Why exposure settings are chosen!

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Postby mark jeffs » Sat Dec 03, 2011 2:11 am

Hi everyone, I am new to this forum and an avid amateur underwater photography desperately trying to master the techniques and produce consistently good photos. I have devoured numerous books but they all seem to omit a fundamental thing for budding new photographers...that is, why photographers choose one exposure setting over another.

When I read book I look at the sample photos and try and guess what exposure setting the photographer has used, to try and understand why he used those setting to get the shot...why he chose a particular F stop to get the background, why he chose a particular shutter speed to freeze the action...sometime I get it right, more often than not I dont.

So can someone give me some simple rules to follow? I got told Shutter speed controls the background, aperture controls what the flash hits...that now seems a bit odd as a recent book I was reading recommended F8 1/125 for a general catch all setting for wide angle (gives blue water background), faster shutter speed gives sharper photos, then it all goes different for macro ;) ...etc.

I am sure there are lots of tips more experienced photographers have...how do they teach these to new photographers..? I would appreciate any advice I can get.

Mark
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Postby bvanant » Sat Dec 03, 2011 5:05 pm

You are on the right track. Shutter speed controls motion and the ambient exposure. The faster the shutter speed, the less background exposure you will get. You will also get less motion blur from a fast moving animal. There is a limit though, most cameras have a maximum shutter speed that can sync with a strobe so you shouldn't try to go faster than that. In general I start at 1/160 sec for most of my shooting. The f-stop controls DOF and light from the strobe. Small f-stop (like f16) mean sharp DOF but you need a lot more strobe power than at f8. So it is a trade-off between how much light you need and how sharp you want the detail to be. I like to start at f11 or f16 and see how the scene looks. For really nice blurred backgrounds, I shoot at f5.6 or sometimes f4 and turn down my strobes.

For practice set up a flower on your kitchen table and shoot it at a number of f-stops and shutter speeds to see how your particular camera works.

Bill

Bill Van Antwerp Canon/Nauticam/Subal/Inon Lots of glass


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