brian hanson Posted February 15, 2005 Share Posted February 15, 2005 Do I need a circular polarizer? I know that they are mostly for auto focus cameras, but I have read that they need to be used for proper metering as well. I use T-90s, A-1s, and an F-1 and I am going to buy some new filters because I just got a 20mm 2.8, old style, and I need ND, Polarizer, and UV filters for it. Do I need the thin type for this lens? I plan to buy B+W, but I am open to suggestions, especially if they are cheaper! Thanks, Brian. Link to comment Share on other sites More sharing options...
dpowis Posted February 15, 2005 Share Posted February 15, 2005 Apparently linear polarizers don't just throw off AF, they can also affect the AE system. Therefore, you should get a circular polarizer. Link to comment Share on other sites More sharing options...
brian hanson Posted February 15, 2005 Author Share Posted February 15, 2005 Thanks Dan. I have been using linear polarizers for a long time with my FTb and A-1, and with no problems. But from what I can see on the web is that it may be a problem with my T-90. Does anybody know for sure? Also, Should I buy thin filters to use with this 20mm 2.8 lens? Thanks. Link to comment Share on other sites More sharing options...
peter_white2 Posted February 15, 2005 Share Posted February 15, 2005 A linear polarizer will very definitely cause exposure reading errors with the FTb and with the F-1. I don't know how the A-1 meter works, but the angled beam splitter in the F-1 and FTb focusing screens polarize light. So light entering the lens must be de-polarized with a circular polarizer. Link to comment Share on other sites More sharing options...
trw Posted February 15, 2005 Share Posted February 15, 2005 <ol><li> I've never had a problem with metering using my linear polarizer on my AE-1P with 50mm and 28mm lenses. </li><li>Using 3 filters on a wide angle lens might not be a good idea (due to vigneting). </li><li>Why do you need a neutral density filter? Wouldn't a faster shutter speed or slower film give better results? (I'm assuming you're not talking about a <i>graduated</i> neutral density filter.) </li></ol> Link to comment Share on other sites More sharing options...
david_goldfarb Posted February 15, 2005 Share Posted February 15, 2005 I'm fairly sure the T-90 needs a circular polarizer if you want to meter through the filter. It's generally recommended with most later Canon bodies that use a beamsplitting prism in the focusing screen to direct light to the meter. I wouldn't bother with a polarizer on a 20mm lens. In certain scenes it can work, but in general, particularly for landscapes, you'll get uneven polarization with a lens that wide. In that situation a graduated ND is more effective. Link to comment Share on other sites More sharing options...
peter_white2 Posted February 15, 2005 Share Posted February 15, 2005 It's very easy to know if you need a circular polarizer. And it may not be obvious whether you have a linear or circular polarizer. I'd suggest taking a pair of polarized sunglasses and holding them in front of your lens. The sunglasses are virtually guaranteed to be linear polarizers. Rotate the eyeglass lens while metering a white painted wall. If the meter reading changes, you need a circular polarizer. People may have no problem with a polarizer they assume to be linear when in fact it's circular. Link to comment Share on other sites More sharing options...
awahlster Posted February 15, 2005 Share Posted February 15, 2005 Here is a chart for polarizing filters and Canon FD mount bodies. The way has been mentioned above. http://tinyurl.com/6dcq4 This chart is part of the info found on the Canon Fd group on Yahoo the lastest community of Canon Fd users on the net. Link to comment Share on other sites More sharing options...
vinny_walsh Posted February 15, 2005 Share Posted February 15, 2005 b+w filters are definetely have slimmer rings to start with but i would get a slim circular polarizer anyway. You can always put your pola on top of the first filter that way you don't need one with threads. You won't be able to stack 2 or more on your 20mm though unless you get some step up rings and larger filters like 72mm or 77mm which aren't cheap. Link to comment Share on other sites More sharing options...
chris_ross2 Posted February 15, 2005 Share Posted February 15, 2005 Yes, for your T90. I'm using a regular Hoya filter on my new 20mm f2.8 with no drama. It may be true that you'll get uneven skies with a polariser on the 20 mm (anything wider than ~28 mm will ensure this), polarisers have other uses for removing reflections in rainforest shots and other non metallic refelecting surfaces. Link to comment Share on other sites More sharing options...
peter_white2 Posted February 15, 2005 Share Posted February 15, 2005 Mark, I get a "document not found" at that url. Can you send the entire url? Thanks, Link to comment Share on other sites More sharing options...
awahlster Posted February 15, 2005 Share Posted February 15, 2005 For Peter: http://f4.grp.yahoofs.com/v1/8H4SQg78WvKduj5r0WjVoXYnk-wn-A5FeQk15A2WPQzhNfm639BdMWUPNYPfj6sKpWuZn7mvYuBxAyanop1VKtQyHwIuDYo/polarizing%20filters%20and%20canon%20bodies.jpg good luck cutting and pasting Here's the info from the chart These bodies can use a Linear Polarizer: EF AE-1 AV-1 AE-1P AT-1 A-1 T50 T70 And these bodies need a Circular polarizer: F-1 F-1n F-1N FTb FTb-n TLb AL-1 T80 T90 The FTb FTb-n and TLb bodies I added to the Circular Polarizer list based on their metering system Link to comment Share on other sites More sharing options...
peter_white2 Posted February 15, 2005 Share Posted February 15, 2005 Hmmm, I had an AT-1. And as I recall, it had the same rectangular metering pattern as the FTb I used before it, and the F-1 (stock screen, immediately replaced by a spot screen) I replaced it with in 1986. I thought it used the same beam splitter design as both the FTb and the F-1. Am I not remembering correctly? Link to comment Share on other sites More sharing options...
peter_white2 Posted February 15, 2005 Share Posted February 15, 2005 Sorry. I found an online AT-1 manual. It had center weighted metering. So, yes, it wouldn't have required a circular polarizer. Link to comment Share on other sites More sharing options...
brian hanson Posted February 15, 2005 Author Share Posted February 15, 2005 Thanks so much for all of your help. I will buy the circular polarizer. This forum is such a great resource! Link to comment Share on other sites More sharing options...
awahlster Posted February 15, 2005 Share Posted February 15, 2005 Peter the AT-1 does have center weighted metering the same as the AE-1 AV-1 A-1 and AE-1P the reason the AL-1 needs the circular polarizer is due to it's focusing assist system. The AT-1 uses the smae focusing screens as the AE-1 a non interchangable screen that would require the prism to be taken out of the camera to change the screen. The Chart is accurate as I typed it this info has been checked back and forth a bunch of times on the Canon group on Yahoo where it is posted. Link to comment Share on other sites More sharing options...
peter_white2 Posted February 16, 2005 Share Posted February 16, 2005 Yeah. I must be getting old. Just can't remember much of anything any more. ;-) But I do remember now how happy I was when I got the F-1 and again had some control over what I was metering. I had bought the AT-1 because it was lighter, not thinking about the different metering pattern. I was very used to the center rectangle on the FTb. And of course the spot metering screens for the F-1 were even better. Link to comment Share on other sites More sharing options...
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