Problem with Canon 300mm 2.8 PL Mount.

[Christian Munoz D]

We just bought a used Canon FD 300mm 2.8 series L - PL Mount from a well known photo gear retailer. Today when we tested the lens on our Red One we founded this problem on the image (See Picture).

Does anyone have seen this kind of issue? I have a similar problem 20-25 years ago with a Sigma zoom. Never got fixed… at the end I sold the lens to a lens repair business.

Any input will be appreciated.

Thanks!

 

[Jacek Zakowicz]

it looks like condensation on the elements- usually happens early in the morning...

 

[Christian Munoz D]

Thanks Jacek!

That was my impression initially, but after 7 hours the problem still the same...

I own a few different Canon telephoto still lenses modified to PL. None of them have had this problem.

 

[JD Holloway]

is there a filter in the rear slot? There should be. At least a clear glass.

 

[Jacek Zakowicz]

It could be ghosting from the edges of iris blades. I recall having to baffle a 600mm canon once because of that. Does the size of the spot change as you change the aperture?
Or it could be an uncoated filter in the back reflecting onto OLFP? remove it or get a coated one - Tiffen MC filter for example...
Let us know here what you find....

 

[Christian Munoz D]

Yes, the filter in on place...the issue is present with o without filter.

is there a filter in the rear slot? There should be. At least a clear glass.

 

[Christian Munoz D]

Today we did several tests. Definitely is not condensation or the filter.

Jacek, I believe you are right. The size of the spot change when I change the aperture. The spot is more visible when the lens in pointing to a bright subject.

Do you think is worth to fix it or just dump the lens?

Thanks again for your help.

It could be ghosting from the edges of iris blades. I recall having to baffle a 600mm canon once because of that. Does the size of the spot change as you change the aperture?
Or it could be an uncoated filter in the back reflecting onto OLFP? remove it or get a coated one - Tiffen MC filter for example...
Let us know here what you find....

 

[Dave Blackham]

We use Canon 300mm f2.8 here to PL mount. No issues.

 

[Matthew Duclos]

Does anyone have seen this kind of issue?
Thanks!

It's caused by internal reflections. Shiny surfaces within the lens, usually at the rear of the housing, allow light to bounce around and cause such flaws. It can be fixed depending on the culprit surface or surfaces.

 

[Christian Munoz D]

Matthew, Thank you for your feedback. I am emailing you with a couple of questions.

 

[Russ Fill]

I have the same setup with my Canon 300mm and never noticed something like that. Maybe if its part of the modification or screw on the back for the PL mount system you can barrow or trade out that part to see if it does it with other similar products. Just for the record my setup is using a Century mount conversion on the back. Don't know if someone like Dulcos lens service might be abel to shed more info on it. I wouldn't just dump the lens just yet.

 

[Craig Weeding]

I have seen a look similar to this before, it looks like left over residue (water spot) on the elements from condensation.

If the lens gets very cold and is brought in doors without taking safety measures condensation will form on the internal surfaces of the lens. Even when the lens returns to room temperature and most of the visible condensation has gone, there is still what amounts to water spots, on the internal elements of the lens. The lens most likely will need to be disassembled and have the surfaces cleaned by a professional lens tech.

When filming the Iditarod in Alaska (-35 below zero near Nome), we had the process of taking our cameras putting them in plastic trash bags and squeezing all extra air out of the bag and tie it shut, while we were still outside, when we brought the cameras inside we did not open the bags for at least two hours. When following this process the lenses were fine. The one time a cameraman did not follow this process his lens ended up creating a look like yours and had to be pulled and sent in for service.

 

[Christian Munoz D]

Craig,
Thank you for your feedback.
The lens was fully tested and the problem is derivative from light reflection inside the unit.

 

[Rogerhaugen]

Christian sent you pm.

I ended up with the same lens or at least problems.
I was about to send it back when I seem to found the problem. Because I read your post about internal reflections I unscrewed the black ring behind the pl mount. The inside of this ring causes major reflections. I already have a lens made by Van diemen in Uk and this lens doesn´t have that ring. The white ring was gone after I removed it


Roger Haugen
Fokus Film AS
Norway

Roger@filmfotograf.no

 

[Christian Munoz D]

Good catch!... I PM you too.