Nexus
wet supplementary lens
by
Mark Webster
Reproduced
from in focus 68 (June
2002)
How
often have you found yourself close to that perfect macro
subject with your 105mm lens only to find that it is just
too small to fill the frame? It is at times like these that
you wish you had put on that +2 or +3 diopter which would
give you that extra magnification. Fitting a diopter, extension
ring or tele-converter can be very committing for a dive,
unless you are certain that subject will be there - a better
alternative would be a wet close up diopter rather like those
available for the Nikonos/Sea and Sea camera systems. Well
now that solution is available from the Japanese manufacturer
Nexus and I have found it to be extremely usefuI in many situations.
|
Nexus
wet supplementary lens |
There
are two versions of the wet lens available - firstly a single
glass element lens mounted in aluminum with a flexible silicone
skirt costing $61 plus $22.5 PandP and secondly a twin element
sealed unit that is designed only to fit the Nexus 105mm port
and costs $250. I had good reports of the single element lens
from some American photographers and at the relative bargain
price decided to give it a try.
The
lenses are supplied in two sizes 90 and 100mm diameter, but
they are both a little small to fit to a standard Subal port.
However, I use 'third party,' small diameter, ports with my
Subal housing so the lens I bought fits well as standard.
It would not be too much of a challenge to make up a mounting
ring to fit the front of the standard Subal port and the performance
seems to be unaffected by the distance from the lens. |
| The
lens is intended for use with the 105mrn macro lens and is claimed
to give a reproduction ratio of 1.9:1, almost twice life size.
I would estimate that this is a pretty accurate appraisal and
have found that it will work as well with either a 60mm or 180mrn
macro lens. Using it with the 60mrn is quite limiting as the
distance between the port and subject is minimal, but with the
105mm and 18Omm it is a joy. I used it to great effect on a
recent trip to Belize with various shrimps and secretary blennies
with the 105mm and got some good shots of shy jawfish with the
18Omm. The lens has no impact on exposure (unlike an extension
tube or tele-converter) but does of course reduce the depth of field as do the other options, but it slips easily into your
BC pocket until you need it. However, I would recommend a lanyard
and clip so that you con attach it to the housing when in use
on wall dives! |
Nexus
wet supplementary lens on Subal housing |
