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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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 ...
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3answers
126 views

Why isn't glass transparency part of the exposure calculation? [duplicate]

The F number is a ratio calculated purely from the focal length of the lens and the size of the aperture. Any light meter talks in terms of F, Shutter, and ISO. Different glass, or just different ...
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2answers
80 views

Aperature/f stops/lenses [duplicate]

I am interested in landscape photography and a common point I hear thrown around is that a higher aperture (f11-f22) is best for landscape photos. However, every blog, YouTube video and photography ...
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2answers
57 views

How do constant aperture zooms produce identical exposure, even though focal length is larger? [duplicate]

My understanding is that a larger focal length corresponds to a larger working aperture diameter, since the numerator is larger. Why doesn't a larger working diameter correspond to a brighter image? ...
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1answer
65 views

How is the diameter of a non-circular (effective) aperture actually measured?

An f-number is determined as the ratio of the focal length to the diameter of the entrance pupil. But the actual aperture diaphragm is usually not a perfect circle. Its shape is determined by the ...
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5answers
833 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 ...
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2answers
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Can I use a Speedbooster with a Canon EF-S DSLR?

Could you please give me some advice about a speed booster? I have a Canon EOS 750D. Lately I have been taking quite a few night event photos. I do not have a fast lens (and can't afford one) and my ...
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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!
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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 ...
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2answers
429 views

My Tamron 100-400mm f/4.5-6.3 jumps to f/6.7 beyond 360mm

I got a brand new lens today: a Tamron 100-400mm F/4.5-6.3 Di VC USD. I have mounted it on my Nikon D80. This lens seems to have a problem with its aperture: At 100mm, I can operate from f/4.5 ...
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223 views

depth of field and f-stop

I have a thorlabs DCC1545M camera. https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=4024&pn=DCC1545M e.g. it has a 1/2 inch format, a sensor size of 6.66mm*5.32mm, with 1280*1024 ...
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3answers
1k 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 ...
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1answer
282 views

What are some general rules for astrophotography?

What are the generally accepted guidelines for iso, f-stop, aperture, etc. that help take better pictures of the stars? In the past I've mostly used a small webcam that fits over the eyepiece of my ...
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1answer
478 views

Will the F-stop Loka or Ajna fit a Macbook Pro 15"?

I'm currently looking at getting a new camera bag that I can use to fit a bit of gear (listed below) and wanted to know if anyone has/had one of these bags and in particular if it will fit a 15" ...
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5answers
385 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 ...
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1answer
199 views

How does focus breathing affect DOF?

Like explained in this question Does focus breathing make a lens slower when close focusing? focus breathing does change the effective F-stop. At the same time, the lens behaves, as if it was a ...
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4answers
691 views

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 ...
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4answers
646 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 ...
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3answers
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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?
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1answer
356 views

How to choose f-stop / depth of field? [duplicate]

I am fairly new to photography and I have read many "beginners guides" and watched youtube tutorials. One thing that remains elusive to me is how to properly pick what f-stop to use. I use a 35mm, ...
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2answers
1k views

Flash guide number f/stop calculation

I have been reading the B&H Speedlight Buyer's Guide. I am confused specifically about the guide number calculation. I understand the principle and how the inverse square law is used. Here is the ...
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4answers
152 views

Can cameras set exposure in more precise increments than third stops in automatic exposure mode?

If I shoot in manual I set the exposure to the nearest 1/3 stop. If I use one of the automatic modes does the camera do the same thing or can it set the dependent variable to a resolution finer than 1/...
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5answers
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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....
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1answer
2k 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 ...
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1answer
409 views

Why don't the Shutter Speed, Exposure Time, Lens Aperture, and F-Number metadata values from my camera make sense?

I was just looking at some digital image properties, and it did not seem to make sense. Shutter Speed: 1/16 sec. Exposure Time: 1/11 sec. Lens Aperture: F/1 F-Number: 2.8 I would have thought that ...
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3answers
916 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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1answer
63 views

Recommended F-Stop for older Canon 35mm F/2 [duplicate]

I have a few year old Canon 35mm F/2 lens (Here it is on Amazon). I've been shooting wide-open, but I realize that doesn't make for the sharpest photos. What would you say would get me the sharpest ...
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2answers
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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 ...
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1answer
111 views

Why does Photoshop say the f-stop is f1.6 in the summary but 1.4 in the details at the bottom?

Here is the picture; photo shot in RAW. Why is it that at the bottom it says f1.4, but the summary on top says f1.6? Plus, I am pretty sure flash fired too but again it is saying flash did not fire.
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2answers
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How is depth of field usually measured and how can I get depth of field measurements for a lens

I really like a deeply washed out background as a backdrop. I expect using a 35mm film camera that f-stops is inversely related to depth of field. I assume this remains true for compound lenses. But ...
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2answers
558 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, ...
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1answer
331 views

I want to know about the relationship between focal length and aperture [duplicate]

I have Nikon D7000 and I know the basic relation of shutter speed, aperture, and iso. All I want to know is focal length and aperture relation. As I zoom in the camera the f/stop increases (e.g. it ...
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1answer
297 views

How to photograph oil and pastel art works with DSLR? [duplicate]

I'm using a Nikon D800 with a prime Sigma 50mm f1.4 lens to photograph a selection of artwork for producing an art book. I will shoot in raw format. My questions are: What light source will look ...
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2answers
1k 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 ...
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2answers
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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-stop that the camera changes the ...
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1answer
99 views

How to shoot the sequence of adjusted exposures wanted for a ColorChecker?

I'm trying to shoot a sequence of photos needed for calibration. As instructed, I'm in manual mode, with fixed ISO 100 (camera dafault), and other values read from the lightmeter ... and now: Can you ...
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3answers
813 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 ...
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4answers
1k 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 ...
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1answer
169 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, ...
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4answers
559 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 ...
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3answers
2k 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 ...
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4answers
1k 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. ...
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1answer
19k 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 ...
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4answers
7k 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 ...
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3answers
3k views

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 ...
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2answers
8k 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 ...
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3answers
2k 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 ...
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2answers
460 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 ...
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2answers
183 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?
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0answers
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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 ...