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Adjusting manual exposure

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daveco View Drop Down
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Joined: January/15/2015
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Post Options Post Options   Thanks (0) Thanks(0)   Quote daveco Quote  Post ReplyReply Direct Link To This Post Topic: Adjusting manual exposure
    Posted: January/15/2015 at 02:16
I'm no photography expert, but one thing I find handy is remembering the following, when shooting in Manual exposure mode.
In manual, if I have got the exposure nailed, but wish for more blurry background, and say I am shooting at f/8 and 1/200 sec, I know I can achieve the same exposure at f/2.8 and 1/1600 sec, so I can switch to this without worrying.
Going from f/8 to f/5.6 to f/4 to f/2.8 doubles the volume of light hitting the sensor, for each change(one stop), and so I have to halve the shutter speed for each change(one stop), 1/200 to 1/400 to 1/800 to 1/1600, to achieve the same volume of light for a perfect exposure.(somebody check my math!)
Sure, you can look at your meter, but I generally do this in my head while shooting.
There are times, too, when you may desire to not change both aperture and shutter speed, in which case you can change your ISO, and either aperture or shutter speed.
ISO 100 to 200 to 400 to 800, doubles the light sensitivity for each change.  Maybe I am shooting at f/8 and like that depth of field for my shot, but I am shooting at too slow a shutter speed and want to increase it to ensure stopping subject movement.  I change my shutter speed from 1/60 to 1/240 sec (two stops) and change ISO two stops, from ISO 100 to ISO 400; the same exposure level is achieved.
Oh, and maybe your camera won't let you shoot at 1/240 sec, and you have to shoot at 1/250 sec, but you will still be very close to the same exposure.
I like to look at light in terms of volume, and liken it to a bucket of water, in which filling the bucket to a certain line represents the perfect exposure.  I can use a narrow diameter hose (small aperture) to fill the bucket to that line, running the water for a relatively longer time(shutter speed), or I can fill the bucket to the line using a large diameter hose(aperture) for a shorter period of time(shutter speed).  In both cases, the same volume is achieved.


Edited by daveco - January/15/2015 at 02:42
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RifleDude View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RifleDude Quote  Post ReplyReply Direct Link To This Post Posted: January/19/2015 at 16:36
Originally posted by daveco daveco wrote:

I like to look at light in terms of volume, and liken it to a bucket of water, in which filling the bucket to a certain line represents the perfect exposure.  I can use a narrow diameter hose (small aperture) to fill the bucket to that line, running the water for a relatively longer time(shutter speed), or I can fill the bucket to the line using a large diameter hose(aperture) for a shorter period of time(shutter speed).  In both cases, the same volume is achieved.


Good analogy!
The technical aspect of photography becomes much easier once one fully understands the "exposure triangle."
Ted


Money can't buy happiness... but it's much more comfortable to cry in a Porsche than on a bicycle.
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kyhds View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kyhds Quote  Post ReplyReply Direct Link To This Post Posted: January/04/2016 at 02:32
What you say is like a expert in my eyes.
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