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Questions tagged [f-stop]

The f-stop of an optical system expresses the diameter of the entrance pupil in terms of the focal length of the lens; in simpler terms, the f-stop is the focal length divided by the "effective" aperture diameter. It is a dimensionless number that is a quantitative measure of lens speed, an important concept in photography.

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What does f-stop mean?

What does f-stop mean? Is it the same thing when people say "2 stops" for example?
matt burns's user avatar
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36 votes
4 answers
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How do you find out the "sweet spot" of a lens?

I've tried googling this, but have never found a satisfactory answer. I've heard the term "sweet spot" thrown around by some photographers to mean the f-stop of a lens which results in the highest ...
andy's user avatar
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23 votes
7 answers
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How can aperture be f/11 on a lens with an aperture range designation of 3.5-5.6?

I made a series of outdoor shots with Nikon D5000, with the 18-55mm 1:3.5-5.6G VR kit lens. On some shots, I see in the EXIF info f/11, and in another shot, f/9. How can that be, that the f-number ...
Andrei's user avatar
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31 votes
10 answers
85k views

What is an easy way to remember the full stop scale?

If you were teaching someone new to photography the full stop scales, is there a better way then flat out memorizing these values? Does anyone have an easy way that they remember the scale? Would it ...
dpollitt's user avatar
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8 votes
3 answers
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Does autofocus work better with f/2.8 lenses vs f/4 or slower?

I read following in a web site (http://realphototips.wordpress.com/tag/ai-servo/) Lenses with maximum apertures of f2.8 allow the camera to use all high precision sensors. In low light or other ...
Niranjan's user avatar
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24 votes
7 answers
11k views

Why don't compact digital cameras have the aperture range of DSLRs?

Why is it that on compact digital cameras the aperture never seems to go any smaller than about F8 ? Even on high-end compacts such as the Canon G10 or Panasonic LX5. Is there some practical or ...
Matthew Dresser's user avatar
3 votes
2 answers
4k views

What's the difference between real and effective aperture?

I understand that the simple idea that f-stop is focal length divided by aperture really applies to a simple single-glass lens, not the compound lens systems used to provide good image quality in ...
mattdm's user avatar
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15 votes
4 answers
10k views

Does using an extender actually change the aperture of the lens?

I just bought a Canon 2X extender and I always believed that it would only result in 2 stops' loss of light and not change the aperture. However, when I tested this extender on a Canon 135mm f/2 ...
Viv's user avatar
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14 votes
5 answers
37k views

What does the f-stop printed on the lens refer to?

I have read this,so I know what an f-stop is, but what does the number on printed the lens signify? Is this is the maximum f-stop, the ideal, or something else?
John's user avatar
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20 votes
3 answers
3k views

Why are DSLR lenses measured in F stops instead of T stops?

I understand the difference between f-stop and t-stop, but why are cinema lenses measured in one, and dSLR lenses measured in another?
Barney Chambers's user avatar
14 votes
5 answers
1k views

Why are only certain shutter speeds or apertures available?

For the exposure control function DSLRs there are specific shutter speeds available. For example there are 1/4, 1/100, 1/500. Why, even in high end DSLRs, is there no option to use a custom shutter ...
SamB's user avatar
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3 votes
4 answers
1k views

Why does illuminance stay the same for a given f-stop even when focal length changes?

I'm trying to wrap my head around the math/physics of how illuminance on the film/sensor plane remains equal for a given f-number regardless of the focal length of the lens. Since a longer lens will ...
the_meter413's user avatar
6 votes
2 answers
1k views

How does sensor size affect the brightness of an image given the same field of view and aperture?

Lets say we have two image sensors, each one with 1MPixel resolution but differing in size. The first sensor has the size 1/3", the other one 1". Each sensor is equipped with a suitable lens (for the ...
Echo88's user avatar
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12 votes
2 answers
3k views

Do lenses with the same f-stop but different focal length gather the same amount of light? [duplicate]

I'm taking images of a light source in a scientific labratory, and I thought I had a good grasp on all these things, but now i'm second guessing myself after some results. The most important thing is ...
mrsoltys's user avatar
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11 votes
3 answers
898 views

What is the limiting factor in lens construction when it comes to f-stop values?

This widely praised Nikon 105mm macro lens has a maximum f-stop value of 2.8. I've held it in my hands, it's a big lens. Meanwhile, this 50mm Nikon lens can go up to f/1.2, despite being 25% cheaper ...
Drew's user avatar
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9 votes
2 answers
8k views

What does "N stops" mean when describing an image stabilizer?

If you ever purchased any lens with IS then you have heard this term like "3 Stop Stabilization" or "4 Stop Stabilization". Now, I am familiar with this Stop for ISO and Aperture. But this I don't ...
Hasin Hayder's user avatar
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4 votes
1 answer
25k views

What is the largest aperture on a commercially available lens? [duplicate]

Out of pure curiosity, what is the largest aperture, or lowest f-stop, a commercially available lens has. I have seen the 50mm prime lens from canon with 1.2, but not lower than that. What are the ...
user-2147482637's user avatar
22 votes
6 answers
8k views

How many stops can a digital camera capture?

How many stops can a digital camera capture? Additionally, does anybody know what the dynamic range is for negative and positive film, the human eye, computer monitor, the television, etc...
Aristos's user avatar
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21 votes
5 answers
11k views

Where does the term "f-stop" come from?

Does anyone know the origins of the term?
Casebash's user avatar
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9 votes
2 answers
662 views

Is there something special about f/3.5-5.6?

The vast majority of the kit lenses sold with entry-level (or even upper entry-level) interchangeable lens cameras, tend to have an aperture range of f/3.5-5.6. This seems to be independent of whether ...
Philip Kendall's user avatar
6 votes
3 answers
3k views

Why are f-stops not linear?

Why don't we use a linear scale for f-stops, rather than one based on square roots? A linear scale will be easy to remember (in fact, there will be nothing to remember) and to calculate how much ...
Kartick Vaddadi's user avatar
5 votes
4 answers
19k views

What shutter speed to use when shooting video?

My camera is Canon 60D and I will be using it to shoot a short parkour video, that means: a lot of motion, moving subjects, moving camera focal length usually from 24 mm to 75 mm, but there will also ...
Frantisek's user avatar
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4 votes
3 answers
588 views

Choosing first lens for Nikon D-90 body

I'm looking to get a prime lens to go with the Nikon D-90 body. I'm looking at 50mm or 35mm and f/1.8 or f/1.4 and AF or AF-S. It appears that VR (Vibration Reduction) is not an option for any of ...
WilliamKF's user avatar
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19 votes
2 answers
4k views

Does a specific f number across all lenses denote same amount of light?

When we say a light source emits 1500 lumens of light, it does not really matter if the light source is incandescent, CFL, diode etc. Similarly, when I say f/1.8 can I assume that all lenses pass the ...
Regmi's user avatar
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13 votes
2 answers
622 views

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 ...
Imre's user avatar
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11 votes
4 answers
3k views

Why are 1/3 stop apertures uneven numbers apart?

Why do 1/3 stop apertures go like 8, 9, 10, 11, 13, 14, 16, 18? There's a difference of 2 between 11 and 13, it goes back to 1 between 13 and 14, and it goes back up to 2.
clickbait's user avatar
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11 votes
2 answers
6k views

How to stop a high F number from appearing blurry?

I have been out taking some evening photos (just after sunset) and I have noticed that in a number of instances the higher f numbers ( 14+ ) are appearing more blurred than the lower f numbers ( < ...
IconicPhotos.co.uk's user avatar
10 votes
4 answers
699 views

Are the aperture, ISO and shutter speed stops perfectly interchangeable?

Imagine you have an scene with shutter speed 1/60, f/8 and ISO 200. Then you change the configuration to get an equivalent exposure: speed 1/120, f/5.6, ISO 200 (plus one stop in speed, minus one stop ...
rodripf's user avatar
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4 votes
5 answers
597 views

F-stop vs T-Stop - how do I quickly grasp a videographers view of the world?

I'm aware this is flirting with video rather than photography, but the question really relates to how each world can be understood by the other. Very briefly - I am an amateur photographer who ...
Tetsujin's user avatar
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3 votes
3 answers
2k views

Confused about T-stop number. Does it account for crop factor?

I understand that a T/stop number deals with how much light is let in, instead of the sensor size vs. aperture like the f/stop number. However, what I haven't found is whether or not that T/stop ...
Tyler VanDenBerg's user avatar
2 votes
2 answers
885 views

Why are the area of aperture, focal length, and amount of light specified in these terms?

So I'm looking at the wikipedia article on Aperture, and I'm a bit confused. I understand aperture to be the diameter of the hole that lets light in. In the article, someone states that The ...
Chaosphere2112's user avatar
0 votes
5 answers
14k views

Why doesn't the f-stop on my D7100 change when I hold +/- and change the dial in manual mode?

On my Nikon D7100, the f/stop will not go down from 14 when I hold down the +/- button and turn dial. All I get is a little number below but the photos do not change exposure when I change this number....
Katy Pauls's user avatar
0 votes
2 answers
13k views

How is f-stop a measure of dynamic range?

As far as I have read f-stop is a measure of the aperture. This affects the amount of area in the foreground and background which is in focus. While having a look at the dynamic ranges of cameras I ...
jinkx's user avatar
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