"Tim Rylance" wrote in message
...
David Nebenzahl writes:

One question: are you sure of the spelling of this item (Da Yi)? I
Googled for it unsuccessfully. Either it's spelled [spelt]
differently, or it's one of the best-kept photographic secrets on the
Internet.

From Peter's excellent description and review it sounds as if this
may be the same back as the Shen Hao sold by Robert White in
the UK. The description at

http://www.robertwhite.co.uk/shenhao.htm#Label617

has photos of the back, and says the longest lens you can use
without vignetting is 150mm.


Interesting - no, it isn't the same, though it obviously works in just the
same way. The Da Yi seems to be made largely of machined aluminium
castings, while the Shen Hao on Robert White's site looks as if it uses more
sheet metal. Probably means the Shen Hao is lighter, though the Da Yi
_may_ be more rigid - only experience with both would answer that one, and
I'm not about to buy another 6x17 back just to find out! The bellows shade
for the GG is different too: the Shen Hao seems to have it run on a rod at
the bottom, whereas the the Da Yi uses a pair of folding struts top and
bottom: I would expect that to make the Shen Hao's system more robust, but
the Da Yi has the advantage that you can angle the hood up or down a bit.

150mm sounds about right to me for where I'd expect vignetting: a 150mm
Symmar-S on mine is free of vignetting, but there isn't much room to spare
for anything longer.

What I'm beginning to wonder is whether a telephoto design lens that has a
focal length longer than 150mm, but a flange to film plane distance that
isn't any more than that might still be vignetting free - I need to
experiment with that. Unfortunately I don't yet even know whether any of my
telephoto lenses will cover 6x17, and currently they are all on the wrong
lens plates (the whole point of me owning telephoto lenses is to be able to
use long lenses with my 'travel' 6x9, which has limited bellows draw, so
they don't genrally get fitted to a 4x5.)

Anyone happen to know what the coverage circles are for the Schneider
Tele-Xenar 180/5.6, 240/5.5 and 270/5.5...? (No, the figures aren't on
Schneider's web-site!)




Peter