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09-27-2011, 11:28 PM   #1
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CA on FA31 Ltd

Hi guys, recently i tested a copy of the FA31 Ltd, and when shooting at high contrast areas i've found images to have visible CA at 100% crop from wide open, decreasing as i stop down until I reach f7.1.

Of all the things that i know about this lens and also from the reviews in the lens database, people commenting on the presense of CA have been few and far between.

What I'd like to know is whether the lens is really resistant to CA, and why I am seeing the CA up to f7.1. As it stands i'm not too wavered in my decision to get one, as the aforementioned CA is not visible on a full screen, but only but clearly visible at 100% crop. Any feedback from owners of the lens?

Much appreciated!

09-28-2011, 12:51 AM   #2
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My lens can produce pretty bad purple fringing in some situations (eg. water from a river on a sunny day).
09-28-2011, 03:45 AM   #3
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strange, I don't get much fringing at all with my FA31mm f/1.8 Limited (MiJ) - and I tend to stick around the f/2.8~f/5.6 aperture range.
09-28-2011, 04:54 AM   #4
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I've never seen purple fringing on my copy, and I tend to shoot wide open due to lack of light.

09-28-2011, 05:50 AM   #5
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recently i was helping to my friend to buy fa31.... the one on stock was made in vietnam my is made in japan the difference was like comparing old russian glas to modern L class prime - ca was unbearable so we decided not to take this one....
09-28-2011, 11:46 AM   #6
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Oh well, maybe my 31mm isn't as great as I thought it was compared to others?

Here is an example:
All sizes | Visible Purple fringing with the 31mm | Flickr - Photo Sharing!
Exif | Visible Purple fringing with the 31mm | Flickr - Photo Sharing!
09-28-2011, 02:40 PM   #7
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I haven't used my FA31 much since digital but I do know that QC of this lens (well actually pretty much anything Pentax these days but...) is rather loose for its non-helical design so don't be surprised if some of them are dramatically better or worse. Good luck on fishing a perfect one.

BTW, you pic looks pretty bad consider it's f7.1 Either it's mis-focus or misalignment. I am incline toward the latter but only a proper test will tell.
09-28-2011, 03:21 PM   #8
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QuoteOriginally posted by wlachan Quote
I haven't used my FA31 much since digital but I do know that QC of this lens (well actually pretty much anything Pentax these days but...) is rather loose for its non-helical design so don't be surprised if some of them are dramatically better or worse. Good luck on fishing a perfect one.

BTW, you pic looks pretty bad consider it's f7.1 Either it's mis-focus or misalignment. I am incline toward the latter but only a proper test will tell.
I can't see how it would a focus issue as the lens appears to produce sharp images and the photo there was probably shot at infinity focus. The WIKI on PF doesn't really explain a situation of why as you said f7.1 should mitigate the problem. I'll say the photo was an extreme situation though. I'd like to see others take a similar photo around noon shooting toward the sun of a river with a Pentax K-5 specifically (no UV filter because I was testing the lens for a comparison article).

09-28-2011, 05:18 PM   #9
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Based on the reviews and my experience, there could be a huge sample variation for this lens. I've seen great samples, but my own AIV copy is just average. I'm looking for a good MIJ to replace it.
09-28-2011, 06:22 PM   #10
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My AIV copy seem fantastic to me, I've not noticed any CA problems. MAybe I need to pixel peep more
09-28-2011, 07:48 PM   #11
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Mine is AIV and superb optically. However, I had to change the lens cap because the wiggle in the hood, especially when taking that stupid metal cap off, was very concerning.
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