Photo Blabs – exposure

This post has been sitting in my drafts for awhile now. I wanted it to brew into something more user friendly and clear, but the fermenting process didnt want to cooperate, so I stopped it ;)

I hope its useful to somebody. At least one of you.

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See, I pulled the big guns for you – an old kiddie chair, some left over half cut up paper and sticky tape! The Japanese doll was the only lovely thing involved, but I thought since you will be seeing it for awhile, I would be nice and make it pleasant.

You wanted tips, I give you big blabs. Really, before one can give tips, one must know at least the basics of taking a correctly exposed image and what that entails.

Exposure

Photography is about light. It started with the simple exposure of a specially coated, light sensitive, paper to light. It grew, it evolved and changed. Film is mostly left for the hard core purists, but its still about exposure, only now we are doing it to light sensitive chips.

The starting point is a jet black canvas. When its exposed to light it starts to get lighter – the brighter the light  or longer the time of exposure, the lighter it gets, eventually becoming white.

Look at the set up above, there is a certain amount of light that the chip/film needs to be exposed to, in order to make a ‘correct’ exposure – good looking image. Too little and the image will be too dark. Too much and it will be too light. The camera has three ways to control the amount of light coming in – shutter speed, aperture and ISO speed.

In short,
Shutter speed is how quickly the shutter will open and close for the chip/film to be exposed to the light.

1/1000sec, 1/500sec , 1/250sec, 1/125sec, 1/60sec, 1/30sec, 1/15sec, 1/8sec, 1/4sec, 1/2sec, 1sec
from faster to slower ; from less light to more light
from freezing movement to blurring it

A perture (f stop, focal point) is how wide open the “hole” to the chip is – wide open=more light; tiny=less light

f/1, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, f/32
from wide open to barely opened ; from more light to less light
from narrow field in focus to more in focus

ISO speed comes from film, but is applied to digital photography in the same sense – how sensitive to light is the film/chip – more sensitive needs less light to produce an image, but it will be more grainy/noisy. Less sensitive will need more light, but the image will be with less grain/noise.

So, lets say , as a very crude example, you need 100 points of light to hit the chip to get a good exposure of a scene. You can get 40 of it from ISO, 30 from the shutter speed and 30 from the aperture. You can play around and have 20 from ISO, 50 from shutter speed and 30 from aperture. Or any other combination of those. As long as they all add up and provide the needed light to the chip, they will all give a good exposed image, be it with different characteristics.

Here is our beauty. You can see the photo was taken at 200 ISO, with aperture of 5.6 and the shutter speed of 1/15 sec.
It looks ok. The white paper is nice and bright, but not too white.

The picture looks the same, but this one had a wider opened aperture of 2.8, which meant that we had to shorten the shutter to 1/50 sec. We provided more light with the aperture, but took the same amount with a faster exposure, essentially coming up to the same amount of light overall. Hence the picture looks the same.

Still the same?

Well, not really. Now we have a higher ISO, which makes the chip more sensitive to light and needing less of it and to counteract that the shutter needed to be shortened even further to 1/125 sec.

Now I closed the aperture a bit to f4, but since that reduced the amount of light for the shot, I extended the exposure time to 1/60 sec. Took it with the aperture, but gave it back with the shutter.

Here is what would have happened if I did not change the shutter. The light would have not been enough and the image would be darker than I wanted.

If I had slowed the shutter too much, then the light would have been too much and the image would be overexposed – blown out highlights – areas of pure white without any detail.

Even more – notice the slower shutter of 1/15sec.

This is usually handled by the cameras of today automatically. And you are wondering why the hell should you worry about this stuff, all the photos look the same anyway. The reason is obvious. Isnt it? Well, there are more than one really. One is that cameras are machines and they have no real clue what you are trying to capture. They will average the scene and try to reach a leveled brightness – grey. It works most of the time, but in a situation like the one we have here, it doesnt work.

This is what my camera thinks the shot should look like:

This is the auto setting. The poor computer is all mistaken. It sees all this white and tries to average it to a lovely grey, so it exposes the image less. A stop less than what I wanted. The opposite happens as well. If you have a dark setting with your subject amongst it, the camera automatic setting will overexpose, as it doesnt know that the image should be mostly dark.

Another reason is that it gives you freedom to get the image you want. If you want an extra fast shutter speed to freeze an action shot, that means you will need to get the light in the camera with a faster ISO or/and with a smaller aperature (more open).

If you want to capture image in the dark, but without a tripod, which means at the very least 1/60sec, then the light will have to be provided by an open aperture and a high ISO.

If you want the smoothest image you can get, then you would opt for a small ISO – eg.100. Then you will need more open aperture and/or longer shutter speed.

If you want to blur the background of your subject – which is achieved with a wider aperture – then you will have faster shutter and/or slower speed ISO.

You have choices and can make the call about what you can sacrifice or how your camera should capture that image.

The setup stayed in the living room for awhile and the kids played taking pictures. Look what Little B took:

Then later on, when it was dark, I returned and thoght it might be good to use my laziness in picking up the set up to show how well this works.

Knowing what you want and how to get it will give you the freedom to use any light. Bellow you see the shot on the left, which is pretty similar to the ones I took during the day, but the actual light is on the right. I can show you both things I wanted to, while my camera’s auto setting wouldnt have been able to deliver either.