On 5/7/2020 1:28 PM, Charles Geilfuss wrote:
I've been playing around with a recently acquired 600mm Vivitar Solid Cat.
Looking through it the images appear very sharp but camera shake is a bear.
Need to dig in the E-620 manual to figure out how to pre-fire the mirror.
Are you sure it's that?
1. It's simply impossible to hand hold a 1200 mm eq. lens without IS, in this case IBIS.The IBIS in the E-620 is an
early design, much less effective than later versions for µ4/3.
DPR had this to say: "The E-620 doesn't have the top-tier IS system we saw in the E-30 but Olympus is still confident
enough to claim a 4-stop advantage for this IS system (though our tests have never shown an improvement on that scale)."
And "As you can see, [50 mm lens] there's a clear 2 stop advantage to the camera's IS system. While this isn't the best
performance we've ever seen, it's enough to drastically increase the number of sharp, stable images you get."
When I first started using two cameras around my neck in the field, one was an E-M5, for the 75-300 zoom. The other was
an E-PM2 for the 12-50. I loved many aspects of the E-PM2, but in the end it became obvious that the IBIS wasn't up to
the job, particularly for macro, which suffers from some of the same high magnification problems as long tele.
The review of the E-PM2 doesn't mention IBIS. I suspect that, 3.5 years later, it's at least no worse than the E-620.
With an F8 lens, I imagine you've not been using really high shutter speeds, either.
2. At that magnification, even the tiniest subject movement causes blur. With the recent advent of Topaz Sharpen AI,
I've been impressed, occasionally amazed, at the improvement the Stabilize Mode has made in images where I would have
credited some softness to lens quality and air movement.
3. Tripods are not all created equal. You may recall that Gary's lens tests didn't look so good for the 600/5.6 and
1000/11 OM Zuikos. He went so far as to use a lens support and/or two tripods, with the tripod legs frozen into the rink
ice. He later said he had gotten much better results resting the lenses on heavy sandbags on the roof of a car.
Walt was an advocate of bags of shotgun pellets resting on top of camera and lens. The common solution of hanging a
weighty bag from the camera center column is not nearly as effective, especially with mid weight aluminum tripods.
4. Contrast! These lenses are low contrast. What we call sharpness is a technically undefined idea that combines parts
of resolution, overall contrast and edge contrast. Take an image of a Yin/Yang symbol, manipulate contrast so white
areas are 129 and black are 127, and it all appears to be neutral gray. Yet, resolution is exactly the same as if black
is 0 and white 255.
This effect is definitely going on with long shots with mirror lenses.I am, coincidentally, working up a demonstration
of this on a moon photo. It's not so big a deal these days for those with post processing abilities, but it was a big
deal in film days.
The VivSCat is pretty low contrast. Here's a site where the guy summarizes the old PopPhoto mirror lens tests and adds
his own MTF tests. Two of the mirror lenses I have, Sigma 600/8 and Oly 500/8 are included, along with your Vivitar.
<https://jimchungblog.com/2017/03/07/the-most-ultimate-mirror-lens-shootout-in-the-world/>
Low contrast tends to make photos look like they are not sharp.
5. Resolution. The PopPhoto tests make the Viv the lowest resolution, by a fair margin. The MTF tests aren't as
different, perhaps a little lower than the Sigma 600. So it's not clear just how low it is, but its resolution is
apparently not all that great. OTOH, I think my Sigma 600/8 is a pretty good lens, on a solid tripod, remote release, no
wind, etc.
Sooo . . . There are several factors that affect the final result, in some
combination or other.
And . . . If you want a mirror lens, especially for hand held, the OM 500/8 is
the likely candidate.
--
What if the Hokey Pokey *IS* what it's all about?
--
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