Hi folks,
I have been using a Betterlight Super 6K scanning back to test an original single or
perhaps uncoated Sironar 300 mm 5.6 against a Sironar -N MC 300 5.6
and the older lens simply out performs the newer lens by a noticeable amount.
What gives? I would have expected the newer (Sinar Engraved on the front Cell)
lens to be much better. It is in pristine shape.
Grant
Sample variation?
How have you been testing them?
Is the one with Sinar on the front cell in a copal shutter? The cells could of been transfered from a Sinar board without checking for proper spacing. Also the Sironar_N is corrected for 1:20 while I think the original Sironar was optimized for smaller ratios. I am not a lens expert, maybe someone else with more knowledge could confirm this.
Hi, There are shims in place in the mount for the Sinar DB lens.....I also have Apo Ronars
The Sinar Branded lens is in a Sinar stamped DB mount... no shutter. I tested both
on a painting repro focussing at the taking aperture using the Betterlight focssing aid
after Zig Aligning both the standards and then the whole rig to the wall. The original
Sironar is a much heavier lens in a Copal 3. It is 105 mm front thread while the newer Sironar N-MC is an 86 mm front thread. Then I did medium distance and infinity.
That an older lens in a "line" can perform better than a newer lens in the same "line" is not new news. See http://www.hevanet.com/cperez/testing.html , which reports on formal resolution tests.
Anything is possible, at least when it comes to narrowly-defined tests of apparent sharpness or resolution. And sample variation is a consideration.
But "out performs" could mean many different things. I happen to have used both the 300 Sironar and the 300 Sironar-N, and in general pictorial use with three-dimensional subjects they sure don't look the same. There was a distinct change in the Rodenstock plasmat formula between the original Sironar generation and the N series, even beyond the change from single- to multi-coating early in the N generation. They're both competent; which is "better" would be in the eye of the beholder.
Not sure about the 300mm Sironar but the shorter lenses like the 150mm were a very different optical design between the early originals and the later Multi-coated versions.
The coatings on the original Sironar's is also almost as good as modern Multi-coating, I have both and it's very difficult to see any difference when using the lens. The very early Sironar's suffer badly from de-lamination, which is why they changed the design.
I'm inclined to agree there may be a shim problem.
Ian
The Sironar-N MC does have 1 shim in it. The lens is in such good shape that it
does not look like it was ever used. It is possible that a previous owner removed a
shim or 2. I mentioned that I also have several Apo Ronars. One is in a (Factory
supplied shutter), and it is multicoated. I have heard that Rodenstock spaced these
elements to perform better at Infinity. I will remove the shim in the Sironar and see
if it improves at closer distances and I will try a few more tests for distance as well.
I will try several distance images separating the cells a bit further each time. I will
repost in a few days. Thanks for the input.
Grant
I have finished the tests.
At 1:20 both lenses performed equally well. At infinity the Sironar-N MC was a little better. Close up the older convertible Plain Sironar was much better. Tests were shot at f11. The shim was definitely needed for the Sinar DB Mount. What I found interesting
is that when I installed the shim while the lens was mounted on the camera the engraved Sinar Logo was perfectly centered but when I installed the shim while the lens was off the camera pointing straight up the Engraved logo was off center clockwise by about 10 minutes. It seems incredible that this small amount would make a difference.
So another question would be; Did Sinar always make sure that there logo was straight up?
Grant
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