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05-10-2015, 07:51 AM   #1
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Pentax Adapter Q for K Mount Lens vignetting at faster speeds

I'm noticing a significant vignetting when using the genuine Pentax Adapter Q for K Mount Lens with telephoto lenses.
Up to 1/320 looks OK, but from 1/400 to 1/1000 all the pics look like old time photos (not bad, but I don't always want that).

Anybody else experience this?

05-10-2015, 08:20 AM   #2
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Ummm...no. More information please.
05-10-2015, 10:17 AM   #3
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QuoteOriginally posted by vonBaloney Quote
Ummm...no. More information please.
I think he means "photos please."
05-11-2015, 06:51 AM   #4
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I'll try to post some images, but it's not really necessary - talking about vignetting, strong vignetting (even on all sides) and it only occurs at speeds over 1/320 and up.
Obviously this is related to the leaf shutter in the K->Q adapter, but how? Could the shutter be defectives somehow?

05-11-2015, 07:53 AM   #5
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QuoteOriginally posted by digital029art Quote
I'll try to post some images, but it's not really necessary - talking about vignetting, strong vignetting (even on all sides) and it only occurs at speeds over 1/320 and up.
Obviously this is related to the leaf shutter in the K->Q adapter, but how? Could the shutter be defectives somehow?
Well, it shouldn't do that -- the last thing a K-mount lens should do on a Q is vignette (especially if it is a full frame lens).

Are you using a flash? That won't work at those shutter speeds and you will get weird effects (and it shouldn't even fire at all unless you are using a separate trigger somehow). But that wouldn't cause even vignetting, so I'm assuming no flash, right? But in daylight no flash, should work fine, and if only at certain shutter speeds I guess it could be the shutter but I'm not sure that would make a vignetting pattern, sounds strange.

So, what lenses exactly are you using? Is this happening with more than one? If only one, does it work right on a non-Q K-mount camera? How are you stopping down (with the adapter ring or with an aperture ring on the lens)? Etc etc...
05-11-2015, 09:25 AM   #6
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QuoteOriginally posted by digital029art Quote
I'll try to post some images, but it's not really necessary - talking about vignetting, strong vignetting (even on all sides) and it only occurs at speeds over 1/320 and up.
Obviously this is related to the leaf shutter in the K->Q adapter, but how? Could the shutter be defectives somehow?
Which flash, if any, are you using? If you are using the OBF (on-board flash), are you using it in the raised or lowered position?
05-11-2015, 09:40 AM   #7
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No flash in this case, this is with long lenses 300mm, 400mm. If I expose exactly the same with Pentax K->Q w/shutter VS generic k->q adapter the vignetting is very noticeable.
05-11-2015, 09:45 AM   #8
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QuoteOriginally posted by digital029art Quote
No flash in this case, this is with long lenses 300mm, 400mm. If I expose exactly the same with Pentax K->Q w/shutter VS generic k->q adapter the vignetting is very noticeable.
So you get the "vignetting" with the genuine adapter while you get a "better" picture with the generic adaptor?!

05-11-2015, 10:07 AM   #9
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QuoteOriginally posted by digital029art Quote
No flash in this case, this is with long lenses 300mm, 400mm. If I expose exactly the same with Pentax K->Q w/shutter VS generic k->q adapter the vignetting is very noticeable.

How are you operating the aperture? Do the lenses have aperture rings? What is the setting on the dial on the adapter?
05-12-2015, 07:31 AM   #10
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QuoteOriginally posted by reh321 Quote
So you get the "vignetting" with the genuine adapter while you get a "better" picture with the generic adaptor?!
Yes, except for the rolling electronic shutter effect which happens frequently with long lenses.

---------- Post added 05-12-15 at 10:33 AM ----------

QuoteOriginally posted by vonBaloney Quote
How are you operating the aperture? Do the lenses have aperture rings? What is the setting on the dial on the adapter?
Right, these are MF lenses, so aperture is set on lens and I have the adapter set on L (closed).
05-12-2015, 07:48 AM   #11
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QuoteOriginally posted by digital029art Quote
Yes, except for the rolling electronic shutter effect which happens frequently with long lenses.

---------- Post added 05-12-15 at 10:33 AM ----------



Right, these are MF lenses, so aperture is set on lens and I have the adapter set on L (closed).
Unless these same lenses are acting funny on some other body, I'd say your K-Q adapter is defective. Mine works great with a variety of long lenses and fast shutter speeds. Here's some I took with a 600mm last week:

https://www.pentaxforums.com/forums/136-pentax-q/209474-adapted-lenses-tested...ml#post3242100

I don't think the adapter can even detect when a lens is mounted -- try leaving the lens off and just watch the shutter from the front -- able to see anything funny going on? (Don't happen to have a super-slomo video rig sitting around, do ya?)
05-12-2015, 08:47 AM   #12
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Thanks! I just tried shooting a sequence with no lens attached into a lamp, starting at 1/1000 and down. Results show significant vignetting, more so on the left side, worst at faster speeds. Tried two different Qs, same result. So it looks like my adapter could be decentered??

P.S. Using only the electronic shutter I get even illumination at all speeds, albeit with some horizontal lines..
05-12-2015, 08:48 AM   #13
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QuoteOriginally posted by digital029art Quote
Thanks! I just tried shooting a sequence with no lens attached into a lamp, starting at 1/1000 and down. Results show significant vignetting, more so on the left side, worst at faster speeds. Tried two different Qs, same result. So it looks like my adapter could be decentered??

P.S. Using only the electronic shutter I get even illumination at all speeds, albeit with some horizontal lines..
I hope you're within the return window -- send it back, it's broken.
05-12-2015, 11:38 AM   #14
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Yes I am (it's a 1 year warranty right?), my first warranty claim with the Pentax / Ricoh, hope it goes smooth!
05-12-2015, 01:05 PM   #15
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QuoteOriginally posted by digital029art Quote
So it looks like my adapter could be decentered??
Maybe not "decentered", which applies to elements in a lens . . .

QuoteOriginally posted by digital029art Quote
Using only the electronic shutter I get even illumination at all speeds, albeit with some horizontal lines..
. . . but most likely unevenness in the way the leaf shutter opens.
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