Aperture & Shutter Speed (A Beautiful Relationship)

So today I want to hit a bit more on aperture and shutter speed.

As I said in the last post...

Aperture = Size of hole in the lens. Bigger hole equals more light. Smaller hole means less light. Bigger hole means shallower depth of field (less in focus in front of and behind your subject). Smaller hole means larger depth of field (more in focus in front of and behind your subject).

Lets add a bit to what we've already learned. The size of the aperture is referred to as an F-stop.

This is the confusing part... This will be tough for many people to wrap your heads around. I know it was for me at first

The larger the F-stop number (ex. F/22), the smaller the hole opening.

The smaller the F-stop number (ex. F/2.8), the larger the hole opening.

Let's lay this out in a table of sorts:

• Little number, Shallow DOF, More light
• F/2.8
• F/4
• F/5.6
• F/8
• F/11
• F/16
• F/22
• Big number, Large DOF, Less light

if you set your camera to manual and read the instructions on how to change aperture...

scroll through the numbers by changing the aperture. you'll notice there are other numbers between these that I have listed. i didn't list them because the numbers above are 1 full stop of light each. just know that you can change the F/number in smaller increments perhaps 1/3 a stop by using one of these other numbers.

So now what is a stop or an F stop?

A stop is how we measure how much light is being allowed to hit the sensor through the cameras aperture.

So lets say we shot a photo and it was really bright and overexposed. One way of fixing this is changing the size of the aperture, perhaps reducing it one stop of light (meaning a bigger F/number). This would in turn reduce the size of the aperture opening allowing less light to reach the sensor.

Shutter Speed - Length of time the shutter is open allowing a given amount of light to pass through the aperture opening to your cameras sensor. Slower shutter speed means more light. Faster shutter speed means less light. Slower shutter speed blurs movement. Faster shutter speed freezes the movement.

Again with the confusing part. When referring to shutter speed, a seemingly large number (1/1000) is actually a lesser amount of time than a seemingly smaller number (1/15). One one thousandths of a second is a very short period of time whereas one fifteenth of a second is a considerably longer amount of time. Keep this in mind.

• Small Number, Shorter period of time, Less light, Freezes action
• 1/1000 of a second
• 1/500
• 1/250
• 1/125
• 1/60
• 1/30
• 1/15
• 1/2
• 1 second
• Bigger number, Longer period of time, More light, Blurs movement

again each number in the table above represents one full stop of light. your camera settings will likely show numbers between these numbers but they are in increments of 1/3 of a stop.

So how does aperture and shutter speed relate to each other. It's rather genius really...

To keep a set exposure, but change the artistic effects, you can change either the aperture or shutter speed to reach the desired effect. If you change either of these things you will throw your exposure off soooooo: If you reduced the aperture by one stop to get a desired effect, you can increase the shutter speed by one stop to maintain the proper exposure. So what you do to one, you have to do the opposite to the other!!

Lets say you have a photo where you've nailed down the exposure. It's really great. The only problem is that the photo is blurring the movement and you really want to capture that car moving by freezing the action:

Sample Settings for desired exposure: 1/30th second & F/11

If you refer to the above table you'll see that you change your shutter speed to something more suitable for a moving car say... 1/250th of a second. That's 3 stops of light. You must then drop the F/stop down by 3 stops. The trusty table above will show the appropriate F/number to maintain your exposure is F/4.

We've just changed the artistic effect without hindering our desired exposure.

Another example:

You have a portrait and you'd like the background to be blurrier or more out of focus (OOF).

Current settings: 1/30th second & F/8

We want to make the f-number smaller or the hole larger (don't forget that trickery). To do this we may stop down the F-number to something like F/4. Conveniently F/4 is exactly 2 stops of light less than F/8. To maintain our desired exposure we should then increase the shutter speed by two stops. Trusty table above says 2 stops of light difference would be 1/125th of a second.

So again we've changed the artistic effect without changing our shutter speed.

it should also be noted that since your camera allows you to choose stops in 1/3 increments as mentioned above....three clicks of the wheel in either direction would adjust your setting 1 full stop. so if you want to decrease you're aperture one full stop you'd click the aperture wheel 3 clicks to the left. in turn, you'd click the shutter speed wheel 3 clicks to the right to maintain that desired exposure.

To wrap this up, let's take a glance at a few examples of the artistic effects available with aperture and shutter speed.

Desired Effect: Blur everything closer than and beyond our focal point (the little knob sticking out of the tree). We need a large aperture opening to gain the desired effect aka a small F/number.

F/4, 1/80th second

Desired effect: Subject (people) and background in focus. We need a small aperture opening (large number) to gain this desired effect.

F/22, 1/100th second

Desired effect: Freeze the action. We need a fast shutter speed.

F/2.8 1/4000th second

Desired Effect: Blur the movement. We need a slower or longer shutter speed.

F/4.5, 1/25th second

In conclusion: Whatever you change in either aperture or shutter speed, you must then change the other in the opposite direction to maintain a desired exposure.

This has been aperture and shutter speed "From The Ground Up!"