Back to Basics: Exposure triangle

[comycus]

Since there is a forum dedicated to photography, going to start afresh by sharing some of the basic photography tips and tutorials from one of my fav website: DPS.

The three basic elements of photography when we start venturing from “auto” mode to “manual” mode are:

1. Aperture – the size of the opening in the lens when a picture is taken

2. ISO – the measure of a digital camera sensor’s sensitivity to light

3. Shutter Speed – the amount of time that the shutter is open

It is at the intersection of these three elements that an image’s exposure is worked out.

Most importantly – a change in one of the elements will impact the others. This means that you can never really isolate just one of the elements alone but always need to have the others in the back of your mind.

I found it tough in the beginning to differentiate between the 3. The window metaphor helps me remember better.

The Window

Imagine your camera is like a window with shutters that open and close.

1. Aperture is the size of the window. If it’s bigger more light gets through and the room is brighter.

2. Shutter Speed is the amount of time that the shutters of the window are open. The longer you leave them open the more that comes in.

3. Now imagine that you’re inside the room and are wearing sunglasses (hopefully this isn’t too much of a stretch). Your eyes become desensitized to the light that comes in (it’s like a low ISO).

There are a number of ways of increasing the amount of light in the room (or at least how much it seems that there is. You could increase the time that the shutters are open (decrease shutter speed), you could increase the size of the window (increase aperture) or you could take off your sunglasses (make the ISO larger).

For those interested in more in depth discussions, I will expand on these in the next few threads.

http://digital-photography-school.com/learning-exposure-in-digital-photography

[Ketchup]

For me, of the three, usually the thought process will be APERTURE > SHUTTER SPEED > ISO

Why so? For example, i want to shoot a subject, say some chiobu called DESI

I first have to determine if i want to isolate her (i.e. large Aperture)or to include some background for interest (i.e. some nice scenery). So assume i want to isolate her, which is typical portraiture, i have to determine what aperture to use and what lens.

For portraits, F4 to F8 is probably the best. Usually anything less than F4 may results in situation where nose is sharp, ears are blur (yes, it will happen ) Lens choice will probably be 80mm- 125mm for full frame camera or 50mm to 100mm for cropped camera like D90 etc.

Next consideration is then Shutter Speed. Say, for example, i think F4 is the most ideal aperture and my shutter speed can support the shot without me shooting some blurry picture (can use 1/focal length of lens as a guide for shutter speed i.e. 100mm lens will be shutter speed should be no lower than 1/100 sec.)

If it gives me a reading of say 1/30sec, i know for sure i will end up having a blur picture unless the camera/lens has some image stabilising mechanism or i have rock steady hand or using tripod/flash. So my choice will be to change the aperture bigger (which will results in faster shutter speed at the expense of having part of the image more blur) or to change the ISO to make the shutter speed up to 1/100sec. This should be the thought process, which will comes naturally as you shoot more and experience different situation and know what you want.

Hopes this help.

[jackywongto]

Why so? For example, i want to shoot a subject, say some chiobu called DESI

politically so correct......

[LaW]

politically so correct......

yeah i agree as well.

[desideria]

[teebs]

Why so? For example, i want to shoot a subject, say some chiobu called DESI

I first have to determine if i want to isolate her (i.e. large Aperture)or to include some background for interest (i.e. some nice scenery). So assume i want to isolate her, which is typical portraiture, i have to determine what aperture to use and what lens.

What Ketchup means is that he wants to shoot some chio bu but since Desi is also in this forum, must give face lah...

Then in the next sentence he says he needs to determine whether he wants to isolate her or include some "background"...

[teebs]

Anyway, when talking about the exposure triangle as our SRC photography lecturer has said, I think it would be prudent to consider what type of photos you are taking first and what type of effects you are striving to achieve before deciding how to set the parameters of the camera.

Also, one needs to take into consideration the amount of sunlight and where the sunlight is coming from before deciding the ISO, aperture and shutter speed to use.

Typically speaking, if you are taking photos of the F1 race, you will need to preset your shutter speed first and then the ISO. In this case, most people would be using Shutter priority where the camera will decide on the aperture to use after you have preset the ISO and shutter speeds.

For portraits and landscapes, you would probably be adjusting the ISO and Aperture only and would likely be using Aperture Priority on your camera.

[Ketchup]

Yup... subject is always the first consideration. ISO is just a backup plan.. funny i was just talking to some senior photogs and they were so happy you can change ISO so easily in Digital cameras these days...

[teebs]

Yup... subject is always the first consideration. ISO is just a backup plan.. funny i was just talking to some senior photogs and they were so happy you can change ISO so easily in Digital cameras these days...

When I was using film SLRs 20+ years back, you are basically stuck with the film that you loaded into your camera so DSLRs these days really offer much more flexibility.