How to Shim your Nikon to Canon Lens Adapters and Help Track Focus

by Barry Andersson3 Comments

Everyone is always asking for more information on lenses they should buy for their cameras. The common debate is between Canon vs Nikon glass because those two are the largest in the industry.

However, there are times where it is nice to have both. Nikon lenses usually have the aperture ring on the lens whereas Canon lenses do not and so you don't have the ability to full control the aperture.

You may be aware you can use your Nikon lenses on your EOS mount camera by simply using an adapter.

However, I wonder how many people test their lenses after they put on the adapter?

Here is a great article by Alister Chapman on how to properly adjust your lens adapters and make sure your focus marks on your lens still match up properly. He includes a step by step process as well as photographs you can easily follow.

Have you done this with your lenses in the past? Does this compel you to start doing this or do you feel you don't need that accuracy for your type of shooting?

Shimming Nikon to Canon Lens Adapters

Excerpt from Alister Chapman's article:

Now a problem with a lot of these adapters is that they are a little bit too thin. This is done to guarantee that the lens will reach infinity focus. If the adapter is too thick you won’t be able to focus on distant objects. This means that the focus marks on the lens and the distances your focussing at don’t line up. Typically you’ll be focussed on something 3m/9ft away but the lens markings will be at 1m/3ft. It can mean that the lens won’t focus on close objects when really it should. If your using a zoom lens this will also mean that as you zoom in and out you will see much bigger focus swings than you should. When the lens flange back (distance from the back of the lens to the sensor) is correctly set any focus shifts will be minimised. If the flange back distance is wrong then the focus shifts can be huge.

So what’s the answer? Well it’s actually quite simple and easy. All you need to do is to split the front and rear halves of the adapter and insert a thin shim or spacer. Most of the lower cost adapters are made from two parts. Removing 4 small screws allows you to separate the two halves. Make sure you don’t loose the little locking tab and it’s tiny spring!

Remove the 4 small screws as arrowed.

Remove the 4 small screws as arrowed.

Split the two halves apart. Then use the smaller inner part as a template for a thin card spacer that will go in between the two parts when you put the adapter back together. The thickness of the card you need will depend on the specific adapter you have, but in general I have found card that is about the same thickness as a typical business card or cereal packet to work well. I use a scalpel to cut around the smaller part of the adapter. Note that you will also need to cut a small slot in the card ring to allow for the locking tab. Also note that when you look at the face of the larger half of the adapter you will see a small lip or ridge that the smaller part sits in. Your spacer needs to fit just inside this lip/ridge.

The adapter split in two. The shim needs to fit just inside the lip arrowed.

The adapter split in two. The shim needs to fit just inside the lip arrowed.

Continue reading the instructions on Alister Chapman's article “Shimming Nikon to Canon Lens Adapters. Helps get your zooms to track focus.”

Note: it is our policy to give credit as well as deserved traffic to our news sources – so we don't repost the entire article – sorry, I know you want the juicy bits, but I feel it is only fair that their site get the traffic and besides, you just might make a new friend and find an advertiser that has something you've never seen before

(cover photo credit: snap from Alister Chapman)

Barry Andersson

Barry Andersson is an award-winning director and cinematographer. Mr Andersson takes his real world experiences and shares those images and lessons with everyone from the US Marine Corp combat camera teams, many of the leading teams of the four major sports leagues, leading universities around the US as well as leading productions looking to take advantage of the latest technology.

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Comments

  1. I’ve been tremendously happy with the semi-permanent solution from www.leitax.com. I fitted these mounts onto my set of Nikkor High Speed Primes (Cine-modded from www.RPLens.com). It has saved me so much time in the field, not to mention wear and tear on the lenses themselves from moving the adaptor from one lens to another.

    Shimming is such an exact process and getting it wrong will have sharp consequences.

    Buy once, be happy. There is a time and a place for DIY and a time and a place for just getting it done right.

  2. GreggMcNeill I agree.  I use Leitax mounts for my Leica and my Zeiss ZF lenses for my EOS mounts.  Couldn’t be happier.  But some people still like the flexibility of changing mounts and if so shimming is still a necessity.  Great feedback though.

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