[rollei_list] Re: xenar test roll is back
- From: Eric Goldstein <egoldste@xxxxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx
- Date: Thu, 4 Feb 2010 12:50:58 -0500
This is just the tip of the iceberg relative to lens and camera
testing... so many variables and so much to go wrong. Not to mention
the preconceived notions and biases of the testers. I'm always
suspicious of someone who tells me that, realtive to Rollei Xenar
versus Tessar or Xenotar versus Planar, one is generally superior to
the other, as the design specifications for these lenses was the same
from F&H...
So I'll say again that my own biased experience is that the Xenar on
my 'cord III is about the same performer as the recalculated Tessar on
my T under substantial enlargement. They both need to be stopped down
to about f/8-11 to get sharp in the corners, and they are fine even at
f/4 in the center...
Eric Goldstein
--
On Thu, Feb 4, 2010 at 11:45 AM, <Newhouse230@xxxxxxx> wrote:
> I agree. Even the smallest amount of camera motion will degrade the
> performance of even the finest lenses, and, in my opinion camera shake is a
> far greater cause of unsharpness than lens issues in most of our images.
> Any lens test or comparison in the field is best done with the camera on a
> sturdy tripod and a cable release attached. If no cable release is on hand,
> activate the self timer so that your body is not in contact with the camera
> or tripod during the exposure. That 10 seconds is also important to let any
> vibration caused by you focusing, changing settings etc. to settle down.
> Though there are some folks with 'steady hands" (I am, unfortunately not
> one of them) it's almost impossible to hold a camera without some minimal
> amount of shakiness. I have known some photographers who claimed they could
> shoot between beats of their own heart; I'm still working on that one!
>
> In any case, hand holding a camera is fine for most purposes, (witness
> Carlos' many excellent hand-held images) but not so good for judging
> comparative performance at various apertures.
> Charlie Silverman
>
>
>
> In a message dated 2/4/2010 9:43:56 A.M. Eastern Standard Time,
> daxelb@xxxxxxx writes:
>
> Hi,
>
> I suspect that's slower shutter speed is the true culprit in the softness of
> your images. I have to say that I've never been able to shoot at less than
> 1/100 with any camera without some evidence of camera shake. I would retest
> shooting wide open at the faster shutter speeds.
> Just my two cents,
>
> David Baumbach
>
>
>
> -----Original Message-----
> From: Richard Knoppow <dickburk@xxxxxxxxxxxxx>
> To: rollei_list@xxxxxxxxxxxxx
> Sent: Thu, Feb 4, 2010 1:53 am
> Subject: [rollei_list] Re: xenar test roll is back
>
> ----- Original Message ----- From: "Stephen Attaway"
> <stephen@xxxxxxxxxxxxxxxxxx>
> To: <rollei_list@xxxxxxxxxxxxx>
> Sent: Wednesday, February 03, 2010 10:10 PM
> Subject: [rollei_list] xenar test roll is back
>
> Hi all ...
>
> Got the test roll I shot last weekend back. This was with my 'cord IV with
> Xenar.
>
> I did three wide open pix - good contrast, color and focus was spot on - but
> frankly a bit soft.
>
> Especially compared with the results stopped well down (f11-22). Sharpness
> was really excellent and held well into the picture edges. Contrast was
> moderate, giving a pleasing, classic drawing.
>
> In fairness, I think there was just a touch of camera shake in the wide open
> shots, because I was at 1/50 and am not quite used to the 'cord shutter
> release. Later, in soft sunlight, with Provia 400x, I was up at 1/100 and
> 1/250 - and my handheld shots all looked like the 'cord had been bolted to a
> granite plinth.
>
> I even tried the Xenar with a Mutar 1.5x and bay I rings. The sharpness of
> this combination was also very impressive, but contrast had dipped, perhaps
> partly due to a touch of underexposure. I had opened up about 1/3 to 1/2
> stop with the Mutar (I get good results that way with my Planar), but should
> have opened up 2/3 of a stop to a full stop on the Xenar.
>
> I'll post a few 100% crops from my scans this weekend, in case any of you
> are also pixel peepers like me.
>
> My conclusion: the Xenar is a fine performer stopped down but I'd be
> reluctant to open it up past f5.6. Its really splendid at f11-22. The 'cord
> IV is a very good match for Provia 400x, which is good because I bought way
> too much of that stuff when it first came out.
>
> And the 1.5 mutar is quite usable with the old 'cord, if you can overlook
> the really nasty vignetting in the ground glass. Just a touch of vignetting
> in the actual picture, though.
>
> But I think I'll be using the 'cord IV more as a lightweight, less imposing
> option to the 'big ride' for daytrips, with a minimum of accessories. Its
> obviously capable of really first class results, if you are aware of its
> limitations and respect them.
>
> And obviously there is nothing wrong with my Xenar ... no need to trade in
> or trade up.
>
> Thanks for everyone's help, advice and wisdom. I've learned a lot the last
> few days.
>
> Stephen
>
> FWIW, the main residual aberrations in a well-designed Tessar type lens
> are all reduced by stopping down. For many lenses of "normal" coverage the
> residual aberrations are essentially gone over the field when stopped down
> about two stops. For an f/3.5 lens this is around f/7 so stops of about f/8
> or smaller should be quite good. The "optimum stop" may be somewhat smaller,
> probably about f/11. Beyond this the loss of resolution due to diffraction
> begins to become significant. This is the reason that lenses on small camras
> rarely stop down beyond f/22 while those on large cameras often go to f/32
> or even f/45 to f/64. At f/64 a Rollei lens would be very blurred.
> Beside the improvement in sharpness there may also be some improvement in
> contrast as the optimum stop is approached. This is because spherical
> aberration and its relatives like oblique spherical and coma also tend to
> scatter some light and reduce contrast. For the most part well-designed
> Tessars do not have much residual spherical, mostly they have some oblique
> spherical. This is similar to coma and, like coma, increases with image
> angle and decreses as the lens is stopped down.
> Adding more elements is a way for the designer to control higher order
> aberrations. For fast lenses, or wide angle lenses additional elements over
> a Tessar are necessary if the lens is to have good performance and decent
> speed. Note that some quite simple lenses (wide angle Protar) will cover
> surprizingly wide angles (around 100 degrees) but onlyl at very small stops
> (c f/64).
>
> --
> Richard Knoppow
> Los Angeles, CA, USA
> dickburk@xxxxxxxxxxxxx
>
> ---
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