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View Full Version : A thought: Making a EF 28-90 f/2.8 IS USM


Lightstream
15th of November 2006 (Wed), 18:20
I am guilty of much lens hackery, see these pictures for the explanation in a nutshell (NO, these are not PhotoChopped.. this time it's real)

http://pix.lightrefineries.org/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=802&g2_serialNumber=1

And I was thinking, it might actually be possible to CREATE an EF 28-90 f/2.8 IS USM. Let me explain. Initially this lens was slammed, but I've always realized that there is no functional equivalent in EF land. Not if you want f/2.8 and IS, so that's a healthy serving of cake and the ability to eat it too. Let's not go into "how useful is IS" - some of us want it, and we will go and get it.

There's enough mirror clearance on a 1D to allow me to mount and use the 17-85 lens at all focal lengths. However, there is a small vignetting problem:

http://pix.lightrefineries.org/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=790&g2_serialNumber=1

Of course one can get around this problem by cropping. It so happens, for maximum image size without the vignetting, you'll apply a 1.6X crop in software, thus the lens will yield the equivalent of a 28-90. Regardless of the 1.3X, 1.6X or FF camera you mount it on.


So....has anybody tried doing the EF conversion of a 17-55 f/2.8 IS USM? I don't have one or believe me I would try. :D

Cathpah
16th of November 2006 (Thu), 00:32
So....has anybody tried doing the EF conversion of a 17-55 f/2.8 IS USM? I don't have one or believe me I would try. :D


oh good golly that would be sweet. can't speak for how the lens performs...but that would destroy the 16-35 vs 17-40 issue.

some brave soul needs to do this soon!

Lightstream
16th of November 2006 (Thu), 01:05
It would probably affect metering (use partial/center) and I suspect the mirror would not clear on full frame, hence my suggestion of a 1.3X crop cam. But oh what a wonderful mod that would be. :)

Plus, framing could get complicated. Wonder if you could 'score' a focusing screen with a small x-acto knife to provide the framelines.