Aperture ring FA Limited does not function on K-x

Smolk · 02-20-2017, 05:28 AM

I recently acquired two FA lenses which I used on a K-x to test them. One is the FA 1.9/43, another Tamron AF Macro 2.8/90mm.
In Av mode, I can easily change the aperture by using the scroll wheel on the back of the camera, with the lens aperture ring on the A-setting.

But I cannot change the aperture by using the aperture ring on the lens itself, it remains full open, whatever position I take it, and the viewfinder gives no value for the aperture either. [Aperture ring is set to permitted in the menu.] This value is shown when the lens is switched to A. Not being able to use the aperture ring seems odd.
This applies to both lenses, which seem to be fine, so that I suspect that I'm either missing something, or the camera has an issue. Any ideas?

Not a Number · 02-20-2017, 06:07 AM

I'm not familiar with the K-x control set but it should have a DOF preview. Set it to Optical in the settings menu and when you operated the DOF preview (should be one of the buttons on the K-x) the lens will stop-down.

In manual mode pressing the green button will also stop-down the lens in order to take a TTL meter reading.

Auto/Open aperture metering has been a feature of SLRs for decades. The iris will remain wide open except when using the DOF preview or during the exposure.

**boriscleto** · 02-20-2017, 06:25 AM

Set the Green button in M mode to Optical Preview...

Smolk · 02-20-2017, 07:02 AM

Originally posted by dcshooter

This is normal behavior.

Google "crippled K mount" for the long explanation. Quick and dirty: when using the ring, you have to use the green button for metering, since newer bodies are not mechanically aperture coupled.

Ah, I was under the impression this only applied to K- and M-lenses. Always imagined A-lenses would work normally in Av-mode—which they do, just not with the aperture ring. Thanks for the clarification. It is nicer anyway to have the aperture value in the viewfinder.

Quote:

Set the Green button in M mode to Optical Preview...

Don't seem to find this option under the Green button menu item.

mcgregni · 02-20-2017, 07:07 AM

FA series lenses are 'automatic aperture', without manual option. This means that the aperture remains fixed wide open always until the moment of exposure, when it stops down to that set on the lens aperture ring. This is to help with focusing and composing by always letting in the most possible light. So turning the ring has no noticeable effect.

As already explained, when not in the A position the lens functions as a K or M type, needing the stop - down process to meter.

For info, K, M, F, DA and D FA lenses are all automatic aperture as well. We have to go back to the Takumars and M42 mount I believe to get manual aperture lenses. I have a Tamron Adaptall 135mm from 1975 that has a handy M/A switch, allowing in the M position a fully manual aperture, which is useful when using basic extension tubes (when the camera can't stop down the lens). It gets very dark through the viewfinder though when trying to shoot close up shots at F16 !

RMabo · 02-20-2017, 07:23 AM

About using the Green button on the K-x, please note that K-x does not have a separate DOF-button but the Green button can be programmed (in the settings menu) to be a DOF-preview button, but if you change the Green button to DOF-preview then you loose the Green button functionality.

mcgregni · 02-20-2017, 07:31 AM

DOF preview is almost the same thing as stop-down metering, at least the physical process. It stops the lens down for an assessment through the view finder .... I'm not sure if DOF preview performs any metering?

Holding the switch will hold the aperture in position, whereas green button stop-down is a 'one shot' action regardless of how long you press the button for. These days, with digital, I wonder if DOF preview has gone the way of the hand held exposure meter ....? It's the only way to see the true DOF effect in the viewfinder .... Otherwise we use digital preview on the LCD our just take a test shot now.

**boriscleto** · 02-20-2017, 08:05 AM

Originally posted by smolk

don't seem to find this option under the green button menu item.

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stevebrot · 02-20-2017, 08:24 AM

Originally posted by Smolk

But I cannot change the aperture by using the aperture ring on the lens itself, it remains full open, whatever position I take it, and the viewfinder gives no value for the aperture either. [Aperture ring is set to permitted in the menu.] This value is shown when the lens is switched to A. Not being able to use the aperture ring seems odd.
This applies to both lenses, which seem to be fine, so that I suspect that I'm either missing something, or the camera has an issue. Any ideas?

There are many good suggestions above, but I figure it is useful to summarize:

What you are seeing is normal
The iris diaphragm on K-mount lenses remains fully open until exposure time or unless optical depth-of-field preview is active. This is this is true for all K-mount cameras and almost all K-mount lenses regardless of whether they have an aperture ring. The full name of this feature is "auto aperture actuation" and is common to almost all modern lenses except for those with "manual" or "pre-set" apertures.
The "A" position on your FA lenses' aperture ring supports a feature whose full name is "auto aperture control". When in that position, the aperture may be controlled by the body rather than the ring.
When the aperture ring is not in the "A" position, your lens behaves the same as earlier K and M-series lenses, meaning that you are limited to stop-down metering on your K-x and that "F---" shows in the viewfinder and LCD displays instead of an aperture value.
The "A" position is usually the best position for you to leave the aperture ring when shooting with your K-x. Exceptions would be with film camera bodies or accessories lacking contacts on the mount face (bellows, extension rings, and such).
Your two new lenses are compatible with every K-mount body (film and digital) ever made

Details about how to do stop-down metering on your K-x are good things to know, but not pertinent to lenses having having an aperture ring with the "A" position.

Steve

Not a Number · 02-20-2017, 08:28 AM

Originally posted by mcgregni

DOF preview is almost the same thing as stop-down metering, at least the physical process. It stops the lens down for an assessment through the view finder .... I'm not sure if DOF preview performs any metering?

It does on the "flagship" models (K10D, K20D, K-7, K-5/ii/iis,K-3,K-3ii and K-1). On non-A lenses in manual it turns on the EV bar and you can center the metering reading by adjusting the aperture ring or setting the shutter speed with the eDial.

mcgregni · 02-20-2017, 11:33 AM

OK, good to know, thanks

stevebrot · 02-20-2017, 12:12 PM

Originally posted by Not a Number

On non-A lenses in manual it turns on the EV bar and you can center the metering reading by adjusting the aperture ring or setting the shutter speed with the eDial.

Originally posted by mcgregni

OK, good to know, thanks

Yes, it is a super cool feature that requires much more effort to describe than to actually use.

Steve

02-20-2017, 05:28 AM	#1
Smolk Pentaxian Join Date: Feb 2010 Location: Eerbeek Photos: Gallery \| Albums Posts: 1,857	Aperture ring FA Limited does not function on K-x I recently acquired two FA lenses which I used on a K-x to test them. One is the FA 1.9/43, another Tamron AF Macro 2.8/90mm. In Av mode, I can easily change the aperture by using the scroll wheel on the back of the camera, with the lens aperture ring on the A-setting. But I cannot change the aperture by using the aperture ring on the lens itself, it remains full open, whatever position I take it, and the viewfinder gives no value for the aperture either. [Aperture ring is set to permitted in the menu.] This value is shown when the lens is switched to A. Not being able to use the aperture ring seems odd. This applies to both lenses, which seem to be fine, so that I suspect that I'm either missing something, or the camera has an issue. Any ideas?

02-20-2017, 07:07 AM	#5
mcgregni Veteran Member Join Date: Sep 2012 Location: Surrey, England Posts: 2,603	FA series lenses are 'automatic aperture', without manual option. This means that the aperture remains fixed wide open always until the moment of exposure, when it stops down to that set on the lens aperture ring. This is to help with focusing and composing by always letting in the most possible light. So turning the ring has no noticeable effect. As already explained, when not in the A position the lens functions as a K or M type, needing the stop - down process to meter. For info, K, M, F, DA and D FA lenses are all automatic aperture as well. We have to go back to the Takumars and M42 mount I believe to get manual aperture lenses. I have a Tamron Adaptall 135mm from 1975 that has a handy M/A switch, allowing in the M position a fully manual aperture, which is useful when using basic extension tubes (when the camera can't stop down the lens). It gets very dark through the viewfinder though when trying to shoot close up shots at F16 ! Last edited by mcgregni; 02-20-2017 at 07:16 AM.

02-20-2017, 08:24 AM	#9
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by Smolk But I cannot change the aperture by using the aperture ring on the lens itself, it remains full open, whatever position I take it, and the viewfinder gives no value for the aperture either. [Aperture ring is set to permitted in the menu.] This value is shown when the lens is switched to A. Not being able to use the aperture ring seems odd. This applies to both lenses, which seem to be fine, so that I suspect that I'm either missing something, or the camera has an issue. Any ideas? There are many good suggestions above, but I figure it is useful to summarize: What you are seeing is normal The iris diaphragm on K-mount lenses remains fully open until exposure time or unless optical depth-of-field preview is active. This is this is true for all K-mount cameras and almost all K-mount lenses regardless of whether they have an aperture ring. The full name of this feature is "auto aperture actuation" and is common to almost all modern lenses except for those with "manual" or "pre-set" apertures. The "A" position on your FA lenses' aperture ring supports a feature whose full name is "auto aperture control". When in that position, the aperture may be controlled by the body rather than the ring. When the aperture ring is not in the "A" position, your lens behaves the same as earlier K and M-series lenses, meaning that you are limited to stop-down metering on your K-x and that "F---" shows in the viewfinder and LCD displays instead of an aperture value. The "A" position is usually the best position for you to leave the aperture ring when shooting with your K-x. Exceptions would be with film camera bodies or accessories lacking contacts on the mount face (bellows, extension rings, and such). Your two new lenses are compatible with every K-mount body (film and digital) ever made Details about how to do stop-down metering on your K-x are good things to know, but not pertinent to lenses having having an aperture ring with the "A" position. Steve

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02-20-2017, 06:07 AM	#2
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	I'm not familiar with the K-x control set but it should have a DOF preview. Set it to Optical in the settings menu and when you operated the DOF preview (should be one of the buttons on the K-x) the lens will stop-down. In manual mode pressing the green button will also stop-down the lens in order to take a TTL meter reading. Auto/Open aperture metering has been a feature of SLRs for decades. The iris will remain wide open except when using the DOF preview or during the exposure.

02-20-2017, 06:25 AM	#3
boriscleto Loyal Site Supporter Join Date: Dec 2009 Location: North Syracuse, NY Photos: Gallery Posts: 16,475	Set the Green button in M mode to Optical Preview...

02-20-2017, 07:02 AM	#4
Smolk Pentaxian Join Date: Feb 2010 Location: Eerbeek Photos: Gallery \| Albums Posts: 1,857 Original Poster	Originally posted by dcshooter This is normal behavior. Google "crippled K mount" for the long explanation. Quick and dirty: when using the ring, you have to use the green button for metering, since newer bodies are not mechanically aperture coupled. Ah, I was under the impression this only applied to K- and M-lenses. Always imagined A-lenses would work normally in Av-mode—which they do, just not with the aperture ring. Thanks for the clarification. It is nicer anyway to have the aperture value in the viewfinder. Quote: Set the Green button in M mode to Optical Preview... Don't seem to find this option under the Green button menu item.

02-20-2017, 07:23 AM	#6
RMabo Veteran Member Join Date: Jul 2007 Location: Sweden Posts: 845	About using the Green button on the K-x, please note that K-x does not have a separate DOF-button but the Green button can be programmed (in the settings menu) to be a DOF-preview button, but if you change the Green button to DOF-preview then you loose the Green button functionality.

02-20-2017, 07:31 AM	#7
mcgregni Veteran Member Join Date: Sep 2012 Location: Surrey, England Posts: 2,603	DOF preview is almost the same thing as stop-down metering, at least the physical process. It stops the lens down for an assessment through the view finder .... I'm not sure if DOF preview performs any metering? Holding the switch will hold the aperture in position, whereas green button stop-down is a 'one shot' action regardless of how long you press the button for. These days, with digital, I wonder if DOF preview has gone the way of the hand held exposure meter ....? It's the only way to see the true DOF effect in the viewfinder .... Otherwise we use digital preview on the LCD our just take a test shot now.

02-20-2017, 08:05 AM	#8
boriscleto Loyal Site Supporter Join Date: Dec 2009 Location: North Syracuse, NY Photos: Gallery Posts: 16,475	Originally posted by smolk don't seem to find this option under the green button menu item.

02-20-2017, 08:28 AM	#10
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	Originally posted by mcgregni DOF preview is almost the same thing as stop-down metering, at least the physical process. It stops the lens down for an assessment through the view finder .... I'm not sure if DOF preview performs any metering? It does on the "flagship" models (K10D, K20D, K-7, K-5/ii/iis,K-3,K-3ii and K-1). On non-A lenses in manual it turns on the EV bar and you can center the metering reading by adjusting the aperture ring or setting the shutter speed with the eDial.

02-20-2017, 11:33 AM	#11
mcgregni Veteran Member Join Date: Sep 2012 Location: Surrey, England Posts: 2,603	OK, good to know, thanks

02-20-2017, 12:12 PM	#12
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by Not a Number On non-A lenses in manual it turns on the EV bar and you can center the metering reading by adjusting the aperture ring or setting the shutter speed with the eDial. Originally posted by mcgregni OK, good to know, thanks Yes, it is a super cool feature that requires much more effort to describe than to actually use. Steve