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20

For f/stops, there is a precise multiplied difference of 1.122462 X intervals (cube root of √2) between all third stops. The precise third stops are actually numbers like 8.98 or 10.08. My meaning of the Precise Numbers is of course the theoretical precise goal numbers that the camera designer certainly aims for. There can be no question about those (even if ...


19

Let's start with lenses at the same location, and then address the moving the longer lens farther away to get the same field of view. Lenses at the same location The 50mm f/1.4 lens has an effective aperture that's twice the diameter, and four times the area, of the 25mm f/1.4 lens. The 50mm will, therefore, collect four times as much light (four times as ...


19

This is really simple when you think about it. The additional element changes the focal length of the lens, without changing the apparent size of the aperture. That means that the relative size of the aperture decreases, so the f number does in fact actually change. (If this is unclear to you, see the bit about f numbers in this other answer.) This is also ...


19

Because in cinema, it's common to change lenses within a shoot while preserving identical exposure. This is rarely important in still photography (and even less so with the flexibility of digital). You might say But t-stops are more accurate, allowing me to be more precise! — and that's basically right, but the main thing is that precision is overrated in ...


18

You've hit the diffraction limit. That link has some amazing answers with a lot of detail, so I won't be redundant, but in short, once the aperture gets to be below certain physical size, diffraction causes inevitable blur. For your camera (and any other camera with an APS-C-sized sensor), the limit is a little beyond f/11. The amount of light let in doesn'...


17

Dynamic range is not measured in f-stops, it is measured in stops. A stop is often used to refer to a change that doubles the value or, in the case of cameras, the amount of light. Changing the aperture by one f-stop doubles to amount of light allowed in, so in the case of aperture, a stop is an f-stop. Similarly, cutting the shutter speed in half is a ...


17

To add to mattdm's great answer: In addition to the added exposure precision, which is not important to photography, T-Stops are LESS precise in other ways which ARE important to still photography. F-stop is the literal proportion of the aperture to focal length. T-stop adjusts this for exposure, but this raw value is important to depth of field. Depth of ...


16

No, this is not the case. Aperture F stops are calculated on pupil size and focal length of the lens. From wikipedia In optics, the f-number (sometimes called focal ratio, f-ratio, f-stop, or relative aperture1) of an optical system is the ratio of the lens's focal length to the diameter of the entrance pupil.2 It is a dimensionless number that is a ...


15

The pupil (aperture opening) area is proportional to the square of the focal length (at the same f-stop). So 105mm being about twice the focal length of the 50mm, it would need 4x the pupil (area) to be f/1.2. In other words f/1.2, or any f-stop, doesn't correspond to a fixed diameter - it increases for larger focal lengths. That also assumes both lenses ...


15

F-Stops matter most when you care about knowing your composition and depth of field, T-Stops matter most when you care about knowing your exposure. Photographers want to control composition first and adjust exposure as needed. Cinematographers need to control exposure first and then compose as needed. The critical difference with photography is that we can ...


14

Most DSLRs let you choose shutter speed and aperture at 1/3 of a stop difference (3 clicks of the dial to double or halve the amount of light), I'm not a camera designer but I would guess that since 1/3 of a stop is a small difference being able to set exact shutter speed isn't worth the extra electronics and software to support it. For aperture also add to ...


14

The f-stop is more directly relevant to photographers because it normalizes out the focal length. It then gives you a measure of how bright the image will be on the sensor relative to the scene brightness. For example, if a scene is well exposed with a 50 mm lens at f/8 and 1/200 second, then it will be well exposed with any other lens at f/8 and 1/200 ...


13

An f-stop is a mechanism for setting the aperture of the lens, or how wide it is opening to let in the light. There's two parts to it: f and stop. First, the maths. f-number An f-number is a number in the form f/2.0 which specifies the size of the aperture opening. f refers to the focal length. f/2.0 means the diameter of the aperture opening is the ...


13

It's not linear because it's based on area rather than lines. Or, to put it another way, the scale isn't based on square roots. It's based on the actual math that represents the physical properties of the system, and it happens that exposure doubles when aperture size opens by a factor of the square root of 2. If you remember back to your elementary-school ...


13

"Therefore lens 2 has a larger maximum aperture than lens 1 and therefore capability to allow more light. This is where your understanding is not quite right. The physical size of the aperture is indeed larger in the longer lens, but it does not allow in more light, because the longer focal length means that the field of view is narrower. This means that ...


13

If you look at filter #209 you'll see "Reduces light 1 stop (Transmission = 51%)". That is what you expect to see. Filter #210 reduces light 2 stops and has transmission of 24%. Again, what you expect. So what is the matter with filters 207 and 208? They are COLOR filters not neutral. They a) reduce light, and b) reduce it differently in different ...


13

Crop factor has nothing to do with T-stop. T-stop is strictly about light transmission which affects exposure. If a lens could be 100% transmissive the T-stop and f-number of the lens would be the same number, but they would still be measures of different things. T-stop measures how much light is passed through the lens, f-stop measures the size of the ...


12

In this context, a "stop" refers to exposure duration. As an approximation, the distance a handheld camera moves during an exposure is directly proportional to the duration of the exposure: double the time the shutter is open and you double the movement. That (again approximately) doubles the amount of blurring in the image. Normally, to achieve an ...


12

Needless complexity. This isn't a technical challenge, it's a usability one. Sure the mechanical tooling could be adjusted to do that, and in some high end cell phone cameras you do see some truly bizarre shutter speeds to adapt to their limited range of aperture... but WHY? What technical advantage would it present you to be able to do 1/19th instead of 1/...


12

Historically, the unit of exposure was a doubling or halving of the exposing energy. This is the origin of the f/stop. Initially, this adjustment was made by inserting a thin metal plate with a circular hole, into a slit in the lens barrel. The photographer had a series of these metal slides called Waterhouse Stops after John Waterhouse circa 1858. The ...


11

ISO Bracketing This will create images with different amounts of noise in them. I call this grain, others just call it noise. Depending on the ISO range that you are using, you may or may not cause issues by doing this. Higher in the range, if you combine different areas of a ISO bracketed image you will see different noise profiles throughout and that may ...


11

Whole f-numbers are an expression of the powers of the square root of two (√2). Every odd-numbered or fractional power of the square root of two is a non-integer with an endless number of places to the right of the decimal. Such a number is defined as an irrational number. In photography we round the actual values of many irrational numbers to a simpler ...


10

It's convenient for shutter speed, aperture, and ISO to operate in stops, because then it's easy to interchange them. Minus one stop of shutter means plus one stop of aperture or ISO, for example. Using fractional stops adds some versatility, but at the expense of having to cycle through more options. My DSLR lets me choose whether I want operate in third or ...


10

The intention is that the actual exposure should be exactly the same for equivalent exposure settings, but there are small deviations. There are also some other differences to the images other than the obvious (e.g. different depth of focus for different apertures). Here are some differences that you may experience when choosing a different setting with the ...


10

In a theoretical sense, these things are perfectly interchangeable. See the second half of my answer to What is the "exposure triangle"? (after I get done ranting about the terminology). This is actually exactly the point of the "stops" system — you can think in terms of Exposure Value (measured in stops) and not need to worry about any complicated ...


9

The monopod removes three degrees of liberty: distance from ground is fixed, and roll and pitch are linked to position in space. But you are overlooking that you are no longer lifting the (potentially heavy) lens, so its shaking is no longer caused by your muscular control, itself affected by muscular fatigue(*). Of course the 55-250mm is a rather light ...


8

That is true, and very noticeable in macro lenses. For example a Nikon 105mm f/2.8 VR (at infinity) is f/4.8 at it's closest focus distance of 30cm or so.


8

There's quite a bit more to it than a longer lens needing a larger diameter to maintain the same relative aperture. For a couple of examples, spherical aberration and coma are both proportional to the square of the lens' aperture. If we took the design of the 100/2.8 lens and doubled the diameter of each element, we could expect to get a 100 f/1.4 lens -- ...


8

It is mainly about the cost/benefit ratio of making cheap lenses. It doesn't cost a lot more to make a lens f/3.5 than f/8 at an 18mm focal length since the entrance pupil (sometimes referred to as the effective or apparent aperture) is still well within the diameter of the mounting flange used by most interchangeable lens camera systems. As the lens is ...


8

There are two factors determined by physics that favor autofocusing with wider apertures. More light An f/2.8 lens lets in twice as much light as an f/4 lens. The more light an AF system has to work with the faster and more accurate it can be. Signal-to-noise ratio affects performance of the sensels on PDAF sensors the same way that it affects performance ...


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