Techie question

I have tried my set up today in daylight by using the furthest view I can
find from my house. I have also tried a different lens. By screwing the DSI
adapter out a few turns thus increasing the register I am more able to gain
focus at different zoom settings. I am going to try and contact the
manufacturer of the adapter to see what they have to say.
"Sjouke Burry" wrote in message
...
Tony Pagett wrote:
What I don't understand is that if I can focus at one setting of the lens
then why not at all settings. Surely the focus point should be at the
same
place regardless of zoom otherwise I would have the same problem with my
SLR.
"Robin Leadbeater" wrote in message
...

"Tony Pagett" wrote in message
.co.uk...

Hello Robin.

Thank you for your help.

I have just measured the register as you say and if I am measuring to
the
correct place then it is only 41mm.

I just did some experimenting with my Canon EOS 35-80mm lens. It looks
like
the correct spacing could be very critical. Small errors throw the focus
out
significantly across the zoom range. While you would get away with being
a
couple of mm too close with a fixed focus lens, this may not be the case
with a zoom.

Robin





AFAIC only very expensive zoom lenses keep in focus
while zooming,for the rest you have to slightly readjust
your focus.