Photography - SLR cameras

[fairy!]

I'm having trouble getting my head around apertures & shutter speeds... how do you know which one to alter? Like, if I was doing a portrait would I use a certain shutter speed & change the aperture depending on the light? Or vice versa?

Thanks x

[ludwig]

Ignoring flash photography for a sec, the exposure is determined by a combination of both aperture size and shutter speed. The aperture is a circular hole within the lens, the size of which can usually be set manually by the ring around the lens. The bigger the hole,
the more lights gets in.
The shutter is a plate which moves across the front of the 'film' which has a gap in it that lets light through. The slower the shutter, the more light gets through.
so -
biggest aperture + slowest shutter = maximum exposure
smallest aperture + fastest shutter = minimum exposure.
and every combination of the 2 in between those extremes.
If you are shooting in dark conditions you would obviously want more exposure, so you'd
select either a large aperture, slow shutter speed or both.
Depending on your camera, one or both of these can be set manually, or it can be completely automatic - ie the camera works out the best combination
of the two depending on the available light.
There are other factors which determine which settings you would want to use, e.g do you want a large depth of focus, or is the subject moving etc.

hope that helps.

[Clanad]

The shutter speed and aperture opening (f-stop) can be manipulated in a variety of ways to achieve desired effects.  The faster the speed and smaller the aperture the less light arrives on the film or electronic recording device and any combination of either will produce the correct amount of light and stop motion...

Check here:

 

http://www.ncc.sdccd.cc.ca.us/resource/qtvr/qtvrlm2/lm2p 4.html

[Clanad]

Ahhh... synchronography strikes again... Good answer Ludwig... 

[fairy!]

Thanks guys.

Ludwig... you've said that either I'd select a larger aperture, slower shutter speed, or both... but how do I know which one to change?

Say it was a portrait... I'd want a fast shutter speed coz I don't want the image to blur if the person moves (?) so do I just choose a shutter speed (how do I know which one?) & then use the camera's light meter to change the aperture?

[landie]

You need to expose the film to a prescribed amount of light, this varies wi the ISO rating of the film that is in the camera (100, 200 400 etc.) There is normally a wheel at the top of the camera to alter this setting which must agree with the film for the internal light meter to work.

For hand held photography you will need to use a sufficiently 'wide' aperture to give you a shutter speed at least equal to the focal length of the lens as a rule of thumb.

[ludwig]

Fairy!, for a portrait you shouldn't be too bothered about
the shutter speed because I'm assuming the subject would be posing and not moving. Having said that, If you are holding the camera (ie not using a tripod or sitting it on something), you need to make sure that the speed is at least 1/125 so that you don't get a
blurred image because of your hand movement.
Typically for a portrait, the textbooks will tell you to select a large aperture, so that the subject was in focus but the background blurred -
this is so the attention is focused on the subject and the background isn't distracting in the final picture.
Again, it all depends on your camera, and what you want from the picture.
I would set the aperture to a fairly high setting, and let the camera worry about the shutter speed - with the proviso I mentioned above.
It's a case of fiddling with it really, until you get the result you want.
good luck with it.

[secretsquiz]

this won't answer your whole question, but i think it's a quick and useful way to remember what to do with your aperture (oo-er!).

my dad once told me to think of a penny and a pencil...

a pencil is narrow (small aperture) and long (for long distance photography)

a penny is wide (large aperture) and short - or thin (for closer photography)

so you would use a small aperture for longer focus, and a large aperture for short, close focus (such as portraits)

hopefully that makes sense!

[fairy!]

Thanks everyone... it's still a bit over my head though!!

Basicly, if I went in to a studio to take some portrait pics, would my priority be to sort out the aperture or the shutter sreed first?  & is trial & error the only way to know if I got it right?  (if I'm using 35mm I wouldn't know til I got the film developed...)

Thanks secretsquiz... v handy!

[landie]

For portrait photography a lens with a focal length within the range of 70 to 100 gives the most flattering rendition of facial features. It also helps set it at the wider end of its aperture range (smaller numbers f 4 or f 5.6) to minimise the depth of field (the amount of the picture in focus (background to foreground). You will need to focus accurately however and sidelighting rather than front on is preferrable.

[Tweed]

The speed of the film is how sensitive to light it is - the faster, the more sensitive. For non-flash photography, you can use a light meter, you can set the film speed on it and hold it towards the subject, it will then tell you some combinations of shutter speed and aperature size. And (I think) the further away the subject is, the lager the aperature should be.

[fairy!]

Thanks everyone... you've been very patient with me trying to get to grips with this!! :-)

[BillyNoMates]

Great to see someone making the effort to learn about the basics wrt to true photography.

All too easy these days to get a digital, point and shoot.  Whilst digital photography has its merits I go for 35mm and an SLR every time.

Enjoy doing 'real' camera work. If you get into developing your own too, it can be very rewarding.