Looks like I have inadvertently started a storm here.

Thanks to all for the replies that closely answered my query.

Maybe I should have explained the request better.

I live in Western Australia and we have very many wildflowers here which I
like to capture. I used to to this a number of years ago on my totally
manual SLR with a Zeiss 50mm prime and a set of extension rings.

Now that I have a DSLR I wised to do the same (rather than scan my old
slides). So I am able to take manual exposure photos (still have my old
light meter) if necessary but was anxious to know whether I could use my
existing zoom lens with rings and still use the built in functions of the
D50. I know I am not technical about photography but measure my satisfaction
by the resultant photos.

Anyway on balance you have convinced me that using rings with the Tamron is
probably not a good idea and I may be better off looking for a relatively
cheap 50mm prime plus the rings or even (possibly better) a second hand
macro lens.

Once again thanks.

Gerrit - Oz