Saturday, October 1, 2011

Return of the 15,- Pentax 6mm 1.2 (a succes story!)

grind down more on the side, as shown in picture
Ever since I bought my Pentax 6mm 1.2 cctv lens, I have not been able to focus on infinity. I paid someone €20,- to shave down the rear barrel of my lens but to no avail. I started grinding my c-mount adapter but that was not succesful either.
The problem is -and I know other buyers are struggling with the same thing- is that you don't know exactly how much to grind down of the barrel. People didn't get it and I didn't, either... It's not that the person who 'discovered' this cheap wide and fast lens, Seb Farges, wasn't helpful. He shared pictures of the mod but he was not able to explain exactly why simple 'shaving off a few millimeters' didn't work. But then, upon close examination and with the help of blogger Obakesan I finally noticed what I was supposed to do: shave off the outer side of the barrel a few millimeters more, untill you reach the screw on the side.
I bought a €35,- Dremel (electric tool) to do the job and after a few rounds grinding down the barrel... tadaaaa! Infinity! I am infinitely happy with the results... I will post some footage I shot with the Pentax soon. (Note: this is not a dirtcheap lens anymore: 15,- for the Pentax, 2 c-mount adapters@ 19,- together, 35,- for the Dremel... But the Dremel is a lovely tool: I used it to slice through metal today and it lived up to the task!)



  1. Congratulation~now I hope mine works too...

  2. no...but I'll pay someone for it...:D

  3. I paid someone and wound up doing it myself anyway... If you look carefully at the pictures from Seb Farge, you should be able to see how to modify your lens. Start conservatively and then grind down mm by mm, checking if it works. (if I can do it, anyone can..;-)

  4. Jeroen, I am totally new to the GH2 and I purchased one at My purchase did not include the original lens. Instead I have 6 security lenses, one of them the Pentax 6mm. What adapter did you end up using? I want to film my kids sports events and wonder if I should go to all this trouble with these C mount lenses or sell them and buy something else? I would be too scared to try and shave down the barrel since I have no clue what I'm doing. Could I send you my lenses and see what you think?

  5. @ifOnlyIknew,- Sorry I didn't respond earlier- was on a trip in France and no internet!
    You should be able to use any old c-mount to m43 adapter off eBay. Read this post:

    Not all security camera lenses are useful for the GH2, but I am not an expert at lenses. Sending me your lenses is therefore not a good idea ;-)

    Why didn't you buy proper M43 lenses in the first place, if I may ask? It seems like you would be best off with the stock lens or the Panasonic 14-140 zoom lens. These lenses do very well on autofocus, which is what you want for sports.
    I have the 20mm 1.7 pancake lens and love it, but it's obviously not as versatile as a zoom lens. But with the ETC mode you can get that extra zoom nonetheless...

  6. Thank you Jeroen for your reply. When I bid on my GH2 on e-bay I did not pay attention to what I was doing and I accidentally won the bid...stupid me. (I have very little e-bay experience) Oh well, lesson learned. Anyway, the seller had already sold the stock lens that came with the camera and instead included the CCTV lenses. Thank you for your link to the adapter. And, thanks for your advise as to what lens I should use for sports. Very helpful!

  7. You're very welcome- glad I could help.

  8. hey wow ... my pages helped someone :-)