Another Nikkor Q 13.5cm LTM Question!

[leica fan]

Hi Everyone,
my lovely Nikkor Q 13.5cm ltm f3.5 arrived today, the glass and coatings are great, my uv/ir filter screwed right on, the focus ring moves butter smooth, apertures click nicely into place, and it's black and chrome finish it looks great on my black M8. Even better, the images are lovely with smooth falloff between in focus and out. Even wide open it has more contrast and clarity than images from my 135 Hektor stopped down to f11. I can easily see why Nikon made the design for so long for rf and slr.

However, not all is beer n skittles in RFLand. The lens is front focusing at all distances.

It's my only lens that does it - my 28 & 75 CV's, my Forty Rokkor, my Ninety Elmarit, and my 135 Hektor, all focus appropriately. (yes, I was lucky and all were accurate straight away). I even used the ltm/m from my 28 to make sure I was using an adapter known to be good when testing my Nikkor 135. I'm now trying to rule out other factors before sending the lens off for adjustment.

Query: does the d.o.f. Scale on ltm Nikkors usually end up at top of the lens when attached to a Leica body? Cuz mine ends up off about 1/4turn towards frame preview lever. The tripod ring is off center an equall amount.
The CV28 lined up just fine on this adapter on my M8 prior to using it to attach the Nikkor.

All input and advice appreciated. This is my first Nikkor lens of any kind and it looks like won't be my last.

Richard in Michigan

 

[Dez]

Nearly all LTM lenses have the focus index off to the right somewhat (facing the front of the camera) when screwed in all the way. There will be a little bit of variation in the threading of different bodies and lenses, but this seems consistent. I really don't know why they are designed that way- possibly someone on the list has a perfectly plausible story about why this is so. The important thing is that the focusing cam is well centered on the rolling follower. If you look at the back of your lens, holding it so the focus cam is exactly at the top, you will see where the focus index line is expected to lie.

I also just received one of these lovely lenses, a bargain on ebay, and I have not tested it yet. Hopefully I don't have a focus issue. When screwed in well to my trusty IIIb, the index line points exactly at the right-hand RF window. There is a screw at the bottom of the barrel near the mount which looks like it allows the barrel to rotate in the mount, but doesn't seem to do so.

When the lens is focused at infinity, does the RF agree? If so, the focus cam is probably OK, and the problem is the position of the optics relative to the focus mount. Assuming you have made sure that the threads aren't plugged or damaged, so it screws in properly, and that the camera's RF is correct, it looks like there may be some sort of shimming issue, but I have never had one of these apart, so I am guessing. How far off is it? Sometimes lenses are put together with the wrong multi-start thread engaged, but in that case, it will be WAY off.

Cheers,
Dez

 

[leica fan]

thx dez

thx dez

Hi Dez,
it very much appears to be that the focusing cam of the lens and the roller arm of my M8 are mating up well. I would note that my 'front focusing' problem is not by a glaringly obvious amount. It is also remarkably consistent in scope through most of my tested distances. To describe it, the area of sharp focus (d.o.f.) at f3.5 is landing so the spot I focused on is at the front edge of the depth of field.

It's an issue not present with my Elmar 135, my 90 Elmarit, or my CV-75, so I tend to discount it being a camera issue or a 'me' issue (eg:misfocussing the bugger!). I've also gotten a 1.25x focus magnifier and had my vision checked along the way.

The current vector I'm working on is testing different LTM to M mount adapters to see if they are the source. I've purchased a new 6bit 28/90 adapter from JinFinance on the 'bay to go with the others ones I have from him and a CV one I purchased with my 75. Only compared 2 adapters so far, but they both produced identical results so far.

For the record, I very much like the lens!
Produces images that please me aesthetically and operationally I enjoy shooting with it - though it startles me routinely when my aperture rotates, too when I focus :-D.

Richard in Michigan