It is important to note that the rotational play does NOT cause optical or performance issues, it is just an annoyance. Even beloved Canon lenses have some rotational play when mounted. A number of my Canon lens shifted on the Canon 5D, but were very tight on the Canon 1Ds Mark II. Aside from knocking sensation, the other ill effect is a slight lag time between when the focus ring is turned and when focus actually begins to move (this may happen if a lens has a very stiff focus ring). The first bit of rotation is “used up” by the adapter rotating on the mount until it presses against the locking pin. Once adapter has come rest against the locking, then there is enough resistance for the focus ring to begin to move. Again, this is just an annoying side effect.

There is no “fix”, nor any way to know beforehand if an adapter’s locking pin hole (or groove in the case of some adapters) is over-sized or not. Also, this added rotational play may not bother some photographers. It has been discussed on the photography forums, so I know I’m not the only person who notices things like this!

FOCUS CONFIRMATION ADAPTERS

My preferred Contax Canon EOS adapters are the newer focus confirmation adapters sold by HappyPageHK on Ebay. As the focus ring is turned, the AF light in the Canon viewfinder blinks and the dSLR beeps when focus is achieved. In my experience the AF confirmation adapters have proven accurate and I no longer need a split or prism viewfinder focus screen. I have used HappyPageHK focus confirmation adapters on the Canon 40D, Canon 5D, Canon 1Ds Mark II, Canon 1Ds Mark III. Contax lenses I have used with focus confirmation adapters include the Contax 16mm F2.8 (AE), 28mm F2.0 (AE), 35-70mm F3.4 (MM), 35-135mm F3.3-4.5 (MM), 100mm F2.0 MM and 135mm F2.8 (MM).

In my opinion the focus confirmation adapters are the best choice currently available for focusing manual lenses - especially for those us with aging eyes. Without focus confirmation the next best options are focusing aids (especially on a APS-C dSLRs like the Canon 40D or Rebel 450D) such as a split screen, prism screen and/or viewfinder magnifier. According to Canon user manuals, split and prism viewfinder screens can interfere with Evaluative metering which has proven true (for me) with the Canon 1Ds and 1Ds Mark II. A split-screen or micro prism focus screen does not guarantee accurate focus. Some Canon cameras require shimming. These screens have the focus aid are just in the center of the screen, so focus & recompose is more likely - and this can introduce signifiant focus error when shoot at faster apertures.

Focus confirmation works better with primes (fixed focal length lens) than zooms.  I think this is because the adapter PRAM is coded to a specific focal length (50mm is default value used by most companies). Using the Contax 35-135 Sonnar-Vario zoom as an example, the DOF is different at 35mm vs 135mm. Using 50mm to calculate the DOF at 135mm is not a tight enough tolerance. I used the Contax 35-135mm Sonnar-Vario with a HappyPageHK focus confirmation adapter and experienced mixed results.

HappyPageHK now encodes each adapter’s chip to the focal length and aperture specified by the customer. For the 1Ds Mark II and Mark III, my adapters are coded to match the focal length of the lens being used (such as 100mm) - and all the apertures have been coded to F2.0. Coding to F2.8 or faster allows the Canon auto-focus system to utilize its cross-sensor auto focus sensors. Coding an adapter to an aperture faster than F2 has met with mixed results. I have always selected F2 for my adapters - which worked fine on the 1Ds Mark II and 1Ds Mark III. When it come to metering, the Canon 5D and Canon 40D need additional exposure compensation as the lens is stopped down. This may have changed during 2008 because HappyPageHK has updated the firmware on the adapter.

Lastly, the Canon 1-series has a tiny micro switch at about the 11:00 position on the lens mount. When a Canon auto focus lens is mounted, it trips this switch and the auto focus system is turned on. The HappyPageHK adapters have a tiny screw on the side of the adapter wall - when mounted on the Canon dSLR, this screw “turns on” the auto focus loop. Not all adapters brands include this micro switch - make sure you buy an adapter that does. It appears Canon has changed their design and the 1Ds Mark III and 1D Mark III no longer have this micro switch set-up, so this could be a non-issue in coming years.

ADJUST THE ADAPTER FOR BEST FIT

To ensure the best performance, adapters need to be snug against the lens. The picture to the left shows a slot than can be expanded to hold the lens tightly against the adapter (adapters usually have three such slots). Insert a small jewelers screwdriver into the slot, twist the screw driver slightly to expand the slot. Expand each slot an equal amount. The goal is even pressure at all points between the lens and the adapter.

If the slots continually collapse over time, try placing a small small piece of aluminum foil into the slot. The piece of foil should be repeatedly folder until it is .25 to .50mm thick. Over expand the slot slightly, insert the foil and then close the slot so the foil is held in place. With the tabs properly expanded, the adapter and lens should be snug with no fore or aft play or wiggle.

Some adapters use a lock screw to keep the adapter from spinning or wiggling from side to side. It really does not matter if the lens slips (ie - rotates slightly) against adapter while focusing, but it can be annoying.  The slippage suggests the adapter and lens are not tightly mated, so the slots should be adjusted.

The picture to right shows the adapter’s locking tab resting in the notch on the lens mount. The start and stop of the rotational slippage is determined by the notch size. Sometimes if there is not enough spring in the tab, the tab will not sit squarely in the notch - thus allowing slippage. To ensure a good crisp fit, bend the angled tab to ~45 degrees.  This forces the tab deep into the notch. I also like to bend the spring part to add some extra tension. The picture shows the clip squarely seated in the notch.

These adjustments will not change the adapter’s performance, but it does keep the lens from spinning slightly which can be annoying.  And if the adapter completely works itself out of the notch, then the lens could come off of the adapter while the adapter remains attached to the body.

Lastly, there are two causes of the rotational play - the adapter slipping against the lens, and the adapter slipping against the camera body (mount). Resolving the lens / adapter rotational play is usually just a matter of playing with the locking tab. This rotational play (so slippage) can be resolved and eliminated. The adapter / camera mount rotational slippage is not easily fixed.