My Aperture looks weird stopped down help!

pepler · 07-07-2017, 04:19 PM

Just purchased a pentax 67 with a SMC takumar 1-5 f 2.4. Camera works great but the lens has a weird aperture issue I havent seen before.

When I stop down to f 16, 22 the aperture goes from totally symmetrical to more rectangular. Other than changing the bokeh circles can this do anything to affect picutres.

Thanks so much!

mikeSF · 07-07-2017, 04:48 PM

sounds like you could be missing blade(s) or some are stuck. Got any pics?

pepler · 07-07-2017, 04:51 PM

Originally posted by mikeSF

sounds like you could be missing blade(s) or some are stuck. Got any pics?

Here are two pictures. Im sure all the blades are there. Just looks weird when its stopped down.

photoptimist · 07-07-2017, 05:00 PM

It's not uncommon, especially in older lenses. Manufacturing variations, wear, and dirt on the blades can cause them to close a little lop-sided like that.

It can affect the shape of the bokeh and uniformity of the starbursts but won't affect sharpness, contrast, or other overall image quality.

mikeSF · 07-07-2017, 05:04 PM

Originally posted by pepler

Here are two pictures. Im sure all the blades are there. Just looks weird when its stopped down.

oh, that's not too uncommon, just slight misalignment of one or two blades as the aperture closes. You may like the bokeh better this way, lol.

pepler · 07-07-2017, 05:05 PM

Originally posted by photoptimist

It's not uncommon, especially in older lenses. Manufacturing variations, wear, and dirt on the blades can cause them to close a little lop-sided like that.

It can affect the shape of the bokeh and uniformity of the starbursts but won't affect sharpness, contrast, or other overall image quality.

Thanks for the info! Im not too concerned with bokeh, starbursts. Just want the lens to function properly and the meter to be accurate

Adam · 07-07-2017, 06:55 PM

I think both are normal- certainly nothing wrong with the almost wide open aperture. The narrow one definitely looks asymmetric, but I've seen this on many of my old lenses too.

Adam
PentaxForums.com Webmaster (Site Usage Guide | Site Help | My Photography)

PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

07-07-2017, 04:19 PM	#1
pepler New Member Join Date: Jul 2017 Posts: 7	My Aperture looks weird stopped down help! Just purchased a pentax 67 with a SMC takumar 1-5 f 2.4. Camera works great but the lens has a weird aperture issue I havent seen before. When I stop down to f 16, 22 the aperture goes from totally symmetrical to more rectangular. Other than changing the bokeh circles can this do anything to affect picutres. Thanks so much!

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Keeping AdaptAll Lens Stopped Down	reh321	Pentax SLR Lens Discussion	7	11-25-2018 05:49 PM
K-50 overexposing when stopped down	bhbrake	Pentax K-30 & K-50	12	08-11-2016 12:44 AM
Stopped down vs. same native aperture	6BQ5	Pentax SLR Lens Discussion	8	07-16-2013 03:23 PM
K-x aperture problem: always fully stopped down on DA lenses	amrocha	Troubleshooting and Beginner Help	4	11-03-2011 03:47 PM
Down down down down...	innershell	Post Your Photos!	5	08-06-2009 05:45 PM

07-07-2017, 04:48 PM	#2
mikeSF Pentaxian Join Date: Jan 2009 Location: East Bay Area, CA Photos: Gallery Posts: 6,622	sounds like you could be missing blade(s) or some are stuck. Got any pics?

07-07-2017, 05:00 PM	#4
photoptimist Pentaxian Join Date: Jul 2016 Photos: Albums Posts: 5,128	It's not uncommon, especially in older lenses. Manufacturing variations, wear, and dirt on the blades can cause them to close a little lop-sided like that. It can affect the shape of the bokeh and uniformity of the starbursts but won't affect sharpness, contrast, or other overall image quality.

07-07-2017, 05:04 PM	#5
mikeSF Pentaxian Join Date: Jan 2009 Location: East Bay Area, CA Photos: Gallery Posts: 6,622	Originally posted by pepler Here are two pictures. Im sure all the blades are there. Just looks weird when its stopped down. oh, that's not too uncommon, just slight misalignment of one or two blades as the aperture closes. You may like the bokeh better this way, lol.

07-07-2017, 05:05 PM	#6
pepler New Member Join Date: Jul 2017 Posts: 7 Original Poster	Originally posted by photoptimist It's not uncommon, especially in older lenses. Manufacturing variations, wear, and dirt on the blades can cause them to close a little lop-sided like that. It can affect the shape of the bokeh and uniformity of the starbursts but won't affect sharpness, contrast, or other overall image quality. Thanks for the info! Im not too concerned with bokeh, starbursts. Just want the lens to function properly and the meter to be accurate

07-07-2017, 06:55 PM	#7
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,608	I think both are normal- certainly nothing wrong with the almost wide open aperture. The narrow one definitely looks asymmetric, but I've seen this on many of my old lenses too. Adam PentaxForums.com Webmaster (Site Usage Guide \| Site Help \| My Photography) PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers: