I use a sunpak 433d and an old metz 45ct-1, both with thyristor. This with my old canons t90, a1, av1, eos 620, and my new eos digital rebel.
For large groups (30 to 80 people) on interiors I use the 433 on camera and the metz on a light stand with slave.
I select the a position for f:4 on the sunpak and the same f:4 on the metz and use f:4 on the camera lens. For speed I use anything equal or under the synchro speed depending on how much natural light I want on the image and taking care not to use a too slow one that will give a too blurry image. You will have to read on the manual of the D70 it's synchro speed.
Now the thyristor flashes are a bit tricky as they are reading how much flash light comes back and can be fooled by a large room when you are near your subject, or if you take the picture outside as much of the flash light won't come back. This may give you overexposed frames.
On the other hand if there is too much white it will give you an underexposed frame. Think of the thyristor as an exposure meter that cuts the time the flash lights when the received light is enough for a good exposure. It behaves in a similar way as the centerwheighted exposure meter of the camera. On dark backgrounds it will overexpose and with bright ones it will underexpose.
In this scenarios I use the manual position calculating the distance flash-object and looking the corresponding f number on the table on the back of the flash and using this value on the camera.
I suggest testing this method before actual shooting as generally flashes give an optimistic f value and exposures tend to be a bit under exposed with what they suggest. My experience is that my flashes give half the light they say they do. This is from using a flash meter. With the digital cameras now is very easy to check this.
Also take note on what Herschel says about "Depth of exposure". Just to complement this you con use the following rule to previsualize what happens with the light. At double distance it will arrive 1/4 of the light (2 f stops less light), at triple distance 1/9 of the light (3 stops), at 4 times distance 1/16 (4 stops). and for nearer objects: at half distance 4 times the light (2 stops more), at 1/3 distance 9 times (3 stops) and at 1/4 distance 16 times more (4 stops).
In another words, if you have correct exposure at 3 meters someone that is 1,5 meters from the flash will be OVER-exposed 4 times and someone at 6 meters will be UNDER-exposed 4 times.
Hope this helps
Alberto
At 10:08 a.m. 12/05/05, you wrote:
Good Morning Everyone:
I have gotten a manual flash to use with my Nikon D70. Its a Sunpack 555 Thyristor unit, and I actually love it, however, I am not sure how to properly use it. Getting it connected and making it fire is not the issue, but rather how to effectively use it to take flash pictures. In addition I have an optical slave which i can attach to an older Promaster flash, and I would like to know how to use them together with the on camera flash to the best advantage.
Specifically -- this weekend, I will be shooting individual and team pictures of a group of 11 and 12 year olds at their baseball game. I am suspecting that I am going to need some fill flash etc, and I want to do this correctly.
Any help, or suggested readings etc would be greatly appreciated.
If you need to contact me directly with questions etc, you can reach me on the list, at w8tah@xxxxxxxxxxxxxxxx, via Yahoo IM at W8TAH, or via AOL IM at W8TAHHAM
Thanks in advance for all your help
TIM
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