iTTL vs Manual
Sailor Blue wrote:
iTTL and E-TTL where the focus distance is read from the lens is better than plain TTL but as far as I'm concerned I only use any type of TTL when shooting snapshots or if the subject to light distance keeps changing. In the latter case I take the time to establish the correct Flash Exposure Compensation setting before getting serious.
The reason for not using TTL in controlled lighting is that if you change the ratio of the subject to the background by zooming the exposure may change. Try it with a subject in dark clothing against a light background and you can clearly see the exposure change with each zoom of your lens. The exposure variation will be less with a fixed focus lens that reports your changing distance to the subject but it will still be there.-- hide signature --
Living and loving it in Bangkok, Thailand. Canon 7D - See the gear list for the rest.
Good answer. Another variation:
Use regular TTL (actually iTTL probably OK for this) and a good size 18% gray target with FV lock for proper exposure. Cheaper and slightly faster than a meter. It is usually better to have your exposure meter timer on infinite (in Nikon camera menu). Depending on your target, you can establish a white balance reference as well.