K-mount adapters for Pentax new-mount cameras

Started 11 months ago | Discussions thread
Barry Pearson
OP Barry Pearson Veteran Member • Posts: 8,723
Re: Something to think about...

Alex Sarbu wrote:

Barry Pearson wrote:

Alex Sarbu wrote:

The D FA* 50mm required an unprecedentedly (at least, for Pentax) tight construction.

It was found - late in the process - that the barrel couldn't properly support the heavy front group, which led to a slight but significant misalignment - impacting the optical performance.

Long story short, they solved that issue with special support components. Also, the lens mount has "the highest number of screws ever used" - for structural rigidity.

What would happen when you add an adapter? Can it be rigid enough? I believe Lloyd Chambers warned about adapters introducing such misalignments.

Where might the problems lie?

Between the lens and the adapter,

yes

Ouch!

That case is the same as "between the lens and the camera body" when there isn't an adapter.

I expect to use my D FA* 50mm on my K-1ii on a tripod much of the time.
(Not because of inadequate lighting, but as an aid to composition).

I think I need to investigate some sort of support. Perhaps an Arca Swiss plate that can be fastened at the back to the K-1ii tripod bush, and support the front end of the lens, (behind the lens-hood). Two points of support for the combination.

(The lens hood falls below the base level of the K-1-series, so probably isn't a good supporting point).

or
Between the adapter and the camera when the adapter has this lens attached?

yes

The ultra wides are impacted more. See https://diglloyd.com/blog/2009/20090802_1-UltraWideAlignment.html

So far I don't appear to encountered this problem with my Laowa (Venus) 12mm f/2.8 on my K-1ii. But I tend to use it stopped down a bit. (I guess that counts as "ultra wide"?)

 Barry Pearson's gear list:Barry Pearson's gear list
Ricoh WG-6 Panasonic LX100 Ricoh GR III Pentax K-7 Pentax K-3 II +27 more
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