# Tag Info

67

An f-stop is kind of a combination of two terms. First off, f/N is generally the notation used to indicate the size of the diaphragm opening, or aperture, in a camera. Let me give a little detail about how that notation came about, before I go on to explain the meaning of a stop. Aperture Values and f/Stops Aperture openings are measured as fractions of ...

65

It's an extra two-thirds of an f-stop, with all that comes with it: Narrower depth of field (perhaps marginal in comparison to the f/1,8) Brighter viewfinder; great in low-light situations Might be the difference between getting the shot or not, also in low-light situations Lenses tend to get sharper when stopped down. At f/1,8 the f/1,4 lens is stopped ...

63

To increase readability and avoid exceeding the answer length limit, this answer has been split across two posts. General information and APS-C cameras are covered in this post; full-frame and APS-H cameras are covered in a separate post below. TL;DR answer In general, Canon DSLRs require a maximum aperture of at least f/5.6 to autofocus, although EOS-...

51

There have been some very good answers, however there are a couple details that have not been mentioned. First, diffraction always happens, at every aperture, as light bends around the edges of the diaphragm and creates an "Airy Disk". The size of the airy disk, and the proportion of the disk that comprises the outer rings, and the amplitude of each wave in ...

37

It's likely the sum of a few factors. Firstly, although you state "the same f-stop", it's important to realise that the manufacturer stated focal length and aperture values are often rounded, and not always in the way you'd expect. It might be the case that the Samyang is f/1.45 in reality, not f/1.4. The next factor is vignetting, wide aperture lenses are ...

36

Aperture simply means "opening", and in photography we use the term to refer to the diameter of the opening in a special adjustable diaphragm within each lens. When this diaphragm is constricted, there's less physical space for light to get in, so naturally the exposure is darker, and a more-open aperture allows more light and results in a lighter exposure. ...

35

Firstly the iPhone 5 lens has to be f/2.2, due to the small pixel size, the effects of diffraction which start to creep in at f/11 on a DSLR, start to creep in at f/1.45 on a 5.6mm (diagonal) sensor! I though that in order to have a big aperture such as f/2.2 a big amount of light should be able to enter to the sensor and in order to do it, a big lens ...

34

Broadly speaking wide aperture lenses are easier to design the longer the focal length. The reason that you don't see any 400mm f/1.4 lenses is due to manufacturing difficulties, e.g. keeping dispersion low while producing elements of the size required for such apertures. It's worth restating that the designation f/1.4 means that the size of the aperture ...

32

I was recently trying to figure this out myself, and found this question. I didn't feel the accepted answer was quite complete, so here's my shot (no pun intended!): The first thing to understand is that the light that reflects off any one point on a surface isn't one beam of light, but many, coming in at many different angles and reflected off at many ...

32

The aperture range on your lens only shows the maximum aperture for your lens at the extremes of the zoom range; i.e. f/3.5 at 18mm and f/5.6 at 55mm. There is nothing to stop you using a narrower aperture; remember a larger number is a smaller hole (the f number is the diameter of the hole as a fraction of the focal length).

29

Why the wide aperture blurs the background more Let me start with Wikipedia figure: Above we have a wide open aperture. Only point 2 is in focus. Points 1 and 3 are out of focus. Due to wide aperture, the rays coming from them through different parts of the lens intersect the screen 5 (a film or a digital sensor) in different points. We may also tell ...

28

The aperture affects not only the amount of time required to take a photo, but also the depth of field within it. With a wide aperture (so a low number, like f/1.8) gives a shallow depth of field - sometimes less than a millimetre with a macro lens. Because a lot of light is reaching the sensor (be it film or digital), this allows for fast shutter speeds ...

27

Get a flash! Seriously, even the small external flashes make a huge difference. You can also (at least on my Nikon SB-400) direct the flash at the ceiling, which both annoys people less and also nearly always eliminates red-eye.

27

Noise is better than blur (and much less of a problem than you might think from reading the internet), so don't hesitate to vigorously boost ISO. Underexposing won't help; it's basically the same as increasing ISO w.r.t. noise. The only time to do this is when you've already maxed out the ISO adjustment. Consider a "fast fifty" - you can get a 50mm f/1.4 ...

27

Depth of field depends not only on aperture but also on distance to the subject. Depth of field increases as the subject gets farther away. If the wave and boats were all relatively far from the camera, but not terribly far from each other, then it's not surprising that they were all reasonably sharp. You can use DOFMaster to run the numbers yourself. Some ...

26

Although the relative aperture numbers — the ƒ stops — are the same regardless of format, the actual focal lengths of the lenses on small cameras are quite low: 5mm or 6mm at the wide end. That in turn means that the real aperture is small, which means the diffraction limit kicks in sooner, reducing sharpness as one stops down. The smaller format also means ...

26

F-stops deal with doubling/halving the amount of light hitting the sensor. Everything revolves around twos. With the shutter speed, it's easy to understand, as you say. Every shutter f-stop is (roughly) half/double the amount of time as the previous one. Personally, I don't even bother paying attention to the numerator ("1/") part of the shutter speed; I've ...

26

I'm going to crib from my answer to an earlier question on aperture: When the aperture is very small, the admitted light is highly "collimated", which is a fancy way of saying "all the rays are nicely parallel to each other". This results in a sharp focus for all the light that comes in. When the aperture is more open, only the rays which closely match ...

26

do most photographers avoid using zoom No. If "most photographers" avoided zoom lenses with variable aperture, there'd be fewer zoom lenses with variable aperture on the market. Furthermore, there are plenty of fixed aperture zoom lenses available at a range of focal lengths, so it's safe to say that photographers don't have to avoid zooms just to have ...

25

F-stops are purely geometrical, the ratio of aperture to focal length, regardless of actual light transmitted. But all lenses absorb a part of the light passing through them, and the amount being absorbed varies lens to lens. So, in situations where even the slightest change of lights being transmitted affect the output, i.e cinematography, where many images ...

24

First of all, it was an issue on film. If Bryan Peterson wasn't aware of it at the time, it just shows what he didn't know, not that it actually wasn't a problem. There were differences though. First of all, we didn't have EXIF data, and most people didn't keep careful enough notes to really know why shot X came out quite a bit sharper than shot Y. Even for ...

24

Well, one way of remembering the f-stop scale is to remember that every other value is a multiplication by two, or in more photographic terms...every four-fold jump in light availability is twice the f-stop number. As an example: Double-stops starting at the beginning: 1, 2, 4, 8, 16, 32, 64 Double-stops starting skipping the first stop: 1.4, 2.8, 5.6, 11.2 ...

24

No - the aperture is set by the physical blades in the lens when you take the photo; a RAW "image" contains the readings from the sensor when the photo was taken, so there's no way you can go back and modify the light which was captured by the sensor. While it's not as obvious, this is equivalent to asking "Can I modify what the camera was pointing at from a ...

24

The blur is caused by the people moving while you were taking the photograph with a slow shutter. Honestly, I think it improves this particular photo a lot: it shows that the people are dancing, rather than just standing in weird positions. If you want to, the only way to avoid it is to use a faster shutter speed. This necessarily involves compromises. If ...

23

It's now more common to control aperture through the camera. The mechanical aperture ring adds cost, mechanical complexity which can lead to equipment breaking, and it can be confusing to users (if it's set to something other than the smallest aperture many cameras will give a confusing error on a lot of modes). It also prevents Nikon from putting a seal ...

22

The sweet spot of a lens is probably just as dependent upon the type of image capturing surface used as the lens itself. Both film and digital sensors have a limit of detail they can resolve (although large-format film has the tendency to capture FAR more detail than 35mm or digital sensors at much tighter apertures, around f/22.) Assuming you have a lens ...

22

Yes, there are several reasons for this. Larger apertures allow for a smaller depth of field, and generally better bokeh. Faster/more accurate auto focus, because more light is available to the focus system. Much more versatility, because more light falls on the sensor at a wide aperture, which opens up your options in lower-light settings. Better image ...

22

Looking at your samples, the answer seems clear to me: that's not grainy, that is, actually, out of focus. Here's a 1:1 crop of your wide-open image: It seems pretty apparent that the wooden sign is sharp but the dog isn't, and the appearance of the blur looks completely in line with what one would expect from out-of-focus blur, not noise or grain. ...

21

I'm not sure about with Nikon, but one of the biggest differences I see mentioned between the Canon 50mm 1.8 and 1.4 lenses is the build quality - plastic vs metal among other things. This is probably what accounts for most of the price difference.

21

f1.4 will always be 2/3rds stops faster than f1.8. The diameter has nothing to do with whether or not part of the sensor is hidden. That is a separate measurement referred to as vignetting, and not the image circle's light level. The image circle's light level/brightness is directly affected by the aperture of the lens design. FF lens simply means the ...

Only top voted, non community-wiki answers of a minimum length are eligible