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Thread: how to get the first composure

  1. #1

    Default how to get the first composure

    HI
    I was actually reading some threads for newbies on how to calculate stops.
    Below example from

    7. How do we calculate stops?
    Assuming the light entering the camera remains constant, we can play around with the value of the ISO, shutter speed and aperture value while maintaining the same exposure.

    Ex 1: Assuming ISO 100 is constant. f/8 at 1/250s is equivalent to f/11 at 1/125s. Why? When we set the aperture from f/8 to f/11, we are reducing the light by 1 stop (half the amount of light now enters the camera). So to maintain the same exposure, we need to increase 1 stop from the shutter speed, hence 1/250 to 1/125 (time now is double, so we have double the light).

    The question for me is how to determine the initial ISO, Aperture or shutter speed?
    Better said, to take picture in a restaurant with warm light, what should be the initial shutter speed or aperture or ISO ?

    or how do I get the correct exposure.

  2. #2
    Moderator catchlights's Avatar
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    Default Re: how to get the first composure

    Quote Originally Posted by ltshaft View Post
    HI
    I was actually reading some threads for newbies on how to calculate stops.
    Below example from

    7. How do we calculate stops?
    Assuming the light entering the camera remains constant, we can play around with the value of the ISO, shutter speed and aperture value while maintaining the same exposure.

    Ex 1: Assuming ISO 100 is constant. f/8 at 1/250s is equivalent to f/11 at 1/125s. Why? When we set the aperture from f/8 to f/11, we are reducing the light by 1 stop (half the amount of light now enters the camera). So to maintain the same exposure, we need to increase 1 stop from the shutter speed, hence 1/250 to 1/125 (time now is double, so we have double the light).

    The question for me is how to determine the initial ISO, Aperture or shutter speed?
    Better said, to take picture in a restaurant with warm light, what should be the initial shutter speed or aperture or ISO ?

    or how do I get the correct exposure.
    use the built in camera exposure meter.

    or using a handheld light meter.

    or by experience
    Shoot to Live, Live to Shoot
    www.benjaminloo.com | iStock portfolio

  3. #3
    Senior Member Kit's Avatar
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    Default Re: how to get the first composure

    It largely depends on what you are taking in the restaurant and what you have to assist you in taking those photos. You should also be using the appropriate exposure mode to do the job.

    These are really fundamental questions which are explained since I can't remember when and is easily accessible on the net. Familarise yourself with what aperture / shutter speed do.

  4. #4
    Moderator ziploc's Avatar
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    Default Re: how to get the first composure

    Quote Originally Posted by ltshaft View Post
    HI
    I was actually reading some threads for newbies on how to calculate stops.
    Below example from

    7. How do we calculate stops?
    Assuming the light entering the camera remains constant, we can play around with the value of the ISO, shutter speed and aperture value while maintaining the same exposure.

    Ex 1: Assuming ISO 100 is constant. f/8 at 1/250s is equivalent to f/11 at 1/125s. Why? When we set the aperture from f/8 to f/11, we are reducing the light by 1 stop (half the amount of light now enters the camera). So to maintain the same exposure, we need to increase 1 stop from the shutter speed, hence 1/250 to 1/125 (time now is double, so we have double the light).

    The question for me is how to determine the initial ISO, Aperture or shutter speed?
    Better said, to take picture in a restaurant with warm light, what should be the initial shutter speed or aperture or ISO ?

    or how do I get the correct exposure.

    Sounds familiar. Think it was written by me. Sorry arh, that article was written many years ago intended as hand out for newbie classes and might not be very clear in some aspect without explanations.

    http://www.clubsnap.com/display.php?...graphy101.html

    The answer to your question is actually in the section titled "metering" (please take a look as I won't be repeating what's already written in the article). Modern DSLRs are quite accurate with the metering, especially the matrix (evaluative) metering mode. You could depend on your camera's light meter to measure the correct exposure needed.

    Now let's consider the following shooting modes: A (aperture priority), S (shutter priority) and M (manual). Which one to choose will depend on what you would like to achieve.

    For example, if you would like to control the DOF, you'll choose A mode, set the desired aperture value to achieve the DOF, and let the camera choose the shutter speed (it does this by using the exposure measurement mentioned above).

    Similarly, if you would like to control the shutter speed (to freeze motion or make light trail, e.g.), you would shoot in S mode and let the camera select the aperture value.

    If you want full control of the aperture and shutter, you would shoot in M mode, but you are not left alone as the camera will still tell you whether your setting is "just right" or over/underexposed (refer to your camera's manual for more details).

    So far we've discussed about aperture and shutter, so what about ISO? Which value of ISO to select will depend on the lighting condition during your shoot. So let's use your example of taking your gf's picture in a romantic (read "dimly lit") restaurant.

    Now because you're shooting portraiture, you want to control the DOF and so you choose to shoot in A mode. Let's say at f/2.8, ISO100, the shutter speed is 1/15s (measured and set by camera) and you're using a 50mm lens. According to the rule of thumb, min shutter speed needed to avoid camera shake is 1/(focal length) => 1/(50x1.5) => 1/75s. Obviously the current shutter speed of 1/15s is too slow.

    In order to get higher shutter speed, you need higher sensitivity from the sensor, so what you need to do is to set a higher ISO. You will need 3 stops: 1/15->1/30->1/60->1/125. So ISO now needs to be increased from ISO100->200->400->800. Since higher ISO introduces more noise to the pic, you would want to set the ISO to the min needed to achieve the exposure. Of course if you camera allows half or 1/3 stop increment, you can also do that and not necessary stick to 1 stop increment.

    So there you go, final setting needed would be: ISO800 (set by you), f/2.8 (set by you), 1/125s (set by camera). Now go take your camera and play with the settings mentioned above and see the effects yourself.

    Hope that helps. Cheers.
    Last edited by ziploc; 18th December 2009 at 11:13 PM.

  5. #5

    Default Re: how to get the first composure

    Quote Originally Posted by ziploc View Post
    Sounds familiar. Think it was written by me. Sorry arh, that article was written many years ago intended as hand out for newbie classes and might not be very clear in some aspect without explanations.

    http://www.clubsnap.com/display.php?...graphy101.html

    The answer to your question is actually in the section titled "metering" (please take a look as I won't be repeating what's already written in the article). Modern DSLRs are quite accurate with the metering, especially the matrix (evaluative) metering mode. You could depend on your camera's light meter to measure the correct exposure needed.

    Now let's consider the following shooting modes: A (aperture priority), S (shutter priority) and M (manual). Which one to choose will depend on what you would like to achieve.

    For example, if you would like to control the DOF, you'll choose A mode, set the desired aperture value to achieve the DOF, and let the camera choose the shutter speed (it does this by using the exposure measurement mentioned above).

    Similarly, if you would like to control the shutter speed (to freeze motion or make light trail, e.g.), you would shoot in S mode and let the camera select the aperture value.

    If you want full control of the aperture and shutter, you would shoot in M mode, but you are not left alone as the camera will still tell you whether your setting is "just right" or over/underexposed (refer to your camera's manual for more details).

    So far we've discussed about aperture and shutter, so what about ISO? Which value of ISO to select will depend on the lighting condition during your shoot. So let's use your example of taking your gf's picture in a romantic (read "dimly lit") restaurant.

    Now because you're shooting portraiture, you want to control the DOF and so you choose to shoot in A mode. Let's say at f/2.8, ISO100, the shutter speed is 1/15s (measured and set by camera) and you're using a 50mm lens. According to the rule of thumb, min shutter speed needed to avoid camera shake is 1/(focal length) => 1/(50x1.5) => 1/75s. Obviously the current shutter speed of 1/15s is too slow.

    In order to get higher shutter speed, you need higher sensitivity from the sensor, so what you need to do is to set a higher ISO. You will need 3 stops: 1/15->1/30->1/60->1/125. So ISO now needs to be increased from ISO100->200->400->800. Since higher ISO introduces more noise to the pic, you would want to set the ISO to the min needed to achieve the exposure. Of course if you camera allows half or 1/3 stop increment, you can also do that and not necessary stick to 1 stop increment.

    So there you go, final setting needed would be: ISO800 (set by you), f/2.8 (set by you), 1/125s (set by camera). Now go take your camera and play with the settings mentioned above and see the effects yourself.

    Hope that helps. Cheers.
    Hi Ziploc

    Thanks for the detail explaination. Will go and play with my camera.

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