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Mir-11 12.5mm Lens quality


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#1 Ian Cooper

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Posted 22 May 2008 - 08:28 AM

I've used the Mir-11 12.5mm lens with my K3 a fair amount now. Whilst it's stopped down in bright sunny weather the image is of similar quality to the standard Meteor zoom. What I've noticed in lower light conditions, with the lens wide open, is that the picture's noticeably soft.

Now I realise a lens never gives it's best wide open, but this is quite obvious without needing to stare at resolution charts! I'm also aware that the depth of focus is reduced for shorter focal length lenses, and is further reduced when they're operating at wider apertures than when they're stopped down.

Is the Mir-11 12.5mm lens known to be particularly soft wide open? Or is it likely the flange focal distance on the camera is slightly off the mark, and only showing itself up with the wider lens at maximum aperture?



Ian.
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#2 Olex Kalynychenko

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Posted 23 May 2008 - 04:05 AM

I've used the Mir-11 12.5mm lens with my K3 a fair amount now. Whilst it's stopped down in bright sunny weather the image is of similar quality to the standard Meteor zoom. What I've noticed in lower light conditions, with the lens wide open, is that the picture's noticeably soft.

Now I realise a lens never gives it's best wide open, but this is quite obvious without needing to stare at resolution charts! I'm also aware that the depth of focus is reduced for shorter focal length lenses, and is further reduced when they're operating at wider apertures than when they're stopped down.

Is the Mir-11 12.5mm lens known to be particularly soft wide open? Or is it likely the flange focal distance on the camera is slightly off the mark, and only showing itself up with the wider lens at maximum aperture?
Ian.


Mir-11 12.5 mm lens good sharp lens and have good optical characteristics at maximum opened position of aperture too.
I think, the your camera and your lens have different flange focal distance.
You need test of camera and lens on collimator.

Any case, we told about factory assembled Mir-11 lens.
You need inspect of condition of body of lens.
The all stop-screws must be on holes.
The rear draw-ring of last glass of optical block must be jammed and stop-screw must be inside hole.
The rear draw-ring of optical block bust be jammed too.
The lens mount don't must be loose.


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#3 Ian Cooper

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Posted 26 May 2008 - 05:02 AM

Thank you for those hints.

I've checked the points and they all seem ok, apart from the lens mount. There appears to be a small amount of rotational play between the mount and the rest of the lens where it slides back and forth to focus, although I can't detect any spare forward or backwards motion.

I suspect I could do with getting the FFD checked.
At least I now know the lens should be sharp.

Regards,
Ian.
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#4 Olex Kalynychenko

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Posted 27 May 2008 - 08:11 AM

Thank you for those hints.

I've checked the points and they all seem ok, apart from the lens mount. There appears to be a small amount of rotational play between the mount and the rest of the lens where it slides back and forth to focus, although I can't detect any spare forward or backwards motion.

I suspect I could do with getting the FFD checked.
At least I now know the lens should be sharp.

Regards,
Ian.

The lens can have dry lube on main multiple-thread screw and other parts and dry lube can give you additional gaps.
The re-lube of lens can be good idea too.
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The Slider

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Ritter Battery

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Visual Products