linear/circular polorizing filters

[Conk]

It was touched on in a different topic but I wanted to repost to get some concrete answers regarding linear and circular polorizing filters.
When I picked up my lens adapter I was told by the sales person that I could not use a linear polorizer. I was then told here that this is not necessarily true.
Can some people please reply with the answers telling me if I can in fact use a linear polorizer on my A40 and if not why?
What type of camera's are the two different polorizers used on?

[henkbos]

Colin,

As far as I know you have to use a circular polarizer on autofocus cameras. Don't ask me the technical details. I'm sure you can find those on the net.

Henk

[jonnaro]

I have actually heard the opposite; that on non-slr digitals (like the g2, for instance), you can use a linear. This is because the autofocus system doesn't focus 'through' the lens, or at least that's what I believe I read on another website somewhere.

I personally have not yet shot with a polarizer of any sort on my G2 so could not tell you from personal experience.

[Conk]

Ok. It has been finalized.
The Canon A40 does not need to use a circular polarized filter. Took a little research but I was able to get the definite answer I needed.
Mitch was kind enough to provide me with an article that described some technical details about what the necessary attributes of a camera are in order to utilize circular as opposed to linear polarizing filters.
Here is the last paragraph from the article that describes what is a necessary element for a camera to have in order to utilize either filter.

"Bottom Line:
They both affect light exactly the same way for making a photograph and are both used exactly the same way. If your camera does not have a beam-splitter to divide the light into portions for the prism/viewfinder and sensors behind the mirror, you can use either one. If your camera does have a beam-splitting mirror with sensors behind it, you must use a circular for the sensors, especially light metering ones, to work properly (i.e., as designed).

I then e-mailed Canon support to ask if the A40 did indeed have a beam splitter. First reply to come back said "To my knowledge it does not".
I was not satisfied with a "To my knowledge" answer so I re-sent the e-mail explaining a little more and the importance of a "Definite" answer.
Here was the reply:

Dear Mr. Colin Perrin
Thank you for your E-mail reply.

I have double
checked your inquiry and see the PowerShot A40 does not utilize a beam splitter.
The cameras CCD captures color by passing the image through red, green and blue filters.
Should you require further assistance, please feel free to email us or visit our customer support website at http://www.canon.ca

Sincerely,

David M.
Technical Support Representative
Customer Information Centre
Canon Canada Inc.

Absolute bottom line, the A40 can use a linear polarizing filter.

[terryfn]

I have both 49 mm Marumi Linear Polarizer and 58 mm HOYA Circular Polarizer with my G2. I must admit they produce the same effect and result... and I think all PowerShot series digicams don't have beam-splitting mirror.. so go with the Linear PL!