Strange problem with Scarlet Canon mount plus CP.2 lenses

[Slobodan Milivojevic]

Hi,

I don't know will I be clear enough, so you can understand my problem, but let me try.

Basically, I am director/editor, not a DOP, but I know a lot about optics, cameras, chips etc...

We have Canon mount Scarlet, with set of CP.2 lenses plus another set of Canon L series photo lenses.

Recently, we have filmed some architectural shots, and we have noticed that there is a problem with long distance focusing on all lenses.

Example: We have a building which is around 500 meters from us. We try to focus on that building, but we come to end focus point (infinity), while the building is still not in proper focus, and also background (infnity) is blurred! It was really strange. We tied combinations of different f-stops, but its all the same!

Immediately, we tried with Canon L photo lens (16-35 2.8), and it worked fine. We can focus on that building, and then when you go to infinity, that building goes out of focus, while infinity is sharp.

When we went back to studio, we did a test with focus chart, and everything seems to be ok with the lenses (up to 4 meters) - the focus is showing correct distance measures.

Have anyone faced the same problem? Should we adjust the back focus? IS something wrong with the lenses?

 

[David W. Jones]

I would make sure the camera lens mount is adjusted properly, as well as your CP.2 lenses which have interchangeable mounts and may not have been shimmed properly.

 

[Scott Crawley]

Yes, if the L's work and the CP.2's have an issue I would look at the lenses first.

I would make sure the camera lens mount is adjusted properly, as well as your CP.2 lenses which have interchangeable mounts and may not have been shimmed properly.

 

[Joesef o.]

Someone did a bad job on the CP.2 canon conversion. It's the shims under the canon mount on the lenses. Most likely it wasn't done properly and they are slightly off.