Nikon iTTL problem

Archived from groups: rec.photo.digital (More info?)

I have a Nikon D70 + SB600 flash. A very serious problem is that either with
the build in flash or the SB600, the preflash that is used to TTL calculate
the power of the main flash is well separated from the main flash about
20-30 msec. So every time you can see two distinguished flashes. Some very
sensitive people can close their eyes after the first flash, so when the
main flash lights, they have eyes closed. This effect in a wedding for
example can be a disaster, as 90% of the shoots finds the bride with the
eyes closed.

I have test a Canon 20D + 550EX flash and the preflash was so close to the
main flash so subjectively we could see only one flash. This means less than
10 msec. No one could close his eyes so fast, so there was no problem.

My question is: Is a specific problem to the build in and SB600 flashes, or
is general in Nikon iTTL; It is the same with SB800; What are your
experiences;
--
Dimitris M

Archived from groups: rec.photo.digital (More info?)

"Dimitris M" <nospam@ath.forthnet.gr> writes:
> My question is: Is a specific problem to the build in and SB600 flashes, or
> is general in Nikon iTTL; It is the same with SB800; What are your
> experiences;

There is a short lag with the SB800. Not long enough to cause eyeblinks
as far as I know. I do get eyeblinks with the Canon S100 point-and-shoot.
I seem to remember with the SB800 (and probably also SB600) there is a way
to pre-meter the flash exposure, so there's no preflash needed.

Archived from groups: rec.photo.digital (More info?)

Dimitris M <nospam@ath.forthnet.gr> wrote:

>I have a Nikon D70 + SB600 flash. A very serious problem is that either with
>the build in flash or the SB600, the preflash that is used to TTL calculate
>the power of the main flash is well separated from the main flash about
>20-30 msec. So every time you can see two distinguished flashes. Some very
>sensitive people can close their eyes after the first flash, so when the
>main flash lights, they have eyes closed. This effect in a wedding for
>example can be a disaster, as 90% of the shoots finds the bride with the
>eyes closed.

It doesn't seem all that likely to me that a 30 msec lag is enough to
cause a blink which disturbs the picture. When a blink response is
elicited by a flash, and measured by the EMG signal (not even the
moving eyelid) the latency seems to be around 55 msec in adults.
The blink itself takes 200 msec to complete, so eyes closed would be
100 msec or so after the flash as I make it.

http://tinyurl.com/7hyed 57.0 +/- 4.9 msec in adults

The "startle reflex" seems to be faster for acoustic stimulus than
flash. Given that the mirror moves and the shutter opens well in
advance of the flash, perhaps it's a case of the person reacting
to the sound of the camera in anticipation of the flash? Maybe
some cameras are better or worse at that.

>I have test a Canon 20D + 550EX flash and the preflash was so close to the
>main flash so subjectively we could see only one flash. This means less than
>10 msec. No one could close his eyes so fast, so there was no problem.

>My question is: Is a specific problem to the build in and SB600 flashes, or
>is general in Nikon iTTL; It is the same with SB800; What are your
>experiences;

--
Ken Tough

Archived from groups: rec.photo.digital (More info?)

Pepe <pepe@home.nl> schrieb:
>
> Here you can learn more about NIKON D70 and flash.
><http://www.mir.com.my/rb/photography/companies/nikon/htmls/models/digitalSLRs/D70/index.htm>
> Not all functions are avilable with SB600 better go for SB80DX.

No, the SB80DX doesn't work with iTTL, and the D70 doesn't do DTTL.
Avoid this combination.
In case you meant the SB800, it has the same problem with the preflash
as the SB600.

Walter

Archived from groups: rec.photo.digital (More info?)

Dimitris M <nospam@ath.forthnet.gr> schrieb:
>
> My question is: Is a specific problem to the build in and SB600 flashes, or
> is general in Nikon iTTL; It is the same with SB800; What are your
> experiences;

I noticed the same problem. I see three solutions:

Use FV lock to trigger the preflash well before the main flash. This
works, but it is a daunting to use. Also, the metering in the camera is
different. I think it switches to center-weighted metering, but I'm not
completely sure. I couldn't find it in the manual. On some pictures the
exposure is off due to this.

Disable the preflash. Switch the flash to "A" mode (not "AA", there is
still a preflash). It is in the custom setting of the SB800, maybe the
SB600 doesn't have it. This works well, but you have to set the
aperture, ISO value and zoom manually on the flash. I don't know why
there is still a preflash in the AA mode, I see no reason for it.

Use GN mode (SB800 only). This is manual mode without preflash. You have
to dial in the subject distance on the flash which is easy and quick,
everything else gets transmitted automatically.

Walter

Archived from groups: rec.photo.digital (More info?)

On Mon, 20 Jun 2005 02:06:30 +0300, "Dimitris M" <nospam@ath.forthnet.gr>
wrote:

>I have a Nikon D70 + SB600 flash. A very serious problem is that either with
>the build in flash or the SB600, the preflash that is used to TTL calculate
>the power of the main flash is well separated from the main flash about
>20-30 msec. So every time you can see two distinguished flashes. Some very
>sensitive people can close their eyes after the first flash, so when the
>main flash lights, they have eyes closed. This effect in a wedding for
>example can be a disaster, as 90% of the shoots finds the bride with the
>eyes closed.
>
>I have test a Canon 20D + 550EX flash and the preflash was so close to the
>main flash so subjectively we could see only one flash. This means less than
>10 msec. No one could close his eyes so fast, so there was no problem.
>
>My question is: Is a specific problem to the build in and SB600 flashes, or
>is general in Nikon iTTL; It is the same with SB800; What are your
>experiences;

I've not yet got either an 800/600 (I'm thinking about it, so I'm prowling
threads about them) but:

Presumably the flash is being held to one side, as presumably the D70
wouldn't have to issue command-flashes to SB600/800 if it was mounted on
the hot-shoe?

Although less convenient than the "wireless" mode the D70/SB600/800 use,
could you connect a shoe-extension code (I assume they exist) between the
two, and would this stop the communication pre-flashes?


Regards,
Graham Holden (g-holden AT dircon DOT co DOT uk)
--
There are 10 types of people in the world;
those that understand binary and those that don't.