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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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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definition of focal length inconsistent [duplicate]

I have been learning about cameras recently and I got incredibly confused about the use the word "focal length". In the wiki https://en.wikipedia.org/wiki/Focal_length and other resources, it is ...
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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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97 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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177 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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165 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
170 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
157 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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198 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
216 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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Is there a way to measure a dip from a straight line in an image? [closed]

We have an image of a piece of brick walkway with a dip in it and we need to know the approximate measurements of that dip. Is there any way to get that from a photo. My boss's description is rather ...
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1answer
42 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
68 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
74 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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142 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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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
735 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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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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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
122 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
91 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
116 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
176 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 ...
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1answer
48 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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117 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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85 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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171 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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129 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
173 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
190 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 ...
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1answer
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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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222 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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226 views

How to calculate the new focal length when usng a lens mount adapter

I'd like to know how to calculate the new focal length when using a lens adapter. Is there any formula? To be more specific: I need to attach my old lens (four third) to new micro four third system ...
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1answer
102 views

What focal length to use for full-body photography of a chubby person? [duplicate]

Recently I took pictures of someone that was slightly chubby. Close-ups using a 50mm lens went very well, but trying to get some distance in to get a full body shot were not really that satisfactory. ...
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128 views

Does field of view change for different lens model for the same focal length?

I am using two lenses - Tamron 75-250mm F/3.8-4.5 Model 104A and AF-P DX NIKKOR 70-300mm. When shot with lenses set to 250mm of focal length, the field of view for the Tamron lens is greater than the ...
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5answers
1k views

Would a 50mm lens on a Canon APS-C crop produce the exact same image as an 80mm lens on a full frame camera?

Scenario: I put a 80mm lens on a FF camera and take a picture I put a 50mm lens on a Canon APS-C crop camera (1.6x crop) and take a picture Going by the 1.6x crop, I understand the fields of view of ...
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201 views

A projection of a real-image is one fixed perspective, but looking through the lens with my eye, I see many perspectives. Why?

Assume that I have a camera obscura (with a large lens - something like a magnifying glass) setup projecting an image of some still life. I look at my projection on my projection plane and I see one ...
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2answers
173 views

Why can my eye focus on the real image of a convex lens at many distances from the lens, but a projection only works at a specific distance?

Say I have a single convex lens. I set it up like a camera obscura, shine a light on my object and project the image onto a projection plane. Given the focal length of my lens, the projection plane, ...
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2answers
151 views

How can the focal length for shake reduction be determined when the lens is mounted using a reverse lens adapter?

My camera (Sony A7RII) offers image stabilisation (SteadyShoot). I shoot macros using a 50mm and a 28mm Olympus lens reverse mounted with anadapter. What values should I enter in the menu to ...
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35mm for portraits

Ok everybody knows 35mm is not the most flattering focal length for a portrait and by portrait I mean somewhere from chest and above... and of course it gets worse as we get closer to the subject. So ...
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844 views

Why are lenses characterized by focal length and not the effective field of view?

In photography, it's the accepted norm to say that if you know the sensor size of your camera and the focal length of your lens, then you know the field of view of your system. However, in optics, it'...
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789 views

Dogs & Portraits: Should I buy the Canon 50mm f/1.4 or the Tamron 35mm f/1.8 for my APS-C DSLR?

I recently purchased a Canon EOS 77D (which offers an APS-C sensor) with a Canon 70-200mm f/4. Now, I am looking to purchase a prime lens. My research suggests a choice between the Canon 50mm f/1.4 ...
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232 views

How to take pixel-for-pixel aligned pictures with a DSLR and iPhone 7?

The Plan So I am trying to take two pictures, one with a DSLR and one with an iPhone 7. Why an iPhone 7? That's just what I own currently I want the photos to be aligned so that they are exactly the ...
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1answer
264 views

Pixel diameter of a given field of view calculation equisolid (equal-area) fisheye lens

I have a 180° equisolid (equal-area) fisheye lens with a focal length of 8 mm. I want to crop images to a circle defined by an angular field of view from the zenith angle of the lens (i.e. the middle ...
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301 views

What factors affect the detail and clarity of a photo taken by a digital camera?

By clarity, I mean to preserve as much detail as possible when zoomed in. For example, I take a photo of my cat 10 meters away, and I want to zoom in and able to see each single fur as clear as ...
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4answers
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how many f stops should I allow for a given change in focal length - ISO and shutter speed remaining constant?

There are charts that show me what how many stops in shutter speed or ISO to allow when, for example, using an ND filter but given that a longer focal length reduces light available is there a chart ...
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2answers
73 views

Measure in photo formula help

Good Day I am trying to measure the width of an object in a photo as accurate as possible using the formula found in a previous question. Distance to object(mm)=f(mm) x real height(mm)x image ...
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4answers
5k views

How to find the focal length used by looking at image contents without examining metadata?

By looking at a photo, how can one tell what focal length was used without looking at the photo metadata?
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178 views

How is wide field-of-view possible using a tiny sensor?

From looking at the FOV tables on this page, I can see that FOV is greatly reduced as sensor size decreases. It seems that 1/2.3 sensors would produced fields-of-view that are tiny, even at the ...
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How can I see the equivalent focal length of the current zoom of my Nikon P900?

I have a P900 that I use for birding. It's great for carrying around and not so great when (as usual) the light is low. I'm considering using an alternate set-up, for example a D500 coupled with a ...

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