12-22-2013 01:49 AM
Using Takumar M42 lenses on my new K50, how do I make it meter in manual mode?
I have a collection of Takumar M42 screw mount prime telephoto lenses bequeathed to me by my uncle. For several years I have used them successfully on a *ist DL2 and a K200d to shoot wildlife. I used them in both Av mode and Manual mode with no problems. Metering was more accurate in Manual mode. I got consistently better exposures.
Now I have 'upgraded' to a new K50. Using the M42 lenses, the camera meters OK in Av mode, but does not meter at all in Manual mode.
Yes, I have set Aperture Ring to Permitted.
Yes, I am trying to use the green button to meter. I have also tried to use the RAW/FX button set to Optical Preview to make it meter - no luck. It seems to work in Live View, but in live view with the M42 lenses the camera rattles!
If this is the xpected behaviour, if it is not meant to work with M42 lenses in Manual mode, if Pentax/Ricoh are phasing out compatibility with old lenses, then I am very disappointed.
02-13-2014 08:47 AM - edited 03-11-2014 10:03 AM
Screwmount lenses (with the Mount Adapter B) work differently on the K-50 and K-30 than they do on the K-5II/IIs and the K-3. Even with Aperture Ring set to Permitted, the Green Button assigned to Tv Shift in Manual exposure mode and the RAW/Fx button set to Optical Preview, the K-50 and K-30 will not automatically set the shutter speed when the Green button is pressed (this does work on the K-5II/IIs and K-3).
It is expected that the camera will not stop the lens down automatically when using the Mount Adapter B, but even with the lens stopped down using the Manual/Auto switch on the screwmount lens, the K-50 or K-30 will not set the shutter speed automatically. Likewise, neither the K-50 nor K-30 will display the exposure scale in Manual exposure mode when using either a screwmount lens or an M-series lens. The exposure scale in Manual exposure mode will only be displayed when an A-series (or newer) lens is used.
03-06-2014 08:01 PM
JoeV - Are you sure what you said is correct? I am shocked. I just ordered a k-50, it is waiting in it's box for me to get home from a trip. I have several M42 lenses that I was planning to use with it, and some K-mount M lenses as well. All of the Pentax literature I have seen makes a big point of the ability of Pentax cameras to use legacy lenses. I have been using my old Pentax lenses for the last couple years with my Sony NEX 5N (with M42 and K-mount ot E-mount adapters) and that camera sets both shutter speed and ISO just fine with the lenses stopped down manually. I usually don't even need to change the Sony from whatever function setting (PASM) I am using before mounting the lens, it just goes ahead and sets exposure correctly. Can it really be possible that a Sony is more compatible with legacy Pentax lenses than a brand new Pentax?
03-11-2014 10:22 AM
Yes, M42 lenses mounted on a K-30/K-50 (using a Mount Adapter B/Mount Adapter K) will not operate in the same way as these lenses mounted (with adapter) on a K-3 or K-5 IIs. With the K-7, K-5, K5 II, K-3 for example, all that is needed to setup the camera to work with these older lenses is to enable Use of Aperture Ring (in the Custom Settings menu) and assign "Tv Shift" to the Green button (in E-dial Customization). Stopping the lens down to shooting aperture and pressing the Green button (in Manual Exposure mode) will then measure the light coming through the lens and set an appropriate shutter speed.
However, when an M42 lens is mounted on a K-30 or K-50, pressing the Green button will not automatically measure the light coming through the stopped-down lens and set an appropriate shutter speed (using the same camera settings).
An M-series lens mounted on a K-30 or K-50 setup for older lenses will operate differently than an M42 lens, i.e. pressing the Green button will stop the lens down to shooting aperture, measure the light coming through the lens and automatically set a shutter speed for a good exposure.
06-11-2014 12:31 PM - edited 06-13-2014 09:24 AM
I have just purchased K-50 and have had little trouble using an m42 lens with the a-m switch set to manual. No, the green button will not set the shutter setting as described in normal view, but will in live mode. Av mode also works for me in normal mode.
My point is that some people may get the impression from this thread that ALL m42 lenses won't work. Only lenses without the a-m switch won't work. With the a-m switch you can of course stop the lens down manually and not have to worry about the camera doing it.
I'm sorry but I'm still kind of confused over this as JoeV wrote: 'but even with the lens stopped down using the Manual/Auto switch on the screwmount lens, the K-50 or K-30 will not set the shutter speed automatically. '
My camera seems to be setting the shutter speed just fine whith fixed ISO set and mode set to Av. It works just like a Pentax Me this way. The shutter speed will set when the shutter release button is depressed halfway just as it normally does. The pictures seem to be correctly exposed.
Right now I'm testing the camera with a Helios 44m lens that has an a-m switch. I'm going from f2 to f16 and the camera seems to be giving me good shutter speeds automatically with whatever fixed ISO values i use.
Yes, I'm a bit confused about this.
05-04-2016 07:39 PM
Did you finish your testing? Are you still sure your K-50 is setting proper exposure with the stopped down M42 lenses? Since my original post, I've found that the K-50 indeed does not set exposure properly for the M42 lenses. Maybe it does in live view, I don't know. I think it does work with the k mount M lenses, but they have conductive metal on the lens mount. I understand that some people have had some successes shorting out the pins on the camera mount with foil to fool the camera into setting the shutter speed correctly with M42 lenses.