Sorry but that does not compute. The two sides of the comparison must be measured in the same units in order to produce a repeatable ratio. Strapping a tape measure around your waist to produce an estimated weight is just not acceptable. It might do for weight watchers but this is a serious forum where we demand absolute accuracy (Matt).

You forgot to mention the ratio between the surface areas, which is 2.341780729, and the perimeter which is 1.530612245

amosstarz,

You may find this article interesting. As a rule of thumb it is safe to use 1.5x as the multiplier for the change in focal length. The alternative, if you want to be absolutely precise, is to add a calculator to your digital camera bag.

I've not used studio flash but I'm assuming you need an adapter with the PC (or X-Synch) socket. As far as I know, the only one Pentax make (or made) is the Hotshoe Adapter MV. You can see one here. It only has two contacts, trigger & ready.

Now all you have to do is find one. Personally, I'd take Don's advice. Radio slaves will keep the studio relatively free of cables which is safer for equipment and humans, and allow greater flexibility for camera positioning.

Regards,

If your 18-55mm lens has the Pentax name on it, it has the SMC coating. If its a Sigma of course, or any other third party lens it can't have the SMC coating.

My personal opinion is that the residual value (the amount you'll get if you sell it) will be greater with the Pentax badged product.

For the same reason I might decide to by Volkswagon instead of Skoda, same car, very different prices.

Matt,

So using the 16-45mm lens as an example. With the lens set at the 30mm mark, what would you expect the gun to show 20 (30/1.5), 30, or 45 (30*1.5)?

I can't actually check it myself because once again I find myself seperated from my gear (so to speak)

Regards,

The AF360FGZ is a pre-digital age flash so you have to read the camera manual, rather than the flash manual to discover how the flash behaves or rather, how it is controlled. The camera should instruct the flash to zoom to the correct focal distance for the lens in use. EG: If the lens is at 30mm in its zoom range, the flash should show (30 X 1.5 crop factor =) 45mm'ish. That's my understanding anyway.

P-TTL = Pre-Flash TTL

Camera fires a pre-flash (seen through the viewfinder)
Camera metering works out correct flash configuration
Camera fires second flash to make the exposure

This is not the same as red-eye reduction.

Thanks Brian. Sorry if you were disappointed. I didn't really think I'd win it with my max bid. I hope it cleans up OK then I can sell my equivalent Sigma which is an 'A' lens. I think this one is an SMC-P-M lens.

Regards,