K-r not working with SMC M 2.8 28mm

After many years of canon ownership I have got back into SLRs and bought myself a K-r twin lens set up. Very pleased with the kit and have been doing a bit of investigating the wonderful world of Pentax. I was very interested to learn of the back compatibility of Pentax lens so i thought I'd dip my toe into the water and purchased a SMC pentax-M 2.8 28mm prime. I got the lens today and put it on the camera and found that nothing worked . The rear display refuses to read an aperture value and the shutter button is in operative. I am cool with not getting any digital readouts with an old manual lens but it would be nice if I could actually take an image!
I am sure there is something obvious here. The camera is fine with a DAL lens and while I cannot check the manual lens it seems to be OK and was sold to me as being in good working order.
Any help and guidance no matter how basic much appreciated.
Rob

Custom setting "using aperture ring" needs to be set to "permitted" after which you can use your M series lens in manual mode. You need to stop down the lens to take a meter reading and the reading may not be accurate, but you can use the lens.

To avoid any of this inconvenience, any lens that has an "A" on the aperture ring will be fully functional. This means lenses from the A series onwards.

You need to change the apperture ring setting on the camera menu to accept manual lenses.. All will be fine and dandy then. Cant be more exact not got the manual at hand..

Oops John beat me to it...lol

You may also need to turn the body onto manual focusing if you are trying to take an out of focus image (or one where the the point of focus is not central).

You will not get the aperture value on the body as it has no way of knowing what it is (see John's comment about A series lenses).

I have heard that the K-5 stop-down metering with older lenses is more accurate than it was with the K10/K20. I'd be interested to know if this is the case with the K-r.

K.

i used the same link that blythman has given and it works with my k-r and a few m series lens's that i have and a couple of vivitar lens's i use and they take good images just remember to stop down the lens and meter with the green button.
geordie

Thank you all. I have now got the camera set up and am enjoying my new lens!

I am off to Svalbard in late February so am hoping for some Northern Lights. Ideally I need something wider and faster but budgets are budgets.

Very happy with the K-r even if the weather has been so bad I should have stretched a little and gone for the K7

The K-R low light performance was the final factor in the end. The K5 would have been lovely but ££££££££

Rob