Followup: 25mm is FRONT FOCUSING on G7 (examples)

Started Jan 3, 2016 | Discussions thread
ForumParentFirstPrevious
Flat view
Big D in SP Regular Member • Posts: 434
Followup: 25mm is FRONT FOCUSING on G7 (examples)
3

Followup to a previous post regarding sharpness of the 25mm f1.7:

Viewing a good number of shots with the 25mm had me suspecting this.  On some landscape shots at 300-400 yards, objects at a middle distance were very sharp, but the target looked soft.  So I set up this test.

A lens should show max sharpness at point of focus and a drop-off of sharpness BEHIND the point of focus that is approximately 1 1/2 times the fall-off in FRONT of the point of focus.  Notice how the 25mm is sharper in FRONT of the point of focus (15/blue mark) than ON it and the fall-off is faster behind it.  The Sigma 30mm shows perfect focus characteristics.

This explains the lack of sharpness of the 25mm.  What I don't understand, is it the lens or my G7?  When I have time I'll compare it to two G6's I own.  That should answer the question.

If it's the lens, would Panasonic warranty it??  (There is no firmware update for the lens yet.  The G7 has the latest update.)

Blue peg inserted at 15". At 45 degrees leading edge is even with middle of 15.

25mm @ 1.7  Notice how the sharpest point is at 13 rather than 15

25mm @ 2.8   Same thing here.  13 sharper than 15.

Sigma 30mm @ f2.8 (wide open).  Perfect focus!  15-18 sharper than 13-15.

Sigma 30mm @ f4.  Again, perfect.

The 14-42II kit zoom, 14-140, and 60mm Sigma all focus perfectly.  That would seem to indicate a lens problem, but it puzzles me.  Contrast Detect focusing (theoretically) should eliminate this kind of focus inaccuracy.  Since it's happening wide-open as well as stopped down it shouldn't be attributed to focus shift upon stopping down, should it?

Anyway, still working on it!

Regards,

Warren

Panasonic Lumix DMC-G6 Panasonic Lumix DMC-G7 Panasonic Lumix G Macro 30mm F2.8
If you believe there are incorrect tags, please send us this post using our feedback form.
ForumParentFirstPrevious
Flat view
Post (hide subjects) Posted by
(unknown member)
ForumParentFirstPrevious
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark MMy threads
Color scheme? Blue / Yellow