Friday, October 1, 2010

Super Manual Flash

David Hobby ( recently posted an interesting tip for manual flash users that will allow the camera to track the ambient exposure automatically, even with variable ambient light conditions: . Clearly, there's some benefit from not having to keep adjusting flash or ambient exposure as conditions change. Taking that a step further, wouldn't it be cool if you've setup the shot and have nailed the flash and ambient exposure, and the flash was smart enough to adjust power automatically to maintain that flash exposure even if you reposition your lights or adjust your exposure? OK you saw this coming... I'm talking of course about TTL flash.

If you're a manual-only flash user, and you do any photography other than setup shots, I really would strongly recommend adding TTL flash to your repertoire. The great thing is, if you already know manual flash, you already have a leg up.

Common criticisms by manual flash users about TTL flash include unpredictability and variability:
- Unpredictable in that "you never know what you're gonna get".
- Variable in that TTL uses the reflection from preflashes to guess the correct flash exposure and is thus subject to reflection-based metering weaknesses. For example, even though aperture, ISO, flash-to-subject distance, and the flash's guide number are held constant, flash exposure can vary depending on the reflectance of the image in the frame (which in turn can vary based on the reflectance of the subject or other elements).

OK, guilty as charged on both counts. In theory, you never know with 100% certainty what flash exposure you're going to get with TTL until you take at least that first test shot. In reality though, TTL gets reasonably close to an ok flash exposure. This is not that much different from using manual flash without a flashmeter or calculator (for GN calculations). The difference is that instead of you guessing the amount of power you need, the camera and flash offer a ballpark estimate. If you don't like the flash exposure you get, you simply adjust with flash exposure compensation - the same way you would adjust your power upward or downward if you didn't like the flash exposure you got with your test shot on manual flash mode.

It's also true that TTL can be variable even under conditions when flash exposure should be constant. Fortunately, if this theoretical variability is truly a dealbreaker for you, there are a few answers for that.

1. For Canon, Nikon and Olympus:
Spot meter a gray card when you take the shot. TTL will set flash exposure to render that gray card as middle gray (within the flash's power limits). This will work even in conditions that would normally fool TTL such as including a highly reflective object in the shot. Adjust flash exposure upward or downward if you wish using flash exposure compensation. Then use FV lock (aka FEL or FV Flash Lock) to lock the desired flash exposure. You will get the same flash exposure consistency that you will get from manual.

2. For Sony, Pentax, and other cameras that don't have FV Lock:
Include a gray card in your test shot, and adjust TTL flash exposure (with flash exposure compensation) to render the gray card as gray. When you do this, don't spot meter from the gray card because if you remove the gray card then the flash exposure will change. Just use the gray card in the frame as a guide for an "accurate" flash exposure.

In real life, TTL shooters don't use a gray card because we just use FEC to adjust whenever we don't like the flash exposure. Plus, most of the time (at least for me), the flash exposure doesn't really vary all that much anyway (except in unusual cases).

Ready to give TTL a try? Don't worry - it doesn't bite. :)

1. Set the ambient exposure as you would with manual flash.
2. Take a test shot with TTL flash.
3. Estimate the flash over- or underexposure and adjust the TTL flash accordingly, using flash exposure compensation.
4. Feel free to change shutter OR aperture OR ISO OR subject-to-flash distance OR any combination of the above. You can even change modifiers or filters or gels. TTL will keep the flash exposure the same!
It may help to think of TTL flash as a smart manual flash that can give you a reasonable guess of the right amount of power automatically upfront (which you can adjust), and also adjusts power automatically to keep your flash exposure the same from shot-to-shot, except that it isn't perfect so it needs tweaking upward or downward.

And if you're a TTL-only user reading this, check out these related posts:
TTL vs. Manual: a False Dilemma
Therapy for TTL Addiction


  1. Hi Mic
    I tried to take picture during a show with horses.
    With manual flash I succeed to take 0 acceptable pictures. The distance to my subject was changing all the time .
    TTL was the salvation.
    Unfortunately it was TTL on camera so welcome red yes.
    I believe the ideal solution is pocket wizards and TTL flashes.
    When the subject is moving randomly manual flash is a pain. In this condition I really prefer TTL and PW
    So till I get the PW no more running horses late evening

    BTW I was the only one havin flash off camera . Even the official photograph used on camera flash…not even a diffuser..

    And you advise for TTL is useful. Now tell me how I trigger the flash

  2. Hi Robert. I'm glad TTL worked for you. The lowest cost off-camera triggering solution for TTL is a TTL cord. A third-party version is available for around $30. If you're willing to spend more, Nikon's SC-29 cable offers a built-in AF Assist Light (around $75).

    If you have a CLS-compatible flash, a very good option for off-camera triggering is Nikon Advanced Wireless Lighting (or the Canon or Olympus equivalent). A lot of people say the flash has to be within line-of-sight and can't be used in daytime. That's not true. CLS AWL is very reliable under most conditions. You can also switch from TTL to manual remotely.

    A great alternative if you're willing to spend even more is radio TTL. Chinese-made ones like Pixel function like the TTL cord except that it's wireless. The best option for Nikon right now is the Radiopopper PX system which has the same functions as AWL except that it uses radio. Pocket Wizard has a radio TTL solution for Canon (ControlTL) but the Nikon version isn't out yet.

    More power to you!

    Best regards,

  3. Thanks Mic for the tips.
    Do you know any triggers able to dial the output flash from one remote?
    Basically everything exept the TTL

  4. Hi Robert. Do you mean remote adjustment of multiple manual flash units? If so, besides CLS AWL, I know of the Radiopopper JrX Studio and Radiopopper PX. There's also the Yongnuo YN460-RX and YN460-TX. Hope this helps! If that's not what you meant, please feel free to email me at info at

    Best regards,

  5. Thx Mic , yes the info is the one I was looking fr
    Very good news with the triggers from Yongnuo...they are hot
    Thx again Mic

  6. Thanks! Yes, I'm really hoping the Yongnuo YN460TX and YN460RX work as advertised, and that the price is reasonable...

  7. Hi Mic

    I think you've got the wrong end of the stick on this one Mic.

    You have to remember that when taking picures with flash you're actually recording two exposures at the same time, there are two lighting components the ambient and the flash.

    With manual flash it works like this.

    1) Shutter speed controls just the ambient component(the flash is much faster than the shutter speed)so altering the shutter speed does not effect the flash component.

    2) Flash power controls just the flash component.

    3) ISO and aperture alter both the flash and ambient components.

    Most strobists use manual mode on their cameras so that they can control each component separately, what David Hobby is saying here is that by using Aperture Priority your camera will maintain the aperture and adjust the shutter speed (which has no effect on the flash component)this will maintain the ambient part of the exposure as the light darkens at dusk, so maintaining the flash to ambient relationship that you set up.


  8. Hi Chris. Thanks - you're absolutely right and I'm not sure what I wrote that suggests otherwise but thanks for clarifying and adding to the discussion.

    Best regards,


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