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?
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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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31 votes
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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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24 votes
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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
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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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22 votes
6 answers
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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...
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Where does the term "f-stop" come from?

Does anyone know the origins of the term?
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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
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2 answers
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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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15 votes
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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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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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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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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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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 ...
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4 answers
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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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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
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3 answers
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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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10 votes
4 answers
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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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2 answers
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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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What motivated lens makers to now use 1/3 f-stops rather than say 1/4 or 1/2 stops?

I've noticed that many older lens have just hard f-stops for lens (2, 2.8, etc). However, since the aperture wheel for some is continuous you can "stop" are some arbitrary point and shoot. From my ...
unsignedzero's user avatar
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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
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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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Do top-of-the-line lenses transmit more light at the same f-stop?

We usually refer to the F number to compare how fast is a lenses with another one. I understand that the optic quality should help as well — so would a L series in Canon (or whatever is the equivalent ...
Julien Gagnet's user avatar
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4 answers
2k views

Is f/number more relevant than aperture and/or shutter speed?

I've seen on Flickr that the photographers specify values for four settings about their photos (where exif data is available) - Shutter speed F number ISO Focal Length An example can be found here. ...
Buzut's user avatar
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Bracketing with ISO or exposure time?

With old cameras, you had film with fixed ISO and you could bracket your shots by either adjusting the f-stop or exposure time. Normally, if I have enough light, I prefer to keep the f-stop constant ...
WilliamKF's user avatar
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What's the formula for f-stop equivalence between different sensor sizes?

The famous Group f/64, to which Ansel Adams and several other prominent photographers of that day belonged, were named that because of the f-stop: The term f/64 refers to a small aperture setting ...
tchrist's user avatar
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6 votes
3 answers
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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
6 votes
3 answers
1k views

Why does Rosco's filter page show that 33% transmission is 1 stop rather than 50%?

I was taught that each stop halves/doubles the light throughput. So one stop up is double as much light, one stop down is half as much light. Now, according to this Rosco table: https://www.rosco.com/...
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6 votes
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How does sensor size affect minimum front element size for a given f-stop and focal length?

Does the sensor size affect the needed size of the front element given a focal length and f-stop? My intuition tells me that a bigger image circle would require a bigger front element to maintain the ...
lijat's user avatar
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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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5 votes
6 answers
2k views

How many extra stops do monopods offer for tele photographs?

I have often wondered what the purpose of monopods is. It seems to me that they remove only two degrees of freedom out of three possible degrees of freedom of camera shake. And the situation is even ...
juhist's user avatar
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5 votes
4 answers
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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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5 votes
7 answers
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Is there any way to stop down the aperture of a Canon PowerShot SD780 IS?

I have a Canon PowerShot SD780 IS point-and-shoot which I use as my carry-around-everywhere camera when I don't want to drag my SLR about. This tiny little camera works great and takes fabulous ...
Adam Franco's user avatar
4 votes
5 answers
593 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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4 votes
2 answers
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What's the difference between aperture value and f-number?

In macOS Finder it says a photo taken at f/2.8 has an aperture value of 3. What is an aperture value, and how is it different from f-stop?
clickbait'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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4 votes
1 answer
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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
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
3 votes
2 answers
2k views

How does physical aperture size relate to f/stop?

There are two lenses on the market I am comparing AF Micro-Nikkor 60mm f/2.8D AF-S VR Micro-Nikkor 105mm f/2.8G IF-ED If I use the formula for calculating apertures of both the lenses I will use the ...
Black Dagger's user avatar
3 votes
1 answer
6k views

Can a lens exist with an f-stop of less than 1? [duplicate]

As I understand it, the F-number of a lens is equal to the aperture diameter divided by the focal length. So f/1 would mean that the aperture is as wide as the lens is long. Question: Is it ...
MathematicalOrchid's user avatar
3 votes
4 answers
346 views

What is the useful range of apertures for lenses?

Assuming for example a lens has a range of f/1.8 - f/22, for an ideal picture which apertures should I avoid, and for what specific reasons? Now if the answer is "do not use the first two and the last ...
Regmi's user avatar
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3 votes
5 answers
3k views

Do you get more bokeh on a APSC sensor with a full frame 50mm f/1.8 lens or a APSC 30mm f/1.4?

I am trying to compose a detail shot where I want to get as much background blur as possible. I am using Sony a6500 camera (APSC 1.5x crop factor body). I am considering two lenses: Sigma 30mm f/1.4 (...
user5359531's user avatar
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
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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3 votes
2 answers
832 views

Why does my lens refocus when the f-stop is changed?

I have a prime Sigma f1.4 50mm lens on my Nikon D90 in P mode and focus mode on a set point of the field and notice that when I am using a tripod and change the f-...
WilliamKF's user avatar
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3 votes
1 answer
433 views

How do I properly understand what f-stop is? [duplicate]

I don't quite understand why most lenses seem to have approximately the same diameter aperture regardless of focal length. F-stop is, by definition, a ratio of focal length to diameter, so a 20mm ...
Octopus's user avatar
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3 votes
0 answers
96 views

My lens is capable of f-stops higher than the label [duplicate]

I searched on here and I read everything on this page: http://www.geometer.org/beginner/lenses.html But I still don't understand what's going on with my lenses and how they are labeled. I have a ...
Jasmine's user avatar
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2 votes
5 answers
3k views

Why do lower f-stop numbers mean larger apertures? [duplicate]

I thought this would have been asked before but it seems not. I don't understand how f-stops are numbered. From what I read, the lower the f-stop number, the larger the aperture. That is, f/2 is ...
CodyBugstein's user avatar
2 votes
2 answers
1k views

Does crop factor affect exposure time?

I'm confused on this, even after researching: Given 2 cameras- one full frame with 50mm lens, one Micro Four Thirds (2x crop factor) with 25mm lens, let's pretend the cameras are beside each other, ...
user3833000'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