Here's my verdict on the Tamron 17-50VC.

1. Slower than 18-105VR focusing speed but still acceptional. Did events with it and had not much problem.
2. Quick worth for it's value as 17-55 is like 2x the price.
3. Reason I'd want to sell it ain't because it's slow. It's because I want to switch everything to Nikon 
4. Back and front focusing problem happens. Just get it caliberated by the disti. Most of the latest batch have no problem with it anymore.

I was quoted Sandisk 4GB class 10 - RM52 by the below forumer.

http://forum.lowyat.net/topic/1134827

What you think? Too cheap?

got imitation memory cards?

I got my Extreme 3s from him. So far so good. Burst away at 1/4000 shutter at 4.5fps. Able to hit 100 images before actually stopping due to limitation of D90.

actually can reach, if you use 200mm focal length and stick your lens right at his face.

---

Added on March 12, 2010, 10:40 amthanks for all your concerns. well, at rm52, if it reaches only class 4 speed, it's still ok price right?

because the maximum zoom that it can cover is up until 85mm(stated inside the manual)..but i think,if manually set the power at 1/1 it might can cover until 100-110mm..

If you zoom to 200mm, but your range with your subject is maybe short distance (some headshot portrait maybe?) the flash will still reach. Instead of covering for 200mm only, it'll cover for 85mm instead. Meaning some light would be wasted la.

the light will still reach,but wont as bright as a sb900 if im not wrong...anyway,anybody can explain to me clearly about GN numbers??

My understand is that, when you shoot at 200mm the light is more concentrated. Meaning it will be able to go further since it will only light up a small portion when compared to a wide end like 18mm or something.

Celciuz is correct.
The SB900 will concentrate its coverage only on the relevant area, area which the camera/lens is capturing. Its like .... why you have to flash the whole damm hall if youre zooming in tight at 200mm to only capture the table at a corner right ? So the flash knows what sort of coverage the lens is at ... because its no longer a dumb flash like those before it ... no offense SB8 / SB6 /SBwateva .. RIP~
Anyway ...its kind of an intelligent stuff that Nikon put in their new flash... not verrryyy intelligent but i dont hate it either
Actually the whole techincality bla bla about this 'mechanism/technique' on the SB900 is available on Nikon's website for you to read .. i think. You should try go there
Good luck.

To put it bluntly ... yes SB600 is less intelligent than SB900 plus its just built that way ... not enough power. The SB600 has a moving head inside to adjust for a more focused beam just like the SB800/900, but it doesnt have the whole snooty winged bla bla built inside for a more advanced concentration like the SB900 has.
But personally, ive seen the SB600 working just fine at 105mm full power .. but thats it. For my need and style of photography, the SB600 wont do it at ...say 110 and longer.