Faster sync for D2x

Hi,

The D2x has an X-contact and max. sync. speed 1/250 s.

Shorter sync. only with SB-800 and FP-shortsync-mode on.

My camera is connected to 2 subtronic minis by Nikonos plugs.

Is there any possibility to achieve a shorter sync speed?

Thilo

Not unless you house a Nikon Gun. Which is unfortunate. I wrote an article a while ago wishing that instead of trying to crack iTTL and eTTL that UW manufacturers would concentrate on other flash features - like high speed synch and rear curtain synch for Canon.

That said 1/250th is pretty fast and I haven't found it limiting. Is there another way to achieve the image you want?

Alex

I would use faster shutter speed to achieve a black background, but with 1/250th and very small aperture it will work as well.

Until now I did not really miss a shorter synch underwater.

Thanks for your confirmation. No need for me to think about this anymore...

Thilo

The conversion circuitry in the Ikelite iTTL housing for Nikon D70 allows rear curtain sync and should be added to the web site. This is probably true for D50, but haven't had a chance to prove. The Canon system is so much more complicated that we did not attempt............

http://www.ikelite.com/web_pages/2nikonittl.html

Technically, if you only have 3 pins connected on the bulkhead, you can fire the manual strobe at whatever shutterspeed you like, just like the Nikon d70.

However D2x has this annoying mechanical shutter that gets in the way at anything above abou 1/320s, you will see a black bar. Not much at 1/400s and very noticeable at 1/500s.

I am not clear exactly how SB-800 and FP-short sync mode gets around the problem. Here is a shot taken at 1/500s with Ikelite strobe.

The black background was due to the mechanical shutter!

Maybe the SB800 is capable of flashing more than once during the exposure when the curtains of the shutter are revealing different strips of the sensor. I nearly said film, there!

Alex

Maybe the SB800 is capable of flashing more than once during the exposure when the curtains of the shutter are revealing different strips of the sensor. I nearly said film, there!

Alex

<{POST_SNAPBACK}>

That was also the explanation that I was given. What made me confused though is that, for example, Ikelite DS-125 takes about 1/250s to give a full dump so if I shoot at 1/500s, the strobe should light the entire area of the sensor as the shutter make it way pass the sensor so the mechanical shutter should not block out the light entirely. The Ikelite certainly has not problem with fast shutterspeed as I used it with Oly c5050 and D70 at 1/2000s with no problem before. I am not enough of an engineer to understand this but am willing to accept this annoying black bar and once it awhile, the effect is not so bad

I think that you are slightly wrong with your timings.

The Ike probably takes less than 1/500th for a full dump. And if you set your shutter for 1/500th each strip of the sensor is only exposed for 1/500th, but the whole exposure takes longer than this, say 1/250th. So your flash only lights the first strip of the sensor. It has finished firing before the next strip of the sensor is revealed by the shutter.

If you regularly need faster shutter speeds you should use your D70. It is a case of choosing the right tool for the job.

Alex

Alex, I am not absolutely sure, just thought I read somewhere in the past that it takes about 1/250s for the DS-125 to fully reach its peak power in a full dump. Anyhow, if what you said is true, let say that DS-125 completes a full dump at 1/1000s. Then technically if I shoot at 1/1000s or faster, there should be enough light to light all the strip of the sensor. Too bad, my strobe/housing etc are all in Indonesia right now so I cannot try this out. Also at slow speed, say 1/80s, then the Ikelite would not be on long enough to light up all the various strips (presumably). Very confuse Why can't D2X just use electronic shutter like the D70

I don't shoot all that often at high shutterspeed except when I want really tiny DOF for macro. Luckily the 70-180mm gives me enogh working space that dropping the strobe power usually do the trick. With my old C5050 where I was very very close to the subject, at minimum power setting, ISO 64, F8, I still need to use much higher shutterspeed to get any black background.

If the shutter speed is 1/500s and the strobe needs 1/250s to dump its light,- the shutter will already be closed before the strobe has fired most of its power!

In this case the strobe is limiting but not the camera!

Thilo

Very confuse

<{POST_SNAPBACK}>

The way shutters work is that they have two curtains. The first curtain travels vertically across the frame to let light onto the sensor and then the second one follows and closes it. At slow shutter speeds (on the D2x 1/250th or less) the first shutter has completely crossed the sensor (so it is totally open) before the second one starts to close it. When the shutter is completely open the camera fires the strobe (front curtain synch). The alternative is that the camera fires the strobe just before the second curtain starts to cross, to end the exposure (rear curtain synch). The flash must go while neither curtain is over the sensor.

This is the bit that you are confused about. At higher shutter speeds (>1/250th) the second curtain starts to cross the the sensor before the first one has cleared it. And therefore it is impossible to light an entire frame with the flash.

The usual way that high speed synch is achieved is to fire the flash several times synchronised precisely with the movements of the curtains across the sensor - in fact exposing it in strips.

Hope that this is clearer.

Alex

Electronic shutters are not as accurate as mechanical ones. Which is why the D2X doesn't use one.

Alex, thanks for the explanation. Front and rear curtain sync also make a lot more sense now! I think I start to see the light

Seeing the light is what photography is all about!

Alex

Alex,

now, after reading your post I see that my assumption of the timings is not totally correct, taking into account the moving shutter strip at speed above 1/250s.

Thanks a lot,- your lessons are very much appreciated.

Where can we learn more about the detailed functioning of shutters / lenses etc.?

Thilo

I can't think of anywhere right now. But these things come up pretty regularly here on Wetpixel and on other forums.

Alex