Fri 30-Nov-12 10:54 PM | edited Sat 01-Dec-12 07:33 AM by gfinlayson
>That is disappointing. The reason I asked about concerns the >need for CW or Spot metering in conjunction with a flash. In >order to get TTl mode (not TTl-BL) I wanted a quick way to >shift camera metering to coordinate with TTl on a speedlight >in the camera hotshoe. > >You know, the whole subject of Nikon CLS lighting is >marvelous, but intricate and baffling. >I know that if I select CW or Spot metering on the camera >through menus or the metering button and rear command wheel, a >mounted strobe can't be configured for TTl-BL. > >But that is real slow. And I thought I'd read in the mountain >of CLS literature here in my room that setting the SB800 to >TTl (not BL) would shift camera metering simultaneously. You >know, the strobe talks to the camera, and the camera talks to >the strobe. > >I was mistaken. I wanted TTl and yet in my shots got a lot of >unwanted ambient light with an odd color. So, even though the >strobe was set to TTl, it exposed for ambient light. Which, it >shouldn't do in true TTl. > >A few folks, including Thom Hogan, advise that setting EV +/- >or flash modes is quicker on the flash itself than through the >camera menus or buttons. Any thoughts?
You've made an incorrect assumption about CW there. TTL-BL DOES work in CW mode. CW does still meter the whole frame, but biases the exposure towards the centre, therefore balanced fill is still possible.
If you set the flash to TTL-BL with the camera in matrix or CW, and then switch the camera to spot metering, the flash will default to straight TTL. However, changing the flash from TTL-BL to TTL or vice versa does not change the camera's chosen metering mode.
If you want to switch between TTL and TTL-BL, the best way to do it is on the flash. You can then choose your metering mode to suit the scene and your creative intentions.
Bear in mind also that +/- EV on the camera is global, i.e. it affects both flash and ambient exposure. +/- EV on the flash only adjusts the flash exposure.
If I want to use flash as my sole means of exposure, I set the camera in manual at 1/250, choose my aperture, check that I'm under exposing plenty and then set the flash to TTL (or set the flash to manual and adjust the output to the right exposure).
For balanced fill, I'll usually set my ambient exposure to where I want it (manual or exposure comp), then set the flash in TTL and adjust the flash exposure to get the result I want.
TTL-BL lets the camera/flash take control and for me that's just like shooting in AUTO. You're giving up creative decision making to your camera, and while the camera might be clever, it's not as clever as you!
I highly recommend 'The Hot Shoe Diaries' by Joe McNally as a great way to learn about the creative side of CLS. It's written in a light-hearted, entertaining and non-technical way and is liberally sprinkled with practical examples.