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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What is "angle of view" in photography?
I read on the Lens Buying Guide @ neocamera:
Focal-length determines the angle-of-view seen through a lens for a
given sensor-size. With a full-frame sensor a lens gives the same
angle-of-view ...
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How do I convert lens focal length (mm) to x-times optical zoom?
What is the rule to convert the 'mm' notation to the 'optical zoom' notation? I searched a bit and found this one:
$$\text{Optical zoom} = \frac{\text{Maximum focal length}}{\text{Minimum focal length}...
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Do professionals really never use a 24-70 lens?
I was reading lens reviews on the Rockwell site — mostly because it came up as first result in Google search — and he was saying professionals don't need and don't use mid-range zoom lenses like ...
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Which focal-length lens is usually used for portrait photography, and why?
What focal length or range of focal lengths are usually used for portraits?
What is used by professionals? Why would one select a certain focal length? What are the advantages and disadvantages of ...
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What is crop factor and how does it relate to focal length?
I'm reading that a 50mm lens is recommended as a first prime lens for DSLR owners as it's supposed to give a 'natural' perspective, but when used on (most) DSLRs, the view is cropped, as if you were ...
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How do I calculate the distance of an object in a photo?
If I took a picture of a windmill on the horizon — given that I know the sensor size and the focal length of the lens and other factors to do with the shot — could I calculate how far away an object ...
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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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Is crop-factor a bad thing?
It seems to me that there is a preference for full-frame sensors rather than cropped sensors, and I'm curious as to why. It seems to me, that the cropped sensor means that I get more bang for my buck ...
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What does it really mean that telephoto lenses "flatten" scenes?
This is another perspective distortion question. I understand that perspective distortion is primarily a function of capture and viewing distance, but I am still working on fully understanding the ...
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Does my crop sensor camera actually turn my lenses into a longer focal length?
So, I mount a 200mm lens on my Canon 450D. It effectively becomes a 320mm lens. Is this the equivalent of 320mm on a full frame camera? That is, from what I've figured out I get an equivalent field of ...
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How to capture the scene exactly as my eyes can see?
What settings of my DSLR camera will emulate the scene exactly as I can see through my naked eyes?
I think it's not possible to get the contrast and colors exactly as my eyes can see, and it may vary ...
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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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Does changing the focal length change focus?
When using manual focus or back focus on D60, I sometimes zoom in the lens, set the focus, and then zoom out. Does changing the focal length (zooming out), also change the focus?
In case the answer ...
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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 ...
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What is the shape of the focal plane?
This is something I just realised I don't entirely know the answer to, so I'm going to ask it here as I think it's interesting.
In most non-scientific writing on depth of field, diagrams generally ...
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How can a 18-55mm lens focus on objects beyond 55mm?
I guess this is a total noob question, but doesn't 18-55mm mean that it can focus only up to 55mm?
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What lens focal length most closely resembles the perspective of the human eye?
For example, if I have a lens that is 16mm-50mm, which focal length would be the closest to the human eye's view? (I don't have a camera yet, so I'm just curious.)
Would 50mm be more zoomed in than "...
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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....
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Estimating focal length range required for shooting scenario
Is it possible to estimate (or calculate), in advance, the range of focal lengths you might need for shooting in a given scenario?
For instance, suppose you will be going to the zoo (with your APS-C ...
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Why doesn't the picture become darker the more you zoom in?
As your lens's focal length gets longer, fewer photons pass through the lens to hit the mirror/sensor.
Why don't you see darkening when you look into the viewfinder and zoom in with a zoom lens, and ...
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How can a lens with a single focal length focus on more than one plane?
By definition, a prime lens is a fixed lens system with a fixed focal length.
Then, simple physics tells us that it should be able to focus only on one plane (at a fixed distance) in front of it. But ...
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Why is depth of field affected by focal length?
As the focal length decreases, the depth of field increases as well. Why is this? I'm not so much interested in a physics lesson as I am interested in a simple, down-to-earth explanation.
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What focal length gives a "normal" field-of-view on APS-C cameras?
I wish to purchase a "standard angle-of-view" prime lens for my Canon Rebel, which has an APS-C sized sensor. Various articles note that the popular "nifty 50mm" lenses are a little too much of a ...
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What else changes with zoom?
Let me start with the general question:
Consider the following situation. I want to take a picture of a particular object (that is, not a scenic shot). I can alter my distance from the subject ...
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Is there construction-agnostic term for a lens with a long focal length?
Turns out that telephoto refers to a specific construction of a long-focal-length lens, i.e., one where the lens is physically shorter than the focal length.
Is there a generic term for referring to ...
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How to test actual focal length?
From Matt Grum's comment to my previous question, I learned that manufacturers may casually "round" actual focal length of a lens to some nice number that gets printed on the box and stored into EXIF. ...
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How does changing focal length affect depth of field?
I'm curious about how my "area of acceptable focus" changes when the focal length of the lens I'm using changes as I zoom (or switch lenses). In particular, I'd like to know how the front & back ...
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Why do we talk about focal-length when frame sizes are different?
I keep seeing people talking about focal-length of lenses without saying how large the frame is. Is there a more sensible way to talk about how much a lens “zooms”?
(I have seen so many adverts etc ...
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Can I use my APS-C kit lens as a reference for choosing between 50mm or 35mm prime lenses?
I'm looking at getting a second lens in addition to my Nikon D7000's kit lens.
I want to know if it's possible to use my 18m-105mm kit lens to get an idea of the focal length for a 35mm lens vs. a 50 ...
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What is a parfocal lens and how beneficial is it to photography?
I heard someone say that after using a parfocal lens for the first time, they would never switch back. What is a parfocal lens, how is it different from any other lens, and what are the advantages and ...
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Why does a 50mm lens appear to give a human perspective, rather than a normal lens?
I grew accustomed to the notion that what one sees through a normal lens equates (or is close to) what can be seen with the naked eye (although that is not the "pure" definition of a normal lens, ...
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How do zoom, magnification, and focal length relate?
Zoom lenses and cameras with superzooms are often sold with a times ("×") zoom number — like a 12x zoom or 30x zoom. The question How do I convert lens focal length (mm) to x-times optical zoom? ...
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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 ...
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What are the different focal lengths of macro lenses and their advantages?
I am interested in macro-photography. I see there are macro telephoto (zoom?) lenses (e.g. 200mm), or smaller macro lenses (e.g. 40mm) ...
What are the different types of macro lenses and their ...
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What is a normal lens?
I've heard people call 50mm lenses "normal lenses".
For a lens to be considered normal, does it have to be exactly 50mm or is there some leeway? Does the normal focal length depend on crop factor of ...
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How do zoom lenses restrict their widest aperture at the telephoto end?
Does the aperture ring lock the apertures beyond, say 5.6 at length lens's telephoto end?
Does the lens introduce an obstacle to the aperture ring so the lens can't be opened anymore beyond the ...
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Will a 50mm f/1.8 work for general outdoor photography?
I want to know if it's advisable to use 50mm lens for general outdoor photography. I'm torn between 35mm and 50mm primes, and have read all the pros and cons. I understand that 50mm could be tight in ...
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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 ...
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What differences between point and shoot zoom versus DSLR zoom cause the price disparity?
I'm just getting into the world of photography, stepping up from a point-and-shoot. I've just purchased a Nikon D3100 and it should be here in a couple of days.
I've done lots of research, but ...
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How useful is image stabilisation below 200mm, really?
Image stabilisation is all the rage, and hardly a new lens from Nikon or Canon is missing this "crucial" feature. To me this seems to be the new megapixel race (like when the manufacturers tried to ...
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How to calculate the FOV in degrees from focal length or distance?
How does one to calculate the field of view (or angle of view) in degrees from the following details:
sensor size (for example, 1")
distance to target (for example, 7 feet)
focal length (for example,...
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Does focal length affect diffraction, in addition to aperture?
The reason I ask is that f/18 on a 24mm lens = 1.5mm, and f/18 on a 180mm lens = 10mm. I thought diffraction is due to the small physical size of the aperture, rather than the f-ratio, yet I only ever ...
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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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Do bigger focal lengths capture more light?
I never understood what the f really stands for in the f-stop values, like f/1.8. Wikipedia explains it in various articles, but I still find it very confusing. What I understand, though, is that it ...
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What is the formula for percent of frame filled at a specific distance and focal length?
I am thinking about buying a new lens specifically to take photos of distant targets (birds, bears, etc). I currently own the Canon 70-300 IS USM, which is a nice lens, but I find that if I want to ...
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What is a good focal length for street photography?
With a long lens you don´t disturb people but you are left "out of the scene", while with a short focal lens you are "inside the scene" but you may disturb people.
What is a better alternative for ...
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What is it called when an object appears to be the same size with the eye and through the camera viewfinder?
I have a Canon 18-135 lens. I am looking into the camera viewfinder with my right eye and not through the viewfinder with my left. I start from 18mm and keep zooming in till I see a particular object ...
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When I use FX lenses on a DX camera, does the focal length or minimum aperture change?
If I put a Nikkor 35mm f/2 FX lens on a DX camera, is it still 35mm f/2, or has the effective focal length or minimum aperture changed, because it is being used on a smaller format than what it was ...
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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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Does focus breathing make a lens slower when close focusing?
I've heard that focal length of some lenses will become noticeably longer when focusing to a close distance, an effect called "focus breathing". Since f-number is focal length divided by diameter of ...
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