Wednesday, June 16, 2010

Lesson 02 - Camera Types

As promised, here is my next 'educational' post.  In it, I'm going to explain the basic differences between a few types of cameras, but first - a quick recap of lesson 1.
A camera consists of a lens that focuses the light coming in; behind the lens is an iris that adjusts the size of the hole the light comes through; the shutter is a set of curtains that opens and closes very quickly (or slowly if that's what you want...) and lets the light through onto the sensor or film which records the image.  The sensor (or film) might be super-sensitive and react to small amounts of light (e.g. ISO1600) but have 'noisy' results, or a more normal sensitivity (ISO100) that requires more light but produces sharper quality images.

The main thing you should have learned (apart from all the technical names) was that you need to balance the size of the hole (aperture), how long it is open (shutter speed), and the sensitivity (ISO setting) so that just the right amount of light falls on the sensor to create a nicely exposed image.

Ah - that leads me to just one more important term, that I didn't mention - exposure.  Exposure is the collective term for the balance of all those things.  If you get them all right, then your exposure is correct.  Too little light (for whatever reason) will mean your picture is under-exposed (or too dark), and too much will mean it is over-exposed (and too white).  You may hear a photographer ask "what exposure did you use?", by which he means "what shutter speed did you use, and what aperture... oh, and ISO setting?" (but that's all a bit of a mouthful...).

So now on to lesson 2 - Camera Types.
Cameras fall into 2 broad camps - the simpler "Point & Shoot" variety, and the more complex SLR (or dSLR).  SLR stands for Single Lens Reflex (and the 'd' for digital).  You can also get mobile phones with cameras in them, and webcams, and video cameras that take stills (and still cameras that take video), but for the purposes of this article, I'm going to assume you have what I'd call "a proper camera" that falls into one of those two main camps.

Important Note
The images I have included are just examples of Nikon cameras that happen to fit the headings.  I am in no way implying anything (good or bad) about these specific cameras (except the D3000 which in my view is brilliant - coz I've got one).

Point & Shoot.
These cameras are built with ease of use in mind.  They don't have interchangeable lenses, though they often have zoom capability.  The cheaper Point & Shoots may not have a mechanical shutter, and so may suffer from a phenomenon called shutter-lag.  This means that when you press the button to take a picture, the camera has a lot of housekeeping to do, and decisions to make (to make life simpler for you), and all this takes time.  There may be a delay up to half a second (or more) before the picture is taken.  This may not sound like much, but can mean the difference between getting and missing the shot you wanted - especially if something is moving. 

Another key identifier in P&S cameras, is the size of the sensor itself - they are generally very small.  By this, I mean their physical size, rather than the number of megapixels (though obviously one influences the other).  For technical reasons that I won't go into just now - small is less good... (yes - size DOES matter) in that it imposes certain restrictions on your photographic creativity.  Don't get me wrong - they are great for their intended purpose!  But you may outgrow this type of camera if you are getting serious about photography...

(Advanced Point & Shoot)
The cheaper P&S cameras don't let you have much control over your settings (remember those three elements you need to balance?).  They generally have a few preset combinations where two of the three are fixed, and the camera sorts out the other one based on how much light is available, or perhaps you set the ISO and leave it... "Ideal" I hear you say... BUT, perhaps you are taking a photo of your friends skiing - all that snow is very white and will fool the camera into making a wrong decision.  The more advanced P&S cameras get one step closer to an SLR camera, and allow you to take more control over the aperture, shutter speed, and ISO settings, to get just the right balance in your picture.  As well as having more of the preset type modes to choose from, these cameras may also have another one or two modes - aperture priority and/or shutter priority.  These mean that you set the aperture or shutter speed you want, based on the type of photo you are taking, and the camera works out the other setting for you.

NB - The Nikon P100 shown has P and M modes as well - see below for definition!

Single Lens Reflex
SLR cameras are 'aimed' at the more serious photographer, though most of the major manufacturers have 'entry-level' versions that have scaled down functionality and cheaper lenses, to make them more affordable to a wider market.  SLR cameras have interchangeable lenses, so you can upgrade to better quality lenses or lenses specialised for a specific purpose (such as fisheye or macro lenses), without changing the camera body.  SLR cameras have a few of the preset combinations I mentioned earlier, as well as a fully automatic mode and aperture and shutter priority, but they also have 1 or 2 specific modes that are generally not available on the P&S cameras (except maybe the most expensive ones).  The first of these is 'Program' mode (P) - in this, the camera decides on the balance of aperture and shutter speed, but then allows you to adjust its settings (either aperture or shutter speed) while it makes the appropriate adjustments to keep the exposure correct.  This is very useful when getting to know how different settings can have an affect on the resulting image (but more of that in another lesson).  The final mode is 'Manual' mode (M).  In this, you have complete control - so you can force the camera to over- or under-expose the picture to get creative effects, or you can keep the shutter open for minutes at a time to take pictures of the night sky.  You can still use an SLR camera in Auto mode for your everyday snaps (and I'm sure that's all a lot of people ever do - sadly), but the four modes (P, A, S, and M) especially manual mode, are what unleash the creative side of a photographer - and where it all starts to get really exciting.

SLR cameras have a moving mirror inside them, that allows you to actually look though the lens to line up your shot.  When you take the photo, the mirror flips up out of the way, and the light then passes straight through to the shutter and sensor.  P&S cameras either have a separate lens for the viewfinder, so you don't quite see what the camera will see, or something called live-view where there is no viewfinder at all.  Instead, the image that is being collected by the sensor is relayed straight to the display panel on the back of the camera the whole time.  More expensive SLR cameras now have live-view as well.

The other thing about SLR cameras, is the size of their sensor - MUCH bigger than the P&S varieties.  The more expensive dSLR cameras have a sensor which is the same size as a 35mm negative, and most of the cheaper ones use a format that is around 2/3 that size (Nikon call it DX, and Canon call it APS-C, while the full size versions are FX and APS-F).

Here is a link to a wikipedia article that explains a bit more detail about the mechanics of an SLR camera, for those that yearn for more...

So much for my promise to keep the lessons short - apologies to all.
Untill the next time...
Happy Shooting.

1 comment:

  1. Very good blog so far! I just recently purchased a D3000 and am loving it immensely. I have subscribed on my mobile phone for when you post updates.