Nikon digital vs. non-digital flash

[Revolver]

I'm considering purchasing a Nikon D70 in the very near future. My current set-up is an N70 with various lenses and flashes. My question is the compatabilty of the non-digital flashes that I currently own and the cords and cables that connect them. I have two Sigma EF-430 Supers, Nikon cords to connect them to the camera and the SU-4 remote flash controllers. Will the flashes work properly while attached to the camera, either directly or by an SC-17 cord? Will they work properly (TTL or on manual) connected to the SU-4 and used as slaves with the built in camera speedlight as the master? Will they work at all? Also, if I upgrade to a Nikon Speedlight, will the cords/SU-4 work with it, and will the new Speedlight work with the N70?
What exactly is the differance between digital and non-digital flash?
Thanks in advance.

[Franglais]

I'm considering purchasing a Nikon D70 in the very near future. My current set-up is an N70 with various lenses and flashes. My question is the compatabilty of the non-digital flashes that I currently own and the cords and cables that connect them. I have two Sigma EF-430 Supers, Nikon cords to connect them to the camera and the SU-4 remote flash controllers. Will the flashes work properly while attached to the camera, either directly or by an SC-17 cord? Will they work properly (TTL or on manual) connected to the SU-4 and used as slaves with the built in camera speedlight as the master? Will they work at all? Also, if I upgrade to a Nikon Speedlight, will the cords/SU-4 work with it, and will the new Speedlight work with the N70?
What exactly is the differance between digital and non-digital flash?
Thanks in advance.

Film cameras like the N70 use a technique called OTF (off the film) to meter the flash during exposure. There is an exposure meter in the camera that looks at the film during exposure and cuts off the flash at the right moment.

OTF works because most films have a dull surface with about the same level of reflectivity. It doesn't work with digital because the digital sensor is shiny. Nikon first tried the E-TTL system which has now evolved into the i-TTL system on the D2 series and D70 with SB600 and SB800 flashes only (plus compatibles from Sigma and Metz).

In i-TTL all the metering is done via the regular meter with the mirror in position, before starting to take the photo. The camera sets off two brief flashes to figure out what the exposure should be. Then it flips up the mirror, stops down, opens the shutter, fires the flash for the right length of time and finishes up.

i-TTL is totally incompatible with your Sigma flashes and the SU-4. (The Sigma flashes don't know how to talk to the D70 and the SU-4 will mistake the pre-flashes for the real thing and trigger while the shutter is closed). The only way you're going to be able to use your existing equipment is to forget about TTL and go back to flash metered by the flash units themselves. You can use the D70 to set off the flashes either by the standard hotshoe or by setting the built-in flash to manual 1/16 power and use it to trigger the others.

If you buy an SB600/SB800 this should work with the N70 as it can emulate previous flash units. I don't know the SC-17 cords (the D70 has only a hot shoe, no external flash plug). You should be able to use your SU-4 if you're using one of your Sigma flashes as master to measure the light - the SU-4 will cut off the flash as soon as the main flash cuts off.

Charles

[christopher_platt]

One other thought regarding the flashes that you have that WILL work with the D70. Paraphrased from the SB800 instruction manual: The length of time that a flash actually fires changes the color temperature of the light that it gives off. The SB800 calculates and communicates precise color temperature information to the D70, giving more accurate color.