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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1answer
2k views

Decrease the focal length of lens

Reading about tele extenders for lens and how they change the focal length/field of view I came up with the idea if there is something/some way to shorten the focal length of the lens. And the ...
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How to get a clear image of a distant subject?

i have to shoot a subject which is 300 meters far and i need the image as clear as a portrait i took by a 18-55mm lense. Which lense i can use?
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FX & DX Lenses on DX Body [duplicate]

If I use a 50mm prime FX lens on a FX camera, I will get 50mm. If I use a 50mm prime FX lens on a DX camera, I'll get 75mm (assuming 1.5x crop factor). Now, if I use a 50mm prime DX lens on a DX ...
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Confused about different optical zoom on different lens [duplicate]

I'm looking at 3 different lens mainly for distance shots but with a bit of Macro occasionally. Tamron AF 70-300mm F/4-5.6 Nikon AF-S DX NIKKOR 55-300mm f/4.5-5.6G Sigma 70-300mm f4-5.6 The bit ...
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3answers
617 views

Effective focal length with crop sensor, and detail of image

I have in fact read the other threads, and I am still not clear on this topic. For any given lens, say a 400mm EF or FX telephoto, I am shooting a subject in low light, for arguments sake lets say I ...
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2answers
261 views

Transmission, Aperture, and Focal Length in Low Light Situations

I've been looking for an affordable lens I can use for nighttime shooting, including astrophotography. The two lenses I have found that seem best suited for this are the Samyang 16mm f/2 and the ...
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Is focal length internal or external? [duplicate]

I just wanted to check because I've encountered various distinctly different assertions. I was originally taught that focal length referred to the optimum distance from subject| ←→|lens, where ...
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Is focal length measured relative to the sensor or the lens? [duplicate]

I'm very (very) new to photography world.. I've been trying in the past few days to explore very deeply to this world.. But the more I dived in the more confused I became. For example most of the ...
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How is Focal Length defined for 180-degree fisheye lenses?

The definitions of Focal Length I saw seem to implicitly assume that the field of view is finite, which isn't true for 180-degree lenses, or presume parallel transport of certain rays passing through ...
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What is the formula for determining where infinity focus begins?

I'm having difficulty find any info on determining where infinity focus begins. I'm assuming there's a formula involving focal length and... Can anyone help?
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Same focal distance, narrow FOV but bigger sensor. How is possible?

The iPhone 7 Plus, according to the exif, has 4 mm focal distance 28 mm equivalent. The iPhone 8 Plus, according to the exif, has 3.99 mm focal distance 29 mm equivalent. The iPhone 8's field of view ...
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2answers
858 views

What's the relation between sensor size and maximum aperture

Is there any relation between the maximum aperture of a lens and the size of the sensor? I'm looking at the smartphone. A smartphone has 4 mm focal length (equivalent to 28 mm) and f/1.6 aperture ...
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1answer
354 views

Understanding Lens Viewing Angle and Focal Length Relationship [duplicate]

I have a camera module with a lens viewing angle of 185° and a focal length of 1.8. But as far as I can tell, this camera module is not classified as a fish-eye lens. The working distance is ...
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1answer
226 views

How much longer can my shutter speed be for a given focal length with OIS on a Fujifilm X-series camera?

I have the XF 50-140mm and the XF 100-400mm zooms for Fujifilm X-T2. I heard for crop sensors to use the 1/(2× focal lenth) rule rather the 1/(1× focal length) for full frame. So, without OIS on a ...
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Does sensor size matter when I'll be cropping the image anyway?

Background I like taking photos of formula 1 cars. I try and sit close to corners where they're going as slow as possible; this means sitting about 100m/330ft away from cars going 100kph/60mph. I'm ...
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7answers
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Are lenses marked with the true focal length?

Does the true focal length of a lens equal to the numbers written on the lens? For Example, is the focal length of 70 mm or 200 mm really 70 mm or 200 mm or smaller? Example: 69.5 and 199.7.
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How big is the sun in an image made with Canon APS-C and 300mm focal length?

I am trying to decide what lens should I use for eclipse and I am wondering if my 70-300 IS USM would be enough or should I get (rent) a lens with higher magnification. Since my solar filters are ...
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does focal length change across an image?

If an image is taken of a flat surface parallel to a (presumed perfect) lens, is the scale of objects (and therefore focal length) uniform across the whole image? eg. Would an object in the centre of ...
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2answers
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How photo and lens looks with 1mm focal length?

Are there lens with 1mm focal length? What is the shortest focal length possible for full frame sensor? And can it be rectilinear lens? There is Sigma EX 4,5mm, but it's for APS-C and still far from ...
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1answer
297 views

What does a pair of numbers in parentheses mean as a focal length value in metadata?

I have extracted the metadata from an image. One of the values was: FocalLength: (3680, 1000) How can we read the above value?
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Are there any drawbacks to using a T-Mounted lens?

I am looking to buy a mirror lens for the upcoming solar eclipse. I am using a Canon with an EF mount. Most of the lens options I see require a T-Mount adapter to fit on my canon. Are there any ...
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3answers
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Should I quote focal length using equivalent focal length in a photobook?

I'm putting together a (non-commercial) photobook from a year in a foreign country. I took all the photos with the Canon EOS-M3 which has an APS-C sensor (crop factor 1.6). I want to quote the ...
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How should I arrange a scene to test the relative sharpness of lenses with different focal lengths?

I want to compare sharpness of two lenses, consider 50mm f/1.8G vs 35mm f/1.8G from Nikon on a crop sensor camera by taking some photos (from some small size text on a paper) and review the results. ...
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5answers
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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 ...
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1answer
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Why do my 50mm APS-C and 50mm FF lenses have the same angle-of-view on my APS-C camera? [duplicate]

This feels like it should be obvious, but I'm failing to figure it out. I own a Sony a5100 -- an APS-C camera with a 1.6 crop factor. I have long owned the SEL50F18, a 50mm f/1.8 lens designed for ...
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2answers
697 views

70-200mm lens or 18-200mm lens for small studio like 25 feet? [closed]

I am new to fashion photography. I have Canon 700d (cropped body) with 50mm 1.8 lens. I have few soft boxes and other studio equipment. I want to buy a new lens. From a canon training workshop guy ...
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2answers
700 views

At what distance will I start seeing atmospheric effects?

I've got a Panasonic Lumix FZ72: a 20-1200mm superzoom. It's pretty good, and has pretty decent image quality for the price. Unfortunately, I've noticed that if I take any pictures past roughly ...
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2answers
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I'm hoping to prove this distance to camera equation:

D = f*H/h where D = distance from lens to object (d = distance from lens to 35mm film) f = focal length H = height of object h = height of object's image on 35mm film I've seen some form of this ...
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How to get a blurred background using a Canon 18-55 STM lens? [duplicate]

I'm totally new to photography and need your help. I've read much about ISO, Aperture and Shutter speed. I know to get a blurred backround: use a wide aperture. Also I know the distance between ...
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3answers
636 views

Focal length equivalence in Sony lenses E vs FE vs compact

I think I almost get the concept of equivalence and the fact that a 70mm lens mounted on a full-frame body is not the same as 70mm on aps-c sensor. Let's work with some concrete examples: Sony A7 II ...
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3answers
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Is there a difference between increasing focal length vs. cropping? [duplicate]

Other than the difference in the quality of the image (increased focal length will produce more quality than the equivalent cropping of the image), is there a difference? For example, if I increase ...
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3answers
990 views

(theoretical) what is needed in determining focal lengths in pictures?

Base Case. Assume a well-lit plain white (no depth and like really white) background, and a magically levitating black micro ball (such that, it would yield a very small object -of a few pixels- in ...
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2answers
153 views

Intuition regarding focal length; can one learn/train this?

My main go-to equipment: Sony A7s II, Sony FE 55mm f1.8 and Sony FE 16mm-35mm f4. Within this range of focal length I have quite a good feel for what picture is at what focal length. I recently ...
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2answers
3k views

Full frame 16-35 mm vs crop 10-22mm [duplicate]

I'm using a Canon EOS Rebel with 1.6 crop factor. In terms of focal length- Is an EF 16-35 mm full frame lens on a full frame camera equivalent to an EF-S 10-22mm lens taking into account my crop ...
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2answers
236 views

Trade Off / compromise to zoom lenses with longer focal ranges [duplicate]

I'm new here- looking for a community of folks to learn from. My love for photography was sparked on my honeymoon in Iceland last year. Now I can't get enough. My question to you is- what's the trade ...
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5answers
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Can I convert binocular zoom to equivalent lens focal length?

I read another SE post that shows how focal lengths can be converted to optical magnification, but it isn't clear to me how it would work the other way around. My binoculars are adjustable from x10 to ...
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1answer
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Why does my Samsung S7 with fixed focal length of 26mm have a wider angle of view than my 18-55mm DSLR lens? [duplicate]

Maybe I am missing some camera basics, but from experience with both devices, i notice that with my Samsung S7, I am able to take full buildings in pictures at a close range. It has a wider field of ...
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1answer
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How can I calculate sensor size (width and height) from focus length, vertical, and horizontal angle of view?

How to calculate sensor size (width/height) when knowing focus length, vertical & horizontal angle view (FOV)?
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1answer
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Calculate the distance of an object in a photo Android [duplicate]

https://photo.stackexchange.com/a/12437/61513 here is a formula for calculating distance if we know the size of the object. Can I use this method for photos/frames made by Android cameras? And if I ...
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1answer
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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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3answers
543 views

Apparent size and field of view [duplicate]

i am sure there is a simple answer, but i have seem to have forgen it. How do you calculate the relative apparent size of the subject i have seen a formula with the field of view and tangent, but i ...
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1answer
527 views

Zoom, Aperture size and focal length [duplicate]

I am very new to photography and have been working my way through a few books and magazines trying to learn how to use my camera more effectively. I keep getting stuck on the differences between the ...
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1answer
219 views

How does the focal length help in capturing wider or narrower picture?

I have been trying to understand the science behind cameras and photography. I started with "camera obscura" and understood that * when rays of light are passed through a small hole (aperture) of a ...
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4answers
2k views

Why would I need a portrait lens if I have a telephoto zoom lens covering the same focal length?

I am using a Panasonic Lumix G Vario 35-100mm F/2.8, a MFT telephoto lens. I am learning about photography by reading articles and reviews and in one review it was mentioned there is a great portrait ...
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6answers
3k views

Why can't I see the focal length (“zoom”) when I'm composing a shot?

My Canon 1300D DSLR stores the focal length used in the EXIF data of each photo, but there's no way to see this information while I'm composing the shot? Is there a technical reason why the focal ...
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3answers
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How far can a Nikon P900 focus?

A Nikon P900 has an effective focal length of 2000mm. What's the farthest away that I could get an object in focus with it?
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6answers
1k views

Longer Zoom Lens

I have D5000 Nikon and am looking for a longer zoom to take pictures of wildlife (live in Montana Rockies). I also have a Canon Powershot with 40x zoom - and the lens I have for my Nikon has a ...
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5answers
624 views

Focal length on Full frames and cropped sensors

Yes, this subject again. But I have a slightly different question and I was unable to find an answer here or anywhere else. I understand a 50mm lens is a 50mm lens ALWAYS. I understand that "...
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1answer
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What do these six lenses in EXIF mean, for the iPhone 7 Plus?

The iPhone 7 Plus has two back cameras, but the lens field in EXIF has six different values: iPhone 7 Plus back camera 3.99mm f/1.8 iPhone 7 Plus back camera 6.6mm f/2.8 iPhone 7 Plus back ...
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2answers
159 views

Am I doing something wrong or do I need a new lens? [DOF and focal length] [duplicate]

I'm new to photography and I can't get a nice DOF. I read up on all the technicalities that involve DOF and I still can't get it right. For example, if you take a picture very close to an object, ...

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