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Inconsistent TTL flash exposure means always using manual flash?

MBPhotoMBPhoto Member
edited May 2011 in flash & lighting
I have been trying out the SB900 with Softbox and controlled by PW FlexTT5 on a monopod. It seems that when I set the AC3 to A (automatic) I get very inconsistent flash exposures. Is this always the case? What setting should I be using? Manual Exposure and Manual Flash? I prefer to shoot in Aperture mode.

Comments

  • StephenStephen Member
    The two routes are
    1) manual exposure + TTL flash
    2) manual exposure + manual flash

    If you want exposure consistency with every shot, you shoot manual exposure + manual flash. If you want convenience and being able to adjust to the situation, you shoot manual exposure + TTL flash, but you give up consistent flash exposure.

    http://neilvn.com/tangents/2011/05/20/off-camera-ttl-flash/
  • Neil vNNeil vN Administrator
    TTL flash, by its very nature as an Automatic metering mode, will be inconsistent if you change your composition, or have a different background / subject in front of the camera.

    If you keep everything the same, the exposure from frame-to-frame should be consistent.

    Ultimately though, if you have a static setup, the manual flash is your best option.

    Could you upload an example or two?
    Just so we can see that it isn't your changing ambient light (via Aperture mode), which gives you inconsistent exposures.
  • You could always use manual + TTL flash in combination with Flash Value lock.

    On Nikon (depending on camera) program the function button to enable FV lock, then if you make a frame you really like and the value is bang on, give it a quick tap. It will stay locked until you tap the button again.




  • I have a nikon d300s and sd900 my question is on the same lines, to use manual + ttl would you set the camera to 1/250 sync speed and may be aperture F11 ? And sb900 ttl then use +/- to make small adjustments. (friends wedding)

    Martin
  • Neil vNNeil vN Administrator
    Martin .. the specific settings would depend on where you are working and what the available light would be.
  • Martin, it's best to experiment, read and learn the ins and outs of your gear and stay humble about what you're willing to take on until you're confident in the basic and your gear. Beware the thrifty family member or friend that comes to you because you have a big camera because it can turn into a bad experience for their wedding as well for your confidence. The balance of shutter speed, aperture and ISO for a proper exposure should be well understood before adding flash to the mix as it literally piles on ANOTHER layer of metering and complexity. The Nikon CLS system is a godsend as far as I'm concerned that makes a lot of things easy if you understand what it's up to. When something goes screwy though...well...lets just say it's definately not something you want to try debugging on a friends wedding day.

    1/250 is the maximum sync speed of your camera. Generally used to freeze movement or cut ambient light while not wasting too much light with auto-fp.

    f/11 is a pretty small aperture that will give you a deep depth of field but rob the sensor of more light.

    The combo of these two might be a good starting spot for a sunny day outside but it's YOUR responsibility to know what and how to tweak things for the best results. Anything indoors (or if things cloud up outside) will require some fairly drastic adjustments depending on your choice of lens and how you're planning on using your flash.

    Get to know the fundamentals of exposure first and foremost though.

    As for flash: I started off reading a fellow nikonians blog at http://nikonclspracticalguide.blogspot.com/2008/01/nikon-flash-two-separate-metering.html ...this is where it all came together for me. Your mileage may vary.
  • ZenonZenon Member
    That is a good link. At one time I was (to put it mildly) petrified of using a flash. I had to finally force myself as I was asked to shoot a wedding. I took a lighting course, fortunately found this site and purchased Neil's book about On Camera Flash Photography. I have summed up my flash world with these two statements. I always think of these two things when I shoot.

    1.Flash photography’s primary goal is obtaining a pleasing exposure of the subject followed by the background exposure. This does mean that the background is less important. Every flash photograph is two exposures in one – flash exposure and ambient (or background) exposure. “Flash photography requires managing both exposures”.

    2. The ultimate goal is for your image to look natural - like you didn’t use a flash.

    When I can I prefer to shoot with camera and flash on manual. If it is run and gun such as a reception then the flash goes on TTL. Outdoors I can change it up to AV which essentially turns your flash into fill flash. Be careful shooting with AV indoors because if your ISO is too low you may be shooting at 1/10 shutter speed and may not notice when you are busy. I read many threads about people frustrated with this. It is important to understand how your system works when camera is in Manual and AV.

    I agree that f/11 is pretty small. The lack of DOF produces typical snap shots. Opening it up will reduce flash power quite a bit and produce interesting images. Many shoot at 2.8 or wider. You may have to stop it down a bit for group shots. I recently shot a photo booth at a wedding and set it to f/8 as it was just portraits.

    Judging shutter speed is the most challenging thing I think. At a darker reception I shoot at about 1/60. If the ambient background is bright or I need to kill florescent light I will go to max sync speed. If you watch Just Give Me the F Stop through B&H photo Neil talks about the benefits of sync speed. Those are good videos.

    One trick I learned that is if your camera is in manual and the light meter shows at least two stops underexposed your flash will freeze the subject even at 1/10 shutter speed. This because the flash is more dominant than the ambient As stated you might get motion blur in the background. Try this at home. Put your cam with flash on a tripod, set the ambient conditions so the camera's light meter is showing at least two stops underexposed and wave your hand in front of your lens as you take the shot. A good trick to have in your hip pocket.

    Next time you are indoors in a darker location set your camera to manual, open up the aperture (2.8 if you can), ISO 1600, start with shutter of 1/60 but you can bump it up to 1/125 or 1/160 to reduce background blur. It helps to have a high ISO capable camera.

    Just to finish I had a hard time when I started to learn this stuff. I could not wrap my head around why the camera meter was showing underexposed with the flash on. Then I finally realized that it is measuring ambient light only and has no way of predicting flash output so it does not try. The flash will provide the light to illuminate the subject so essentially you just ignore the light meter. I had to learn to trust the process. I think that was what prevented me from learning until I was forced to. Can't get enough of it now.
  • If you are shoot in aperture mode, then you should shoot in manual exposure with TTL flash. It can give you a better result. 
  • betwa2982betwa2982 Member
    edited October 2018
    You can use exposure + manual flash for consistency. And exposure + TTL flash for convenience. These two options are available for you.
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