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by Bart Arondson

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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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51
votes
4answers
36k 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
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...
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 ...
18
votes
9answers
21k 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 ...
16
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 ...
16
votes
2answers
2k views

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

Does anyone know the origins of the term?
15
votes
2answers
863 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 ...
13
votes
5answers
707 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 ...
11
votes
2answers
405 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 ...
10
votes
5answers
6k 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?
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 ( < ...
9
votes
2answers
523 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 ...
8
votes
2answers
695 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 ...
8
votes
3answers
449 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 ...
7
votes
4answers
376 views

Would I gain 1 Stop with a L lenses

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 ...
6
votes
4answers
240 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
4answers
665 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 ...
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 ...
6
votes
2answers
315 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 ...
6
votes
3answers
410 views

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 ...
5
votes
4answers
11k 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 ...
5
votes
1answer
464 views

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 ...
5
votes
7answers
2k views

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 ...
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 ...
3
votes
4answers
203 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 ...
3
votes
2answers
569 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 ...
3
votes
1answer
306 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 ...
3
votes
0answers
63 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 ...
2
votes
3answers
643 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 ...
2
votes
2answers
280 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 ...
2
votes
2answers
420 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 ...
2
votes
3answers
172 views

How is the number of stops of benefit provided by VR determined?

I hear people talking about vibration reduction giving you extra 'stops' on a lens, thus giving you extra shutter speed to play with. How do people work this out into an amount of stops? E.g. by ...
2
votes
1answer
240 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 ...
1
vote
4answers
169 views

What is the equivalent f/stop for 50mm?

If f/8 And Be There is the rule for 35 mm, what is the best f/stop if I am using 50mm? Context: Street Photography Note: Though one can say that "it depends", this is a very specific question. When ...
0
votes
2answers
392 views

True or False: A two full F/stop change to either side of the starting F/stop will either double or half the amount of light from the original F/stop

Explain. A two full F/stop change to either side of the starting F/stop will either double or half the amount of light from the original F/stop.
0
votes
1answer
486 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 ...
0
votes
1answer
74 views

what is the barriers of making fast lenses? [duplicate]

I know there are lenses like f/0.7 However as a beginner I'm wondering what's the barrier of making ultra fast lenses like f/0.01 ? Also if lens manufacturers willing to make wide aperture lenses, ...
0
votes
1answer
121 views

Can someone give me an. Example of when you would want to stop down? I do this manually? I just purchased a Canon 3Ti with a Canon 18-200 lens [duplicate]

Can someone give me an. Example of when you would want to stop down? Do I do this manually? I just purchased a Canon 3Ti with a Canon 18-200 IS lens. We will be shooting outdoor sporting events also ...
0
votes
0answers
28 views

AF points, focusing at f1.0-2.2 [duplicate]

I am considering the canon 5d mark iii or the 6d. Between the mostly negligible differences between those cameras, the AF point system of the 5d has many more "points". Having never really relied on ...
-3
votes
2answers
83 views

Low f/stop = fast lens? [duplicate]

I have heard of lenses being described as fast that have f/stop values of f1.2 and f/2.8. My question is why are such low f/stop lenses called fast?