Welcome to the second part of the "Quick and Simple Guide to your SLR" series.
Last time we covered the basics, what an SLR is, roughly how it works, and a bit about the automatic and manual modes. If you missed that part, please
click here to check it out.
I am not intending to cover every aspect of photography, nor cover every aspect of each item I cover, this is purely a "Quick and Simple Guide", covering some principles, basics and such like, and if this whets your appetite, there are many good books out there - ask using comments below or
via our contact page - and I can advise of some particularly good titles.
A Good Exposure
We have all seen photographs which are too light or too dark to make out what's in the shot, and generally photos need to be between those two extremes - as what we call a "good exposure" - just the right amount of light has been received by the film / sensor to make the shot good.
Two Factors
There are really three factors which affect the exposure of a photo, but we are going to focus on two for now.
We are all familiar with the click a camera makes when it takes a photo - and some dodgy electronic noises of modern phone camera etc - but in most SLRs the click is actually the shutter.
Now we can adjust the time that shutter is open for, and also the size of the opening behind the shutter, both of which control the amount of light passing through to the film / sensor.
Tapping Resources
To better show this, using an everyday example, below are two taps (fawcets) - one with a narrow pipe and a narrow opening, the other with a wide pipe and a wide opening.
 |
| Wide Tap Opening (Aperture) |
 |
Narrow Tap Opening (Aperture)
|
The grey container below (The Film / sensor) is where we want to catch the water (Light) to make the picture.
Assuming we want 2 litres of water - in photographic terms is the amount of light we need for our desired exposure for this scenario.
With the smaller tap we need to leave it running for longer than we do with the wider tap, to achieve the desired 2 litres in each container.
The time taken is our shutter speed (time the shutter is open for), and the size of the tap opening is the size of our aperture opening.
Based on this we can see that in terms of exposure alone, that both
Bigger Opening (Aperture) + Shorter Shutter Speed
and
Smaller Opening (Aperture) + Longer Shutter Speed
will produce the same exposure (give or take for exact settings etc)
In summary, using only the two factors of Aperture Size and Shutter Speed - we can see how the two work together, and those overly light photos either had the shutter open for too long, or too big an aperture set, and those overly dark photos left the shutter open for too little time, or used a small aperture.
Apertures and Shutters basically work as above, but the two seemingly simple controls offer so much more, but this will be covered in the next part.
ISO
The third factor affecting exposure is the ISO - which when using a film camera relate directly to the type of the film you have in the camera, but in the digital cameras - means simply altering a setting.
I will cover ISO another time, but essentially it relates to how well the film / sensor picks up the available light, and the resultant photo quality.
Basically:
Low ISO: Where light is good, clean photo produced.
High ISO: Where light is poor, noisy / grainy / dotty photo produced.
That's the end of part 2, so if you like what you have read, get that SLR out of Auto mode and have a play around with the Shutter and the Aperture - have a quick look in the manual for the camera if you are unsure how.
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page on the main website and
contact us if you have any queries.
