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03-10-2016, 12:48 PM   #1
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Are there lenses that are "green button resistant"?

Hey friends,

I know of and use the green button method to meter my manual lenses on K5 II (latest firmware). I got today two from ebay. One porst 35-105 and a Exakta 80-200.
I put on the Porst first and went in the city to test the lens. Choosing aperture and optical preview (turning the shutter button), metering with green button. works flawless.

Back home I tried the Exakta and all of a sudden the green button is not working. Put on 50 1.7 green button does his job. Porst?Still working.
Exakta, nothing. Are there Lenses that are some kind of not working with green button metering, or is the lens broken?

I am glad for any help! Thanks in advanced! Let me know if you need more infos or I missed anything.

03-10-2016, 12:59 PM   #2
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Look at the metal of the lens where it contacts the mount face. Does it contact the mount face or does it stand off a short dsitance? If it does contact the mount face, is it bare metal (shiny silver) or anodised (black/same colour as the rest of the lens exterior)?

If it is anodised, there is a failure to short out one of the pins that permits green button metering and stop down. I have struck this issue with my K-5 with an inherited 28mm Vivitar lens. The cure is electricians' conductive tape applied to the back of the lens where it presses against the data pins in the mount.

If it doesn't contact the mount, you might still be able to put some conductive tape across the pins.

Can you post a picture of the rear of the Exakta lens?
03-10-2016, 12:59 PM   #3
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The back of the lens needs to be unpainted metal in order to short the data pins in the camera mount for the green button to work.
03-10-2016, 12:59 PM   #4
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This may be pertinent

https://www.pentaxforums.com/forums/116-pentax-k-r/271872-tests-plated-vs-pai...r-whats-t.html

03-10-2016, 12:59 PM - 1 Like   #5
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Define "not working" ... is this Exakta a m42 lens to begin with?
03-10-2016, 01:25 PM   #6
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thank you guys!
I made a quick capture with my phone (find it attached). It is a K-Mount no 42.
And I would say it is not painted, isnt it?!

I had before that one only primes that are Manual. I just noticed a little noise appearing when I am shaking the lens in my hand.
Dont know if this is normal but maybe the lens got a damage during transport!?
The aperture, the focus, the locallength sounds and feels right, though, hmm

Last edited by i5_david; 05-02-2016 at 12:13 PM.
03-10-2016, 01:28 PM   #7
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QuoteOriginally posted by johnyates Quote
The back of the lens needs to be unpainted metal in order to short the data pins in the camera mount for the green button to work.
...at least with recent model Pentax bodies. The pin that must have contact is the data pin on the body. See diagram (courtesy of Bojidar Dimitrov's K-mount Page):



Steve
03-10-2016, 01:31 PM   #8
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QuoteOriginally posted by npc Quote
Define "not working"
sorry missed your one... not working as doing nothing with the aperture.
Pushing the green button is actually metering the light and changing in different light situations but its always metering open wide (f4.5) but not adjusting the blades.


OH, forgot: if I attach it to my K1000 the apperture is sending some information to the metering system and if I change the aperture it has influence to the light meter at the side

03-10-2016, 01:31 PM   #9
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QuoteOriginally posted by i5_david Quote
thank you guys!
I made a quick capture with my phone (find it attached). It is a K-Mount no 42.
And I would say it is not painted, isnt it?!

I had before that one only primes that are Manual. I just noticed a little noise appearing when I am shaking the lens in my hand.
Dont know if this is normal but maybe the lens got a damage during transport!?
The aperture, the focus, the locallength sounds and feels right, though, hmm
Hmmmm...the base is definitely bare metal. Does the aperture ring work in that it opens and closes the iris with the lens off the camera? When stopped down, does the actuator lever reliably open/close the iris with no binding or hesitation at all click stops? The action should be "snappy".


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03-10-2016, 01:33 PM   #10
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The next thing to check is that the Exakta's aperture is actually working. Set it halfway between full open and full closed, then flick the aperture stop down lever (the one nearest the protective flange). If nothing moves, or it appears to stay wide open, or moves sluggishly, the problem is in the lens.

I've had this happen with a couple of lenses; turns out their aperture blades were oily and jammed open. An easy service job for a competent technician.
03-10-2016, 01:39 PM   #11
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Nope, the lens seems ok regarding the aperture. If I use it the way you describe it it works just as it should. I can adjust the f Number with the ring and it feels snappy and I can open and reclose the aperture with the little metal pin thing.
03-10-2016, 02:32 PM   #12
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QuoteOriginally posted by i5_david Quote
Nope, the lens seems ok regarding the aperture. If I use it the way you describe it it works just as it should. I can adjust the f Number with the ring and it feels snappy and I can open and reclose the aperture with the little metal pin thing.
Well, that is stranger still.

One last thing...are you sure the lens is fully mounted on the camera? I noticed that it has a very prominent actuator guard similar to certain Vivitar models. With those lenses the ears on the bayonet will engage, but the lens will not fully rotate on. The focus index on the lens should be at the top at 12 o'clock when properly mounted.


Steve
03-10-2016, 02:58 PM   #13
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QuoteOriginally posted by i5_david Quote
sorry missed your one... not working as doing nothing with the aperture.
Pushing the green button is actually metering the light and changing in different light situations but its always metering open wide (f4.5) but not adjusting the blades.


OH, forgot: if I attach it to my K1000 the apperture is sending some information to the metering system and if I change the aperture it has influence to the light meter at the side
That's not exactly what's going on with DSLR's. The K1000 or older non-crippled mounts use an aperture sensing lever to know the position of the aperture ring. DSLR's don't use this. The green button is NOT wide open metering. It stops down to whatever f/stop you have selected (it has no idea what this is - it just pushes the lever and meters).
03-10-2016, 09:39 PM   #14
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Is the auto aperture lever bent? If it is not engaging the corresponding actuator in the camera than it's not going to work properly.

Set the aperture on the ring to the highest f-stop (f22-32). Mount the lens and with the camera off look through the front of the lens. Is it wide open (normal operation) or closed down (something is wrong)?

It's normal for many lenses to have something make noise when you shake them. It depends on the lens.
03-12-2016, 03:15 AM   #15
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QuoteOriginally posted by Not a Number Quote
Mount the lens and with the camera off look through the front of the lens. Is it wide open (normal operation) or closed down (something is wrong)?
If I have the Lens in my hand and turn to f22 the aperture is closed. In the moment I put it back on the camera the aperture will open up wide as you describe "normal operation"

QuoteOriginally posted by stevebrot Quote
are you sure the lens is fully mounted on the camera?
Hello Steve, I double checked this and I am quite sure I mounted it correctly.

QuoteOriginally posted by UncleVanya Quote
The green button is NOT wide open metering.
I know that. What I meant is that the metering is working on the K1000, so that there should be at some point any adjustment that delivers information to the kamera (e.g. the lever is moving and working and the lens seems to be ok on the film camera ).


You guys have serious insight! Thanks for your help! Deeply appreciate it. Do you have any other ideas what this could be?
I attached to other shots of that lens. one is showing the 12 o'clock when mounted.
Attached Images
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Last edited by i5_david; 04-29-2016 at 01:41 PM.
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