Could Av, Tv, etc. potentially be enabled with Pentax-M lenses through firmware?

maltfalc · 08-26-2015, 06:31 PM

Just a random thought I had. Currently, M lenses only work in manual mode because the camera has no way to know the difference in light levels wide open vs stopped down. Why not set the aperture ring to the smallest f-stop and use one of the buttons or a menu item to take a series of meter readings while closing down the iris to get the info the camera needs to meter wide open? one extra button press is a small price to pay for enabling all modes with M lenses.

MadMathMind · 08-26-2015, 06:37 PM

The problem is that the camera has no idea what the aperture is like it does for A series and later lenses. The camera measures wide open. Let's say that's f/4. Then it says "Oh, I'm going to use f/8, so I need to double my exposure time to make the light equivalent." With an M lens, the camera has no way to know what the aperture is. It doesn't know it measured at f/4 and doesn't know it will be set to f/8.

The camera does know the difference in light levels wide open vs. shooting aperture but it needs to stop the lens down and then take the metering. It just doesn't know the difference in aperture between those two settings. If the light were perfectly constant, it could deduce the relative difference in f-stop by computing the ratio of light level, but if the user changes the f-stop with the ring, that calculation will be incorrect. And the camera has no way to know that the user made this change.

Adam · 08-26-2015, 06:40 PM

Originally posted by maltfalc

Just a random thought I had. Currently, M lenses only work in manual mode because the camera has no way to know the difference in light levels wide open vs stopped down. Why not set the aperture ring to the smallest f-stop and use one of the buttons or a menu item to take a series of meter readings while closing down the iris to get the info the camera needs to meter wide open? one extra button press is a small price to pay for enabling all modes with M lenses.

Av will work with lenses that have manual diaphragms, but certainly not Tv as that would require the camera to be able to set the aperture. Supporting Av natively would require the "non-crippled mount" / aperture linkage.

maltfalc · 08-26-2015, 07:03 PM

ok, you're both just restating the problem with using m lenses and not getting my proposed solution. the idea is to have the camera take a series of meter readings not while the lens is closed down, but rather while it's transitioning from wide open to closed down, so that it can calculate the specific positions at which there is a 1 stop difference in light levels. the aperture ring would be kept at the smallest aperture, just like a pentax-a lens in a-mode. it'd be t-stops rather than f-stops technically, but close enough, and the max aperture could be set in a prompt at startup just like focal length is for sr.

MadMathMind · 08-26-2015, 07:27 PM

Originally posted by maltfalc

ok, you're both just restating the problem with using m lenses and not getting my proposed solution. the idea is to have the camera take a series of meter readings not while the lens is closed down, but rather while it's transitioning from wide open to closed down, so that it can calculate the specific positions at which there is a 1 stop difference in light levels.

This is not possible because the meter is located in the pentaprism. Once the mirror goes up, no light can reach the meter.

This is why when you use "Mirror Up" mode it takes two shutter presses--one to put the mirror up, one to fire. The meter can't operate while the mirror is up so it would not work to have the mirror up at all times. Note that when you put the mirror up, the exposure is locked.

stevebrot · 08-26-2015, 07:34 PM

Originally posted by maltfalc

the idea is to have the camera take a series of meter readings not while the lens is closed down, but rather while it's transitioning from wide open to closed down, so that it can calculate the specific positions at which there is a 1 stop difference in light levels

Oh, you mean when the green button is pressed? That is the only way it could work is with a manual stop-down. As noted above, the shutter sequence begins with mirror up. There is also the problem that many aperture mechanisms are poorly modulated, meaning that they stop down, even full down, with very little movement of the actuator lever.

Steve

Fogel70 · 08-26-2015, 08:09 PM - **1 Like**

Originally posted by maltfalc

ok, you're both just restating the problem with using m lenses and not getting my proposed solution. the idea is to have the camera take a series of meter readings not while the lens is closed down, but rather while it's transitioning from wide open to closed down, so that it can calculate the specific positions at which there is a 1 stop difference in light levels. the aperture ring would be kept at the smallest aperture, just like a pentax-a lens in a-mode. it'd be t-stops rather than f-stops technically, but close enough, and the max aperture could be set in a prompt at startup just like focal length is for sr.

But what should the camera do with this information? As the stopping down of the aperture goes very quickly it will be difficult to get a accurate readings from the meter during stop down.

The camera will still not know in which position you set the aperture before the lens is stopped down. The aperture will always be fully stopped down before a images is captured, so you always have to set the aperture on then lens to the f-stop you want to use for the image.

The only extra you would get by entering largest aperture is that exif could be updated with an approximation of the aperture used.

Eyewanders · 08-26-2015, 08:13 PM

I'm not sure this is even a problem. You're able to use a near 50 year old series of lenses on brand new camera technology with shake reduction and you can even meter properly using the Green Button. I've never thought a solution was in order for this.

**K-Three** · 08-26-2015, 08:47 PM - **1 Like**

I think that Maltfalc's idea is to set something up to pre-calibrate the lens to the body when you put it on, possibly have a "library" of lenses in the camera's memory so when you put one on you pick the lens (similar to putting a non-AF lens on and telling the SR how long it is).
The challenge I see is that the lens is closed down during exposure by the camera releasing the aperture arm on the lens, and letting the lens mechanism close down to the preset aperture. Think of this as closing down an old pre-set lens just before exposure, you rotate the ring until it stops, and don't have any indication of where that point is, you are just turning until it stops. The camera does not change its arm motion, it just gets it out of the way so the lens can stop down to where its set. There is nothing to calibrate in the motion. It is an on/off motion, no subtle degrees of movement involved.

The only indication to a camera body of where the aperture is set on the old M and K lenses is the tab outside of the bayonet, that coupled to a similar tab in the old film bodies. This is the "Crippled" part of the modern K-mount. The modern bodies don't have this coupling to transfer the lens f-stop data to the metering system.
It is a shame in some ways, likely a cost cutting move, possibly they needed that room in the mirror box for something else, but really for those of us that remember the change from screw to K-mount, not much different. You always had to do stop-down metering with screw mount lenses. Going to the "Modern", open-aperture K-mounts was an "enlightening" experience.
Be grateful you can painlessly mount all those old lenses and use them at all.

**UncleVanya** · 08-26-2015, 09:02 PM

Originally posted by MadMathMind

This is not possible because the meter is located in the pentaprism. Once the mirror goes up, no light can reach the meter.

This is why when you use "Mirror Up" mode it takes two shutter presses--one to put the mirror up, one to fire. The meter can't operate while the mirror is up so it would not work to have the mirror up at all times. Note that when you put the mirror up, the exposure is locked.

How does LiveView meter then?

MadMathMind · 08-26-2015, 09:09 PM

Originally posted by UncleVanya

How does LiveView meter then?

The sensor measures the amount of light electronically and adjusts its drive accordingly. One advantage to live view is that the entire scene is used, as opposed to a discrete number of metering segments like in optical view.

**UncleVanya** · 08-26-2015, 09:14 PM

Originally posted by MadMathMind

The sensor measures the amount of light electronically and adjusts its drive accordingly. One advantage to live view is that the entire scene is used, as opposed to a discrete number of metering segments like in optical view.

My point is that the adjustments could be done using the same mechanism... there are other practical difficulties but metering does not seem like the main issue.

maltfalc · 08-26-2015, 09:42 PM

Originally posted by MadMathMind

This is not possible because the meter is located in the pentaprism. Once the mirror goes up, no light can reach the meter.

This is why when you use "Mirror Up" mode it takes two shutter presses--one to put the mirror up, one to fire. The meter can't operate while the mirror is up so it would not work to have the mirror up at all times. Note that when you put the mirror up, the exposure is locked.

who said anything about the mirror being up? that's not in any way required for this.

---------- Post added 08-26-15 at 11:48 PM ----------

Originally posted by stevebrot

Oh, you mean when the green button is pressed? That is the only way it could work is with a manual stop-down. As noted above, the shutter sequence begins with mirror up. There is also the problem that many aperture mechanisms are poorly modulated, meaning that they stop down, even full down, with very little movement of the actuator lever.

Steve

neither the shutter nor the mirror would be involved in calibrating the camera to a lens. the max aperture would be entered manually when the lens is first mounted, the aperture lever would be run through it's full range of movement and the changes in light level recorded in order to map a specific location of the lever to a specific t-stop.

---------- Post added 08-26-15 at 11:57 PM ----------

Originally posted by Fogel70

But what should the camera do with this information? As the stopping down of the aperture goes very quickly it will be difficult to get a accurate readings from the meter during stop down.

The camera will still not know in which position you set the aperture before the lens is stopped down. The aperture will always be fully stopped down before a images is captured, so you always have to set the aperture on then lens to the f-stop you want to use for the image.

The only extra you would get by entering largest aperture is that exif could be updated with an approximation of the aperture used.

you leave the ring at the smallest aperture. the aperture doesn't need to be fully stopped down. it isn't when using pentax-a or newer lenses. the lens will be stopped down to multiple positions with a meter reading at each then the camera will map out the non-linear movement of the aperture and use that map to determine the correct position of the aperture lever while shooting.

---------- Post added 08-27-15 at 12:07 AM ----------

Originally posted by K-Three

I think that Maltfalc's idea is to set something up to pre-calibrate the lens to the body when you put it on, possibly have a "library" of lenses in the camera's memory so when you put one on you pick the lens (similar to putting a non-AF lens on and telling the SR how long it is).
The challenge I see is that the lens is closed down during exposure by the camera releasing the aperture arm on the lens, and letting the lens mechanism close down to the preset aperture. Think of this as closing down an old pre-set lens just before exposure, you rotate the ring until it stops, and don't have any indication of where that point is, you are just turning until it stops. The camera does not change its arm motion, it just gets it out of the way so the lens can stop down to where its set. There is nothing to calibrate in the motion. It is an on/off motion, no subtle degrees of movement involved.

The only indication to a camera body of where the aperture is set on the old M and K lenses is the tab outside of the bayonet, that coupled to a similar tab in the old film bodies. This is the "Crippled" part of the modern K-mount. The modern bodies don't have this coupling to transfer the lens f-stop data to the metering system.
It is a shame in some ways, likely a cost cutting move, possibly they needed that room in the mirror box for something else, but really for those of us that remember the change from screw to K-mount, not much different. You always had to do stop-down metering with screw mount lenses. Going to the "Modern", open-aperture K-mounts was an "enlightening" experience.
Be grateful you can painlessly mount all those old lenses and use them at all.

the aperture adjusting mechanism in the camera is not a simple on/off motion. with newer lenses it moves the lever to a specific location for any given f-stop setting. the whole point of my idea is to give the camera a way to teach itself what lever position corresponds to which f(or t)-stop setting.

---------- Post added 08-27-15 at 12:14 AM ----------

Originally posted by UncleVanya

My point is that the adjustments could be done using the same mechanism... there are other practical difficulties but metering does not seem like the main issue.

no need even for that. a modified version of green button stopped down metering is all that's needed, with meter readings taken at 10 percent stopped down, 20 percent, etc. instead of just at 100%, then just a bit of connect the dots to calculate the full curve.

fwcetus · 08-27-2015, 06:41 AM

Originally posted by chickentender

I'm not sure this is even a problem. You're able to use a near 50 year old series of lenses on brand new camera technology with shake reduction and you can even meter properly using the Green Button. I've never thought a solution was in order for this.

I'd agree with all of that ~except~ "and you can even meter properly using the Green Button" -- I think the metering is actually quite poor with K and M lenses (and, I assume M42 lenses, too).

Having to use the Green Button is not a huge inconvenience, all things considered, but the non-linearity of metering is very frustrating to me (YMMV).

wombat2go · 08-27-2015, 07:07 AM

Originally posted by maltfalc

the aperture adjusting mechanism in the camera is not a simple on/off motion. with newer lenses it moves the lever to a specific location for any given f-stop setting. the whole point of my idea is to give the camera a way to teach itself what lever position corresponds to which f(or t)-stop setting.

As I understand it:
For the M lenses, the stop down lever is a simple on/off motion that only releases the M lens to spring down to the setting of the ap ring.

For A lenses in A mode, the f/- is sent in binary via 2 ( or 3) gold contacts.
For DA lenses, f/- is sent as data

As mentioned, I think Pentax users benefit from the new cameras still having all the above functionality, duplicated so the old K lenses still work.

08-26-2015, 06:31 PM	#1
maltfalc Veteran Member Join Date: May 2010 Location: Winnipeg Photos: Albums Posts: 396	Could Av, Tv, etc. potentially be enabled with Pentax-M lenses through firmware? Just a random thought I had. Currently, M lenses only work in manual mode because the camera has no way to know the difference in light levels wide open vs stopped down. Why not set the aperture ring to the smallest f-stop and use one of the buttons or a menu item to take a series of meter readings while closing down the iris to get the info the camera needs to meter wide open? one extra button press is a small price to pay for enabling all modes with M lenses.

08-26-2015, 06:40 PM	#3
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,593	Originally posted by maltfalc Just a random thought I had. Currently, M lenses only work in manual mode because the camera has no way to know the difference in light levels wide open vs stopped down. Why not set the aperture ring to the smallest f-stop and use one of the buttons or a menu item to take a series of meter readings while closing down the iris to get the info the camera needs to meter wide open? one extra button press is a small price to pay for enabling all modes with M lenses. Av will work with lenses that have manual diaphragms, but certainly not Tv as that would require the camera to be able to set the aperture. Supporting Av natively would require the "non-crippled mount" / aperture linkage. 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:

08-26-2015, 09:42 PM	#13
maltfalc Veteran Member Join Date: May 2010 Location: Winnipeg Photos: Albums Posts: 396 Original Poster	Originally posted by MadMathMind This is not possible because the meter is located in the pentaprism. Once the mirror goes up, no light can reach the meter. This is why when you use "Mirror Up" mode it takes two shutter presses--one to put the mirror up, one to fire. The meter can't operate while the mirror is up so it would not work to have the mirror up at all times. Note that when you put the mirror up, the exposure is locked. who said anything about the mirror being up? that's not in any way required for this. ---------- Post added 08-26-15 at 11:48 PM ---------- Originally posted by stevebrot Oh, you mean when the green button is pressed? That is the only way it could work is with a manual stop-down. As noted above, the shutter sequence begins with mirror up. There is also the problem that many aperture mechanisms are poorly modulated, meaning that they stop down, even full down, with very little movement of the actuator lever. Steve neither the shutter nor the mirror would be involved in calibrating the camera to a lens. the max aperture would be entered manually when the lens is first mounted, the aperture lever would be run through it's full range of movement and the changes in light level recorded in order to map a specific location of the lever to a specific t-stop. ---------- Post added 08-26-15 at 11:57 PM ---------- Originally posted by Fogel70 But what should the camera do with this information? As the stopping down of the aperture goes very quickly it will be difficult to get a accurate readings from the meter during stop down. The camera will still not know in which position you set the aperture before the lens is stopped down. The aperture will always be fully stopped down before a images is captured, so you always have to set the aperture on then lens to the f-stop you want to use for the image. The only extra you would get by entering largest aperture is that exif could be updated with an approximation of the aperture used. you leave the ring at the smallest aperture. the aperture doesn't need to be fully stopped down. it isn't when using pentax-a or newer lenses. the lens will be stopped down to multiple positions with a meter reading at each then the camera will map out the non-linear movement of the aperture and use that map to determine the correct position of the aperture lever while shooting. ---------- Post added 08-27-15 at 12:07 AM ---------- Originally posted by K-Three I think that Maltfalc's idea is to set something up to pre-calibrate the lens to the body when you put it on, possibly have a "library" of lenses in the camera's memory so when you put one on you pick the lens (similar to putting a non-AF lens on and telling the SR how long it is). The challenge I see is that the lens is closed down during exposure by the camera releasing the aperture arm on the lens, and letting the lens mechanism close down to the preset aperture. Think of this as closing down an old pre-set lens just before exposure, you rotate the ring until it stops, and don't have any indication of where that point is, you are just turning until it stops. The camera does not change its arm motion, it just gets it out of the way so the lens can stop down to where its set. There is nothing to calibrate in the motion. It is an on/off motion, no subtle degrees of movement involved. The only indication to a camera body of where the aperture is set on the old M and K lenses is the tab outside of the bayonet, that coupled to a similar tab in the old film bodies. This is the "Crippled" part of the modern K-mount. The modern bodies don't have this coupling to transfer the lens f-stop data to the metering system. It is a shame in some ways, likely a cost cutting move, possibly they needed that room in the mirror box for something else, but really for those of us that remember the change from screw to K-mount, not much different. You always had to do stop-down metering with screw mount lenses. Going to the "Modern", open-aperture K-mounts was an "enlightening" experience. Be grateful you can painlessly mount all those old lenses and use them at all. the aperture adjusting mechanism in the camera is not a simple on/off motion. with newer lenses it moves the lever to a specific location for any given f-stop setting. the whole point of my idea is to give the camera a way to teach itself what lever position corresponds to which f(or t)-stop setting. ---------- Post added 08-27-15 at 12:14 AM ---------- Originally posted by UncleVanya My point is that the adjustments could be done using the same mechanism... there are other practical difficulties but metering does not seem like the main issue. no need even for that. a modified version of green button stopped down metering is all that's needed, with meter readings taken at 10 percent stopped down, 20 percent, etc. instead of just at 100%, then just a bit of connect the dots to calculate the full curve. Last edited by maltfalc; 08-26-2015 at 10:15 PM.

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08-26-2015, 06:37 PM	#2
MadMathMind Veteran Member Join Date: Dec 2013 Location: Houston, TX Photos: Gallery Posts: 1,717	The problem is that the camera has no idea what the aperture is like it does for A series and later lenses. The camera measures wide open. Let's say that's f/4. Then it says "Oh, I'm going to use f/8, so I need to double my exposure time to make the light equivalent." With an M lens, the camera has no way to know what the aperture is. It doesn't know it measured at f/4 and doesn't know it will be set to f/8. The camera does know the difference in light levels wide open vs. shooting aperture but it needs to stop the lens down and then take the metering. It just doesn't know the difference in aperture between those two settings. If the light were perfectly constant, it could deduce the relative difference in f-stop by computing the ratio of light level, but if the user changes the f-stop with the ring, that calculation will be incorrect. And the camera has no way to know that the user made this change.

08-26-2015, 07:03 PM	#4
maltfalc Veteran Member Join Date: May 2010 Location: Winnipeg Photos: Albums Posts: 396 Original Poster	ok, you're both just restating the problem with using m lenses and not getting my proposed solution. the idea is to have the camera take a series of meter readings not while the lens is closed down, but rather while it's transitioning from wide open to closed down, so that it can calculate the specific positions at which there is a 1 stop difference in light levels. the aperture ring would be kept at the smallest aperture, just like a pentax-a lens in a-mode. it'd be t-stops rather than f-stops technically, but close enough, and the max aperture could be set in a prompt at startup just like focal length is for sr.

08-26-2015, 07:27 PM	#5
MadMathMind Veteran Member Join Date: Dec 2013 Location: Houston, TX Photos: Gallery Posts: 1,717	Originally posted by maltfalc ok, you're both just restating the problem with using m lenses and not getting my proposed solution. the idea is to have the camera take a series of meter readings not while the lens is closed down, but rather while it's transitioning from wide open to closed down, so that it can calculate the specific positions at which there is a 1 stop difference in light levels. This is not possible because the meter is located in the pentaprism. Once the mirror goes up, no light can reach the meter. This is why when you use "Mirror Up" mode it takes two shutter presses--one to put the mirror up, one to fire. The meter can't operate while the mirror is up so it would not work to have the mirror up at all times. Note that when you put the mirror up, the exposure is locked.

08-26-2015, 07:34 PM	#6
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by maltfalc the idea is to have the camera take a series of meter readings not while the lens is closed down, but rather while it's transitioning from wide open to closed down, so that it can calculate the specific positions at which there is a 1 stop difference in light levels Oh, you mean when the green button is pressed? That is the only way it could work is with a manual stop-down. As noted above, the shutter sequence begins with mirror up. There is also the problem that many aperture mechanisms are poorly modulated, meaning that they stop down, even full down, with very little movement of the actuator lever. Steve

08-26-2015, 08:09 PM - 1 Like	#7
Fogel70 Pentaxian Join Date: Sep 2009 Location: Stockholm, Sweden Photos: Albums Posts: 3,062	Originally posted by maltfalc ok, you're both just restating the problem with using m lenses and not getting my proposed solution. the idea is to have the camera take a series of meter readings not while the lens is closed down, but rather while it's transitioning from wide open to closed down, so that it can calculate the specific positions at which there is a 1 stop difference in light levels. the aperture ring would be kept at the smallest aperture, just like a pentax-a lens in a-mode. it'd be t-stops rather than f-stops technically, but close enough, and the max aperture could be set in a prompt at startup just like focal length is for sr. But what should the camera do with this information? As the stopping down of the aperture goes very quickly it will be difficult to get a accurate readings from the meter during stop down. The camera will still not know in which position you set the aperture before the lens is stopped down. The aperture will always be fully stopped down before a images is captured, so you always have to set the aperture on then lens to the f-stop you want to use for the image. The only extra you would get by entering largest aperture is that exif could be updated with an approximation of the aperture used.

08-26-2015, 08:13 PM	#8
Eyewanders Veteran Member Join Date: Jan 2008 Location: Land of the Salish Sea Photos: Gallery \| Albums Posts: 3,343	I'm not sure this is even a problem. You're able to use a near 50 year old series of lenses on brand new camera technology with shake reduction and you can even meter properly using the Green Button. I've never thought a solution was in order for this.

08-26-2015, 08:47 PM - 1 Like	#9
K-Three Loyal Site Supporter Join Date: May 2014 Location: Pugetopolis, WA Photos: Gallery Posts: 937	I think that Maltfalc's idea is to set something up to pre-calibrate the lens to the body when you put it on, possibly have a "library" of lenses in the camera's memory so when you put one on you pick the lens (similar to putting a non-AF lens on and telling the SR how long it is). The challenge I see is that the lens is closed down during exposure by the camera releasing the aperture arm on the lens, and letting the lens mechanism close down to the preset aperture. Think of this as closing down an old pre-set lens just before exposure, you rotate the ring until it stops, and don't have any indication of where that point is, you are just turning until it stops. The camera does not change its arm motion, it just gets it out of the way so the lens can stop down to where its set. There is nothing to calibrate in the motion. It is an on/off motion, no subtle degrees of movement involved. The only indication to a camera body of where the aperture is set on the old M and K lenses is the tab outside of the bayonet, that coupled to a similar tab in the old film bodies. This is the "Crippled" part of the modern K-mount. The modern bodies don't have this coupling to transfer the lens f-stop data to the metering system. It is a shame in some ways, likely a cost cutting move, possibly they needed that room in the mirror box for something else, but really for those of us that remember the change from screw to K-mount, not much different. You always had to do stop-down metering with screw mount lenses. Going to the "Modern", open-aperture K-mounts was an "enlightening" experience. Be grateful you can painlessly mount all those old lenses and use them at all.

08-26-2015, 09:02 PM	#10
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,381	Originally posted by MadMathMind This is not possible because the meter is located in the pentaprism. Once the mirror goes up, no light can reach the meter. This is why when you use "Mirror Up" mode it takes two shutter presses--one to put the mirror up, one to fire. The meter can't operate while the mirror is up so it would not work to have the mirror up at all times. Note that when you put the mirror up, the exposure is locked. How does LiveView meter then?

08-26-2015, 09:09 PM	#11
MadMathMind Veteran Member Join Date: Dec 2013 Location: Houston, TX Photos: Gallery Posts: 1,717	Originally posted by UncleVanya How does LiveView meter then? The sensor measures the amount of light electronically and adjusts its drive accordingly. One advantage to live view is that the entire scene is used, as opposed to a discrete number of metering segments like in optical view.

08-26-2015, 09:14 PM	#12
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,381	Originally posted by MadMathMind The sensor measures the amount of light electronically and adjusts its drive accordingly. One advantage to live view is that the entire scene is used, as opposed to a discrete number of metering segments like in optical view. My point is that the adjustments could be done using the same mechanism... there are other practical difficulties but metering does not seem like the main issue.

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08-27-2015, 06:41 AM	#14
fwcetus Site Supporter Join Date: Sep 2006 Location: New England Photos: Gallery \| Albums Posts: 1,286	Originally posted by chickentender I'm not sure this is even a problem. You're able to use a near 50 year old series of lenses on brand new camera technology with shake reduction and you can even meter properly using the Green Button. I've never thought a solution was in order for this. I'd agree with all of that ~except~ "and you can even meter properly using the Green Button" -- I think the metering is actually quite poor with K and M lenses (and, I assume M42 lenses, too). Having to use the Green Button is not a huge inconvenience, all things considered, but the non-linearity of metering is very frustrating to me (YMMV).

08-27-2015, 07:07 AM	#15
wombat2go Veteran Member Join Date: Jan 2010 Location: Michigan Photos: Gallery Posts: 2,207	Originally posted by maltfalc the aperture adjusting mechanism in the camera is not a simple on/off motion. with newer lenses it moves the lever to a specific location for any given f-stop setting. the whole point of my idea is to give the camera a way to teach itself what lever position corresponds to which f(or t)-stop setting. As I understand it: For the M lenses, the stop down lever is a simple on/off motion that only releases the M lens to spring down to the setting of the ap ring. For A lenses in A mode, the f/- is sent in binary via 2 ( or 3) gold contacts. For DA lenses, f/- is sent as data As mentioned, I think Pentax users benefit from the new cameras still having all the above functionality, duplicated so the old K lenses still work.