17-55 or 24-105?

Started May 24, 2006 | Discussions thread
Don_D
Don_D Forum Pro • Posts: 20,529
Re: 17-75 EF-S f/4.5

SuvoMitra wrote:

Videodoc wrote:

I'm seriously considering the Sigma 17-70. What I really want is
an improved 17-85 or a 17-40 stretched out to a 17-70/80.

The 17-85 range is really very nice to have. I don't know much
about optical design, but it seems that making a high quality 17/18

  • 70/80 is just too difficult to do. Either the wide end gets

woolly with lots of CA and barrel or the long end gets too soft at
larger apertures. Nikon also restricted themselves to 55mm for the
f/2.8 standard zoom for DX. They would have stretched to get closer
to the 70-200 VR's starting point if they could keep up the quality
at both ends. Perhaps this is one disadvantage of the APS-C format.
Top quality standard zooms are possible only within a more
restricted range than in the FF format.

Not so. In the 17-55 design, I suspect Canon traded speed for range.

I have long thought that a 24-105 f/4L could be scaled by a 1.4x factor to a 17-75 f/4.5 EF-S. When I brought this up, I was told on this forum by folks much more knowledgable in lens design that this is very possible in an EF-S design. It should match the 24-105's performance and would not require a new lens design from Canon...just a scaling (much simpler) of a present design and a change from f/4 to f/4.5. Of course it would be relatively slow, but should give good image quality and and a great range on 1.6x cameras.

-Don

'Where do we go when we die?' said Billy.
'I don't know', the old man said, 'Where are we now?'
.....Cormac McCarthy
http://www.pbase.com/dond

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