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
292 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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1answer
136 views

How do I estimate PPI from camera specifications? [closed]

I have an HDL-20D digital camera with 1000TVL horizontal resolution, S/N ratio 54dB and 2200k-pixel 2/3-inch 2x IT-CCD and these are the specifications: How do I calculate PPI from these details? ...
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1answer
358 views

How to calculate Sensor Pixel Pitch?

I need to compute the “Sensor Pixel Pitch (in mm/px)” for some calculation. I have the following data available from the manufacturer: Resolution: 1920x1200 Sensor Type: 2/3” CMOS Pixel size: 4.8 x ...
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2answers
185 views

Would adding an external lens allow one area outside the focal plane to be in focus?

I’m doing high speed scientific imaging. I have a camera mounted in a fixed location with a Micro Nikkor 105mm lens. It’s viewing a fixed subject that has a small mirror oriented 45 degrees underneath ...
2
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1answer
64 views

Can Tamron Tap-in Console solve focal length problems in metadata?

I recently found some issues on my Tamron 24-70mm f2.8 G2 (A032) lens for Canon. The first issue is about the focal length in the EXIF data. While the lens works well in autofocusing, I found the ...
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1answer
123 views

How did they do this beauty setup? What lights and focal length? Help me recreate this

From examination the lighting source appears to be 2 fluorescent panels and a light ring. How many lux/lumens/watts is he using? What's the focal length for the field of view is he using? (35mm ...
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2answers
374 views

Effect of increasing sensor size or focal length on resolution of target object

Suppose I have a camera of sensor size 8mmx8mm, optical class (2/3)" with a compatible lens of also (2/3)". The focal length of my lens is fixed (say 8mm), and the distance to my target object is also ...
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3answers
267 views

Why does Lightroom show the focal length of the Sony RX10 IV as 220mm, when it's marketed as 600mm?

I have a Sony RX 10 IV. I used maximum zoom, 600mm, but when editing in Lightroom in the details it gives the focal length of 220mm. Can anyone explain, please?
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3answers
132 views

What lens do I need on a P&S camera for photographing faces?

I'm just someone who enjoys photography, but I'm not a photographer. I don't know a lot, so please try and keep things simple. I've been using a Fujifilm Finepix S9200, a bridge camera with a 24-...
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1answer
217 views

How do I calculate how high a camera needs to be to fit an object in the frame based on its field of view?

I'm doing a computer vision application related to snooker for my dissertation. In a section of my report, I’m talking about cameras and it would be good if I’m able to do the calculation stated above....
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5answers
250 views

Is 35mm on a cropped sensor good for fashion photography?

I am quite amateur with a camera but I want to become good in fashion photography. A top model has agreed for a photo-shoot for free and in return she wants me to make a portfolio. We are planning to ...
2
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1answer
116 views

Is there theoretical limit on the minimal focal length for a given sensor size?

There seems to be a limit, around 0.33, on the fastest possible aperture. Is there a theoretical limit on how wide a non-fisheye lens can be? That is, what is the minimal possible focal lens for a ...
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5answers
404 views

Does amount of background blur change with focal length given equal framing?

Let's assume I have two lenses, 50mm f/1.8 and 85mm f/1.8. I want to fill the frame with the photographed object. Now, if the object is 50cm wide, I need to take the photograph at a distance of 1.112 ...

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