07-20-2015, 10:24 AM
(This post was last modified: 07-20-2015, 10:25 AM by Brightcolours.)
It is normal for the tele end to be "less bright" than the wide end... You can't make it the other way around and make it be sensible.
Why would you want a lens with 2 focal length settings, rather than a lens with 2 focal length extremes and the freedom to use all focal lengths in between? What is your rationale for that, exactly? Just the impossible wish for a bigger f-value at the long end?
For an APS-C size sensor, you will always need a lens+camera too big for a shirt pocket when you want a portrait focal length... The only thing you can try is to make the lens collapsible (which poses optical engineering restrictions by itself).
The Canon EOS M is a good example. The camera body is similar in size as the Olympus XZ-1, and it has an APS-C size sensor.
http://j.mp/1Or9hJh
With its EF-M 22mm f2 STM pancake lens, it is relatively compact still, with a nice street photography moderate wide angle lens. But slap on a EF 50mm f1.8 STM or Tamron 60mm f2 Di II macro, and its shirt-pocketablility is reduced big time.
A collapsible Canon EF-M 15-45mm f3.5-6.3 IS STM is in the making, which would solve the shirt-pocketabibility to some extent. But then you still lack the big aperture for the portrait end.
No matter how you turn it, you still end up with length and width for longer focal length and bigger aperture. These are at odds with your wishes, so it is not going to happen.
Why would you want a lens with 2 focal length settings, rather than a lens with 2 focal length extremes and the freedom to use all focal lengths in between? What is your rationale for that, exactly? Just the impossible wish for a bigger f-value at the long end?
For an APS-C size sensor, you will always need a lens+camera too big for a shirt pocket when you want a portrait focal length... The only thing you can try is to make the lens collapsible (which poses optical engineering restrictions by itself).
The Canon EOS M is a good example. The camera body is similar in size as the Olympus XZ-1, and it has an APS-C size sensor.
http://j.mp/1Or9hJh
With its EF-M 22mm f2 STM pancake lens, it is relatively compact still, with a nice street photography moderate wide angle lens. But slap on a EF 50mm f1.8 STM or Tamron 60mm f2 Di II macro, and its shirt-pocketablility is reduced big time.
A collapsible Canon EF-M 15-45mm f3.5-6.3 IS STM is in the making, which would solve the shirt-pocketabibility to some extent. But then you still lack the big aperture for the portrait end.
No matter how you turn it, you still end up with length and width for longer focal length and bigger aperture. These are at odds with your wishes, so it is not going to happen.