Camera For Dummies: Basics
Camera For Dummies Basics: Aperture
As we learned earlier a basic requirement of taking a good photo is to ensure correct exposure level. A camera provides you with 2 mechanisms to do this,
1. Change the size of hole/aperture through which the light passes and thus controlling the amount of light OR
2. Change the shutter speed and thus controlling how long you expose the film to light.
We already discussed option 1 "changing aperture" in Camera For Dummies Basics: Aperture.
In this blog we'll talk about the things one can do with shutter speed.
So what can you do with/to the shutter speed of your camera?
Anyone would know the answer to that: "You can increase it or you can decrease it" :)
But what we are here to know is what happens if you increase it or decrease it.
Increasing the shutter speed will make shutter remain open for a shorter time and vise-versa.
Lets see first what happens when you use slow shutter speed.
Lets say on a pleasant evening you are out shopping (I know guys you would rather watch TV) and you hear the sound of a Yamaha engine and just across the road you see a 2012 Chevy Corvette 3ZR waiting for the green. You feel lucky as you have your camera handy. But the speed of your hands is no match for 638hp of it's 7.0L engine. As you fumble to get the camera ready the lights are green and you have just enough time for a quick click before it vanishes from sight. You pray that it was in frame and the "auto" mode your camera did a decent job at deciding the exposure. But you're horrified when you see this in the LCD screen of your camera:
Well lets talk a li'l math and see what we can figure..
What you realize is that the Corvette with it's 7.0L engine had already hit 60mph by the time your fumbling hands got around to click the photo. So you go back check the shutter speed that your camera had chosen for this photo and you see a figure of 1/100 (seconds). So you do quick math
60mph is ~100 kmph viz ~25 meters or 75 feet per second
That means in a 75th of a second the Corvette would've traveled 1 feet.
So?! Well, that means when you clicked your camera the shutter opened and by the time it closed the Corvette was 1 feet away from where it was [1/100 sec before]. And your camera recorded everything that happened between this period. So what you see is just a blur.
Now if that's clear lets see what we can do to avoid this? Given the maths we did it seems pretty obvious that if we can make the shutter speed fast enough so that the Corvette doesn't move (at least not considerably) while the shutter is open we should have a still photo. Assuming that movement of about 5 centimeter is okay (hell, it might make it look cool actually!) then the shutter speed should be: ( 3600 / (100*1000*100) ) * 5 = 0.0018 = ~1/550 seconds.
So what we learned is that in the moving world if you want to take a still photo you must set your shutter speed fast enough to convert the movement into a still photo.
A few other examples are:
- A mosquito flaps it's wings 300 times a second, so if you want to take a still photo of a mosquito you should set your shutter speed to 1/300 seconds (0r faster)
- A formula 1 Ferrari's top speed is around 320 kmph, so to take a still photo you'll need a shutter speed of at least 1/2000 ! (this is the reason why you don't see many photographs of formula 1 cars taken at their top speed, instead people take a photo when the cars are turning at low speed, hey now you know where to sit in the stadium when watching an F1 race !)
So now you'll ask the obvious question: When we can take a still photo mostly at a fast shutter speed why use slow shutter speed ?!
Well, a fast shutter speed is a necessity (in some particular situations) where as a slow shutter speed is something of a leisure, that adds some interesting details/aspects to your photo.
Here for example is my favorite photo (again courtesy photo.net) that shows the delights of slow shutter speed:
Here is the textbook example of what happens when you use fast shutter speed (you can see each individual droplet of water), whereas if you take the same photo by slowing down the shutter speed a bit you get a much better photo, where you can see stream of water instead of droplets:
1. Shutter speed is a specification of camera body (as shutter is part of camera body).
2. Aperture size (min/max) is a specification of a lens (as aperture is part of the lens).
3. As for a good photo one must maintain the correct exposure level, when you slow down your shutter speed you must reduce the aperture size (close it down). At times (given the amount of light around) it's simply not possible slow down the shutter speed if we have reached the minimum aperture supported by the lens. This happens if you have a bright sunny day.
4. The exact opposite of #3, when you fasten up the shutter speed you'll have to make the aperture bigger (open it up). But in low light conditions night/evening/indoors/overcast/cloudy you'll have less light to work with and so you'll soon hit the limit to which you can fasten up the shutter speed at wide open (maximum supported). => This is the reason why you see so many party/night photos where people are blurred.
Here a few more examples of good use of shutter speed.
Fruit in water (fast shutter speed):
Sand Storm (slow shutter speed):
Before we wind up here is some homework. Can you guess how these were taken?!
Mercedes SLS
2012 Chevy Corvette
