The Principles Of Photography

02 September 2020

12 mins Read

Last updated . 02 September 2020

How photography works. Understand this and your photos will get better.

Australian Traveller magazine is filled with great photography. It was one thing to find great photographs. It was another thing entirely to understand how photography works. And for someone looking to buy a camera it can be very confusing. You are bombarded with new acronyms. So here is the basics on how photography works.

Light
Forget anything anyone says. Photography is all about light. When we take a photo – regardless of what sort of camera we are using, the camera decides it needs a certain amount of light. For the purposes of this description we will call this amount of light a “bucket”. Everything from here on will relate back to that bucket.

If you are filling a bucket with water (or light for that matter) you have two options. You can use a really big hose for a short amount of time or a much smaller hose for a longer time. It’s just the same with photography. The size of your hose is your “Aperture” or what is also called your “f Stop”. For very complex and not really relevant reasons, the smaller f/stop or aperture number the bigger the hose. And vice versa. A really big f/stop number means a really small hose.

So we now have decided on the size of hose we want to use. What we now need to do is determine is how long we need the hose to run. This is your shutter speed. A small f stop (big hose) will need a fast shutter speed. And a small hose (high f/stop or aperture) will require a longer shutter speed to fill your bucket with light.

In most cameras, you can decide what aperture you want to use and the camera will change the shutter speed accordingly. Alternatively, you might decide to adjust the shutter speed, and the f/stop will change automatically

So what is an f/Stop exactly?
An f/stop or aperture is controlled by the lens you have on your camera. It is a series of blades that you can open or close to let varying amounts of light into the lens.

Basically, the lower the aperture (or f/stop) number the more light you can let into the lens. Remembering what we said above, the smaller the number there’s more light to fill your bucket and therefore you can use a much faster shutter speed because there is so much light entering the lens. This is why photographers will often call lenses with low f/stops “fast” lenses.

Zoom lenses have a higher f/stops than fixed focal length lenses. Fixed focal length lenses are also called “prime” lenses. Here at the AT Office, we have a 70-200 zoom lens that has it’s lowest aperture of f/2.8. To let that much light into the lens it is a big bulky and VERY expensive lens. I think it cost $3,000. We could have purchased a 70-200 lens that had a lowest aperture number of f5.6 at a cost of around $600. Getting those last few stops of light seems to cost double (or even triple) the stop beforehand.

Prime (non zoom) lenses will often have a much lower aperture. For example we have at the AT office a lovely 50mm f/1.2 lens. That cost us $2,400. We also have a lovely 50mm f/1.4 lens. That lens cost $659. So the cost of getting that 0.2 of a stop cost nearly $2,000! Viewed side by side, you can see the differences in size.

As you can see, the lens on the right is a lot bigger and heavier than the lens on the left. This makes a big difference to the cost of the lens. Especially when you are talking about zoom lenses. For instance a 400mm f/5.6 lens is a great lens, and will cost $2,000. A 400mm f/4 lens is bigger and will cost $6,800. A 400mm f/2.8 will cost – wait for it. A staggering $12,000! Each of these lenses will deliver much the same photograph at say, f/8. But each iteration is simply letting in more light. And that makes a big difference when the available light isn’t that great.

The big question is what does this mean in the real world?

And the answer is “depth of field” or “Bokeh”. Bokeh is a Japanese word that describes having a part of an image in focus with the background pleasantly blurred. Whilst this may not sound important at this stage, as you explore photography further you will find that this a very important photographic technique. It will move the eye to focus on what you have decided is important in the photograph.

In the image above, you can see that background has a blur that ensures that the eye is focussed on the person in the picture. You are not competing with anything else in the photo.

Same goes for the photo above. The photographer has created a dreamy effect of the chocolates on the plate, without having your eye distracted form other elements in the image. This is very important because photography is there to tell a story and using a low f/stop is just one of many techniques that can be used.

Sometimes this is not important. For example, if you are shooting a wonderful landscape, you don’t want the blade of grass in front of your camera perfectly in focus with the rest of the photograph blurred. You want the whole photograph in focus. From near to far. This means you need a higher f/stop. For landscape photography, you will need to use a higher f/stop. Something of around f/16 or so. You don’t need an expensive lens to do that. You need a good quality lens though. And mostly the fast lenses will out perform the cheaper lenses at , say f/16.

Below is a depth of field table for a 50mm lens on a standard digital SLR. It might seem like gobbledy gook, but the important thing is that a low aperture setting and shooting photos of something not to far away our depth of field is razor thin. And I mean really thin.

	f/1.4		f/2.8		f/5.6		f/16		f/22
Distance	Near	Far	Near	Far	Near	Far	Near	Far	Near	Far
(meters)	Near	Far	Near	Far	Near	Far	Near	Far	Near	Far
0.5	0.5	0.5	0.5	0.5	0.49	0.51	0.47	0.5	0.46	0.54
1	0.99	1.01	0.98	1.02	0.96	1.04	0.9	1.1	0.86	1.2
2	1.96	2.04	1.92	2.09	1.85	2.18	1.62	2.6	1.5	3.01
4	3.84	4.18	3.69	4.37	3.42	4.82	2.7	7.7	2.38	12.5
8	7.37	8.75	6.83	9.65	5.96	12.2	4.07	240	3.38	∞
20	16.5	25.5	14	35	10.8	141	5.84	∞	4.51	∞

Look closely at the 1 meter distance. With an f/stop of 1.4 only a 2cm depth of your image will be in focus! (1.01M-0.99M) In this case we could easily end up with a photograph of grandma – with her nose is sharp focus but her ears out of focus! That is truly a paper thin depth of field. To accurately photograph grandma at a distance of 1 metre we are probably going to use an f/stop of 5.6 which will give us a depth of field 8cm or so.

Having a low aperture (a big hose) also allows you to take photographs in worse light. Often indoors you will find that without a flash you will need to have a VERY slow shutter speed. Sometimes as long as one or two seconds. This may sound fine, but it will only work if you have arms of stone so the camera doesn’t move (or a tripod) and that the subject you are photographing stays completely still. Ever tried to get a child to stay perfectly still? It ain’t going to happen.

Shutter Speed

The other tool in our arsenal in filling our fictitious bucket with light is our shutter speed. Going back to our original analogy, the aperture (f/stop) is the size of our hose and our shutter speed is how long we use the hose for. Generally speaking you want to keep your shutter speed quite high. Most cameras will be able to adjust their shutter speed to anything between a couple of seconds to thousands of a second. The main thing about shutter speed is that it can capture a moment in time. Those great swimming photos from the Olympics where you can see the induvidual droplets of water as the swimmer punches through the water? They are taken with very fast shutter speeds. Probably 1/1,000^th or a 2,000^th of a second. Inversely you sometimes see photographs of waterfalls where the water looks like a weird solid sheet. That’s taken with a much slower shutter speed. Perhaps as slow as second.

The shutter speed you use is important. In most photography it is your weapon in the fight against blurry photographs that are created by camera shake. When you are using a long zoom you will notice it is very very hard to keep the camera still when the photograph is taken. The best way of stopping this is using a very fast shutter speed. A rule of thumb is to avoid camera shake you should be using a shutter speed that is AT LEAST the same as the focal length of the lens you are using. So if you have zoomed out to 200mm you want to avoid using a shutter speed of less than 1/200^th of a second. On a 50mm lens you don’t want to be using a shutter speed of less than 1/50^th of a second.

This means that we now have a timeframe in which we need to fill our bucket! If I am photographing my kids playing sport at 200mm of zoom, I now need to ensure that my shutter speed doesn’t drop below 1/200^th of a second. We need to use a bigger hose (lower f/stop or aperture).

And that, my friends is the relationship between shutter speed and aperture.

ISO

Now we need to confuse things even further by introducing an often misunderstood concept. That of ISO.

ISO (or ASA) is a concept borne form the old days of film in cameras. In fact, the only difference between a digital camera and a film camera is that a digital camera uses an electronic sensor to capture the photograph. A film camera uses film, chemically reacts to being exposed to light – and hence producing a photograph for you.

In the olden (pre digital) days you were able to compensate your camera setting by using a different “speed” of film. Simply put, some film reacted more aggressively to being exposed to light. This meant that you could use faster shutter speeds to get similar (and note here the word SIMILAR) results to other film types. In other words. changing the ISO is changing your digital cameras sensitivity to light.

The best way to think of ISO is that what we are doing is changing the SIZE of the bucket that we are filling with light. Each ISO setting doubles the amount of reaction to light.

So it seems simple. Let’s just use high ISO film speeds and then we can use faster shutter speeds. That gives us more flexibility right?

Wrong. The problem with faster film speeds (high ISO) is that the film becomes very grainy. Your photos are simply not that sharp. In digital cameras increasing your ISO will introduce “noise” into your photos. Noise is where you can see the induvidual pixels and they look kind of bloated. And this is not good. The photo below was taken in very dark conditions and we had to adjust the ISO to 3200.

That said, some of the new digital cameras are now showing astoundingly good quality at higher ISO settings like 800 and 1,600. In fact, the Nikon D3 can shoot at a staggeringly high level of ISO 52,000. Sure, the pictures will be grainy, but not as grainy as some other cameras at ISO 1,600 or in the case of some really really cheap cameras, ISO 800.

In the world of digital photography, ISO is now a tool you can use to make sure you get the right shot. Because this would involve physically changing film in film cameras, digital cameras have the ISO adjustment hidden away in their menu settings. In fact, ISO is as important as your shutter speed and aperture, and the sooner that manufacturers recognise this and make it a button on the camera the better.

How This All Works In Real Life;

The trick now is to understand these settings and how they all interrelate to each other. Let’s go through some real world examples.

Let’s say you want to photograph a Christmas tree. We need to go through a mental checklist. We need a fairly small aperture so the whole tree is in focus. Say f/16. Check. We are shooting at 25mm with our zoom for this shot, and the room is a bit dark. The camera is now showing that to shoot at f/16 I will need a shutter speed of 4 (or ¼ of a second). This is a problem. I don’t have a tripod and because I am not an Olympic archer it is impossible to keep the camera still enough to take the photo. I have some options. I can reduce the f/stop tof/5.6 and get a speed of 50 (1/50^th of a second) but I won’t catch the whole tree. So I change my ISO speed to ISO 400. That fixes it, I now have my f/16 shot and a shutter speed of 50. We can now take the shot.

That said, the best way to understand how this all works it set your camera to aperture mode and play around with it. You will very quickly learn how all these factors interelate and be taking better photos in no time.