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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4 answers
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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 ...
12 votes
5 answers
2k 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 ...
0 votes
0 answers
85 views

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 ...
44 votes
10 answers
23k views

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 ...
1 vote
3 answers
320 views

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 "...
2 votes
2 answers
291 views

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 ...
8 votes
3 answers
25k views

How can I calculate focal length from a photograph?

I posted this question over on Stack Overflow, but someone suggested this site might be of more help to me. I'm doing a college project where I'm trying to calculate the focal length of a camera ...
1 vote
5 answers
960 views

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 ...
5 votes
4 answers
2k views

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?
1 vote
0 answers
243 views

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,...
2 votes
4 answers
2k views

Will a macro extension tube eliminate the cropping of an APS-C lens on a full-frame sensor?

I understand using an A-mount lens intended for APS-C sensors on a full-frame camera results in cropping of the image. According to a tech at Sony, you lose 1/3 of pixels (APS-C is a 2/3 sensor so it ...
15 votes
3 answers
8k views

What is the reference point that the focal length of a lens is calculated from?

I understand the idea of a focal length for a single lens, i e the distance from the lens to the point at which parallel rays of light converge. However, in the case of a photographic lens with ...
0 votes
2 answers
2k views

How to determine film size from smartphone image exif data?

I took an image from my phone and got its exif data below. It was a samsung note 4, which uses a 35mm film size (24x36) with a 43.27 diagonal. But what I am trying to figure out is the sensor diagonal ...
1 vote
3 answers
2k views

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 ...
0 votes
1 answer
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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.
6 votes
5 answers
2k views

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 ...
2 votes
3 answers
524 views

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 ...
3 votes
1 answer
556 views

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 ...
30 votes
6 answers
14k views

Is there a difference between taking a far shot on a 50mm lens and a close shot on a 35mm lens?

I am looking for a prime lens to pick up, and I'm wondering if there is any difference between 35mm and 50mm in terms of the end product if I just stand back more with the 50mm. I use the Sony a6000 ...
2 votes
1 answer
1k views

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 ...
15 votes
5 answers
4k views

How can a lens like a 18-55mm have more than one focal length?

How can a lens have a range of focal lengths? Shouldn't it be a single number? Isn't focal length supposed to be fixed for a lens of a particular shape and geometry? What am I missing? How many ...
1 vote
2 answers
236 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: ...
0 votes
2 answers
2k 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 ...
1 vote
2 answers
182 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 ...
2 votes
3 answers
231 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 ...
2 votes
3 answers
575 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-...
3 votes
2 answers
184 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 ...
2 votes
1 answer
303 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 ...
7 votes
5 answers
8k views

Is it exactly true that doubling the focal length makes everything look twice as big?

I had come to the conclusion that if one lens has twice the focal length of another, that means it makes everything look twice as big. Conversely, if a lens has half the focal length, you see twice as ...
1 vote
0 answers
34 views

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.
0 votes
2 answers
239 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 ...
27 votes
4 answers
113k views

How do people shoot very large moon views?

I see pictures of the moon that looks like it is very close to the earth; I am wondering whether they are real or is there a trick to show the moon that big? Here is an example: http://www....
9 votes
2 answers
67k views

What is the focal length on your typical cell phone camera?

I know cell phone cameras are generally wide angle, which makes sense because people wanna go out to dinner, or a show, or at the park with their kids, and they want to get the whole scene. And even ...
1 vote
3 answers
677 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 ...
2 votes
3 answers
657 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 ...
1 vote
2 answers
264 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 ...
0 votes
1 answer
1k 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 ...
-3 votes
3 answers
212 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 ...
5 votes
4 answers
331 views

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 ...
0 votes
2 answers
393 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 ...
1 vote
3 answers
975 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 ...
0 votes
4 answers
172 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 ...
7 votes
2 answers
1k 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 ...
5 votes
1 answer
454 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 ...
0 votes
4 answers
691 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 ...
0 votes
1 answer
326 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 ...
3 votes
3 answers
244 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 ...
2 votes
2 answers
226 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 ...
0 votes
4 answers
501 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 ...
1 vote
2 answers
137 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 ...

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