[Leica] Micro 4/3rds

[henningw at archiphoto.com (Henning Wulff)]

At 4:33 PM -0400 3/31/10, Doug Herr wrote:
>Henning Wulff wrote:
>
>>  while lens based IS does introduce more air/glass surfaces
>>  along with more elements, that should also be the only additional
>>  consideration regarding decentering; ie, more elements, more chance
>>  of decentering.
>
>The operating principle of IS or VR is intentional decentering. 
>That's how it works.

True in a general sense, but that is different than the decentering 
that is seen in most lenses to one degree or another due to assembly 
tolerances. With correct design and assembly the type of image 
degradation that is caused by too loose tolerances in assembly will 
not be a factor due to the IS module's functioning.


Also, the IS unit adds a LOT of air/glass surfaces.  For example the 
EOS 100-400 L IS has 17 elements in 14 groups - that's 28 air/glass 
surfaces.

Yes, but we don't know what the count would be without IS. Canon is 
not known for skimping on number of lens elements in a lot of their 
lenses without IS.


This lens is known for sample variation and weaker image quality at 
the long end.
>

As are a large number of other zooms. In fact, all zooms have 
variable performance through their focal length range. That's a 
given. Where they have their stronger or weaker performance is up to 
the designer and design parameters. No, the 100-400 is no 400/4 or 
2.8 Apo-Telyt, but then the price isn't there either, and it's 
versatility is much greater except at f/4 or f/2.8.


>Another example: the EOS 300mm f/4 IS has 15 elements in 11 groups, 
>22 air/glass surfaces.  Known for poorer image quality than its 
>non-IS predecessor and described to me by someone who compared it 
>with the 280mm f/4 APO as a "cruel joke" (his words, not mine).  The 
>280mm f/4 APO has 7 elements in 6 groups - 12 air/glass surfaces + 4 
>surfaces for the front protective plate and rear filter.  I'd rather 
>not muck with optics to get stability.
>
>Doug Herr
>Birdman of Sacramento
>http://www.wildlightphoto.com
>

If I'm standing on a boat and have to shoot at 1/30 of a second I'll 
generally get a higher quality image with the 100-400 IS than with a 
similar weight and cost 400/5.6 without IS. That's a valid 
comparison. If we're talking about shooting on land with support 
available and comparing the 100-400 IS with a 280/4 Apo-Telyt, that's 
not a valid comparison for a number of reasons.

There is no doubt that the 100-400 IS isn't the greatest lens. While 
not exactly inexpensive, it's not badly priced and the performance is 
quite useable under many circumstances. It's good value for the most 
part.

The IS portion is a compromise. There are possibilities, but not 
certainties for image quality reduction, but there are also strong 
possibilities for image quality improvement under a lot of 
circumstances.

-- 

    *            Henning J. Wulff
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