Taking a family portrait of four people outdoors tomorrow. I plan
to use my 50mm f/1.8 lens.
Should I open the lens all the way? I'm confused about this and
don't want to blow it. Thanks!
What sort of weather are you expecting? Bright sun and f/1.8 don't get along well, without ND filters. Your depth of field will also be very narrow, and you may not have everything in focus that needs to be.
There is an old rule of thumb, called the 'sunny 16' rule. As a starting place, to shoot in daylight, you set your aperture to f/16 and your shutter speed to the ISO in use, as in 1/ISO. If you are using ISO 100, that would make your shutter speed 1/100th second, or the closest setting you have. With digital, it is easy to see how this comes out, and adjust from there.
If f/16 gives you too much depth of field, you can open the lens and increase the shutter speed to obtain the same exposure. So if you opened the lens to f/11, you would increase the shutter speed to 1/200th of a second. This would give you the same exposure as f/16 at 1/100th. If you follow the progression, adding one stop of shutter speed for each wider stop on the lens, you run out of shutter speed before you run out of aperture.
If this is all confusing, and it is at first, you could set the camera to "P", program shift. The camera will make the choice about aperture and shutter to obtain a correct exposure. Check the result, and you can then adjust the aperture or shutter to suit your needs.
There are several good resources available in a library or online, to teach you the basics of exposure.
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Crime Scene Photography