My attempt at easy manual remote.

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My attempt at easy manual remote.

Postby Firebird » Sat Sep 22, 2007 8:13 pm

I've purchased one of these:
http://www.sparkfun.com/commerce/product_info.php?products_id=7815
It's on the way USPS and I'll probably get it next week. My first project is a simple IR pulse to RF and back system. I'll have to borrow a SB600 or SB800 to do the final test and see if the Nikon CLS info will survive the transfer! I had a SB600 but I sold it and the bling paid for 2 Sb28's. So maybe I can sell one of my old hamradio units and get a SB800 with the proceeds. I currently use a D200 Nikon and it has the CLS commander function built in.
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Postby Elv000 » Sun Sep 23, 2007 3:36 am

Great stuff!... my question is (knowing nothing) the main issue seems to be speed, someone was quoting sub 1ms. Thes things don'e seem to give specs like that jsut transfer rate (4800bps).

So do you know the speed or is this a just a trial to start somewhere?
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Postby Breamer » Sun Sep 23, 2007 7:31 am

Speed is the name of the game. It seems the V1 spec is max sync at 1/1000. So the shutter is only open for 1/1000 of a second. That means that in 1msec the transmitter has to encode and modulate the data. This takes time and is going to be one of the factors in choosing components. Then it burst of data has to travel over the air to the receiver. This takes time and the further away the transmitter is the longer it takes. Even at the speed of light it takes time to travel 100m. Then the receiver has to demodulate and decode the burst, and then the flash has to fire. That's a lot to do in a fraction of 1ms.
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speed

Postby Thonord » Sun Sep 23, 2007 11:11 am

At 1/1000 the shutter is never completely open. Its just a slot moving acros the sensor. You need FP (multiple bursts) to use flash at those speeds.
We dont have to worry about timing those bursts. The flash is told to use FP and when triggered it keeps flashing while the curtains are moving across the sensor.
Tom
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Postby JonSenior » Sun Sep 23, 2007 12:38 pm

Thonard said:
At 1/1000 the shutter is never completely open. Its just a slot moving acros the sensor. You need FP (multiple bursts) to use flash at those speeds.


Not true. Certain models of DSLR (Including the Canon 1D and Nikon D70s - IIRC) incorporate an "electronic" shutter which allows synchronisation at any speed. Essentially the mechanical shutter is used up to the normal sync speed, then the electronic one takes over.
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Electronic shutter

Postby Thonord » Sun Sep 23, 2007 9:54 pm

I stand corrected. Never heard about that before.
Thanks for the correction.

Tom
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Postby paulgraham.ca » Wed Sep 26, 2007 11:13 pm

if timing to send the signal is an issue, why not do it in two stages?

1. Individually set the desired power on the transmitter, then send it to each of the slave units wirelessly. This could be done by designating each flash, with dip switches on the slave units. Each time you change the settings on the transmitter you have to re-program the slaves (hit the "send" button).

2. Shutter release is sent and each flash fires at the power level set in step 1.

Does this seem reasonable? You're basically taking the pre-flash info that CLS sends and doing it before (thus removing any shutter lag).
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Postby JonSenior » Wed Sep 26, 2007 11:49 pm

paulgraham.ca wrote:if timing to send the signal is an issue, why not do it in two stages?
...
Does this seem reasonable? You're basically taking the pre-flash info that CLS sends and doing it before (thus removing any shutter lag).


For individual power control (ie non-wireless CLS / E-TTL) this is exactly how I (we?) are looking at doing it. The hurdle is to get any data at all from the transmitter to the receivers in the necessary time.

Jon
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