Help Needed: Cooke Speed Panchro 18mm f1.7 (S2) Focus Marker?

[Joel Hanson Li]

I own one of these beautiful lenses along with a CSP 32mm as well, but mechanically they are different - I use it fine for sure on my GEMINI in manual focus, and I use it wide open at 1.7, which understandably make the image soft.

 

However, I just wanted to make sure that the backfocus on my GEMINI isn't off and contributing to the softness, but for the life of me I've never figured out where the focus marker is on the lens. The aperture marker is evident enough, just not the focus marker.

 

This is not my lens per se, but it is the same and I am linking the video for reference.

 

 

Edited July 23, 2023 by Joel Hanson Li
Misspelliing.

[Dom Jaeger]

This is the older style of Arri Standard mount that needs to rotate inside the camera or adapter mount, while the inside of the lens is located and kept from turning by a tab that fits in the slot at the back of the lens.

The index mark was actually on the camera mount, and if memory serves it  lines up with the centre of the tab slot. It should also line up with the aperture index mark, but if people have fiddled with the lens it might be shifted.

Good quality adapters for this type of lens mount used to have an index mark on them, as pictured in this example:

 

[Joel Hanson Li]

Ah, I actually have this one (I reckon it's the one from Duclos Lens?) and it indeed has a red line than runs through the middle - I take it that the red line is the focus marker, and it doesn't matter which slot I've fitted the adapter's tab in? (there are two slots parallel to each other)

[Dom Jaeger]

Some lenses have two scales, sometimes one metric and one imperial, so there are sometimes two positions to mount the lens.

[Joel Hanson Li]

I just tested it out, and I found interestingly that on one end, both Metric and Imperial scales match up nicely at the Infinity mark with the red line on the adapter; and on the other end (closest focus distance), I can rotate beyond the last marker (FT and M marks in this case).

 

Is it supposed to work like this? If it is, and I'm trying to set focus at 3 feet, I can just rotate the ring till '3' aligns with the red line on the adapter?

 

I'm not clear if the last lens tech I sent it in to shifted the position/alignment of the focus ring.

[Dom Jaeger]

The minimum focus stop doesn't necessarily line up with a mark if that's you're concern, usually infinity is a hard stop though. 

Can you not use your camera to test whether the 3 ft mark lines up with an object 3 ft away?

[Joel Hanson Li]

Ah okay, then the focus ring is perfect - and I found why there isn't a marker for the focus ring, because there is one at the front of the lens just before the aperture ring, that marker lines up with the one my adapter.

 

Before, without knowing where the focus mark was I couldn't know where the 3 ft mark was; I just did try it out, and indeed it lines up but slightly off, then I knew to adjust my back focus abit.

 

This was incredibly helpful information thanks!