[EMAIL PROTECTED] wrote:
> < Most IS designs seem to use more lens elements than their non-IS
> < counterparts,
> < . . . .
> < that some IS lenses perform less well on bench tests than do the non-IS
> < versions.
> I'd have to disagree - from what I hear those Big primes, like 300L IS, 400L
> IS and such perform better than the old ones.
Hi George,
Note that I said "most," not all have more elements, and that "some," not all IS
lenses don't perform as well optically than their non-L counterparts. Certainly
I'd love to have a 500/4L IS or 600/4L IS, but the big teles, in which every
movement is magnified, are a special case, quite a bit different from putting IS
on the 28-70/2.8L (to give an example for which there seems to be some support on
the list), or perhaps more absurdly, the 24/2.8 or 35/2 (which would happen if
all Canon lenses were eventually converted to IS). And then there's the cost:
when the IS versions of the big teles and the discontinuation of the non-IS
versions were announced, I managed to scrape together the funds to buy a 300/2.8L
(non-IS) in order to beat the big price increase, which even with B&H's discount
prices was about 25%. By buying "grey" I was just able, by ignoring some other
demands on my resources, to manage $3700 for the original; there's no way I would
have been able to swing $5400 for the IS, then or now (even though the B&H price
has since dropped by $500).
> Plus it allows a whole new
> window to handhold, where tripods are not allowed, or not convenient.
> Lenses like 100-400L IS are pure pleasure to use and IS does work as Canon
> says it should.
I'm not arguing against this, but again we're talking about a substantial
telephoto lens here (400mm). I don't see anyone clambering for IS on the 100/2.
> So, while IS may not be "needed" on all lenses, it
> potentially could improve all those, without affecting image quality.
It could also have a negative impact in cases where keeping the retail price down
factored into the design. The 300/4L is the prime example, so far; it will be
interesting to see how the 70-200/2.8l IS tests, compared to the older version.
> And as far as reliability - well -
> I never heard of solid evidence that IS causes
> many problems.
Several folks on the list have reported needing repairs to their 28-135 IS lenses
after fairly minor knocks; that's what I had in mind. Not a scientific sampling,
of course, and I'm not making a wholesale claim such as we saw regarding the EOS
3 when the underexposure in some examples was reported (including my own), but
perhaps indicative nonetheless. And there's still the general consideration that
more moving parts means more to go wrong, and any misalignment or malfunction of
moving parts in the optical path is going to have a significant impact on image
quality. IMO this is one case where the adage, "as complex as it needs to be, but
no more" holds true. With all the discussion regarding whether the EOS 3 is as
durable as an F-1, or the EOS 30 as robust as an EOS 3, what drops from view is
the possibility that the real weak point in the system in terms of durability is
the lenses.
fcc
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