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Shutter speed (or exposure time) in photography

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Poorly controlled, shutter speed can spoil your photos or even frustrate you if you don’t understand it at all. On the model of the article on the opening, let’s discover together the theory and the practice on this fundamental aspect of photography. Follow the guide !

Definition

The shutter speed is the time during which the shutter opens on release, that is to say the time during which your sensor is exposed to light. If you prefer the window metaphor: the time you open the window.

On the device

This speed is expressed in seconds, and more commonly in fractions of seconds: 1 / 125s, 1 / 3200s, etc … The higher the speed, the less time you open the window, the less light you let in. Thus, you will let in more light at 1 / 125th of a second than at 1 / 3200th of a second, for example.

Modern cameras generally allow you to use very fast speeds (1 / 4000th or 1 / 8000th of a second for example), very slow speeds (30 seconds or more, for taking long exposures), and of course all more classic speeds between the two.

How to adjust the shutter speed

Here, everything happens a bit like the opening. (for details, see the article on camera modes)

In manual mode (M)

In manual mode, when you turn the dial, you directly change the shutter speed. No, it’s not more complicated than that. And yes, that’s it.

Be careful, on some devices, there are two knobs: one will be used to change the aperture, the other the speed. You just have to test to know which one does what.

Again, changing this speed affects the exposure and you have to compensate with the aperture or ISO. I therefore advise you not to use this mode until you have understood all the ins and outs of the exhibition, or at least the basics (that is to say after the article on ISO!: D)

In shutter speed priority mode (Tv or S)

Once again, I’m going to repeat myself slightly: in this mode, your priority is to adjust the shutter speed (we’ll see in which cases just after). You only set the speed, and the camera does the rest, that is, it takes care of the aperture and ISO (again if you left the ISO auto option).

Motion blur

You have to remember that in the article on the aperture (decidedly), we saw the background blur (or “bokeh”, for those who like the lingo). This blurring is generally intended and can be simply controlled by the aperture.

There is also another type of blur: camera shake, which is due to the movements of the photographer. This blurring is generally undesirable, and you will try to avoid it.

What influences this blur and why am I talking about it in this article about shutter speed?

In fact, the shutter speed strongly influences the presence or not of camera shake for several reasons:

  • The stability of the photographer  : it’s stupid, but if you stand on a foot to imitate the flamingo, or if you have 2g of alcohol / liter of blood (or other neuron-killing substances: P), you will move more and therefore the device too. In addition, you have to hold your device in the right way, and for that I refer you to my article on basic advice!

That said, even if you keep your balance on your 2 feet and have the same lifestyle as a Buddhist monk, there will still be micro-movements that will cause motion blur. Overall, below 1 / 60th speed, you start to risk camera shake if you’re not careful.

  • The  focal length:  longer  the  focal length  (the “zoom”) is  important,  plus  you will be likely to have a  blur  everything ugly on your shots. For this, keep a simple rule: at  50mm, not slower than  1 / 50th, at  100mm, not slower than  1 / 100th, etc …

    (For slightly more advanced users, this requires precision: on small sensors, the focal length must be multiplied by a number between 1.5 and 2 because  of the conversion factor)

  • The stabilization or not the lens (or the camera): Most SLR and modern hybrids are equipped with stabilizers that make up your micro-movements.

    It is sometimes integrated into the body, and therefore active whatever the lens used like DZO Pictor Zoom. And sometimes integrated into the lenses, and in this case it is therefore necessary to ensure that it is present.

    This device makes it possible  to save on average 2 to 4 notches on the shutter speed  (depending on the model).

    In other words, you can reduce the theoretical values ​​mentioned in the previous points by 2 notches. But in theory only, in practice it’s  not always so spectacular (you will especially see the effect when photographing at telephoto and therefore at long focal lengths).

  • The  tripod: If you need to use a (very) low shutter speed (we’ll see for what (s) reason (s) soon after), using a tripod allows you to stabilize your camera enough to set to 1s or more without having motion blur.

Subject motion blur

Conversely, when your camera is relatively stable but your subject moves, your subject (a person, an animal, etc.) may be blurred on the shot. This subject blur is influenced by 2 factors:

  • the speed of movement of your subject: the faster it moves, the more subject blur you will have and vice versa
  • the shutter speed  more it is low (slow), the more you get blur subject and vice versa.

As much as you can’t play with the speed of your subject so much, it’s up to you which shutter speed to use, depending on the shot you want to get. It all depends on whether you want to freeze a fast subject, such as this snorting cheetah (taken at 1 / 500th), or if you want to give an impression of movement as I did with passers-by (photo taken at 1 / 8th).

In this area, it is impossible to give typical cases or advice depending on the situation. For example, in photography sports, we can give an impression of speed in both freezing the movement (with a speed Shutter important) or by creating a little fuzzy about (with a speed shutter more weak).