Old Pentax K lens on K100D Super

[ampguy]

I've got an old K mount 28/2.8 lens (JC Penny) that seems to only work in wide open mode when metering and shooting in Av mode.

The custom settings allow aperture for older lenses, but but there is only one mechanical lever I see on the lens, and even though the lens stops down as you click it towards f22 with the lens off camera, on camera, that single lever keeps it at 2.8 not only for focusing (a good thing), but also in shooting mode, and the stop down mode (the aperture looking position on Pentax DSLRs).

I can't remember if my *ist DL handled it the same way or not.

In a way, this fixed automatic mode seems more of a pain than my M42 to K mount lens, which simply has no function to stay wide open during focusing, and simply reads the light at whatever the aperture is, and adjusts shutter accordingly in Av mode.

The lens works fine in manual mode, but I'm curious if there is a way to get these single lever open aperture lens types to meter on the K100D in Av mode?

 

[bmattock]

Press the green button. That's what I do on my *ist DS, anyway.

 

[cmedin]

Yeah, go into manual mode, hit the green button (or equivalent on the K100D) and it'll stop down and meter. I agree that the M42 lenses are easier to use though...

 

[ampguy]

hmm, just read the manual, and I don't see a green button, anyone know the function of that green button that I can try to cross-reference?

The manual is expecting the lens to have an "A" mode on the aperture ring, and this K-mount lens doesn't. I realize I could bend off the lever that is keeping the aperture open and use as an M42 mode lens, but I have a film K-mount camera that could probably use that lever and still meter (metered manual). Will keep trying things.

 

[Matthew Allen]

On the K100D it's the AE-L button rather than the Green button that stops the lens down to meter. It's the same as on the DL. You want to be in Manual mode (unless you're using the lens wide open). It's not the most elegant system but it's works ok in practice.

Matthew

 

[MichiganBill]

Sorry ampguy, there is no way to stop down the manual lens on your digital camera. This particular lens seems to have a pin or lever, which engaged the old K-mount Pentax camera. The old camera would release the pin or lever (i.e. in "auto mode") and stop the lens down. Your new digital camera has no way to do this, so it will only work wide open.

However you may be happy with the results anyway. You can still control exposure with the shutter speed and ISO controls. I have taken many pretty pictures this way, using a n old Sears lens.

You may also be able to use other old manual lenses just fine. I use a variety of Takumar lenses with my k100d. The pin arrangement of these lenses allow the "manual mode" to work and the pictures are very nice.

 

[bmattock]

I never knew if it was really 'green' or not (I'm color-blind) so I just pressed the button that people called 'the green button' online and wonder of wonders, it worked. I guess it is the AE-L button for me too. If it is not green, sorry - I can't tell. Anyway, you press it, and the camera stops down, meters, and opens back up again - really fast. Then you can shoot. It's pretty cool. I like it better than my M42 lenses for metering, since I don't have to focus and meter through a stopped-down image. However, I like manual-focus A lenses most of all. They're the cool ones.

 

[bmattock]

Sorry ampguy, there is no way to stop down the manual lens on your digital camera. This particular lens seems to have a pin or lever, which engaged the old K-mount Pentax camera. The old camera would release the pin or lever (i.e. in "auto mode") and stop the lens down. Your new digital camera has no way to do this, so it will only work wide open.

That's not true. All the Pentax K mount lenses have the aperture tab. You may be referring to old M42 screw-mount lenses, which had a pin - and yes, they do not get automatically stopped down. But all the K-mount lenses do.

However you may be happy with the results anyway. You can still control exposure with the shutter speed and ISO controls. I have taken many pretty pictures this way, using a n old Sears lens.

I use M42 and K-mount lenses quite happily. The K-mounts lenses meter and auto-stop down just fine.

You may also be able to use other old manual lenses just fine. I use a variety of Takumar lenses with my k100d. The pin arrangement of these lenses allow the "manual mode" to work and the pictures are very nice.

I think you are referring to K mount lenses here, as many "Takumar" lenses were M42, but some were K-mount.

Pentax lenses were M42, then K, then KA, then KA-F, then it all went kind of crazy, but the point is - they ALL work on the Pentax digital cameras. M42 lenses need an M42->K mount adapter and yes, they do not auto-stop down or meter from an open aperture, but they can be manually stopped down and metered through just fine.

In addition, the focus indicator will work with any hunk of glass you can mount on it - assuming you can focus it at all. No other digital camera can do that (without putting chips and such in the lens mount). If the particular Pentax digital SLR has anti-shake, then that works with all the old lenses too.

Pentaxians have it good. Great glass, all the options work, backwards compatibility to the stone age, and millions of surplus and old lenses to choose from. Great world.

 

[ampguy]

Thanks all, I think Bill is correct, the AE-L button doesn't override the mechanical lever on the lens that just keeps it wide open.

However, Bill is right, it does work great at the fixed 2.8 with the high shutter speeds of the DSLR, and I have the kit zoom, which covers this focal range (at slower speed), and a 35 prime M42 f2 that works well in stopped down metered manual mode.

This is still a nice lens, but one of the rare ones I've seen that doesn't meter stopped down on the K100D.

 

[bmattock]

Thanks all, I think Bill is correct, the AE-L button doesn't override the mechanical lever on the lens that just keeps it wide open.

Have you enabled the aperture ring in your CMOS settings? Hitting the AE-L button should stop down the lens and meter, then release it back to wide-open. However, the setting has to be on M, not Av.

However, Bill is right, it does work great at the fixed 2.8 with the high shutter speeds of the DSLR, and I have the kit zoom, which covers this focal range (at slower speed), and a 35 prime M42 f2 that works well in stopped down metered manual mode.

You can of course finagle using every lens wide-open, but not every lens is as good wide-open as it is stopped down a bit. In fact, most are quite soft wide-open, which is an effect many prefer, but not for everything.

This is still a nice lens, but one of the rare ones I've seen that doesn't meter stopped down on the K100D.

All K-mount lenses should stop down automatically when you shoot. If you rotate the On/Off ring to the little aperture setting, it should stop down for you to prove that. To make it METER while stopped down, you put the camera in M mode, then press the AE-L button. But first, you have to turn on aperture ring permitted in the CMOS settings (Custom settings). You only have to do that once.

Anyway, that's how my *ist DS works. I had to dig it out just now and put an old K-mount lens on it to prove it to myself so I wasn't giving you bad scoop, but that is indeed how it works on mine, and should work that way on yours.

 

[ampguy]

Question

Question

I agree, that all Pentax branded lenses probably work with the AEL manual metering or stop down, but this K-mount from whoever OEM'd it to JC Penny did something different and will not close the aperture down from full open to the selected aperture on the ring (although lens works fine, light finger pressure on the lens back when it's off the body stops it down).

I think I've read something about these on dpreview or other forums, and I'm not positive I used it in any mode other than wide open on the *ist DL.

But here's a question, do you have any K lenses that don't have an "A" setting on the aperture ring? If so, I'd be interested in knowing what the aperture lever looked like in the back of the lens. I'm wondering if there are such lenses without an "A" on the aperture ring, (but still wide open viewing, e.g. default spring mode action is wide open, wherever the setting of the ring is) and what the depth of that tab is, maybe these tabs are just longer than Pentax lenses that do work with the AE-L button to stop the lens down at metering or at least at time of shutter depression.

And, yes, focus lock and anti-shake work perfect. I'm not unhappy by any means, I only paid $20 or so for this lens, and it works great on my film K-mount, and on this one wide open. Just curious.

Thanks again all.

That's not true. All the Pentax K mount lenses have the aperture tab. You may be referring to old M42 screw-mount lenses, which had a pin - and yes, they do not get automatically stopped down. But all the K-mount lenses do.



I use M42 and K-mount lenses quite happily. The K-mounts lenses meter and auto-stop down just fine.



I think you are referring to K mount lenses here, as many "Takumar" lenses were M42, but some were K-mount.

Pentax lenses were M42, then K, then KA, then KA-F, then it all went kind of crazy, but the point is - they ALL work on the Pentax digital cameras. M42 lenses need an M42->K mount adapter and yes, they do not auto-stop down or meter from an open aperture, but they can be manually stopped down and metered through just fine.

In addition, the focus indicator will work with any hunk of glass you can mount on it - assuming you can focus it at all. No other digital camera can do that (without putting chips and such in the lens mount). If the particular Pentax digital SLR has anti-shake, then that works with all the old lenses too.

Pentaxians have it good. Great glass, all the options work, backwards compatibility to the stone age, and millions of surplus and old lenses to choose from. Great world.

 

[MichiganBill]

Pentaxians have it good. Great glass, all the options work, backwards compatibility to the stone age, and millions of surplus and old lenses to choose from. Great world.

We are blessed in many ways. I love my Spotmatic and Spotmatic K-1000, and now I have a k100d and a "new" Perkeo folder. They are all so much fun, and the biggest problem is deciding which one to use on a given day!🙂

 

[ampguy]

Hi Bill,

Yes of course I've set my CMOS settings to use aperture ring, I have other manual K mount lenses that work as described.

This lens is a little different. It doesn't have an "A" or "M" setting, and the AEL only locks the AE at the wide open setting (regardless of where the ring is). Turning the ring around the shutter to the aperture icon takes a photo (wide open), where with my *ist DL, it did stop down my manual K mount lenses, but I don't recall what it did with this particular JC Penny 28/2.8 K mount with no "A" or "M" settings. I'd be happy to take photos of it for you if it would satisfy your interest.

 

[bmattock]

Hi Bill,

Yes of course I've set my CMOS settings to use aperture ring, I have other manual K mount lenses that work as described.

This lens is a little different. It doesn't have an "A" or "M" setting, and the AEL only locks the AE at the wide open setting (regardless of where the ring is). Turning the ring around the shutter to the aperture icon takes a photo (wide open), where with my *ist DL, it did stop down my manual K mount lenses, but I don't recall what it did with this particular JC Penny 28/2.8 K mount with no "A" or "M" settings. I'd be happy to take photos of it for you if it would satisfy your interest.

Well, no need to satisfy me, I'm only trying to help you. First of all, I've never seen a K-mount lens with an 'M' setting. They all have an aperture ring, and they either have an "A" setting or they do not. I have only seen "M" settings on M42 lenses that often have an 'auto/manual' switch to enable manual stop-down or pin-actuated stop-down. If they have an "A" setting, then they also have electrical contacts on the rear of the lens mount to communicate f-stop to the camera body. Without that, there is no way for the modern AF Pentax camera body to 'know' what the aperture is.

The default mode of every K-mount lens is (or is to my experience, anyway) stopped down when off the camera. That is, if the lens is set to f/16, and you remove it from the camera, it stops down completely. Pressing on the aperture tab (spring-loaded) opens it up fully. I would presume your lens does this?

When you mount the lens on the camera, it should open up fully. This means that the aperture tab is under spring tension.

When you take a photo with a k-mount lens, regardless of whether you meter or anything, the camera body should remove pressure on the tab, allowing the lens to close down automatically to whatever f-stop it is currently set to. If you try this with a nice slow shutter speed like 1 second, you should be able physically examine this happening.

When you rotate the on/off switch to the 'aperture' looking icon, it is supposed to make a little growly noise and you can again see the lens stop down to whatever it is currently set to. I have been reading the K100D Super manual online, and it appears to be just like my *ist DS - it will also meter during this time if the metering knob is turned to "M."

However, the AE-L button is supposed to do this in one fell swoop. Put the metering in "M", press the button and it quick like a bunny stops down and meters, and there you go. It is essentially Av, because you are setting the aperture ring yourself to whatever you want it to be, so it sets the apropriate shutter speed to that - instant Av mode, even with metering set to M.

Now, I do not have any JC Penny lenses, but I do have el cheapo Sears lenses, and they're great. One small problem - some of them were designed to work on both Pentax and Ricoh cameras, which used a differing means of doing auto-exposure. One of mine had both an "A" and a "P" setting on the aperture ring - and it was NOT the "A" that Pentax likes. In fact, this lens had a pin sticking out of the base of the lens that, had I mounted it on my Pentax, would have wedded them together until the end of time (Google for similar problems with Ricoh lenses on Pentax bodies).

If you have a K-mount lens - and it seems you do - and it behaves as a K-mount lens should (stopped down to the f-stop setting when off the camera, wide-open when mounted), then I see no reason that your aperture ring setting on the on/off switch should not work, or why the AE-L button should not meter when you press it with the exposure knob set to M.

According to your manual, it should. If it does not, then I suppose it means the lens is not truly a K-mount, or it is defective in some way.

I don't know what else to say. K-mount lenses work fine for me, and apparently, the rest of the world as far as I can tell so far. If the K100D Super is somehow different than the rest of the Pentax dSLR bodies, no one seems to be noticing it yet. I'm sorry you're having this problem.

 

[MichiganBill]

But here's a question, do you have any K lenses that don't have an "A" setting on the aperture ring? If so, I'd be interested in knowing what the aperture lever looked like in the back of the lens. I'm wondering if there are such lenses without an "A" on the aperture ring, (but still wide open viewing, e.g. default spring mode action is wide open, wherever the setting of the ring is) and what the depth of that tab is, maybe these tabs are just longer than Pentax lenses that do work with the AE-L button to stop the lens down at metering or at least at time of shutter depression.

This is the Sears 80-200 k-mount zoom lens I mentioned. It doesn't have an "A" or "M" setting, just as you mentioned, and it only shoots wide open on the digital camera. The photo was taken with my k100d, using a Takumar 135mm lens with a macro ring.

All the best,

Bill

 

[bmattock]

This is the Sears 80-200 k-mount zoom lens I mentioned. It doesn't have an "A" or "M" setting, just as you mentioned, and it only shoots wide open on the digital camera. The photo was taken with my k100d, using a Takumar 135mm lens with a macro ring.

All the best,

Bill

I have a Sears 80-200 lens, looks just like yours. No A setting on mine, either. And it works fine and does stop down. I also have a Vivitar 50mm f/1.4, no A setting, just the aperture ring, and it looks like yours on the back too. Also stops down and meters just fine.

I don't know what to tell you. Frankly, I'm not sure what you're playing at. A simple read of the manual online shows that the K100 should work just like the *ist DS. If it doesn't work for you, either your camera or your lens is malfunctioning. A simple Google search will show all kinds of people doing just fine with metering and auto-stop down on K-mount lenses of all kinds.

And again - I've never heard of a K-mount lens with an M setting. They only have an A or they do not. If they have an A, then they also have electrical contacts on the lens mount. If they do not have an A, then they don't. The only exception to this I know is the Ricoh-specific "P" setting that some third-party lenses have - and those should not be used on Pentax digital SLR bodies without modification.

Are you playing silly buggers or are you serious?

 

[MichiganBill]

As you can see from my number of posts, I have been lurking for a while but not posting. I purchased a Perkeo a few months ago, and I've been reading the forums to learn more about rangefinders.

I simply thought that I might have an answer to amguy's question, because I have been using Spotmatics for a few years. Apparently I was mistaken. I apologize, I should have read the earlier posts more carefully. :bang:

 

[ampguy]

Hi Bill and Bill,

OK, just got done examining several K lenses and playing more and have the setup in front of me.

It actually does work, but differently enough from my old *ist DL that I was thrown off. Here's how I am able to take a stopped down photo with this lens and even get a metering:

1. Mount lens, set camera to "M" mode, with enable aperture ring in custom setup.

2. when ready to shoot, rotate collar ring on shutter to aperture pattern, on the K100D, this does a "pre-metering" shot and displays on the LCD with the aperture icon in upper left, and just stays there. Since it is M mode, the preview will likely not be a metered exposure preview, but using some last used or arbitrary shutter speed.

3. You can now take a photo, (that preview did not save to SD card), and it will use the aperture on the lens, and shutter on the LCD.

4. To get a metered shutter value, press the AE-L button, which will set the shutter to the metered value (this may or may not ker-chunk close down the aperture, depending on if you did a stop down pre-meter). As in above step, you can still adjust the shutter with the thumb dial.

5. Take the photo by pressing the standard shutter button, and it will stop down, and use the shutter as retrieved from above metering steps, or as set by you manually, and will close down lens during exposure to whatever dial is set on ring.

BillM - yes, my 28/2.8 manual K lens does that, stopped down to what ring is set at, unless spring loaded lever is gently pressed, then opens up.

MichiganBill, can you verify that the above works for your Sears lens? I realize it's a convoluted way, and I can't understand why the extra steps from the *ist DL, other than the preview mode.

On another note, for those of you with SR, do you set it to jolt dust off the sensor on every power up, or just manually vibrate the sensor from the menus once in awhile?