A request for tech advice. Zoomitar Sr. 254-1581 40mm f2.8 Macro Kilar

[Robert Hart]

Zoomitar Sr. 254-1581 40mm f2.8 Macro Kilar

This is another of the uneconomic-to-repair fungussed and tropically humidified lenses I referred to in a post some time back. Those were two old Cooke Ser 2 lenses and a 90mm Zoomitar Macro Kilar. For lens techs, it is probably not something you would want spreading spores and infection around in your workshop. Given their condition, cost of shipping, low market value and having a bit of facility in cleaning lenses myself, I decided to tackle these, so far with good outcomes given their damage. They cannot be perfect as the coatings were too far gone.

I have been putting this one off. Like the 90mm, there are signs this one had a previous tourist inside in its past as there are two missing screws.

So far so good except that I have run into a snag with the rear optical elements. They have to be dismantled because there is oxide contamination within. Luckily the iris blades are clean this time round.

This group appears to be a doublet, retained from the rear by a metal cylinder and single element in a rear shoulder in this cylinder. The cylinder is retained by an internally shouldered threaded ring which bears on the rear element itself. This is where it gets tricky. There is a buildup of metal bloom. With patience I have been able to get the threaded ring off. However the rearmost element is wedged into the cylinder which itself is stuck. It does not appear to be a swaged cell as there is about 0.5mm of the optical element protruding and the sides are square, not chamfered for swaged retention. The 90mm of similar design had no swaged cells.

I am also unable to find any screws which release the two extending focus barrel segments. With the 90mm it was not necessary to dismantle this section. However with the 40mm, to entirely remove the rear optical/iris assembly, either the focus barrels must be screwed out or there are two sections to a rear fixed body which screw together. There is a machined seam in the rear body but no sign that this is a joint. There are neither locking screws nor any holes/slots for lens tools. If this section has been pressed/bonded together, then that's my lot.

If any lens-smiths out there have it within their generous souls to advise, this would be muchly appreciated.

 

[Robert Hart]

If there was a ranking for mindless monotonous undertakings, hand-polishing fungus pits out of a one centimetre diameter plano convex-optical element has to rank right up there. However success at the end takes some of the sting out of it.

As for the lens - 30% there, now to figure out how to get the rear group out. Should be an easier fix as only one surface of each of two elements is involved. Any advice besides "give up you fool" will be appreciated.

As macro lenses go, it is apparently a lesser performer even in as new condition compared to modern designs but was revolutionary in its day. Some novel assembly and component retention technique too, such as springloaded ball latches for holding a cover piece in place and interestingly a variation on heavy transport rear driving axle technique for supporting the aperture ring so that the iris assembly floats and is not mechanically stressed.

Looks like this only the silver bits are black anodised for the ARRI standard version.

http://www.ebay.com/itm/40mm-F3-5-K...98094462?pt=Camera_Lenses&hash=item48452b0c7e

 

[Robert Hart]

Ended up being a dead end. The rear group is in a cell. The cell was well and truly welded into its receiver. Managed to extract wihout breaking glass. The concave element sits alone and it is good. The damage is within the cell. There is corrosion sediment and condensed moisture within.

The doublet has begun to separate. To fix properly the cell has to be cut open and remade - out of my league. T'was a good thought whilst it lasted.Re-assembled and gave it a try anyway. It is amazing what modern image software can recover from optics with the transparency of a grubby glass covered with milk. Super16mm out of a 35mm format lens is probably a big ask.If you are after a distressed look then this is likely it - after processing ex - SI2K, which is a Super16mm sized sensor.

Interestingly, the Kilfitt Zoomitar Macro-Kilar 40mm f2.8 and 80mm f2.8 both cover the 35mm stills frame and the smaller lens was also mounted to Exacta still cameras, maybe the larger one as well but I found no references. The image quality is rather sad. The subject is another of the fungussed lenses, a Cooke 75mm. Well preserved examples of the Mcro Kilar lenses and a full sized 35mm imaging sensor may work well as a niche thing.

EDIT: A before and after compare of near to full S35 frame width image has been added below. The 35mm format frames were shot with a Sony EX1/Letus Extreme with the Sony set to BBC picture profile. 25 points of sharpen were added to compensate for groundglass. As motion imaging lenses, the 40mm Macro Kilar breathes - a lot. It is very far from being any sort of valid technical test.

 

[Robert Hart]

Here's a corrected image off the Macro Kilar 90mm. This lens was also badly fungussed into all the glass so the recovered image from this one is fairly grim and good only for a distressed look.

Good specimens should be able to do better. Again the image frame is close to S35mm.