The BAT Cave
After getting some weird results with TTL mode on my PocketWizard Mini TT1/Flex TT5 units, I did some testing comparing Nikon TTL with PocketWizard TTL on my Nikon D7100 camera.
As you can see from the tests below (click on the buttons to see the comparison images) PocketWizard TTL produces different results than Nikon TTL, much different results, nearly always with Nikon TTL being superior. Notice the vast overexposure of PocketWizard TTL any time the flash is close to the subject. I don't believe the PocketWizard units even qualify to use the term "TTL", since it seems more like a semi-automated flash power mode than real TTL. It looks like the PocketWizard algorithm is biased toward medium-range flash distance and is incapable of exposing properly for any situation where the flash is close to the subject and not attenuated by a modifier. For example, if I snoot the light, the PocketWizard exposure will be insanely overexposed, but if I put the flash inside a softbox with a 2-stop light loss, the PocketWizard exposure is decent.
Notice how the PocketWizard TTL exposure drops off significantly as the flash is moved farther from the wall, while the Nikon TTL exposure does not. Compensating properly for distance of the flash to the subject is one of the cornerstones of TTL flash, it is not acceptable for the algorithm to work like this.
November 5, 2014 update: I rented a Canon 5D Mark 3 camera and a 600EX-RT flash and did a similar test. Surprisingly, the Canon results match the PocketWizard results more closely than the Nikon TTL, firing too hot up close.
Test conducted October 29, 2014 using a Nikon D7100 camera, Sigma 18-35mm f/1.8 lens, SB-900 flash, Magmods grid system. Ambient exposure 1/250 second, f/5.6. Nikon TTL shots used 0 compensation, Nikon CLS using the on-camera flash as a master. PocketWizard exposures used the AC-9 ZoneController at 0 compensation, TTL mode.
Nikon TTL, 70mm flash zoom, grid:
PocketWizard TTL, 70mm flash zoom, grid:
Canon radio TTL, 70mm flash zoom, grid:
PocketWizard TTL 24mm flash zoom, no grid
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