#1. "RE: What does - 1/3 mean ?" In response to Reply # 0
Rancho Cordova, US
Dick, it sounds like it is giving you EV in 1/3 stop intervals.
When shooting film and using my SB-28 in manual mode (just to try it out), I used to dial in -1.7 EV for fill flash...and it worked great, but I tended to (and still do) trust Nikon's flash tech. Still getting to grips with my SB-910 and D700 but so far, no problems.
#2. "RE: What does - 1/3 mean ?" In response to Reply # 0 Fri 01-Mar-13 01:39 PM by jbloom
Dick, yes, you have it right. When the flash is in manual mode, the output power is given as a fraction of full power: 1/2, 1/4, 1/8 and so on. Each step is of course a full stop difference. Between those full stops, the power is adjusted in 1/3-stop increments. So 1/32-2/3 would be a power level of 1/32 of full power, or 5 stops down from full power, and an additional 2/3 stop lower, giving a total of 5 2/3 stops down from full power.
In TTL mode, the flash power adjustment is just given directly in stops and is relative to the "correct" flash power as determined by TTL metering, rather than being relative to full power. So if you set the flash to -1 2/3 stops, the flash will output a level that is that amount below what the camera thinks is the correct flash exposure for the scene.
Your D200 can set exposure compensation and flash compensation separately. Exposure compensation affects the overall exposure of the image and thus impacts ambient exposure and flash exposure. That is, changing the exposure compensation will cause the camera to modify the aperture or shutter speed it is using for the scene and may also change the amount of flash power the camera calculates as needed for proper exposure.
Flash compensation simply adjusts the power of the flash. When using an external flash such as the SB800, you can set flash compensation on both the camera and the flash and they are additive. That is, if you set -1 flash EV on the camera and -1/3 EV on the flash, the flash power would end up being 1 1/3 stops below the amount the camera calculates for proper exposure. (In TTL mode, that is. When the flash is in manual mode the camera's flash compensation has no effect.)
Personally, I usually just leave the camera's flash compensation set to zero and make any adjustments on the flash. I find that simpler, and it's the way you have to do it if you use a camera body that doesn't have a pop-up flash since those bodies lack the flash EV adjustment.
I hope that clarifies things. Yes, it's a little complicated, but it gives you a high degree of control over the relative exposure of the parts of the scene that aren't illuminated by flash and those that are, such as in this example, where the background is deliberately underexposed to cause the subject to really pop out:
#3. "RE: What does - 1/3 mean ?" In response to Reply # 2
South Easton, US
Anthony and Jon thank you for your responses . I think I understand and hopefully will put it into practice . It seems one must just get out and try it .
If I can stretch my understanding just a bit more let me pose a "what if"
Lets say I am in CLS mode,using the camera pop up as the master,Sb 800 as group A,Sb 600 as group B . All in Manual mode
I imagine that I can set the power levels of the pop up,group A and group B individually from the camera .BUT When I try to add or subtract flash EV from the camera I would think it would be a global adjustment,therefore I would have to set the EV in the individual flashes . I think it will help my understanding if I can grasp it . I imagine the differences would be hard for my 75 year old eyes to see but even so I like to try to understand what it is I am attempting .
#4. "RE: What does - 1/3 mean ?" In response to Reply # 3
Dick, I'm not sure how the camera handles that particular case. I don't use CLS all that much and haven't tried that. Perhaps one of the CLS masters here on Nikonians can give a clue. But it would be a fairly easy thing to test out, and nothing is as instructive as doing it for yourself.
I agree that it is sometimes hard to perceive differences between images on the camera screen. You can use the camera's histogram display to compare the light levels in the test shots, though.