Go Back   Steve's Digicams Forums > Digital SLR and Interchangeable Lens Cameras > Pentax Lenses

Thread Tools Search this Thread
Old Aug 18, 2007, 1:22 AM   #1
Senior Member
Gumnut's Avatar
Join Date: Jul 2005
Location: Perth, Western Australia
Posts: 1,259

i have read and read on the focus trap feature
and still cant profess to understand it
however after a bit of persistance i managed to get my manual M42 400mm lens to work with focus trap
after reading about the contacts being grounded (what ever that means)
i noticed that with the screwmount the contacts were not even covered let alone grounded
so i tried pushing some screwed up alfoil in the area where the contacts were and presto it worked
it was rather hard to keep the foil thre though
i made a shim, ring from an aluminium drink can
with a hole to fit the screw mount and wide enough to cover the contacts
it didnt work
i thought maybe the aluminium has a covering of some sort to protect the drink from the aluminium
so i rubed it in my cement drive
still no go
so thinking back to the alfoil working
i covered the shim with alfoil
and it works

oddly enough there is nothing that i can see that goes into the depressed contact
nor is there on my manual 50mm lens whiich also works with the focus trap
i have no idea why this works
but it does

i am off to shoot some birds

i will let you know how i get on

oh and the screw mount will work in aperture priority, which the manual K mounts wont
Gumnut is offline   Reply With Quote
Sponsored Links
Old Aug 18, 2007, 1:36 AM   #2
Senior Member
Corpsy's Avatar
Join Date: Dec 2005
Posts: 879

I don't really understand why your M42 lense didn't work without all that. I wouldn't think the contacts would matter on a lens it can't communicate with unless the camera was somehow fooled into thinking there was an autofocus lens attached.

I like how an M42 lens can work in aperture priority mode and it really annoys me that it can't be done with a K-mount lens. I wish there was a feature that could allow aperture priority to be used by quickly metering right before shooting, or by just allowing you to keep the camera in DOF preview mode.
Corpsy is offline   Reply With Quote
Old Aug 18, 2007, 4:16 AM   #3
Senior Member
robar's Avatar
Join Date: Mar 2005
Location: D/FW area Texas
Posts: 7,590

you could always cut the tab off the K, M lenses and then they would actually work as M42 lenses.. just kidding,, even tho it's true..
i'll tell you what i find weird. i have a pentax A1.4x-s TC and if i use it with my K,M lens in manual mode, if i don't short out the contacts with a piece of thin plastic(ie: product wrapper, baggie,??) the cam will not close down the lens when i shoot. i keep a small piece of plastic under the front body cap of the TC just for this reason..
robar is offline   Reply With Quote
Old Aug 21, 2007, 5:30 AM   #4
Senior Member
Gumnut's Avatar
Join Date: Jul 2005
Location: Perth, Western Australia
Posts: 1,259

i did the test and it worked
with varying degrees of success, which more depended on the lens
like not having enough light ( i think ) at f8 or f11 to trigger the shutter
it was a bit of a dull day and i could only get it to fire at f 6.3
here are a couple of pics, all hand held

the city is about 20 ks away

a local at minimum focus distance, 30 feet away

small birds were near impossible to keep in the centre of the viewfinder

having auto shutter speed was handy
much easier than pressing the green button
Gumnut is offline   Reply With Quote

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

All times are GMT -5. The time now is 6:38 PM.