Thought I'd share my experiences with you about the TT1 & TT5.
I've got to say that I'm very pleased with them overall, but there's a bit of a learning curve involved with them.
I had a bit of a bad start with them initially, straight out of the box one of the units (turned out to be the TT5) was faulty. Rang Damien Lovegrove who I bought them off, and was promised that someone from PW UK service would ring me within the hour - and they did.
They offered me advice to try and resolve, but I had tried all the possible solutions from online help etc.
Return TT1 and TT5 to PW UK - they found that the TT5 was faulty from the box - well it does happen, and the customer service was very good, and a new TT5 was sent to me.
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So now they work like they should - excellent.
I've played with them in both Manual and ETTL and since bought the AC3, which I would highly recommend , whether you use Manual or ETTL.
I prefer to use them in Manual and use the Sekonic L358 to calculate the flash exposure settings.
In Manual - if you select a shutter speed of say, 1/500th then the PW's automatically select HSS without you having to do anything.
Using the AC3 allows you to review your images and make minor adjustments on the fly (based on your LCD review etc).
ETTL works, but I just find that the exposure is inconsistent (nothing to do with the performance of the PW's), so tend to stick to manual most of the time.
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I did have a pair of RF 602's which forum members recommended to me, and it was useful - as this confirmed that I did want to carryon with off camera flash.
The whole set up is expensive - but I do think it has made OCF easier , even if it means learning a bit of new technology.
I'm reasonable sure that I understand how it works now, after some frustrating moments.