My issue is that I can't achieve focus at infinity. I never noticed it until this past weekend when I was trying to take a landscape photo, which is not how I typically use this lens.
Is the K&F mount known to be slightly too thin? Or is this a common issue with adapted lenses? I certainly have no interest in disassembling the lens to make any adjustments, so I'm hoping it's just an adapter problem, although this seems to be one of the higher quality adapters I've come across.
p.1 #2 · Inability to focus at infinity - adapted vintage lens
The adapter is too thick if it won't reach infinity. If it goes past infinity it's too thin. You could shim the adapter if it's too thin, but maybe simpler to return it and try another brand no matter which.
p.1 #3 · Inability to focus at infinity - adapted vintage lens
mcbroomf wrote:
The adapter is too thick if it won't reach infinity. If it goes past infinity it's too thin. You could shim the adapter if it's too thin, but maybe simpler to return it and try another brand no matter which.
Do you think it is more likely the adapter is too thick, or the lens focus is out of calibration? Asking because as I glance through the product reviews, I don't see complaints about other people not being able to focus to infinity.
I'd like to assume if a company (especially a well known company) is making any adapter, they would get the distances correct for each adapter. That's probably the most important detail other than matching the mounting ends.
p.1 #4 · Inability to focus at infinity - adapted vintage lens
Good question. I've had that problem once (lens) but it was wildly changed or really defective so I sent it back. It's a bit of a generalization but after the early days of dumb adapters when some were too thick the makers (most?) started making them a little thin to account for lens to lens variation to ensure infinity could be reached. I don't know how K&F make theirs but it's possible your lens is off rather than the adapter. If you have good calipers you might be able to measure the adapter.
p.1 #5 · Inability to focus at infinity - adapted vintage lens
Well, I faced the same situation with a vintage lens. My initial thoughts were somebody opened the lens (for cleaning) and messed up the calibration. So, I went ahead, opened the lens myself and try to fix it. I could not. I thought the adapter might be the issue, and bought another one tested. Same issues. As the other user has pointed out, I decided to skim a little bit off of the thickness of the adapter and could not do that. But the thought process was right and the thickness had to be reduced (which eventually changes the flange distance and hence corrects the infinity). Even though I understood the math or physics behind that, could not reduce the thickness due to lack of machine tools to do that.
What I learned from that experience is this. M42 screw mount lenses ( mine was one) are closely tied to the make and model of the camera that they came with and they are calibrated for them. Reason being, the point where the lens latches on to the adapter can be at infinite points based on the make and model of the adapter. That is the reason why I said the lenses came calibrated for the camera models of that era. Second, not all lenses have a wiggle room to adjust the infinity focus properly. Some of them come with a hard pin to stop at infinity (that was the case with my lens).
Check out the link below where I asked for help and how I finally could make a work around. Not the best solution, but it worked. It has some photos as well and hopefully that would provide a lot more clarity of what I am saying. No matter what mount it is, the thickness of the adapter has to be reduced in your case. Yours being a K mount, not sure how that can be done? If there is a possibility to open one side of the adapter(on the side where the adapter goes on to the camera), try sanding the thickness down. Even if you sand it more, not going to do any harm. It is going to focus beyond infinity a bit.
p.1 #6 · Inability to focus at infinity - adapted vintage lens
Fotodiox makes a line of adapters that include a one-centimeter helicoid for adjusting the distance between lens and sensor ("back focus"). The model for mounting Pentax K lenses on Sony bodies seems to be: This one. The item description includes the phrase, "infinity focus or beyond guaranteed."
I haven't tried any of these adapters, but like the idea. And I've had good experiences with a couple of products from the company.
