Joseph Albert wrote:
> Denton writes:
>
> >We could also use a 200 macro, and a couple other fancy zooms, like Canon
> >L, say 17-35. Wouldn't a 17-35 2.8, 35-80 2.8, and a 80-200 2.8 be nice?
>
> nice, but I don't see it as so necessary beyond the 80-200/2.8 sort of
> lens and even that isn't so necesary. a 35-80/2.8 already shoots
> at 35mm, so I'd be more inclined to add a 21mm fixed focal to that
> than a 17-35 zoom, or maybe an 18mm and 24mm pair. so that is already
> supported. the canon 17-35 and 20-35 L zooms are very expensive, a little
> more prone to flare than the primes, and I doubt they focus as closely.
> the wider the lens, the closer it needs to focus since it de-magnifies more
> and you have to get closer in to have the foreground subject be large
> enough. I don't think the Canon wide-angle primes are as good as the
> Zuikos, so the L wide zoom is a more important part of Canon's lineup.
>
> I'd rather see a 180/3.5 macro that focused by extension and maintained
> 180mm at all magnifications. The 200/4 macro's on the market from
> Nikon and Pentax are internal focusing lenses. By focusing internally
> instead of by extension, they avoid light loss due to extension, so
> there is no bellows factor correction to be applied to the exposure.
> This is the good news. The bad news is that the focal length gets shorter
> as the lens focuses closer. At 1:2, which the 200/4 Micro-Nikkor can
> do without extension tubes, the lens is in fact about a 150mm lens only.
> It is only a 200mm lens at infinity. I'm pretty sure a similar situation
> holds
> with the Pentax 200/4 macro, it being an internally focused lens. But you
> don't get the expected working distance of a 200mm lens that focuses by
> extension, and certainly nowhere close to double the working distance at 1:2
> of a 100mm macro lens. If this sounds far-fetched (it did to me when I
> first read it), you can read all about it in John Shaw's book,
> "Close-ups in Nature".
>
> You can add a 1.4x teleconvertor to the 90/2 macro Zuiko and get
> a 126/2.8 or a 2x teleconvertor to get a 180/4 that focuses to
> 1:1 without external tubes and maintains the working distance of
> a 180mm lens.
No you can't. At least not the Zuiko 1.4, cause it has a protruding front
element. The 90 can't accept it.
>
>
> One of the things I like about the Tamron 90/2.5 macro is that Tamron
> makes a matched 2x flat field teleconvertor. It is well corrected
> for curvature of field to maintain a macro-quality lens when attaeched
> to the Tamron 90/2.5, yielding a good 180/5 that focuses down to 1:1.
> Unfortunately, this teleconvertor is adaptall only, no OM or other
> mounts available (it goes between the adaptall-2 adapter and the lens.
>
> j. albert
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