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TTL/BL indoors as well maybe ?

Discussion in 'General flash photography, lighting, and technique' started by Desmond, Jul 26, 2008.

  1. I did some more tests with TTL/BL remembering that it had some varied results indoors and thought it may actually be better for all situations . After the tests though it seems to under-expose in the majority of indoor situations .
    Backlit :

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    ttl slightly brighter than ttl/bl
    Last edited by a moderator: Jul 26, 2008
  2. Slightly different situation , similar results .

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  3. Now the interesting part which I noticed in previous tests , when the subject is close to a white wall ttl/bl gives better results than ttl :

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    I did this particular test again using bounce flash and the result is that ttl/bl gives the exact same result as ttl [ slighly underexposed for the white wall ]

    As we move further from the white background things change around a bit but the difference is not as big between the two as with the previous two .

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    Last edited by a moderator: Jul 26, 2008
  4. jsavitch

    jsavitch Guest

    i don't use the bl feature much on my flash unless i am 100% backlit in bright sun. i find that regular TTL and A are the best modes for my sb800's
  5. what metering mode are you using?
  6. That's interesting because I haven't heard many people say they use "A" mode . But recently I was checking out another site http://www.shootsmarter.com/
    where they say that they believe "A" mode is better than most ttl modes for fill flash .
  7. Matrix metering ona D70S . My old D80 would have blown the highlights on the first picture .
  8. what exposure mode are you using is the real question. all your shutter/aperture combos are the same which leads me to believe that you where in M mode with everything fixed. if you did that, there is no hope for TTL-BL to function properly and it would also pigeon hole the plain TTL mode in some conditions. either way, they would both act the same.
  9. EXIF indicates all were shot in "A" mode with f/5.6 selected.
  10. That's right , of course flash ''default'' speed sets itself at 1/60th which I know can be adjusted . Either way they did not behave the same and I'm sure the results would be the same if I set it manually since the meter would still be available for the flash to do its calculations .
  11. that should be a slow shutter speed limit that you can set. if its bumped against this limit, than it is essentially like fixing the exposure. in BL mode, the camera is locked out of trying to get more background exposure.
  12. RichNY

    RichNY Guest

    Desmond- Make your life simpler and forget about using BL mode; it is inconsistent. When you use TTL you have the ability to dial in +/- EC and it works. When you do the same with TTL BL the camera takes your suggestions under advisement and may decide it doesn't want to do what you've asked. It makes decisions on regular and flash EC without you having a damn bit of control over it.

    TTL BL will give you different results based on the brightness of the scene and doesn't always give repeatable results. Do yourself a favor and forget about this mode.

    Another thing from your other thread is don't use Program mode when using flash- period. The largest aperture you can shoot at at ISO 200 is f/5... at ISO 800 it drops to f/7.1, and by ISO 2000 you won't be able to open up past f/9 regardless of the lens you use and it doesn't work in spot metering mode.

    The best way to use your flash is always to shoot in manual mode setting your aperture for what you want to see creatively, and your shutter speed to give you the exposure you want for ambient.

    You will almost always use some amount of negative flash exposure will TTL the amount depending on whether you want your flash to be responsible for lighting the subject or just providing some fill flash.

    If you want to light the subject I would suggest starting with -2/3 (.7) stops of negative flash compensation.

    If you want to fill flash the subject then I would suggest starting with - 1 1/3 stops of negative flash compensation.

    Take a look at your image and adjust the negative flash EC up or down a 1/3 stop to where you like the look.

    It doesn't get much simpler than this and it works for light and dark situations equally well unlike TTL BL.

    I think your test shots in both threads were misleading because you were shooting w/o using flash EC and just comparing how the system works at its defaults- and it doesn't do a great job that way without compensation. The indoor/outdoor situation you were facing had to do with the type of lighting you were faced with in each situation.

    Hope this helps to explain how our flashes work a little better and how much easier it is to get good and consistent flash exposures using this method.
  13. Thanks , I think this is brialliant advice and I'm in the ''transition period '' of shooting manual . Every now and then I venture into manual mode but not when there is the slightest bit of pressure . I am going to make a concerted effort to go fully manual and as you suggest stick with TTL and , with the excessive pre-flashes of the D70S I am also trying "AA" mode . Indoors the AA mode gives almost identical results to TTL until you get a bit close to the subject . My ultimate goal is to know and understand how all these systems work before making decisions . I now know that TTL-BL fires weaker than TTL outdoors so it is good for fill flash . I have also seen top photographers using "A" mode flash with good results [ mainly canon shooters who don't have good flash systems though ] ..... off to practice some manual shooting .
  14. I have done numerous tess including outdoors shots in "P" mode ....

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    The flash does not take control of the camera . The manual is rather misleading in that it says something like " the flash tries to achieve an even exposure between the background and subject " .
    What really happens is that with TTL the flash doesn't care what the camera meter says but with TTL-BL the flash also takes into consideration what the camera meter reads and flashes accordingly without overpowering the scene as TTL sometimes does . You notice this especially in daylight with fill flash , TTL-BL is normally [ in my guess] about 1 stop weaker than TTL because it takes into account the ambient light - but it does not change camera settings to suit itself .
    I just set my minimum speed to 4 seconds and put the flash on the D70S , in TTL flash the settings were 2.5 F7.1 and in TTL-BL it was 2.5 F7.1 .
    In this situation TTL would add to the exposure and TTL-BL would fire weaker since there is a decent amount of ambient .
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