Patricia,
Shutterspeed even easier! Think of photography as a 3 bowl weight scale
thingie, one bowl is the ISO or film speed if you will and the other bowl is the
aperture and the last bowl is the shutter speed. All must be balanced,for a
correct exposure. If you change the aperture to allow more light to come in, you
then need to shorten the amount of time the aperture is open, to keep the
balance working. If you open the aperture and keep the shutter speed the same,
it will cause an overexposure of the image. If you change the ISO, from 100 to
400, you now have to decide which other"bowl" to change, to compensate for the
"more" film speed you just added,since now, the camera needs less light/time to
make the same image. So you can close down the aperture to a smaller f stop and
keep the balance or you can turn up the shutter speed to keep the balance. But
for now, really one at a time,to keep this simple.
If the scene you're taking has the folowing recipe: ISO 100, shutterspeed
1/30th and aperture is F16, then you can change the ISO to 200 and now the
aperture will stay the same, f16,but you need to change the shutter speed
up,since you increased the ISO, to 1/60th of a second and if you chage the ISO
again, to 400, then the aperture is still f16, but now the shutter speed needs
to go up to 1/125 of a second, to keep the balance working.
Once you understand this very basic "recipe" you then can change ANY of the
three and know what else will have to change. Example: ISO 100, but you andare
handholding the camera now, you left the tripod in the car, and you know you
probably can't hand hold the camera for a short 1/30th shutter speed, so you
will change the shutter speed to 1/125, but now, since you've changed the
recipe, you have to adjust something else, the ISO to 400 OR the aperture to F8,
which will give you the balance you need. You upped the shutter speed 2 stops,
from 1/30 to 1/60(one stop) and then to 1/125 (another stop) for a total of 2
stops(aperture or f-stops), so to keep the image from being dark or
under-exposed, you need to open the aperture 2 stops to F8 and we're back in
balance,
Hope this helped,
Rich
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