Micro Four Thirds Focal Reducer Shootout

Started Feb 20, 2014 | Discussions thread
OP brian Senior Member • Posts: 1,206
Re: Micro Four Thirds Focal Reducer Shootout

MichailK wrote:

Another observation:

The good stuff (Metabones of course! ) shows consistent performance throughout the image circle while the Zhongyi and RJ adapters have inconsistent performance going as far as the specific RJ sample being sharper than the specific Zhongyi sample at the upper right corner while the RJ scores lower in general. I guess this has to do with production & assembly deviations between parts as the rule "you get what you pay for" seems pretty much applicable on this occasion - I wouldn't be surprised of even bigger/narrower differences between the two types based on per-part basis.

So, is the Metabones assembly line thoroughly checked part-per-part before being shipped? This would explain much of the higher cost along with the proper design know-how fees (we are not buying just glass and metal here!). Any idea of the failed quality discarded percentage at the production line?

In this Sharpness test, how much things change stopping down 1-2 stops earlier? Looking at these guys' reviews http://www.youtube.com/watch?v=scowmtIgtPQ and http://www.youtube.com/watch?v=ry0nuJrXhpg the RJ one seems to sharpen quite a lot stopped down which I guess would make things less lacking than the Metabones (proper) one.

Also, in the Hotspotting test, 70.3mm and 149.4mm are the distances from the sensor up to the rearmost glass element of the Sigma lens? Or to the lens mount point? It looks like the RJ version suffers quite less than the Zhongyi one and for me this looks more like a runner-up to the Metabones part despite being less sharp wide open (possibly not an issue in comparison to the Zhongyi one if both are stopped down earlier).

The optical cells sold to Metabones are 100% checked at large aperture (f/1.0) on a lens test projector using a high quality master lens.

Its true that some focal reducers get alot better at reduced aperture.  But I think its more interesting and more useful to make a focal reducer that actually improves the MTF of the attached lens even at very large apertures.

The distances mentioned in the hotspot test are exit pupil distances measured from the image plane.  They have nothing to do with the location of the rear element.  I chose the Sigma 18-35/1.8 as a test lens in this case because it has a wide range of exit pupil distance through the zoom range.  Hotspotting is a ghost image of the pupil.  So exit pupil distance is an important parameter.  The zoom allows you to scan through various exit pupil distances to find the place where hotspotting is worst.

-- hide signature --

Brian Caldwell

Post (hide subjects) Posted by
(unknown member)
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark MMy threads
Color scheme? Blue / Yellow