Tuning adapters for infinity focus and reflections – How To

Since a few people asked this is a short how-to on how I tune my adapters. As you will notice I am far from a perfectionist but so far my method has worked well for me and I think it could solve issues for some of you as well.

Correcting Infinity Focus

The Issue

Most adapters, not only the cheap ones, are a bit too short. This means that the markings on your lens are off and you can focus your lens behind infinity so the infinity hard stop of your lens won’t work. It makes sense for adapter manufacturers to make their adapters a bit too short because your Sony’s flange focal distance varies a bit and so does lens calibration. If their adapters were exactly as thick as specified there would be quite a few cases were people couldn’t focus at infinity which is way more annoying than a focus scale which is a little off.

But a too short adapter can also have negative impact on the image quality if you use a lens with floating elements. Especially with fast wide angle lenses you can get serious field curvature issues as many users of the Metabones Canon EF adapters have found out.

The lens is focused as infinity but the focus scale is way off because the adapter is too short

The Idea

To fix the issue you want to make your adapter thicker. Thankfully this is easily done because on about any adapter I have come across so far you can unscrew the mount and add some spacing material.

Materials

You could use just folded tinfoil from your kitchen which is basically free. I use self adhesive copper foil (affiliate link) which is affordable and easy to handle. You could also make yourself some metal shims like they are used in many lenses but in my eyes that is overkill.

Tools 

  • Finer scissors
  • A fine decent quality screw driver

The Fix

  1. Step: Unscrew the mount of your adapter

2. Step: Add shimming material

This is the only part which is a little tricky. You need to add the right amount of shimming material. So better start with a little less than needed, test and then add some more until infinity focus is spot on.

Step 3: Put the screw back in and test

After you have put the screws back in you need to test if you added the right amount of shimming material. So open your aperture as wide as possible and focus at an object far away. If the focus scale shows infinity you are done. If not go back to step 2 and add some more material.

Limitations of my method

My method won’t result in a super exact alignment of the adapter. It is precise enough for any lens I have tested so far but those were older wide angles which have softer corners at wider apertures anyway which might mask issues. A modern super wide angle like the Laowa 2.8/12 or Nikon 1.8/20 will be more sensitive. My method might be precise enough for them or not, I simply haven’t tested so far.

Adapter Reflections

The Issue

Especially cheaper adapters are often quite reflective which can cause reflections which degrade image quality.

left: After my fix is applied right: Unfixed adapter with strong reflections

Adapter reflections do only happen if you have a very high contrast in your image and some lenses are more susceptible to it than others. See the image below for a demonstration of how adapter reflections can destroy your image.


before: adapter reflections cause annoying flares after: the same scenario with fixed adapter

Adapter reflections do not happen often and you can shoot an reflective adapter for a log time without running into issues but since the fix is easily applied I can only recommend to do it.

The Fix

The idea is simple: You want to cover the shiny inside of your adapter with something which absorbs the stray light. I have seen solutions ranging from light absorbing paint over custom made light baffles to felt like material. I use DC-fix black velours (affiliate link) which absorbs light very well and it is easily applied because it has a self-adhesive backside.

Step 1: Get the right measurements

You could take very exact measurements of you adapter and then calculate the exact measurements you need for the felt-like material. I simply took a piece of paper, took a rough measurement on the correct height, inserted into the adapter and then cut it to length.

Step 2: Cut material to size

I then used this mask to cut my DC-fix black velours to the right dimensions.

Step 3: Apply material

Now I just had to put the material into the adapter and I was done.

Photographing light absorbing material is quite hard but I think it is obvious that the adapter now reflects much less light.

Step 4: Vacuum the adapter

Do yourself a favor and use a vacuum cleaner to remove any fuzz from the velours. I haven’t had any issues with threads on my sensor after vacuuming.

If you have come up with a better method please let us know, so that we can all benefit.

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I like to be outside with my camera and I am also a gear head with a love for manual lenses.

14 thoughts on “Tuning adapters for infinity focus and reflections – How To”

  1. I had one adapter for a Minolta /Nex where the lens wouldn’t lock on the adapter. This can be caused by two issues.
    1: There is a little screw on the back of the mounting plate that is used as a stop. Remove this totally ( put in a white dish 🙂 ) and check does the lens now rotate enough to lock. If it does you have 2 options, put back the screw and file flat the side of the screw that hits the mount allowing it lens to rotate further or file the side of the locking plate that drops into the notch. You can see the plate in the pic in step 3 above. To check how much more you need to rotate to fit the adapter to the lens and look down into with from the camera side. Note: If you leave don’t put back the screw your lens can keep rotating around
    2: The locking plate is too wide for the notch in which case file down to the required width.

    I had one other that I couldn’t fix simply because the piece sticking out of the locking plate was too short to lock into the notch on the lens.

    I am really surprised that manufacture haven’t designed a mount where one part screws into another along with a locking ring to lock infinity position. Apply a bit of loctite or the like to the locking ring then and it would never move again

    Thanks for the info on the flocking, I wasn’t sure what to look for when I considered doing it before

  2. Just one thing looking at the placement of the shim material, Its nit picking but I would recommend getting a piece at the locking side of each screw hole as well so as not to create an issue of the plate bending downwards on that side. Assuming that everything is parallel anyway. From pic 3

    Also if anyone knows the exact specification of the screws so slightly longer ones can be got it would be great info to have. Some are very short if you have to shima lot.

    I also saw a post where one guy after shimming, taped neatly around the adapter where the plate goes on to the adapter to eliminate any possible light leaks in that area. He had shimmed a good bit for one lens but no harm in doing it while you are at the work yourself

  3. If you want to be *really* obsessive you could do what I’ve done a couple of times and make a rectangular mask out of two pieces of flocking (I use self adhesive telescope flocking which may be very similar to your velour) stuck together to ensure that it’s matte on both sides, with the sticky parts left separated at the base to act as tabs. I make one for both ends of the adapter. It’s important to make the rectangular hole just a bit larger than in a purpose built masked adapter, because you’ll never get the alignment exactly right, and you need some room for error. I have seen situations in which this makes a (small) difference…

  4. Can you recommend any adapters that aren’t reflective on the inside? (Particularly for Nikon manual focus lenses)

  5. Hi Phillip, I have a question for you about adapted wide angle lenses: given your vast experience do you see often uneven corner performance caused by the adapter itself? I’m asking because I think I clearly see the problem with all my wides: a 24 fdn Canon, a 20 fdn (with rayqual adapter), a 28 distagon c/y with cheap adapter, a minolta 24-105 @ 24 with ea3 and 4 sony adapter. Is it possibile? Thank you in advance.

    1. In theory adapters can cause such issues and when I tuned one of my adapters in a very crude way I saw a filted image plane. But I have never seen any issues with a normal adapter and with a Rayqual I would be very surprised if your issues were due to the adapter. Do you have access to other WAs which have symmetric corners? Because you camera mount could be the culprit.

  6. I hope the camera mount is ok, but I guess it’s difficult to check it… probably I have a bad combination of lenses+adapter. For example the 24 fdn although in excellent conditions has focusing ring play. I read this can cause problems to the optics. Maybe also the 24-105 af has some decentring. But how can you really understand if the focus plane is tilted or the lens is defective?

    1. If you vave issues with every single lens/adapter combination you own then there is a pretty high chance that your mount has issues. Maybe you can borrow other native lenses/adapters and check if those work better. If they don’g it is almost certaibly the mount.

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