On 7/17/2016 11:34 AM, Jim Nichols wrote:
After seeing Moose's recent fly captures, I became interested in trying an extension tube, though I don't have any of
the modifying optics he has been using.
I have often used extension tubes in the yard, and Auto Bellows and Auto Tube,
in film days.
Examples with three lenses here.
<http://zone-10.com/tope2/main.php?g2_itemId=4514>
Another lens here. <http://zone-10.com/tope2/main.php?g2_itemId=12436>
Theoretically, one could easily conclude that adding lens elements, esp. those not designed for the primary lens, would
give poorer results than extension. There are, however, lenses that just aren't designed to get any farther from the
film/sensor. The OM 21/3.5, is one example I know of where curvature of field that's already a bit much at normal close
focus gets really bad with extension. Longer FL MF lenses, such as this Takumar are fine on modest extension.
My reason for my recurring interest in C-U lenses is mechanical, not optical. The PLeica 100-400 I've been using for
C-Us of bugs (and many other things), is relatively large and heavy, at least in my current world. I am often shooting
in places where there is no place safe and clean to set gear down, so juggling body, lens and tube is the only option,
and puts a fairly expensive lens at risk. It's also not uncommon for there to be a breeze carrying dust. And the process
of putting tube in and out is time consuming, while some subjects, such as insects and other critters, are evanescent.
OTOH, attaching or removing a C-U lens mounted using magnetic rings takes no more than a very few seconds. So I tried
out several C-U lenses. And indeed, all but two of them were obviously poor optical matches for my lens, and one of
those was not really good. But one, for whatever reason(s), works exceptionally well, giving tack sharp images.
My only extension tubes are M42, so I attached the 9.5mm tube to my Takumar 135/3.5 lens. The usable focusing range
seemed to be approximately 2 - 5 feet, not bad for butterflies. To get a few more MP, I used my Oly E-510. This gave
me the equivalent of a 270/3.5 lens.
This female Spicebush Swallowtail flew up and rested for about five minutes on the greenery on my fence. This was the
only view and lighting that I had available. I tried focusing at several stops, and it was not too difficult. I
suspect this was taken at f/8.
http://www.gallery.leica-users.org/v/OldNick/Spicebush+Swallowtail+Female.tif.html
Great pose/composition. Not so obvious, at this size, with this subject, but on the next flutterby, the difference
between the E-510 and the Fuji is pretty obvious, with funny artifacts around the flowers - and it's just not generally
as clear as the recent Fuji X-E1 shot of the American Lady.
It may be useful to note that the Fuji X-E1 and a 4/3 sensor differ hardly at all in multiplication factor in the
vertical direction. The usual smaller multiplier of about 1.5 for the APS-C sensor, vs. the 2.0 of 4/3 is a result of
using diagonal measurements. But the APS-C is 3:2, considerably wider than the 4:3 of 4/3. For these square crops of
flutterbys, the difference in multiplier is quite small, and insignificant compared to the greater resolution/IQ of the
Fuji.
Tech Talk Moose
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What if the Hokey Pokey *IS* what it's all about?
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