Welcome to the forum!

As an adjunct to the Tangents blog, the intention with this forum is to answer any questions, and allow a diverse discussion of topics related photography. With that, see it as an open invitation to just climb in and start threads and to respond to any threads.

ETTL vs. Manual On Camera

Hi - I have been finding in about half the events I photograph, bouncing ETTL flash isn't enough, and I have to switch to manual. Some of these events are in pretty big spaces, and are not amenable to having off-camera flashes set up. It's been working pretty much, but I am curious as to why ETTL, with a +3 boost, isn't cutting it.

Today I tried to figure out how I could measure the output of my flash on ETTL with +3, but of course you really can't do that, or at least I couldn't figure out how to do it.

Does anyone have an idea of how the output power of ETTL flash with a +3 boost compares to full-power manual flash? Is there any way at all to measure what comes out when set to ETTL, as silly(?) a test as that may sound?

Thanks - Dave


  • TrevTrev Moderator
    edited January 2018

    Do you shoot Nikon? Manual Mode on Camera?

    If so you are in luck.

    First, no, you cannot measure with a light meter in TTL, as the meter will measure the 'Pre-Flash'.

    Now, to help with flash power, and this only works if you have Nikon, and the body is in manual mode, flash in TTL, you can use the Camera Body's Compensation feature, by putting a + on it, regardless if using manual.

    Here's why, on Nikon only, and camera body itself is in manual mode, putting the + on the *camera's* compensation increases the flash output by the compensation shown, but will not increase compensation on the body as once in manual mode any compensation is ignored, on the body that is.

    If you use Canon, and I suspect you are since you say 'ETTL' (Canon) instead of 'iTTL' (Nikon), this does not work. :(

    Just a very nice feature in Nikon bodies, the + compensation increases flash power but again, only while the body is in manual mode. If you have both body/flash in manual, than using the -|+ compensation does diddly squat.

    I've used this quite a bit, but there is a caveat, if you forget to dial back the compensation on the body to 0, the next time you go to use your flash you will be wondering why even if a - compensation on the flash head, it's still too much power, it is because of the compensation being left on the body.

    Oh, another thing, the compensation on the body will also be cumulative with the flash's compensation. :)

    The only solution if you have Canon and the +3 is not cutting it, is put the flash in manual, but a quick dial up/down to adjust should be pretty easy with no button pushing to do it, as once in manual on flash head, the dial works immediately, well on Nikon, but as I say, never had to use manual since I can compensate on camera body. Best of both worlds.

    Then once in ball park just shoot, any small variations can easily be adjusted in your Camera RAW Editor


    Edit PS: Also, do you zoom your flash head in, even if shooting wide on camera and if flash head is set to 'Auto' it will spread the flash out, thus reducing power output since the spread will fall off quickly. Always just zoom the flash head in to 200mm or whatever the max is on it, regardless of what the lens is.

    The flash beam being concentrated now will flash more light into your bounce source, and come back stronger than if it had been spread out to begin with. Makes sense? Hope I explained it enough for you.

    Like normal sunlight hitting the ground, get out a magnifying glass, put it under the sun and the concentrated  beam is massive, kill those ants mate. hah! ;)

    Luck Dave.

  • Hey, Trev - Happy New Year! Haven't seen anything from you in a bit, and I hope all is well.

    I shoot Canon, so I don't have that feature. Also, I forgot about the meter measuring the "pre-flash", thanks for reminding me.

    I have tried in the past to zoom the flash, which makes perfect sense. I think I just didn't notice a huge difference.

    I don't mind shooting with my flash in manual, and adjusting it. As long as something is working to get the shots I want. I was really just curious about the differences in power. Is this something the manufacturer would know?

    Thanks - Dave
  • TrevTrev Moderator

    Because the flash is using an algorithm to determine it's output power to what it "thinks" is the right choice, does not necessarily mean it is so.

    A number of factors come into play here when in ETTL.

    1] Distance
    2] Ambient Light
    3] What the camera 'sees' as in wide/zoom - affects the power output
    4] Focus Point, since a flash will 'predict' what power is needed when you focus, again not necessarily correct.

    When in Manual Mode

    1] Bang! Done! That's it, regardless of what ambient/distance/zoom/focus/calculations, it just dumps out the power whatever level you put it on. Done and dusted.

Sign In or Register to comment.