becky_stead wrote:Hi im wanting to try out some long exposures during daylight. Subjects such as streams, waterfalls and the ocean for example. I have a Canon EOS350D and was wondering what type of settings i would need and maybe filters?? I have searched the net, but havent really found much that helps and you peeps have been very helpful to me in the past with my newbie questions lol! Thanks for your time everyone.
Becky
basics first - a formula exists for computing this. if you google for "basic exposure constant," you will see the reciprocal values between iso/asa, shutter speed and aperture openings.
notice from you google search that reduced light situations will allow you to use slower shutter speeds. lower light conditon settings can be computed through the formula.
longer exposures result in blurred motion. longer exposures can be achieved by using smaller apertures (bigger f number) on the other hand, smaller apertures result in greater depth of field. a tripod (as mentioned) is absolutely critical to avoid unwanted blurring.
you didn't mention which lenses you have for the 350d. the "hobby" 18-55mm will close to f/29. (not a "standard" aperture). by the formula, an exposure on a bright sunlighted day is f/16@1/iso (f/16@1/125), you lens will only allow you to work at f/22@1/2/iso. (f/22@1/60)
filters are assigned "filter factors." these are additive as they affect light reduction or loss. that is, stacking a bunch of neutral density filters together will be the same a single of the larges value you will need. although most manufactures have omitted the filter factor from the data sheet, the value can be tested using the above formula.
physics - can't live with it, can't live without it.
happy shooting,
g. smith
assoc. prof. photo. tech.