Can't adjust aperture ring

halfaura · 05-13-2015, 06:18 PM

I recently purchased a second hand Sigma 100-200m f4.5 lens, but when I attach it to my K3, no matter how I adjust the aperture ring, the aperture doesn't change on the lens. For some reason, this lens also has an aperture tab, though there are no pins. Consequently, the aperture is wide open no matter what I do. If anyone knows about this and has a workaround, I would like to know.

Thanks.

Adam · 05-13-2015, 06:30 PM

Originally posted by halfaura

I recently purchased a second hand Sigma 100-200m f4.5 lens, but when I attach it to my K3, no matter how I adjust the aperture ring, the aperture doesn't change on the lens. For some reason, this lens also has an aperture tab, though there are no pins. Consequently, the aperture is wide open no matter what I do. If anyone knows about this and has a workaround, I would like to know.

Thanks.

The aperture will stop down only when you go to take a picture, otherwise it will stay wide-open.

If the aperture ring doesn't have an A setting, here's what you need to do to expose properly:
https://www.pentaxforums.com/forums/54-pentax-lens-articles/110657-how-use-me...k-x-k-7-a.html

Not a Number · 05-13-2015, 06:53 PM

If you have the DOF preview set to optical when you operate the DOF preview lever (on-off switch) it should stop down.

vonBaloney · 05-13-2015, 08:06 PM

That's a pretty early one, probably does not have an A setting (would be next the smallest aperture, so you'd see an A on the apeture ring next to f/22 or f/16 -- whatever it is on that lens). If that's the case, you must use (M)anual mode on the body or it will never ever stop down -- see Adam's link.

halfaura · 05-13-2015, 09:35 PM

Ah, seems to have worked. Thanks.

CNunez · 05-15-2015, 01:32 AM

If you ever come across a lens where you follow all these steps and it still doesn't stop down.

Check if the base of the lens mount is covered by a coat of paint.

Chinon are a great example of this and you need to scrape it off where the pins would normally be. Otherwise the camera cannot detect it.

05-13-2015, 06:18 PM	#1
halfaura New Member Join Date: Dec 2014 Posts: 11	Can't adjust aperture ring I recently purchased a second hand Sigma 100-200m f4.5 lens, but when I attach it to my K3, no matter how I adjust the aperture ring, the aperture doesn't change on the lens. For some reason, this lens also has an aperture tab, though there are no pins. Consequently, the aperture is wide open no matter what I do. If anyone knows about this and has a workaround, I would like to know. Thanks.

05-13-2015, 06:30 PM	#2
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,595	Originally posted by halfaura I recently purchased a second hand Sigma 100-200m f4.5 lens, but when I attach it to my K3, no matter how I adjust the aperture ring, the aperture doesn't change on the lens. For some reason, this lens also has an aperture tab, though there are no pins. Consequently, the aperture is wide open no matter what I do. If anyone knows about this and has a workaround, I would like to know. Thanks. The aperture will stop down only when you go to take a picture, otherwise it will stay wide-open. If the aperture ring doesn't have an A setting, here's what you need to do to expose properly: https://www.pentaxforums.com/forums/54-pentax-lens-articles/110657-how-use-me...k-x-k-7-a.html 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:

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05-13-2015, 06:53 PM	#3
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	If you have the DOF preview set to optical when you operate the DOF preview lever (on-off switch) it should stop down.

05-13-2015, 08:06 PM	#4
vonBaloney Pentaxian Join Date: Oct 2011 Location: Albuquerque, NM Posts: 6,029	That's a pretty early one, probably does not have an A setting (would be next the smallest aperture, so you'd see an A on the apeture ring next to f/22 or f/16 -- whatever it is on that lens). If that's the case, you must use (M)anual mode on the body or it will never ever stop down -- see Adam's link.

05-13-2015, 09:35 PM	#5
halfaura New Member Join Date: Dec 2014 Posts: 11 Original Poster	Ah, seems to have worked. Thanks.

05-15-2015, 01:32 AM	#6
CNunez Senior Member Join Date: Dec 2014 Photos: Gallery Posts: 168	If you ever come across a lens where you follow all these steps and it still doesn't stop down. Check if the base of the lens mount is covered by a coat of paint. Chinon are a great example of this and you need to scrape it off where the pins would normally be. Otherwise the camera cannot detect it.