Sony 16-50 kit lens

Started Dec 3, 2012 | Discussions thread
Bart Hickman Veteran Member • Posts: 7,256
Re: Sony 16-50 kit lens

viking79 wrote:

Has anyone actually measured the focal length? It could be 16mm including the black corners and 17 or 18 mm corrected for example.

Yes, I measured it here:

http://forums.dpreview.com/forums/post/50379046

My issue is other software corrected lenses I have used actually have good corner performance before corrections. The issue is Sony isn't making the image circle large enough so they can make it 16mm. It should really be called an 18 or 20 to 50mm lens.

I believe the 16mm nomenclature is justified.  I've measured other wide zooms in the past and they usually come up 5-10% less wide than the nomenclature (eg., the Tokina 12-24 is really about 12.6mm at the wide end.)  I think the 16-50 is in the ballpark.

I used to think Sony lenses had bad corner performance on the E mount because of short flange distance, but I think I have since decided that the corner performance issues are from using too small of image circles, which appear to be designed for a 1.6 or 1.7x crop factor sensor, at least on their consumer lenses (not the 24mm f/1.8 or 50mm f/1.8).

Just because the flange distance is short doesn't mean the rear lens element is closer to the sensor.  I think they made the image circle as large as it needs to be based on my measurements.  Anyway, this argument only applies to wide angle lenses.  A zoom like the 55-210 gets no optical benefit at all from the shorter flange distance.  There could potentially be a design benefit as you could more easily fit electronics in the empty space created.

You won't ever see IBIS on NEX because of this issue, the shake reduction mechanism would move the sensor out of the image circle.

Of course they could have IBIS.  The lenses they're making now have OIS built in so they'll always work with any future camera with or w/o IBIS.  If they decided IBIS made strategic sense at some point in the future, any newly-designed non-stabilized lenses would just have to have a large-enough image circle (which is a non-issue on telephoto lenses where stabilization is more important anyway.)

Bart

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