D70 and 1/4000 flash sync ?

[clauder]

So If I understand correctly, at a speed of lets say 1/4000 sec, the mechanical shutter would open completely (lets say that would put the mechanical sync speed to 1/250 sec), and then the sensor would shut off recording after 1/4000 sec? sort of like exposing the sensor for 1/250 sec, but it is only turned on for 1/4000? that would make sense...

[maxz]

Yes, that is how I understand it works. Or at least it is the only way I can think of that explain how I were able to take the image above :-)

[dennison bertram]

I think that you guys might be getting caught up in semantics here and getting away from the real (and quite obvious) answer to this question. First of all, I have a D70 and I have taken pictures with flash at higher-that-1/500 speeds. However, the D70 DOES NOT SYNCH higher than 1/500. What this means is that the D70's shutter is only open completly durring exposure at the highest speed of 1/500. That's it's flash sych speed, and what flash synch really means- the highest speed where the shutter is open fully durring exposure.

 

What we are talking about here however, is not Flash Sych. We are talking about a trick that is done using the flashes and not the camera. If you took a really high speed flash with a super short flash duration, indeed you would not get a properlly exposured picture. You would have dark patches at either the top or bottom. However in this situation, the flash duration (as mentioned before) is simply longer than the exposure time so the camera only 'appears' to be synching. Think about it, if you could lengthen the flash duration from 1/4000 (or whatever) of a second, out to 1/250 then 1/100 or 1s or 30s or 5 minutes, you would essentially have a continuous light source, right? So of course it would be evenly exposed. This so called 'trick' would work with a Canon digital as well. Not to mention it would also work for any film camera.

 

The reason why you don't see nikon advertising this as a feature is because it really isn't. It's just standard photography. Additionally you don't see them advertising it because it's not a very reliable method of photography. It's difficult to determine the exact flash duration of a flash. Even more difficult is to determine the color balance of the flash as the Xeon is cooling but still emiting light. Additionally, the flash duration can depend on many other factors. Many flashs will alow you to fire them before they have completly recharged, hence giving a different power output as well as different flash duration. Add that all up with all the varieties of flashes out there and you start to see the difficulties.

 

So, hopefully that puts this one to rest. Or just open a whole new can of worms! -dennison

[maxz]

Dennison,

 

I believe that you are greatly mistaken. If what you say is correct, how do you explain the photograph I took earlier and posted in this thread? (The 14th posting on this page, the one accompanied by the photo of the screws on a green box.)

 

It was taken with a D70 at 1/8000s and a SB-800 set to 1/128th power which according to the specs give a flash duration of 1/41600s. However I had to "fool" the D70 into thinking that I didn't have a flash attached. You can do this by attaching a non-dedicated flash or, as I showed in my later posting, putting a piece of non-conductive tape over the back two contacts of the shot shoe. (Sorry for repeating myself, but the long thread seems to discourage people from following it from the top.)

 

Of course, I do not *know* that the SB-800 only outputs for 1/41600s, I have to take Nikons word for it. But even if it is off by a factor of, say, two it is much shorter than the shutter speed I was using. If it is off by much more Nikon is either going to get sued and/or will lose it's reputation as a manufacturer of reliable photographic equipment.

 

I have not heard of many flashes that output full power for 1/500s or longer. And FP Sync (multiple synchronized flashes that matches the movement of the shutter) is not available on the D70.

 

I don't see this as a "trick". It is rather a characteristic of a hybrid shutter and I already stated my guesses to why Nikon doesn't advertise this as a feature.

[dennison bertram]

Hmm... You know I was reading another thread concerning something similar and I'm starting to change my opinion. It seems as though someone else here has proven that the D70 shutter never opens faster than 1/90 or 1/125th or something like that, and that indeed it uses an electronic shutter on the CCD element with the Shutter only in place to give the CCD element some true 'dark time'. I must say, I don't quite know now what exactly is happening, it really does seem that the camera can sync faster by virtue of an eletronic shutter. Of course then why this wouldn't be advertised is a mystery. -dennison