I found my RMC Tokina Doubler for P/KA serial number 8908151 a couple of weeks ago. I used it on my camping/fishing trip and was pleasantly surprised with it. So I took it fishing with me today and paired it with my new SMC Pentax-M 1:1.7 50mm (thanks Nixarma). I'm having a blast with the M 50mm. I got it thinking I was going to use it mainly with my extension tubes for the manual focus, but now that I found my doubler (Tokina's wording) it gets the call in this situation also. Neither my extension tubes nor the doubler offer AF. This M lens is a joy to use, the focus ring is smooth as butter, the build quality is super, I'm falling in love with the M lens. I love shooting in manual mode.
The only thing I've found so far about this doubler are some references to the fact that there were two versions made and the seven element one is preferred. I'm still not sure which one I have.
I've healed most of them in Lightroom but I left three or four little star shaped reflections (I think, they're reflections) on the froggies side right in front of his hind leg, there were a lot more. I got nine pics of this guy of varying exposures and all of them show the bright areas on his side and lower left of his eye, the sun was behind me. I'm pretty sure this is the fault of the doubler. BUT, I was shooting at iso 800. Aperture was f/8 or 11 @1/160, exif doesn't record aperture with this combo and I don't remember exactly. I wish I could say I shot this at iso 800 to keep my shutter speed faster because this was handheld but of course the reason is I saw a photo opportunity and in my excitement I completely forgot to check. The histogram doesn't show any clipping in the highlights except for a teeny bit of red. Those bright areas, I would think, would show more clipping. Are they noise? What do you guys think?