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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 ...

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52
votes
4answers
38k views

What does f-stop mean?

What does f-stop mean? Is it the same thing when people say "2 stops" for example?
25
votes
4answers
4k views

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 ...
20
votes
4answers
4k views

Why do compact digital cameras not 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 Cannon G10 or Panasonic LX5. Is there some practical or ...
17
votes
5answers
2k views

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 ...
10
votes
5answers
7k 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?
19
votes
9answers
22k 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 ...
3
votes
2answers
601 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 ...
13
votes
5answers
714 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 ...
8
votes
3answers
460 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 ...
2
votes
1answer
305 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 ...
16
votes
2answers
2k views

Where does the term “f-stop” come from?

Does anyone know the origins of the term?
20
votes
6answers
4k 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...
9
votes
2answers
545 views

When using an Extender, does it 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. When I tested this extender on a Canon 135mm F/2 lens, the ...
2
votes
2answers
433 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 ...
10
votes
2answers
1k 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 ( < ...
8
votes
2answers
721 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 ...
4
votes
3answers
533 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 ...
2
votes
3answers
649 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 ...
7
votes
4answers
251 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 ...
6
votes
2answers
1k 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 ...
2
votes
2answers
310 views

How AF works with lenses f/2.8 vs f/4

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 ...
0
votes
1answer
589 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 ...