The Photographic Triangle

Did I throw people into the deep end a bit with my post on Action Photography? Were you reading it and thinking: “Depth of field? Huh? Aperture? Wha-? ISO? Keh? SLR? Well slow down there mister!”

If you weren’t then great! If you were then this next post will (hopefully) be for you. I will endeavour to explain the basic mechanics of photography, put it into layman’s terms for you, and hopefully get you feeling confident enough to turn off your camera’s AUTO function and start messing around with the manual controls.

(This is where years of teaching experience will come in handy I hope.)

So what is the “Photographic Triangle”? Well, to start with I don’t know if there actually is anything officially referred to as the “Photographic Triangle”, it’s just my reference to the three basic areas of control on a camera: Shutter Speed, Aperture, and Film Speed (which I will refer to as ISO from here on in). If you can master these three basic functions and how they relate to each other then you’re on your way to kickin’ ass and takin’ names in your picture taking endeavours.

Changing the settings of one of these will affect the other two and will also have an effect on your image exposure. So let’s go through the three and I’ll explain their basic function/s.

Shutter Speed: This is probably the easiest of the three to explain. This is the speed that the shutter in your camera opens and then closes once you press the button. It can be as fast as 1/4000th of a second (that’s pretty damn fast) or as slow as multiple seconds. Most digital SLR cameras will allow the shutter to open for 30 seconds at its slowest automatic time. The only way to go any slower is to set your camera to its Bulb function. This means you have to press the button once to open the shutter and manually press the button again to close the shutter. This function enables you to have the shutter open for hours on end. This is used for things like night time photography to pull off that cool star trail effect. A slower shutter speed is great for taking shots with motion blur: that ‘misty’ effect of waterfalls or car light trails at night. A fast shutter speed is great for capturing sharp, frozen moments in time or to show the power of something – like a wave at the beach or a thunder cloud rolling in.

On a “typical” daytime shoot I usually set my camera to shoot at between 1/125th – 1/400th of a second. Mind you, this is all dependent on the settings of the other two members of the triangle.

Aperture: This is the iris inside your lens and is what you use to control how much light enters the camera and hits your sensor (or film if you’re going “old school”) at the rear of your camera body. The lower the number the more open your lens is – more light gets in. The higher the number the more closed it will be – less light gets in. With me so far?

Your aperture also affects something called Depth of Field. Depth of field is the distance between the closest and furthest objects in a shot that are in focus (yeah, real clear there smart guy… – Ed.).

I think it’ll be easier to explain via a pretty picture I just made in Photoshop…

Does that help explain it a bit better?

A wide aperture – which will give you a narrow depth of field – is great for portraits and headshots as it allows you to isolate your subject from the background by keeping them nice and sharp while giving the background a soft blurring effect (we call that “bokeh” in the industry, apparently. – Ed.). A narrow aperture – which will give you a wide depth of field – is used in things like landscape shots where you will want to have as much in focus as possible to capture all the detail of your surrounds.

Messing with your aperture will mean you will have to adjust your shutter speed or ISO to get a correct exposure. Like I said earlier, they all interact and affect each other.

ISO (or Film Speed for film users): Back in the halcyon days of film (dude, you are aware that many photographers still use film, right? – Ed.), film speed/ISO referred to how sensitive photographic film was to light. The higher the number on your film the more sensitive it was. For example, a film with an ISO of 100 wasn’t as sensitive as a film with an ISO of 1600. ISO 100 film didn’t perform too well in darker environments whereas a film with a higher ISO did.

“So why didn’t everyone just use a film with a high ISO all the time?” I hear you ask. Well, because of something called “grain”. The higher the ISO of your chosen film the grainier your shots turned out. Sure, you might get a really nice shot but the grain in your image would possibly make it look like crap in a handbasket. (And no one likes crap in a handbasket.) Having said that, grain can make an image look really nice if used correctly.

In the modern digital camera your ISO settings perform the same function as ISO in film. The main differences are: instead of film you have a sensor at the back of your camera; you don’t have to load different films in for different environments (saving you time and hassle), and; “grain” is generally referred to as “noise”. The higher your ISO the more “noise” you get in your shots.

An ISO of 100 is good for taking photos in bright, well-lit environments. ISO of 1600 is for darker, indoor environments. I generally try not to go above an ISO of 800. Mind you, most modern DSLRs handle ISO up to 1600 pretty well without too much obvious noise thanks to some fancy-pants computerised algorithms built in to your wizz-bang DSLR camera. Go beyond 1600 and your images will usually look pretty… blech! (Is that a technical term? – Ed.)

So those are the basic explanations for the three main settings for any SLR camera. But how do they affect one another?

Okay, say you’ve set up a shot but your exposure is too dark. You look at your settings and you have your shutter speed set to 1/500th of a second, your aperture set to f22, and your ISO set to 100. You’re taking a portrait of someone and decide that you don’t want any grain in your shot so decide that you want to keep your ISO at 100.

That leaves your shutter speed and aperture to mess with. You set your shutter speed to 1/125th of a second as that’s fast enough to not get any accidental movement blur from your subject.

Because you’re taking a portrait of someone you figure that you want a really wide aperture to create as narrow a depth of field as possible to make your subject “pop” from their background. You set your aperture to f3.5 to achieve this.

Now you’re letting as much light as possible into the camera and realise that you’re now over-exposing the shot. So what’s your option? You don’t want grain so you’ll leave the ISO where it is and you want to make your subject stand out from their background so you’ll leave the aperture at its most open setting. That just leaves the shutter speed. You can pull that back a bit to 1/250th of a second or even back to your original setting of 1/500th of a second. Now you take your shot and find that it’s properly exposed. Nice!

See how it’s all a balancing act?

I hope this has been helpful and it gives you a bit of confidence to go out and take your camera off AUTO. At the end of the day it’s all about practising and messing about. If you have any questions or comments then please feel free to drop them in the comments section and I’ll help as much as I can.

Until next time friends, keep shooting!

Damien, out.