Century 2000 Canon 400mm T3/2.8 with PL. soft focus at past infinity

[Russ Fill]

Hey all I just got this Century 2000 Canon 400mm and when I try to focus wide open on a near mountain or over a mile away I can't seem to get it to go as sharp as say the trees only a few hundred yard away. The focus barrel stops and I need to have it go just a little more to get it sharp. Anyone have this lens and the same experience? I changed the back focus on my Epic to get the mountain in focus but then all my zooms and other lenses are not working as planned. I have a Canon 300mm FD Century PL conversion and the focus marks seem correct so Im thinking its the 400mm. Is there anything I can do here on location short of changing the Back focus every time I want to use the glass or will it need to go and get looked at.
PS I checked all the mounts and parts to make sure they are all lined up and correct.
And should I just send it off to Century to have them take a look at it?
Thanks all for any info.
Russ

[HD Hildebrand]

Don't have my lens in front of me at the moment, but there is a small screw on on a outer ring that circles the lens (runs parallel with your focus ring) - it serves as a sort of limiter (or stopper) on how far you can pull focus. Loosen that screw so the focus ring can now move freely and go past infinity. Once you find your focus, lock down the screw to make that your new infinity.

[Russ Fill]

Thanks HD for the info but I think that is only on the Canon FD converted lenses. I have one like that on my 300mm but the Century 2000 series has been totally rehoused and does not have that feature. I would love it right now if it did. Maybe Im wrong... Anyone have another info on this.

[John Chater]

Do you have the 40.5mm internal clear filter in place. The lens is collimated with the filter in place and if it is removed that is often the reason for this problem.

Regards
John Chater

[HD Hildebrand]

Sorry Russ, I realized that may be the case after I posted. John has a good point worth checking into though.

[Russ Fill]

I took the clear filter out to put in the N.9 and maybe get to use the polo with the total setup.
So if Im understanding you correctly I need to leave in the clear filter to make the lens have correct focus especially on the infinity end???
Thank you but I have sent in the lens to Century for a once over so Im sure they will tell me the same or at least make sure there are not any other problems.

[Matthew Duclos]

If you're using a 40.5 filter and the lens is collimated WITH a filter (any filter including a clear filter) then you must have a filter in there at all times even if it's just a clear filter.