Olympus OM System to Canon EOS Lens Mount Adapters

Olympus OM System to EOS Lens Mount Adapter with Assisted Focus

I had already decided I would buy a Canon because there is a wide variety of successful lens mount adapters that make it possible to attach my Pentax M42 screw-mount and some K-mount lenses to a Canon digital SLR and achieve infinity focus.  The use of lens mount adapters for these lenses proved to be very successful so I decided to order one for the Olympus lenses.

I should interject here the main criteria for me was that the digital camera have a 24mm x 36mm sensor.  The reason for this is because my lenses are made to cover a 24mm x 36mm image frame.  A different sized sensor would result in changing the effective focal length of the lenses.  From a practical standpoint that means that my ultra-wide angle lenses would not yield ultra-wide angle shots.  My normal lenses would produce short-telephoto shots, and my long telephotos would become extreme telephotos.  That was not an option for me.

The lens adapter mount "industry", if it could be called that, has made some advancements.  When I first started looking, the adapters simply bridged the gap between the lenses I have and the bayonet mount of the camera.  They adapters were nothing more than flanges.  And worse, many were imprecise resulting in cases where infinity focus was not available.

Infinity focus is important because one needs to be able to take pictures of subjects in the distance as well as close-up.  If the adapter does not give infinity focus, the photography using it will be limited to close-working distances.  This is not a full solution and impractical for my needs.

I re-engaged my lens mount adapter search and found that the new products had brought a new feature to the game - chips mounted to "fool" the digital camera into "thinking" that there is a compatible lens mounted, enabling assisted focus.  What this means is that while the camera cannot auto-focus legacy lenses like mine, with these adapters, it can give a signal when the image is correctly focused.  For me this is a huge benefit, as I am very particular about having my images in good sharp focus.

It took me a considerable amount of time to determine, to the best of my ability, which products of this type were going to work.  The web sites and discussion groups had information that in many cases was out of date, not well researched, and in many cases, unreliable or inaccurate.  Sifting through this to make a purchase decision was tough, especially because the products are fairly expensive (~$100 for a single adapter).  I decided I would roll the dice on the product that in my research had come out the best.

I purchased and in four days received the adapter pictured.


The product works pretty well with the lenses listed below.  I do observe with uncertainty that there may be a marginal problem with infinity focus.  I do not feel with a couple lenses when I hit the infinity stop on the lens that the image is in focus for objects at infinity.  Additionally, some lenses were a very tight fit, while others felt as good as the factory Olympus mount.  By adjusting the tangs I was able to relieve the tightness but then the lenses that previously felt OK felt a little sloppy.

The mount adapter activates the auto-aperture pin so that the lens may be stopped down to the desired f-stop.  This means focusing with the lens wide open and then stopping down to the desired aperture before shooting.  Unlike the Super- and Super-Multi-Coated Takumars, the depth of field preview switch on Olympus lenses does not stay activated unless you keep your finger on it so cannot be used in the same way as the M42 lenses with Auto/Man switches.

Then my testing with the Focus Confirm...  With my 24mm lens the focus confirm is not accurate.  When the confirmation tone and light alert, a check with Live View at 10-times magnification reveals that the lens is not in focus.  With longer focal-length lenses, it works better.

This does not match my experience with the M42-to-EOS and K-Mount-to-EOS adapters that I have purchased.  These are wonderful, present no infinity focus problems, and in the case of the M42 adapter, the focus confirmation works perfectly.  My K-Mount adapter has no focus confirmation feature, but lenses are neither tight nor loose, and infinity focus is not an issue.

I posted test images at the links for each lens below.  The indoor shots exhibit no infinity focus problems because nothing is far enough away (with the possible exception of the interior shot with the 24mm) to hit against the infinity focus limit. I have mounted and get assisted focus (in some cases not very accurate) with the following lenses:

The links above take you to each OM System lens specification page and images that were shot with the lens - in all cases, mounted on the Canon 5D Mark II!  The resulting image quality shows that the lenses perform every bit as well as they do with an OM-1

Here are the instructions provided by the seller, explaining how to change the settings that appear in the image EXIF data.

Adapter Description:

  • This adapter allows you to use OM bayonet mount lens on EOS camera with AF-confirmation indication.

  • With this adapter, your beautiful OM Zuiko lenses can be used on digital or film EOS camera.

  • With the incorporated AF-Confirmation chipset, you donít need to guess the correct focus by naked eye, as it will be indicated by the accurate auto-focus system of EOS camera with a beep sound (just like using EF lens in manual focus mode).

Adapter Features:

  • Precisely made of Brass

  • Built-in lens lock

  • Allows focus to infinity.

  • With AF-Confirmation indication


  • The aperture value can be changed from F2.0 to F4.0.

  • The function of each aperture are described below:

    F2.0: always use this for shooting;

    F2.2: set focal length to 21mm;

    F2.5: set focal length to 28mm;

    F2.8: set focal length to 135mm;

    F3.2: set focal length to 200mm; and

    F3.5: set back focal length to default = 50mm.


  • The focal length can be changed anytime to fit your lens.

  • For example, if you use a 28mm lens:

    1. With adapter and lens on camera, set the camera to Av or M mode, switch on.

    2. Change the aperture to F2.5, press the depth-of-field preview button or just take a shot.

    3. Change the aperture back to F2.0, the EXIF will show 28mm focal length now, you are ready to shoot with the 28mm lens with optimal focus accuracy.

    4. You can change the focal length to other values by repeating the above steps.


Return to Canon Camera | Canon Accessory Index | Olympus Lenses | M42 to EOS Lens Mount Adapter | Nikon to EOS Lens Mount Adapter



Click or the [ BACK ] button on your browser to return to the previous page.

Photos, Layout and Design © 2010 Paul M. Provencher All Rights Reserved.
Contents of this Web Site may not be used without written permission.

22-Aug-2010 02:53 PM

Hit Counter Since 18-Jan-2010 06:36 PM