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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177 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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What software can show my most frequently used focal length?

Many people recommend a focal length of 35mm, 50mm, and sometimes even 85mm and upwards for those interested in purchasing a prime lens. I, however, would like to figure out what focal length(s) I use ...
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1answer
295 views

How to overlay the image scaling based on the user distance & focal length

I'm overlaying images on the cameraView and based on the user input of room width & height. The images are displaying proportionally to width & height ratio. but i need to overlay the images ...
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246 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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98 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
84 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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750 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
82 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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1answer
411 views

Will primes become rarer in the 24-70mm range for DSLRs like they did for the 70-200mm?

The trinity 14-24mm, 24-70mm and 70-200mm zooms are lens that professionals rely upon for the convenience of a zoom but a good quality similar to a prime. A lot of development has gone into these as ...
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442 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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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
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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99 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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246 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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2answers
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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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4answers
102 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
788 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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441 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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2answers
524 views

At which focal lengths is it ‘safe’ to have the sun in frame?

I've seen both beautiful wide angle pictures that include the sun as well as camera damage from pointing long lenses at the sun. At which focal lengths is it safe to have the sun in frame? assuming ...
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3answers
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
736 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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What is focal length and how does it affect my photos?

What is focal-length? Are focal-length and zoom synonymous? How does the focal length of a photo affect it? Are there common uses for different focal lengths, and how can I decide what to use when?
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317 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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2answers
409 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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1k views

50mm mirror lens. Does one exist?

I like the bokeh and limitations of mirror lenses. I however, also love my 50mm 1.4. Does a 50mm mirror lens exist? I searched but could not find one. If not 50mm what is the closest to 50mm one can ...
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3answers
978 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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1k views

How does focal length change perspective? [duplicate]

@MichaelClark answered a question I posted about zoom using focal length (emphasis added): You are correct that a focal length twice as long (2X zoom) as the original one will make objects appear ...
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9answers
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How can I explain focal length to someone who isn't into photography?

Context So my friends and family are curious about how far my lens can reach. I usually explain with focal length and show them a few pictures. Question Is there any easier way to explain what ...
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6answers
15k views

What do the mm numbers on lenses mean?

I'm confused about lenses and numbers. Why are some lenses ex. 50mm-300mm Different sizes? Some lenses with the same mm numbers are huge and some are small... What's the difference? Also the prices ...
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2answers
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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3answers
3k views

Do convex lenses make parallel light rays of different wavelength converge to different points?

I'm starting to study cameras and lenses. By reading explanations and watching videos on convex lenses, I learnt that they make parallel light rays converge to a single point called the focal point. ...
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1answer
246 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
235 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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5answers
441 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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1answer
382 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
3k views

Which EXIF tag to set for the 35mm equivalent focal length?

For a manual lens (*Rokinon 8mm f/3.5 Fisheye) I want to add the focal length information to the EXIF metadata in the resulting pictures with exiftool. I use the lens on a Canon 60D body. Obviously I ...
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3answers
211 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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4answers
2k views

Do lens hoods need to be matched to focal length?

Is it true that not all generic lens hoods work on all lenses (provided the filter diameter matches, of course)? I read that the focal length plays a role in it - but I cannot find such readings on ...
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3answers
238 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
229 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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What is the relationship between field of view and focal length for fisheye?

What is the relationship between the focal length and field of view for an equal-area ("equisolid") projection fisheye lens? Alternatively, what is the relationship between the 180-degree image ...
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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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3answers
290 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
674 views

How can I get the same image with the same 50mm lens on both FF and APS-C?

First things first, I'm talking ONLY about framing here. No light sensitivity, no bokeh quality, no pixel quantity, etc. A 50mm in a FF camera will give a certain composition and framing. How can I ...
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6answers
21k views

What is the relationship between focal length and shutter speed?

I am very new to photography and am trying to grasp the basics of it these days. Can someone please help me understand the relationship between focal length of a lens and shutter speed of camera?
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1answer
74 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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