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Archive 2006 · 100 F2 vs 85 F1.8 ?

mirages
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p.2 #1 · 100 F2 vs 85 F1.8 ?

Sam Bennett wrote:
All of my fast primes below 135mm exhibit a lot of birefringence (purple fringing) at f/2 or wider. The 135/2 exhibits almost none. Apparently this is more a function of the focal length than the properties of the glass itself. This is one of the reasons why I would recommend getting the 135 if you already have the 85. The 135 is optically one of the best lenses Canon makes, and being so close to 100mm it's a wortwhile stretch to go with the L instead, assuming the focal length will work for you.

mirages wrote:
So, I am not sure I got this straight. Birefringence is a function of this particular focal length? If so, I may just as well stick with the 85/1.8 I already own, and just get a second copy. That way I can keep the best one home, and send the other out in the field where the potential for a few bumps and bruises is there. Sure would appreciate someone with a good 100/2 copy verifying the same effect outdoors in bright light, or not. TX

Can someone very briefly settle this for me who own the 100/2 - is there a birefringence (purple fringing) issue with this lens outdoors in bright light?

I certainly don't want to beat a dead horse, but would really appreciate a reply from one or two parties who own one, as I am getting prepared to buy one for a trip. I guess I can always go and rent one for a weekend as an option, in hopes I can answer my own question if not.

Thanks again in advance for your help!

Oct 07, 2006 at 06:38 AM

Sam Bennett
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p.2 #2 · 100 F2 vs 85 F1.8 ?

mirages wrote:
Sam Bennett wrote:
All of my fast primes below 135mm exhibit a lot of birefringence (purple fringing) at f/2 or wider. The 135/2 exhibits almost none. Apparently this is more a function of the focal length than the properties of the glass itself. This is one of the reasons why I would recommend getting the 135 if you already have the 85. The 135 is optically one of the best lenses Canon makes, and being so close to 100mm it's a wortwhile stretch to go with the L instead, assuming the focal length will work for you.

So, I am not sure I got this straight. Birefringence is a function of this particular focal length? If so, I may just as well stick with the 85/1.8 I already own, and just get a second copy. That way I can keep the best one home, and send the other out in the field where the potential for a few bumps and bruises is there. Sure would appreciate someone with a good 100/2 copy verifying the same effect outdoors in bright light, or not. TX

Focal length appears to have a lot to do with it since you see the same exact thing on all the Canon 85mm primes at the same apertures. But again, the amount you see is going to depend on how close to you are to your subject, etc. If it's really a problem, simply stop down to f/2.8 and the problem is minimized greatly.

Oct 07, 2006 at 03:30 PM

Kamil Kisiel
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p.2 #3 · 100 F2 vs 85 F1.8 ?

What are you shooting outdoors in bright light at f/1.8 or f/2 that would cause purple fringing?

Oct 07, 2006 at 03:59 PM

trenchmonkey
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p.2 #4 · 100 F2 vs 85 F1.8 ?

Maybe that Purple fringe tree off Main St.

Oct 07, 2006 at 04:11 PM

mirages
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p.2 #5 · 100 F2 vs 85 F1.8 ?

kisielk wrote:
What are you shooting outdoors in bright light at f/1.8 or f/2 that would cause purple fringing?

Actually, it is city structures and associated landscapes where it is most apparent.

Doesn't anyone own the 100/2 lens that can verify birefrengence or not

?

C'mon, someone must have bought this lens...

Oct 07, 2006 at 08:26 PM

cactusclay
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p.2 #6 · 100 F2 vs 85 F1.8 ?

I just shot a telephone line 100/2 @ 2.0 and at 100% you can see purple fringing, but I don't think it is as bad as my copies of the 85 1.8 or the 1.2 .

Oct 07, 2006 at 08:31 PM

timbop
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p.2 #7 · 100 F2 vs 85 F1.8 ?

I specifically asked this a couple days ago. see http://www.fredmiranda.com/forum/topic/459013

Oct 08, 2006 at 08:01 PM

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