A couple of TTL BL and FV Lock facts

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http://www.scantips.com/lights/flashbasics4b.html#FVL

If interested, I added a very simple demonstration of TTL BL direct flash, showing how it is affected by D lens distance in a good case (meaning, which is sometimes accurate, and sadly sometimes not. Primes are better than zooms).

And also showing how FV Lock can affect the metered value, apparently then TTL BL no longer pays attention to the D lens info.

It will be trivial to reproduce this to see it for yourself, which is the purpose. It is something we ought to know, but one point is, if your TTL BL direct flash is coming out underexposed, FV Lock may override it. Only cameras with Commander have FV Lock however.
 
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Wayne,

I think that your last sentence could be misunderstood.

You can use FV Lock in any Flash Mode. Your statement could be misread to imply that you must be in CLS setup.

DG
 
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Agreed, any TTL flash mode, and my example is using hot shoe iTTL, not Commander.

However, what I meant was that only the cameras with Commanders have FV Lock.
(exceptions are the D3 and D4, no internal flash, but still FV Lock)
 
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http://www.scantips.com/lights/flashbasics4b.html#FVL

I really thought that would be of some interest, to cause a few comments. No one cares to read it I guess. It is all easily tried by anyone, to see that it is true.

Frankly, I'm disillusioned with Nikon. I've been a loyal fan since my first Nikon F in the 60s. They could do no wrong then, and with all the Life Magazine photographers back then, there simply wasn't anything else of interest. It seemed clear that if there is a God, he must work at Nikon. They were really good about letting us know every little thing about how the gear worked too, however, that may have been EPOI, the US distributors before Nikon bought them out.

But now... they don't tell us much of anything. Just mysterious marketing buzz words, like Matrix, databases, balanced flash, etc, without describing anything. It leaves it up to us to argue endlessly about what it does. :smile:

Like 3D metering, which we come to know only means the D lens distance acts as a guide number safeguard to prevent TTL BL direct flash from overexposing, when the metering sees the dark background. And it seems to work OK for prime lenses, but many zoom lenses have to refocus (rotating lens barrel) at different zooms, and this turns bad. Worse than ineffective, it turns counter productive, sometimes darkening TTL BL direct flash shots, which has no hope of getting a good exposure (in some combinations). You'd think Nikon would realize how poor this was. And at least offer a menu option to turn the offensive stuff off. Most of the flash gear now is TTL BL only, and most lenses zoom, so it is a factor.

And FV Lock, which seems a workaround for the impossible blinking caused by the commander. Except FV Lock changes TTL BL to be more like TTL, specifically no D lens distance protection for direct flash then, and also no balanced fill flash in sunlight. None of the promised TTL BL features if FV Lock. It works more like TTL, which isn't any more, otherwise. The Exif still calls FV Lock flash as being TTL BL, but it acts nothing like TTL BL (which can be good, it can help offset the incorrect D lens distance numbers). Some of this is downright crummy. Certainly at this price it is.

Anyway, I imagined it could be of interest.
 
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I never use FV lock - there's not enough buttons on my camera! Or is there one on the flash (SB900)?
 
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I never use FV lock - there's not enough buttons on my camera! Or is there one on the flash (SB900)?
FV Lock is a funtion button on the camera. Which camera? Check your camera manual index for FV Lock.
 
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FWIW, here is how FV Lock eliminates TTL BL Balanced fill flash. Easily repeatable by anyone. This is SB-800 and D800. All are ISO 100 f/8 1/100 second.

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No flash. Sun and shadow. Left Bottom Corner Shadow value ... LBCS=73

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TTL BL flash, 0EV. Balanced fill flash. LBCS=129

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TTL BL flash, 0EV, FV Lock - Same as TTL below, No balanced fill flash. LBCS=185

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TTL flash, 0EV. LBCS=194

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TTL flash, 0EV, FV Lock. LBCS=183. FV Lock holds a constant value.

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TTL BL flash, -2EV Flash Compensation. LBCS=89. About -4EV total, including TTL BL balance

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TTL BL flash, -2EV Flash Compensation, FV Lock. LBCS=112. Same as TTL FV Lock, two below

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TTL flash, -2EV Flash Compensation. LBCS=123. This is near same as TTL BL, second from top.

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TTL flash, -2EV Flash Compensation, FV Lock. LBCS=112

Here, this case, FV Lock is a bit less flash than plain TTL, and more then TTL BL, because it eliminates balanced compensation. Otherwise affected by compensation, but not by flash mode.

FV Lock also eliminates the TTL BL direct flash Guide Number overexposure prevention, which is mostly errors anyway, but it doesn't seem as intended.
 
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