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A question about metering...

  • 17-07-2012 5:14pm
    #1
    Daveysil15
    Closed Accounts Posts: 4,301 ✭✭✭


    So I've started using a light meter lately for outdoor portraits. It helps a lot with exposure. My question is this: Suppose you're outdoors taking pictures of someone. You take a reading from the person's face, and say for example it says 100th of a sec at f/11. So I go into manual and enter that information. But suppose I want to blur the background, completely throw it out of focus? I'd need a bigger aperture, say f/4, but then I wouldn't be getting the same exposure the light meter gave me. Also if I'm using off-camera flash, the aperture value has an effect on the light from the flash. Is there a way I can keep the exposure my meter is giving me and still get that bokeh affect?


Comments

  • #2
    magicbastarder
    Moderators, Category Moderators, Arts Moderators, Sports Moderators Posts: 50,891 CMod ✭✭✭✭magicbastarder


    what sort of light meter are you using? the meter should show you the correct exposure for a range of apertures.
    if it's an ambient meter, you won't be taking a reading from the face, but of the light falling on to it, which is a crucial difference (in general, but not a massive issue for a face because it'd probably be within a stop of 18%).


  • #3
    Daveysil15
    Closed Accounts Posts: 4,301 ✭✭✭Daveysil15


    It's a handheld flash/ambient meter, but it usually gives me an aperture of between f/6 and f/11 which wouldn't allow me to blur the background. I like to use my 50mm lens for portraits so I can create a shallow depth of field, but I can't do that if the aperture is smaller than f/6. If I'm not using flash I can just use Av mode to create this affect, but if I'm using off-camera flash I can't do this.


  • #4
    DaireQuinlan
    Registered Users, Registered Users 2 Posts: 6,713 ✭✭✭DaireQuinlan


    does it have an aperture priority mode ? My sekonic has aperture and shutter priority (amongs other things) so I can set the aperture on the meter and read off the metered shutter speed. It has flash metering as well, which gives an aperture reading for the given flash exposure. So I plug in the flash, take a reading, and adjust the flash power or distance until I get the aperture I want.

    Otherwise it's relatively easy to adjust in stops anyway, you just have to give it a bit of thought. So if it gives you f/8 at 1/100 and you want to shoot at f/4 (say) then f/4 is two stops faster than f/8 so you have to adjust your shutter speed up by two stops, 1/400 in this case.


  • #5
    DaireQuinlan
    Registered Users, Registered Users 2 Posts: 6,713 ✭✭✭DaireQuinlan


    ah right, I understand your question, I just read the second reply now. Yeah a flash meter will only give you an aperture value. You have to manually adjust the flash power somehow. Turn it down, physically move the flash further away, or use a modifier like a shoot through umbrella or something.


  • #6
    magicbastarder
    Moderators, Category Moderators, Arts Moderators, Sports Moderators Posts: 50,891 CMod ✭✭✭✭magicbastarder


    very odd that it won't go wider than f6; i think mine goes to f1; it's a polaris lightmeter.


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  • #7
    Daveysil15
    Closed Accounts Posts: 4,301 ✭✭✭Daveysil15


    DaireQuinlan wrote: »
    does it have an aperture priority mode ? My sekonic has aperture and shutter priority (amongs other things) so I can set the aperture on the meter and read off the metered shutter speed. It has flash metering as well, which gives an aperture reading for the given flash exposure. So I plug in the flash, take a reading, and adjust the flash power or distance until I get the aperture I want.

    Otherwise it's relatively easy to adjust in stops anyway, you just have to give it a bit of thought. So if it gives you f/8 at 1/100 and you want to shoot at f/4 (say) then f/4 is two stops faster than f/8 so you have to adjust your shutter speed up by two stops, 1/400 in this case.

    I understand what you're saying. Although If I'm using flash, the maximum shutter speed I could use would be 1/250 if I'm not mistaken.


  • #8
    DaireQuinlan
    Registered Users, Registered Users 2 Posts: 6,713 ✭✭✭DaireQuinlan


    Daveysil15 wrote: »
    I understand what you're saying. Although If I'm using flash, the maximum shutter speed I could use would be 1/250 if I'm not mistaken.

    yes, or more precisely whatever the sync speed of your camera is, but read my second reply. I wrote the first one when I didn't realise you were talking about flash metering.

    The shutter speed (once you're at or below sync) has no influence on the flash portion of your exposure, only the aperture does. So you can set the aperture as given on the meter OR you can power the flash down a few stops or move it away from the subject or whatever, then you can open up a bit. It typically takes a couple of tries at first to get it right.


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