IF YOU HAVE PREVIOUSLY READ THIS POST, PLEASE NOTE TYPO ERRORS IN DIAMETER DIMENSIONS HAVE BEEN CORRECTED.

The supporting components of the higher-end P+S Technik IMS - Nikon "professional" mount are very robust, designed to entirely eliminate lens discollimation due to flange wear and ensure constant firm flange contact. The mount is highly unlikely to fail if modern lenses are correctly offered up and fitted to it.

The precision, fit and finish of all components is typical of the fine work of P+S Technik.

I have recently discovered that it is possible for this mount to become "abused" in a rent out circumstance when an old style Nikon or third party "for - Nikon" lens is offered up to the mount and the infit is found to be tight or baulky.

Adaptor rentals by low-no budget entities can sometimes be accompanied by the entity electing not to rent a set of lenses with the adaptor and instead supply its own sometimes older lenses of an uncertain history.

A circumstance of urgency and equipment abuse typically occurs during "glitch" events like lens misfits and desperate "rescue" measures as the schedule slips to hell.

Such lenses which may be problematic include older Nikon S 55mm f1.2, Micro-Nikkor 55mm f3.5 and Nikon 50mm f1.4, which were manufactured around about the time of the Nikon FM2 camera series.

The "professional" mount has been engineered to consistently accept modern high quality Nikon-mount lenses or the Zeiss for Nikon lenses, from which "professional" results can be routinely and reliably expected.

The older lenses have an iris control ring which overhangs the flange of the lens and will foul the chrome ring on the "professional" mount.

Under no circumstances should the black actuator ring on the "professional" mount be forced if the bayonet lugs on the rotating clasp baulk or jam when one of the older lenses is offered up to the mount.

Force will damage the link pillars between the black ring and rotating clasp. Desperate abuse of the black ring may break the pillars free and the rotating clasp may no longer move. If the lens remains stuck in the mount, a fix becomes very difficult.

If the ring initially baulks and then moves stiffly through part of its rotation because the old lens offered up is significantly worn, the iris ring of a misfitted lens itself may be mechanically damaged by the wedge forces imparted by the robust clasp of the IMS-Nikon mount in combination with excessive force on the black ring. The sign of this is a tight or jammed iris once the lens is mounted.

If you want to routinely mount older style Nikon or third party "for-Nikon" lenses which baulk on the "Professonal" mount, the rebated shoulder on the outer circumference of the chrome flange rim should be measured with a vernier.

It likely will be found to be 57mm diameter and 0.8mm from flange face to face of the rebated shoulder. The mount I have used was one of the very first of the type so a revision of the chrome ring may have occurred in subsequent builds.

The older lenses require older Nikon FM2 mount flange dimensions to fit cleanly. The rebated shoulder of the "professional" mount chrome ring may need to be skimmed rearwards by 1mm to 1.8mm from flange face and inwards 0.5mm to a 56mm diameter.

Obviously if you do this yourself instead of requesting P+S Technik to do the mod, you may void warranty on this valueable piece of kit. So you would be better served by requesting a custom ring from P+S Technik for the older lenses.

So far as I know, the original economic and simpler latch style IMS - Nikon mount by P+S, accepts the older Nikon lenses however I can't speak for the latest builds of the type which may now use the modern chrome ring.

These comments are made without the consent or endorsement of P+S Technik GmbH.

Readers should undertake their own research to verify or refute the comments I have made here. Sensible operators will not continue if a lens will not fit up correctly.

I make these comments in the hope that more desperate users refrain from being heavy-handed with their mounts and then blaming P+S Technik if things go badly.

I have condensed this post for brevity and clarity after consultation with P+S Technik.

If you have the "professional" IMS-Nikon mount and experience baulking difficult infit of older Nikon lenses, unusual tightness of the latching ring on the adaptor or the iris ring on the lens, this may be due to the mount having a flange ring which is suitable only for recent Nikon lens types.

Do not force the latching ring to a closed position as this may damage both the mount mechanism and the Nikon lens.

Check the diameter and depth of the shoulder recess in the shiny flange ring of your mount. If it is 0.8mm deep from front face to rear and 57mm diameter, you may need to contact P+S Technik to obtain the revised flange ring to fit yourself or send the mount to them with a request for a service and fitting of the revised ring.

Nikon revised the relief (cutout) shoulder of their F mount over time from 56mm diameter to 57mm diameter with no change to the front to rear depth of the shoulder cutout.

Their modern lenses apparently do not require the cutout to be any deeper rearwards than about 0.8mm which was the depth chosen for the flange ring shoulder on the initial "professional" IMS-Nikon mount.

I am advised that a revision was made by P+S Technik to the professional mount to enable infit of older Nikon lenses. These have an overhang which fouls the shallower shoulder of the flange ring initial version.

I am advised that no other report has been made to P+S Techink of problems with the mount other than mine, so there may be few unrevised mounts out and about which may jam on old Nikon lenses. The mount here was one of the very first sold directly to the client during his visit to the P+S Technik factory in Munich.

I have furthur discovered that some of the older Nikon lenses which have a fully surrounding overhang on the iris ring, also have bayonet lugs which are thicker from front to back than the AIS and more modern lenses.

Some of these early lenses may baulk the movement of one or more of the lugs inside the professional mount from turning. Force on the clamping ring may make the lugs "jump" over the initial resistance and turn a little, just enough clamp the lens from falling out.

You should not use force as you risk damage to the internal mechanism of the mount.

It is also prudent to remember that the lens is offered up to this mount and secured without twisting the lens as with the normal F-Mount. The "latch" pin on the professional mount functions as a fixed key. The matching slot should be placed over the latch pin and the flange face should be checked as bedded home before the clamping ring is rotated.

There is a donkey trap on the rotating lug ring in the form of a small dimple stamped into the metal. The ring is in correct position for insertion when the clamping ring is turned to its anti-clockwise limit as viewed from the front and the dimple and latch pin are adjacent each other.

In rare circumstances of abusive haste, a lens may be offered up to the mount out of position and the clamp ring may turn partially home on some of the lugs. The pitch of the clamping ring thead appears to be 0.7mm and represents a strong levering force to pull the lens flat to the flange face.

The hardened latch pin is an interference fit in a hole which is drilled deeper than the normal fit of the latch pin. An abnormal fit and violent clamping movement will press the pin in deeper and this feature helps avoid damage to the lens, a nice little precision design touch by the good doctor and his team.

Once the pin has become reset deeper, it may become possible for the lens to be turned in the mount by clamping lugs and not become clamped in place. If the latch pin is not protruding through the chrome flange ring, the mount should be sent to P+S Technik or their agent for repair.

It is possible for the chrome ring to be dissembled from the mount and the end of the latch pin picked up by fine pliers and worked by gentle twisting and drawing action back into position but I do not recommend the practice if you do not have the gentle touch. Too much twisting and you may dress the interference fit to a clearance fit and the pin will become loose.

The P+S professional mount appears to have been designed in such a way that abuse in offering up and securing the lens will likely disable the mount before the lens itself is damaged by any part of the mount.

Some may question why the design has not entirely copied the Nikon mount with its stainless ring pressure spring with three raised shoulders. This spring enables a clamping force which larely ignores variation in lens lug thicknesses. However, for holding a lens steady during focus pulls or if a geared follow-focus is used, this spring is too compliant. On the genuine Nikon mount which is not purposed for motion picture work "walking" of the vision during focus pulls may be evident because the lens can lift away on the flange face a little.

Users of Nikon lenses via adaptors on Canon 5D and 7D cameras may have already discovered this glitch as there may even be two layers of spring compliance existing with some EOS to Nikon adaptor designs.

If a set of entirely identical older Nikon lenses is owned and the fit of all of the lenses to the IMS-Nikon Professional mount is found difficult, it is possible for the mount to be internally adjusted for a match fit to these lenses. Later AIS lenses with thinner lugs will still fit with a little looseness but are otherwise well secured. This adjustment is best left to P+S Technik or their agents to undertake with a sample lens and I shall not describe it here.