Question About Landscape vs. Portrait, Amount of Light...

Discussion in 'General flash photography, lighting, and technique' started by Aqualung, Sep 7, 2008.

  1. hi, I played around w/ my light stands/umbrellas today (newbie) and was surprised to see this difference in light from landscape to portrait and am hoping someone can explain...

    I used two SB-800s on light stands, shooting thru the umbrellas, fired by a SU-800, both flashes in TTL. From Horizontal to Portrait, nothing in the light setup changed, just rotated my camera. I recall that when using on-board (SB-800) and you rotate, a flash bracket helps to keep the flash overhead and all...so I know the rationale there and how to correct.

    Don't worry about background, etc., this was just to test the setup. No PP except for resize for Web...I know I was using an f-stop that was probably too high, but I noticed this at f5.6 too. I was shooting CW so I would think the window light wouldn't affect the exposure either.

    Landscape:

    Horizontal.jpg

    Landscape Histogram:
    Histogram%20Horizontal.jpg

    Portrait:
    Vertical.jpg

    Portrait Histogram, definitely darker:
    Histogram%20Vertical.jpg

    I'm wondering if there is an exposure difference, shouldn't TTL adjust for it? Or should I be prepared to compensate manually?

    Thanks in advance...
     
  2. dan1son

    dan1son

    Sep 24, 2007
    Austin
    Even with center-weighted some of that background window light is going to come into effect. I'd bet if you had a black background you would see the opposite effect. There is definitely more background near the center of the second shot.

    You can always dial in a little extra to help if you notice this. Or spot meter fv-lock and recompose in either mode. That'll get you consistent shots.
     
  3. ok, will try that, thanks....
     
  4. ttl is a 'magic mode',. consistancy comes from taking control and using manual settings,. ittl is good for fast paced enviroments but does not lend itself for repeatable results (slight changes will happen shot to shot)

    agree it's would be good to experiment with a fixed background / framing / subject and just spin the camera through 90degs but really when using lighting like this it's often better to go fully manual
     
  5. There's always the slight possibility that the flashes weren't fully charged for the second shot as well .
     
  6. thanks guys....Desmond I'm pretty sure they were as I took several other shots that were like this, but it's def something I'll verify along w/ setting up my backdrop.
     
  7. It is impossible, as far as I can tell, to get a definitive answer about which flash metering mode is used in Advanced Wireless Lighting.

    It's relatively straight forward for on-camera flash. The usual TTL or TTL-BL with which we're all familiar when using on-camera flash is normally selected by changing the metering mode from Spot (TTL) to either CW or Matrix (TTL-BL).

    These options don't exist on the Commander menu when shifting over to AWL with remote slaves. The only option shown is TTL no matter which metering mode you select; however, there are some of us who are convinced that you ALWAYS get TTL-BL anytime you use AWL in spite of what the menu says. Is that simply a limitation of the menu itself?.......... i.e. three letters only?

    I'm not sure and even though my testing leads me to believe that AWL always operates in TTL-BL, I haven't yet proven it to myself beyond a shadow of a doubt.

    But, assuming it's true, that would explain why you got a flash exposure change when you changed to portrait mode. The background has more white reflective curtain and less dark furniture in the portrait scene as well as more sunlight coming through the window. This would, one could assume, lead to a reduced flash duration (power) and since the exposure was fixed via manual shutter speed and aperture, the portrait image is darker than the landscape image.

    Of course, AWL may not work that way at all, but I'm not convinced that just because the menu doesn't include BL and just because there isn't a clear answer in the Nikon manual, that we know as much about this as we would all like to know. There's plenty of mystery surrounding AWL, that's for sure.
     
  8. rgordin

    rgordin

    623
    Jun 3, 2008
    Washington, DC
    I think I got the same thing using an SB400 bounce (on camera) - portrait settings were over-exposed.
     
  9. One of the reasons I moved from CLS to monolights in my small studio is shot-to-shot consistancy. There may be something happening with exposure when you changed orientation, but I saw that amount of difference between shots frequently without changing orientation. I'm not complaining about CLS. It is a great system, particularly on location where I still use it.
     
  10. I think your results will be more consistent with matrix metering, Chris. In center weighted, you're relying largely on a spot to set the exposure level. In one case, the spot might have been on the white of her eye, and in the other, on the dark brown iris.
     
  11. Centre weighted is a pretty large circle and I doubt it would pick up different parts of the eye - matrix metering on some of the lower end cameras tend toward focus points more so than centre weighted . You may be thinking of spot-metering .
    If anything it's more likely to be the bright sky in the background that causes the most problems .
     
  12. thanks for the suggestions guys...interesting, I attended a Joe McNally 1 day seminar yesterday and there was a discussion about metering, and Joe says he always uses Matrix himself.
     
  13. Chris, I think the only way you are really going to figure this all out is by going into manual mode. At that point, you should see that there is no difference in exposure based on the orientation of your camera. You will also enjoy the control you get in manual when you make adjustments to your flashes and your camera. You have a lovely, willing subject. Make her earn her keep by modeling for you while you experiment.

    If using TTL, I always use matrix metering. I find the results generally pleasing in almost any situation.
     
  14. thanks Mitch, that's what I'm going to work on...LOL, I'll dangle a cellphone as a reward, should keep her modeling for at least two more years :biggrin:
     
  15. No cellphone yet??:confused: I wish I had your willpower!