# Tagged Questions

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 ...

2k 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?
122 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, ...
114 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 ...
101 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/...
241 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....
147 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 ...
108 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 ...
679 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/...
46 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 ...
24 views

### What does it mean to be out of focus [duplicate]

I have browsed dozens of photography and noticed that only a handful actually try to reconcile the photography world with the real world. My ultimate goal is to be able to easily explain to anyone, of ...
211 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 ...
84 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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### 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 ...
102 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, ...
98 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 ...
185 views

### How to photograph oil and pastel art works with Nikon D800? [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 question is first, what light source will look ...
693 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 ...
217 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-stop that the camera changes the ...
80 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 ...
313 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 ...
421 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 ...
116 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, ...
370 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 ...
872 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 ...
847 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....
7k 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 ...
2k 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 ...
914 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 ...
2k 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 ...
1k 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 ...
350 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 ...
113 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?
72 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 ...
1k 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 ...
144 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 ...
1k 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 ...
379 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 ...
273 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 ...
1k 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 ...
2k 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 ( < ...
3k 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 ...
600 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 ...
587 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 ...
843 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 ...
878 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 ...
453 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 ...
46k 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 ...
15k 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 ...