Lens adapter with adjustable back (infinity) focus?

UnknownSouljer
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p.1 #1 · p.1 #1 · Lens adapter with adjustable back (infinity) focus?

This is a common problem with lens adapters, just wondering if there even is a manufacturer that bothers to make adjustable mounts, to get infinity focus to lineup dead on. The issue generally is the mount being too short, and not allowing for infinity. Or now the opposite, being too long, which can affect lenses with floating elements. Both are detrimental to IQ.

Not that I think it's important, but I'm looking for m42 to E-Mount.
I mostly see K&F, Shoten, and then some smaller no-name brands where I am. I'd have to specially order something else, so if there's a better option that would be helpful. And if there isn't and I should just get a K&F, then it is what it is.

Jul 15, 2024 at 06:42 AM

mcbroomf
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p.1 #2 · p.1 #2 · Lens adapter with adjustable back (infinity) focus?

There are a few SLR lens to e-mount helicoid adapters out there. I don't think of them as for infinity adjustment, more for macro, but that can be used for both. For infinity only you could tape it for the lens.

In fact I have a 42-e-mount adapter that I use for macro. Not sure if it's this one but here's a link

https://www.amazon.com/Fotasy-Mount-Adapter-Focusing-Helicoid/dp/B01HG3RYR0/ref=asc_df_B01HG3RYR0/?tag=hyprod-20&linkCode=df0&hvadid=693502990541&hvpos=&hvnetw=g&hvrand=3454697434265265672&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9002139&hvtargid=pla-861448854952&mcid=a660fdc6583b3db99b779caf4f5931e9&gad_source=1&th=1

PS: Make sure you test it for mechanical vignetting as soon as you get it

Jul 23, 2024 at 03:05 PM

Choderboy
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p.1 #3 · p.1 #3 · Lens adapter with adjustable back (infinity) focus?

You may be able to get infinity to line up 'dead on' but it will be for a specific lens and specific body unless you are really lucky. Also, significant temperature difference will mess it up.

Solving too short or too long is feasible but the very small adjustment required may be difficult.

People use shims to compensate for mount or sensor alignment issues.
Rather than using shims to tilt, they can be used to increase thickness, ie, resolve adapter being too short.

https://www.fredmiranda.com/forum/topic/1662397/0?keyword=tilt#15337214

Jul 24, 2024 at 08:07 AM

Choderboy
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p.1 #4 · p.1 #4 · Lens adapter with adjustable back (infinity) focus?

Post #19 of that thread:

If you peruse Roger Cicala's flange distance article, you'll see how much the Sony cameras flange distance varies. About 100 microns of variation, excluding the outliers. This is not insignificant. Typically the lens infinity focus stop is calibrated to within 10 microns precision, so there is little meaning to that when the cameras vary by an order of magnitude more.

Relevant to my point that you may only get infinity 'dead on' for a single lens and body.

Jul 24, 2024 at 08:17 AM


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