How big would a 100-200 f2.8 m43 OIS be?

Started Nov 12, 2012 | Discussions thread
rkeller
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Re: How big would a 100-200 f2.8 m43 OIS be?
In reply to micksh6, Nov 14, 2012

micksh6 wrote:

rkeller wrote:

micksh6 wrote:

Micro 4/3 version of 70-300mm is 1/2 stop slower, not 1/3 stop slower, and that's why it's lighter.

Between 1/3 and 1/2 stop. That's why I put the "~" in there.

According to Wikipedia F6.7 is exactly 1/2 stop smaller than F5.6: http://en.wikipedia.org/wiki/F-number

Hmmm, I must have been looking at the 1/3 stop scale. My mistake.

Also micro starts from 75mm, not from 70.

Good catch: I noticed my typo long after the editing window had closed.

There won't be any significant weight reduction for m4/3 50-200mm lens if it retains maximum aperture at the long end.
It's physics. They can only make the same lens lighter by compromising optical and build quality.

There's more to it than that from a design perspective. For another comparison:

Specs for the 4/3 Zuiko 14-42mm f/3.5-5.6:

  • 10 elements in 8 groups, including 1 ED and 2 aspherical elements
  • Filter size: 58mm
  • 61mm x 65.5mm / 2.4 in. x 2.6 in.
  • 190g / 6.7 oz

Specs for the m4/3 M.Zuiko 14-42mm f/3.5-f/5.6II

  • 8 elements in 7 groups, including 3 aspherical elements
  • Filter size: 37mm
  • 50mm x 56.5 mm / 1.96 in. x 2.22 in. (min.)
  • 112g / 3.95 oz

This time at 41% weight savings going from 4/3 to m4/3. One could argue the build quality is different, but the m4/3 version has, if anything, a higher optical quality.

Short lenses are different story. Wide to short tele lenses are easier to make small on m4/3 because of shorter flange distance. And you see that they simplified design for m4/3 - less lens elements.
Long fast tele lens size/weight won't depend on mount and sensor size that much.

Thanks for the detailed follow-up. I understand that about the wide-angle vs. telephoto.

Actually, your comparison with Canikon 70-200mm is a good example of how aperture at long end matters and sensor size does not.
4/3 50-200mm F2.8-3.5 lens is ~35% lighter than Canikon 70-200mm F2.8 for the same reason why m4/3 75-300mm is lighter than 4/3 lens by similar amount - it is 2/3 stop slower at long end. If 50-200mm lens had F2.8 at long end it would have very similar size/weight to 70-200mm F2.8.

Surely, some of that difference is the required image circle coverage too?

For long telephoto max aperture at long end and max FL define the size of front element group, and this group is the main contributor to lens size/weight.

It should be noted that the front element is the same size (or at least the same filter thread) for the 4/3 70-300mm vs. the m4/3 75-300mm, and the 30% weight savings seems a lot to be accounted for if it's just due to the 1/2 stop darker max aperture?

Anyway, it'll be interesting to see the specs of the rumored 50-150mm f/2.8 if it actually is real. My guess is a weight of 650 grams. Care to offer your prediction?

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