metering the sky at Apeture 2.8 and recompose

Discussion in 'Beyond the Basics' started by hao, Jul 28, 2009.

  1. hao

    hao TPF Noob!

    Joined:
    Jul 10, 2009
    Messages:
    12
    Likes Received:
    0
    Location:
    Vancouver, BC
    Can others edit my Photos:
    Photos OK to edit
    I have been reading "Understanding Exposures" , which is a good book btw.
    In the book, the author metions a technique for shooting backlight, snow, or sunset. What you do is that you meter the sky to get your aperture and shutter speed first then recompose to get a proper exposure.

    What confuses me is that he likes to meter the sky with an 2.8 aperture, and adjust the shutter speed accordingly. Then it comes to recomposing. A bigger aperture number, say 16, is neededfor landscape, so aperture is adjusted to 16 (5 stops) and the shutter speed needs to be decreased by 5 stops accordinly for the correct exposure.

    My question is:

    Why do we need to meter the sky at aperture 2.8 instead of the aperture we need, 16,at the first place? Does it give a better metering result?
    thanks!
     
  2. Tiberius47

    Tiberius47 TPF Noob!

    Joined:
    Oct 4, 2007
    Messages:
    742
    Likes Received:
    46
    Can others edit my Photos:
    Photos NOT OK to edit
    I have no idea why he would do this. You can set your aperture to whatever you want and then adjust your shutter speed to correctly expose for the sky.
     
  3. PhotoXopher

    PhotoXopher TPF Noob!

    Joined:
    May 27, 2009
    Messages:
    3,475
    Likes Received:
    2
    Can others edit my Photos:
    Photos NOT OK to edit
    He just uses the sky to meter the light, aperture has nothing to do with it other than coincidence that he's shooting wide open with his 35-70 a lot in that book.
     
  4. Josh66

    Josh66 Been spending a lot of time on here!

    Joined:
    Oct 31, 2007
    Messages:
    14,604
    Likes Received:
    1,236
    Location:
    Cedar Hill, Texas
    Can others edit my Photos:
    Photos NOT OK to edit
    Yeah, but he's metering, then adjusting his settings (that he just got done setting) by 5 stops!

    I think I would just meter in whatever aperture you plan on taking the picture at... Less to remember that way. "Now, how many stops did I change the aperture...? Oh, crap - what did it say the shutter speed was before I started changing everything...?"


    I'm sure he has a reason for doing it his way, but I have no clue what it could be.
     
  5. Josh66

    Josh66 Been spending a lot of time on here!

    Joined:
    Oct 31, 2007
    Messages:
    14,604
    Likes Received:
    1,236
    Location:
    Cedar Hill, Texas
    Can others edit my Photos:
    Photos NOT OK to edit
    The ONLY time I do something like what he's doing is if I'm going to have to go into Bulb.

    Let's say I want a picture of an old barn in the middle of the night... (That I still haven't made it back to, BTW...)

    You can't really meter past 30 seconds, so you have to do a little math in your head to figure out what it needs to be.

    Let's say f/1.4 is 2 stops underexposed at 30 seconds. That means you need an exposure of 120 seconds (30*2*2). But - what if you don't want to shoot at f/1.4?

    Let's say you want to shoot at f/8. That's another 5 stops. 120*2=240*2=480*2=960*2=1920*2=3840.

    Get your watch ready, because that's 64 minutes.

    OK, so you don't want to sit there that long... f/4 (2 stops less) sounds more reasonable. That would be 16 minutes (960 seconds). You could drop down to f/2.8 and only sit there for 8 minutes too.


    Anyway... I think it's important to know how to figure it out - but don't make it harder than it has to be.


    edit
    (Maybe that's why he says to do it that way in his book - so you'll know how when you need to.)
     
    Last edited: Jul 28, 2009
  6. Big

    Big TPF Noob!

    Joined:
    Apr 22, 2009
    Messages:
    1,228
    Likes Received:
    0
    Location:
    New Hampshire
    Can others edit my Photos:
    Photos NOT OK to edit
    I actually saw a guy do this one day. I was taking a walk on the coast and he was photographing a girl at the ocean and I noticed he kept pointing it up at the sky and then back to her.
     
  7. PhotoXopher

    PhotoXopher TPF Noob!

    Joined:
    May 27, 2009
    Messages:
    3,475
    Likes Received:
    2
    Can others edit my Photos:
    Photos NOT OK to edit
    That'll be the next big feature - exposure preview :D
     
  8. Dao

    Dao No longer a newbie, moving up!

    Joined:
    Mar 24, 2008
    Messages:
    6,252
    Likes Received:
    418
    Location:
    St. Louis
    Here is the reason why Bryan Peter do that in the cityscape type shot.

    He metered the sky. Then change to F/11 and 10s shutter speed based on the metering.

     
    Last edited by a moderator: Sep 11, 2014
  9. bhop

    bhop No longer a newbie, moving up!

    Joined:
    Dec 10, 2007
    Messages:
    2,209
    Likes Received:
    236
    Location:
    Los Angeles
    Can others edit my Photos:
    Photos OK to edit
    Actually, in the video he mentioned that since the subjects were far away, f/stop didn't matter, so he chooses f/8 or f/11, then adjusts his shutter speed (in this case 10 sec), he never actually said why he was metering the sky.

    As a side note.. fancy hairstyle he's got.
     
  10. Garbz

    Garbz No longer a newbie, moving up!

    Joined:
    Oct 26, 2003
    Messages:
    9,713
    Likes Received:
    203
    Location:
    Brisbane, Australia
    Can others edit my Photos:
    Photos NOT OK to edit
    Ha sucker. My D200 has this feature already. I click the shutter button and on the screen comes an exposed preview.

    :p
     
  11. musicaleCA

    musicaleCA TPF Noob!

    Joined:
    May 23, 2009
    Messages:
    2,303
    Likes Received:
    0
    Location:
    Vancouver, BC
    Can others edit my Photos:
    Photos OK to edit
    Considering it's a cityscape, metering off anything else is kinda useless. If you meter the buildings, you might get a reading that turns the lights to neutral, except that's not what you want at all. He's just deciding that the sky should be in the middle of the dynamic range of the image. If you think about it, the why becomes clear.
     
  12. KmH

    KmH Helping photographers learn to fish Supporting Member

    Joined:
    Apr 9, 2009
    Messages:
    38,237
    Likes Received:
    5,008
    Location:
    Iowa
    Can others edit my Photos:
    Photos OK to edit
    But, everyone here understands why he metered the sky, right?

    The exercise with calculating a change in stops the OP mentiones was just to show the relationship of aperture to shutter speed. To maintain the same exposure, if you change one, you have to change the other an equal amount.
     

Share This Page

Search tags for this page
citiscape metering
,

how to meter and recompose photos

,
how to meter then recompose
,
meter and recompose
,
meter on sky the recompose?
,
metering and recomposing video
,
metering recompose
,

metering the sky

,
metering the sky photography
,
what does meter and recompose mean