Chinon lens won't stop down on K3

stevebrot · 04-10-2015, 12:58 PM

Originally posted by BigMackCam

Can you still use the lens in M and Av modes

I usually use it in M mode with exposure based on trial and error when the strange behavior happens.

Steve

**Skodadriver** · 05-09-2015, 08:39 AM

Originally posted by stevebrot

You should only short the "data/digital info" contact to avoid sending mixed signals to the body. See image below from Dimitrov's K-mount site:

Steve

As there is a lip around the outside of the lens on my Chinon 200mm, I scraped the anodise off in the area as shown by Stevebrot's post, (didn't see a need to stick conductive adhesive tape to the lens) and it's now stopping down a treat.

CNunez · 05-09-2015, 09:40 AM

Update: woohoo! I have a working 28mm lens now! Stunning IQ!

I have a chinon 28mm f2.8 that behaves exactly like described here. So all it takes is for me to scrape the paint off the mount?

**Skodadriver** · 05-16-2015, 02:28 AM

Originally posted by CNunez

Update: woohoo! I have a working 28mm lens now! Stunning IQ!

I have a chinon 28mm f2.8 that behaves exactly like described here. So all it takes is for me to scrape the paint off the mount?

It worked for me. I also have a Vivitar 1.5x-22 teleconverter with the mount anodised. I will scrape the paint off to match the required contact and then I should be able to use this at any f stop......I hope.

leodp · 09-20-2019, 05:23 AM

Hi,
I have the same problem on a black-anodized flange on an old Porst 55mm f1.2 mounted on a k-70 body, with firmware version 1.11

Using "M" mode, with the camera set to allow the use of the aperture ring, fixed ISO setting: the green button works intermittently, probably due to a not good contact.

I scratched the flange in correspondence of where the digital communication contact is (exactly opposite to the red dot). This was sufficient to let the camera aknowledge that a lens is attached.
Now the green button correctly stops-down the iris when it should.
Thanks for the thread, it helped me a lot.

Leodp

**pepperberry farm** · 09-20-2019, 06:01 AM

as an alternative to scraping, you could also use conductive tape in the spot suggested, as seen on my Porst 55/1.2:

JamieFletcher · 10-06-2019, 10:05 AM

Glad I found this, I have 3 lenses and worked out what I thought was going on as one has no paint and works the other two have paint and don't work, off to Amazon now to find some tape (as thin as possible)

thanks all

hahayan · 02-21-2024, 05:15 AM

thx you, it solves the stop down issue on two of my lens...by scraping ( am using K-70)

thx you

i suppose some newbie ( same as me) may benefit from this post greatly

05-09-2015, 09:40 AM	#18
CNunez Senior Member Join Date: Dec 2014 Photos: Gallery Posts: 168	Update: woohoo! I have a working 28mm lens now! Stunning IQ! I have a chinon 28mm f2.8 that behaves exactly like described here. So all it takes is for me to scrape the paint off the mount? Last edited by CNunez; 05-09-2015 at 11:11 AM.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
SMC Pentax-M 50mm 1.4 Won't Stop Down	brofkand	Pentax SLR Lens Discussion	10	08-03-2014 12:32 AM
smc pentax m 50mm 1.7 lens won't stop down	pixxmania	Troubleshooting and Beginner Help	5	09-11-2013 03:50 AM
Non-Pentax K bellows unit - lens won't stop down	timh	Troubleshooting and Beginner Help	7	04-29-2012 01:42 PM
K-x won't stop-down meter while using extension tubes?	MikeS	Pentax DSLR Discussion	37	05-28-2011 10:52 PM
K-7 won't stop down with auto extnsion tube fitted.	katanaismybike	Pentax DSLR Discussion	9	06-07-2010 03:14 PM

04-10-2015, 12:58 PM	#16
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by BigMackCam Can you still use the lens in M and Av modes I usually use it in M mode with exposure based on trial and error when the strange behavior happens. Steve

05-09-2015, 08:39 AM	#17
Skodadriver Site Supporter Join Date: May 2015 Location: Hampshire Photos: Gallery \| Albums Posts: 892	Originally posted by stevebrot You should only short the "data/digital info" contact to avoid sending mixed signals to the body. See image below from Dimitrov's K-mount site: Steve As there is a lip around the outside of the lens on my Chinon 200mm, I scraped the anodise off in the area as shown by Stevebrot's post, (didn't see a need to stick conductive adhesive tape to the lens) and it's now stopping down a treat.

05-16-2015, 02:28 AM	#19
Skodadriver Site Supporter Join Date: May 2015 Location: Hampshire Photos: Gallery \| Albums Posts: 892	Originally posted by CNunez Update: woohoo! I have a working 28mm lens now! Stunning IQ! I have a chinon 28mm f2.8 that behaves exactly like described here. So all it takes is for me to scrape the paint off the mount? It worked for me. I also have a Vivitar 1.5x-22 teleconverter with the mount anodised. I will scrape the paint off to match the required contact and then I should be able to use this at any f stop......I hope.

09-20-2019, 06:01 AM	#21
pepperberry farm amateur dirt farmer Join Date: Dec 2014 Location: probably out in a field somewhere... Photos: Gallery \| Albums Posts: 41,656	as an alternative to scraping, you could also use conductive tape in the spot suggested, as seen on my Porst 55/1.2:

10-06-2019, 10:05 AM	#22
JamieFletcher New Member Join Date: Sep 2019 Location: Lincolnshire Posts: 5	Glad I found this, I have 3 lenses and worked out what I thought was going on as one has no paint and works the other two have paint and don't work, off to Amazon now to find some tape (as thin as possible) thanks all

02-21-2024, 05:15 AM	#23
hahayan New Member Join Date: Jan 2024 Posts: 1	thx you, it solves the stop down issue on two of my lens...by scraping ( am using K-70) thx you i suppose some newbie ( same as me) may benefit from this post greatly

Thread Tools	Search this Thread
	Search this Thread: Advanced Search