How to make ANY non-A K mount lens into an A lens.

troglodyte · 11-14-2010, 02:50 PM

Stratman,
That's exactly what I thought. K/M lenses will always stay wide open no matter what and when the shutter is pressed will NOT stop down to the ring setting on the lens. Even though as Jolepp says, the camera will show the correct metering but

Last edited by troglodyte; 11-14-2010 at 02:57 PM.

troglodyte · 11-14-2010, 02:53 PM

won't move the lever on the lens. That's what confused the hell out of me by what Lowell said. He made it sound like to me M and K lenses were working like A lenses but just setting the f-stop on the aperture ring rather than the camera dials. But to the

troglodyte · 11-14-2010, 02:56 PM

I knew the only way to get K and M lenses to meter was to put them in M mode, set the aperture on the lens, hit the green button and snap the pic. Which is why I use m42 lenses which allow Av mode since they stop down on the fly.
Unless I was doing

troglodyte · 11-14-2010, 03:03 PM

with my camera and not how to use K and M lenses? Or maybe the lens was broken? But that's how the wonderful crippled k-mount handles the k/m lenses?

newarts · 11-14-2010, 03:08 PM

Quote:

...That's what confused the hell out of me by what Lowell said. He made it sound like to me M and K lenses were working like A lenses but just setting the f-stop on the aperture ring ..

I think all Pentax cameras don't behave the same in this. As I recall, when I pressed the K100D green button equivalent (AKA Optical Review for DoF) , the aperture lever moved and exposure was computed. This may not be the case for K-x.

jolepp · 11-14-2010, 03:13 PM

Originally posted by troglodyte:

Stratman,
That's exactly what I thought. K/M lenses will always stay wide open no matter what and when then shutter is pressed will NOT stop down to the ring setting on the lens. Even though as Jolepp says, the camera will show the correct metering but won't move the lever on the lens. That's what confused the hell out of me by what Lowell said. He made it sound like to me M and K lenses were working like A lenses but just setting the f-stop on the aperture ring rather than the camera dials. But to the I knew the only way to get K and M lenses to meter was to put them in M mode, set the aperture on the lens, hit the green button and snap the pic. Which is why I use m42 lenses which allow Av mode since they stop down on the fly

M lenses get stopped down in M-mode for exposure, and the aperture mechanism is operated at exposure in Av too (this can be seen looking into the lens), although the body somehow manages to expose fully open, which means it does the actual exposure either before or after operating the aperture mechanism. (Here I'm generalizing what I see with the k-x).

I don't think M42 lenses are stopping down on the fly, they merely stay at the set aperture all the time (and hence Av works with them as it does).

[BTW, your post seems to be broken into multiple two line chunks?]

jolepp · 11-14-2010, 03:20 PM

Originally posted by newarts

I think all Pentax cameras don't behave the same in this. As I recall, when I pressed the K100D green button equivalent (AKA Optical Review for DoF) , the aperture lever moved and exposure was computed. This may not be the case for K-x.

In M-mode with an M-lens the k-x does just this. Without a lens or with a non-conductive base lens mounted (both my M42s are like this) it just sets the exposure time without bothering to operate the aperture mechanism. Without the lens this can be readily seen (not happening) with one of my M42s mounted this I can hear this (or actually the noise from operating the aperture and raising the mirror is absent :-).

troglodyte · 11-14-2010, 03:20 PM

newarts,There's tons of K and M glass I'd love to get.But I just couldn'd get then to work like they do on a K1000 35mm.On my k7 I was only able to use them in M with stopdown metering or in Av with real funky always wide open.The camera wouldn't close it

troglodyte · 11-14-2010, 03:24 PM

Jolepp, Whatever is going on, the camera is ignoring the aperture at the final stage with my k7 and wasn't taking the correct picture. The only way I was getting correct pics was in M with stopdown metering using the green button.
I know I'm probably not

troglodyte · 11-14-2010, 03:27 PM

not using the right term. What I mean is the lens aperture can't move with the m42 lens. So the camera can't try any auto so it does the correct metering. Unlike with the K and M which can move. Apparently have Mr cripple K-mount and aren't playing nice.

troglodyte · 11-14-2010, 03:30 PM

I love you Pentax for making the better mount!
Oh yeah, I'm on Boost Mobile. I get unlimited voice and text. But, unlimited doesn't mean unreasonable. So more than the twitter posts is abusing my 'unlimited'!

newarts · 11-14-2010, 05:07 PM

Originally posted by jolepp

In M-mode with an M-lens the k-x does just this. Without a lens or with a non-conductive base lens mounted (both my M42s are like this) it just sets the exposure time without bothering to operate the aperture mechanism. Without the lens this can be readily seen (not happening) with one of my M42s mounted this I can hear this (or actually the noise from operating the aperture and raising the mirror is absent :-).

You say ".. the k-x does just this." What is "this"? Do you mean with an M lens the K-x moves the aperture lever to set exposure when the green button is pushed in M mode? If so, does it also move the aperture lever to set exposure in other modes with an M lens in M mode?

Dave

jolepp · 11-14-2010, 05:57 PM

Originally posted by newarts

You say ".. the k-x does just this." What is "this"? Do you mean with an M lens the K-x moves the aperture lever to set exposure when the green button is pushed in M mode? If so, does it also move the aperture lever to set exposure in other modes with an M lens in M mode?

Dave

M-mode & M-lens : On green button press it releases the aperture lever (the lens goes to the position set on the ring), meters and returns the lever to fully open. For some reason mirror goes up too while aperture is closed. Stop-down with exposure as well.

Av-mode & M-lens: continuous metering with aperture open, exposure results are the same regardless of aperture ring position although I can see aperture closing to the position set on the ring trough the lens when I press shutter fully. Green button has no effect (with its default setting at least).

With an M-lens other mode dial positions than M result in Av-mode being used. (Except movie, which somewhat surprisingly works with full aperture control with the ring :-)

alohadave · 11-14-2010, 07:29 PM

Originally posted by cyclone3d

Let the discussion begin.

When I finish up getting everything worked out, I will post a full diagram.

I want to get your thoughts before I go and give it away.

What you really need to do is hack the firmware to allow the camera to change the aperture lever movement based on what lens is detected on the mount.

cyclone3d · 11-14-2010, 09:23 PM

Originally posted by alohadave

What you really need to do is hack the firmware to allow the camera to change the aperture lever movement based on what lens is detected on the mount.

It would be more feasable to just hack it to have two seperate aperature curve settings - one for real A lenses and one for converted A lenses.

I'll have to look into the possibility of doing this once I get a chance.

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11-14-2010, 02:50 PM	#46
troglodyte Veteran Member Join Date: Jul 2010 Location: Oz Posts: 408	Stratman, That's exactly what I thought. K/M lenses will always stay wide open no matter what and when the shutter is pressed will NOT stop down to the ring setting on the lens. Even though as Jolepp says, the camera will show the correct metering but Last edited by troglodyte; 11-14-2010 at 02:57 PM.

11-14-2010, 02:53 PM	#47
troglodyte Veteran Member Join Date: Jul 2010 Location: Oz Posts: 408	won't move the lever on the lens. That's what confused the hell out of me by what Lowell said. He made it sound like to me M and K lenses were working like A lenses but just setting the f-stop on the aperture ring rather than the camera dials. But to the

11-14-2010, 02:56 PM	#48
troglodyte Veteran Member Join Date: Jul 2010 Location: Oz Posts: 408	I knew the only way to get K and M lenses to meter was to put them in M mode, set the aperture on the lens, hit the green button and snap the pic. Which is why I use m42 lenses which allow Av mode since they stop down on the fly. Unless I was doing

11-14-2010, 03:03 PM	#49
troglodyte Veteran Member Join Date: Jul 2010 Location: Oz Posts: 408	with my camera and not how to use K and M lenses? Or maybe the lens was broken? But that's how the wonderful crippled k-mount handles the k/m lenses?

11-14-2010, 03:08 PM	#50
newarts Inactive Account Join Date: Dec 2008 Location: Ames, Iowa, USA Photos: Albums Posts: 2,965	Quote: ...That's what confused the hell out of me by what Lowell said. He made it sound like to me M and K lenses were working like A lenses but just setting the f-stop on the aperture ring .. I think all Pentax cameras don't behave the same in this. As I recall, when I pressed the K100D green button equivalent (AKA Optical Review for DoF) , the aperture lever moved and exposure was computed. This may not be the case for K-x.

11-14-2010, 03:13 PM	#51
jolepp Veteran Member Join Date: Oct 2010 Location: Finland Photos: Albums Posts: 3,196	Originally posted by troglodyte: Stratman, That's exactly what I thought. K/M lenses will always stay wide open no matter what and when then shutter is pressed will NOT stop down to the ring setting on the lens. Even though as Jolepp says, the camera will show the correct metering but won't move the lever on the lens. That's what confused the hell out of me by what Lowell said. He made it sound like to me M and K lenses were working like A lenses but just setting the f-stop on the aperture ring rather than the camera dials. But to the I knew the only way to get K and M lenses to meter was to put them in M mode, set the aperture on the lens, hit the green button and snap the pic. Which is why I use m42 lenses which allow Av mode since they stop down on the fly M lenses get stopped down in M-mode for exposure, and the aperture mechanism is operated at exposure in Av too (this can be seen looking into the lens), although the body somehow manages to expose fully open, which means it does the actual exposure either before or after operating the aperture mechanism. (Here I'm generalizing what I see with the k-x). I don't think M42 lenses are stopping down on the fly, they merely stay at the set aperture all the time (and hence Av works with them as it does). [BTW, your post seems to be broken into multiple two line chunks?]

11-14-2010, 03:20 PM	#52
jolepp Veteran Member Join Date: Oct 2010 Location: Finland Photos: Albums Posts: 3,196	Originally posted by newarts I think all Pentax cameras don't behave the same in this. As I recall, when I pressed the K100D green button equivalent (AKA Optical Review for DoF) , the aperture lever moved and exposure was computed. This may not be the case for K-x. In M-mode with an M-lens the k-x does just this. Without a lens or with a non-conductive base lens mounted (both my M42s are like this) it just sets the exposure time without bothering to operate the aperture mechanism. Without the lens this can be readily seen (not happening) with one of my M42s mounted this I can hear this (or actually the noise from operating the aperture and raising the mirror is absent :-).

11-14-2010, 03:20 PM	#53
troglodyte Veteran Member Join Date: Jul 2010 Location: Oz Posts: 408	newarts,There's tons of K and M glass I'd love to get.But I just couldn'd get then to work like they do on a K1000 35mm.On my k7 I was only able to use them in M with stopdown metering or in Av with real funky always wide open.The camera wouldn't close it

11-14-2010, 03:24 PM	#54
troglodyte Veteran Member Join Date: Jul 2010 Location: Oz Posts: 408	Jolepp, Whatever is going on, the camera is ignoring the aperture at the final stage with my k7 and wasn't taking the correct picture. The only way I was getting correct pics was in M with stopdown metering using the green button. I know I'm probably not

11-14-2010, 03:27 PM	#55
troglodyte Veteran Member Join Date: Jul 2010 Location: Oz Posts: 408	not using the right term. What I mean is the lens aperture can't move with the m42 lens. So the camera can't try any auto so it does the correct metering. Unlike with the K and M which can move. Apparently have Mr cripple K-mount and aren't playing nice.

11-14-2010, 03:30 PM	#56
troglodyte Veteran Member Join Date: Jul 2010 Location: Oz Posts: 408	I love you Pentax for making the better mount! Oh yeah, I'm on Boost Mobile. I get unlimited voice and text. But, unlimited doesn't mean unreasonable. So more than the twitter posts is abusing my 'unlimited'!

11-14-2010, 05:07 PM	#57
newarts Inactive Account Join Date: Dec 2008 Location: Ames, Iowa, USA Photos: Albums Posts: 2,965	Originally posted by jolepp In M-mode with an M-lens the k-x does just this. Without a lens or with a non-conductive base lens mounted (both my M42s are like this) it just sets the exposure time without bothering to operate the aperture mechanism. Without the lens this can be readily seen (not happening) with one of my M42s mounted this I can hear this (or actually the noise from operating the aperture and raising the mirror is absent :-). You say ".. the k-x does just this." What is "this"? Do you mean with an M lens the K-x moves the aperture lever to set exposure when the green button is pushed in M mode? If so, does it also move the aperture lever to set exposure in other modes with an M lens in M mode? Dave

11-14-2010, 05:57 PM	#58
jolepp Veteran Member Join Date: Oct 2010 Location: Finland Photos: Albums Posts: 3,196	Originally posted by newarts You say ".. the k-x does just this." What is "this"? Do you mean with an M lens the K-x moves the aperture lever to set exposure when the green button is pushed in M mode? If so, does it also move the aperture lever to set exposure in other modes with an M lens in M mode? Dave M-mode & M-lens : On green button press it releases the aperture lever (the lens goes to the position set on the ring), meters and returns the lever to fully open. For some reason mirror goes up too while aperture is closed. Stop-down with exposure as well. Av-mode & M-lens: continuous metering with aperture open, exposure results are the same regardless of aperture ring position although I can see aperture closing to the position set on the ring trough the lens when I press shutter fully. Green button has no effect (with its default setting at least). With an M-lens other mode dial positions than M result in Av-mode being used. (Except movie, which somewhat surprisingly works with full aperture control with the ring :-)

11-14-2010, 07:29 PM	#59
alohadave Veteran Member Join Date: Jan 2008 Location: Quincy, MA Photos: Gallery \| Albums Posts: 2,024	Originally posted by cyclone3d Let the discussion begin. When I finish up getting everything worked out, I will post a full diagram. I want to get your thoughts before I go and give it away. What you really need to do is hack the firmware to allow the camera to change the aperture lever movement based on what lens is detected on the mount.

11-14-2010, 09:23 PM	#60
cyclone3d Veteran Member Join Date: Nov 2010 Location: Huntsville, Alabama Posts: 511 Original Poster	Originally posted by alohadave What you really need to do is hack the firmware to allow the camera to change the aperture lever movement based on what lens is detected on the mount. It would be more feasable to just hack it to have two seperate aperature curve settings - one for real A lenses and one for converted A lenses. I'll have to look into the possibility of doing this once I get a chance.