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07-29-2013, 08:57 PM   #1
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pentax 31mm limited miv quality

So I have acquire a 31mm limited for 6 months already. Hadn't got a chance to use it much. I have heard that the one made in Vietnam could have quality control problems. So how can I tell if mine is a bad quality one compare to others. I don't have much experience in telling the differences in the quality of the lenses. I paid $900 for the lens and hope its a good one.

07-29-2013, 09:15 PM   #2
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I think that's more of a myth. The AIV ones should be just as good as the MIJ ones.

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07-29-2013, 09:38 PM   #3
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Definitely a myth. Mine is Assembled in Vietnam. I think it is terrific. If you feel suspicious do some tests of it's sharpness at 1.8. Just keep in mind the lens is not supposed to be tack sharp wide open and has a soft glow.
07-29-2013, 09:41 PM   #4
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Go out and take lots of photos with it. Look critically at the images and compare them to the multitude available in this thread. Post them here and we'll be happy to give an opinion if you like.

For what it's worth, my copy is AIV and I think it's bloody marvellous. Some examples are here. I love it even more than my MIJ FA43 and FA77, and that's saying something.

07-29-2013, 10:04 PM   #5
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QuoteOriginally posted by Adam Quote
I think that's more of a myth. The AIV ones should be just as good as the MIJ ones.
I don't believe so, based on my experience. I have tested multiple copies of AIV FA31s across geogrphic areas and over the past year and half and substantially all of them exhibit softness at wide open (some more so than others). Based on my sample size, I believe softness at wide open is actually a characteristic of the AIV FA31 and not merely a quality issue, as I had previously suspected. I think Pentax may have altered certain specification or parts in the AIV copy from their original specification, changed supplier or lowered tolerance on the optics.

I believe there is somthing seriously wrong with AIV copies and I think you should look into this issue on behalf of everyone here
07-29-2013, 10:07 PM   #6
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QuoteOriginally posted by oxidized Quote
Definitely a myth. Mine is Assembled in Vietnam. I think it is terrific. If you feel suspicious do some tests of it's sharpness at 1.8. Just keep in mind the lens is not supposed to be tack sharp wide open and has a soft glow.
FA 31 was designed to be tack sharp wide open and there certainly should not be any soft glow.
07-29-2013, 10:21 PM   #7
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QuoteOriginally posted by chesebert Quote
FA 31 was designed to be tack sharp wide open and there certainly should not be any soft glow.
There are plenty of threads on the subject. One of the reasons why the 31 was so popular in the film days is because of the tiny bit of glow which hides blemishes and renders skin perfectly. And no, it is most definitely not TACK sharp at F1.8. To me, it is TACK sharp past F2.8
07-29-2013, 10:26 PM   #8
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QuoteOriginally posted by oxidized Quote
There are plenty of threads on the subject. One of the reasons why the 31 was so popular in the film days is because of the tiny bit of glow which hides blemishes and renders skin perfectly. And no, it is most definitely not TACK sharp at F1.8. To me, it is TACK sharp past F2.8
There is ever so slight loss of contrast at wide open (i.e., black/white edge definition), but not the kind of "soft glow" that plagues the AIV copies I have handled (e.g., the sample test shown in the other recent post).

Yes, I agree f2.8 is sharper than f1.8, but the difference is not that big in the center and across the frame.

07-29-2013, 10:29 PM   #9
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I reckon mine is reasonably sharp wide open, taking into account that this is hand held at ISO3200.


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07-29-2013, 10:54 PM   #10
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So maybe you guys eye could tell me better. I think it look okay but I have no experience what it should be like consider this suppose to be top tier in pentax line. The first two I shot wide open with a lamp light source and the third is from a room light source. I think the third is at 3200 iso. I really hope this is a good model because there is no way I could return to the store now since it past the return policy date.
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07-29-2013, 11:15 PM   #11
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Assembled in Vietnam. The glass is still Japanese, for what it's worth, if anything!
It's a bit like an IKEA chair may be assembled in the USA. Just following instructions with an allen key in hand.
07-29-2013, 11:37 PM   #12
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QuoteOriginally posted by kokushu Quote
So maybe you guys eye could tell me better. I think it look okay but I have no experience what it should be like consider this suppose to be top tier in pentax line. The first two I shot wide open with a lamp light source and the third is from a room light source. I think the third is at 3200 iso. I really hope this is a good model because there is no way I could return to the store now since it past the return policy date.
They look pretty reasonable for hand held shots wide open. I don't think you have a dud.
Go outside and take some real world shots in good light and stopped down a little and I think you'll fall in love.
07-29-2013, 11:40 PM   #13
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QuoteOriginally posted by calsan Quote
Assembled in Vietnam. The glass is still Japanese, for what it's worth, if anything!
It's a bit like an IKEA chair may be assembled in the USA. Just following instructions with an allen key in hand.
In theory, yes, however, it is entirely possible that Pentax went with cheaper optic sources or altering the spec on optics over time to save money. Once you put more recent copies of AIV next to MIJ copies, you will notice the difference.
07-29-2013, 11:48 PM   #14
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QuoteOriginally posted by kokushu Quote
So maybe you guys eye could tell me better. I think it look okay but I have no experience what it should be like consider this suppose to be top tier in pentax line. The first two I shot wide open with a lamp light source and the third is from a room light source. I think the third is at 3200 iso. I really hope this is a good model because there is no way I could return to the store now since it past the return policy date.
Can you take some photos at infinity with fine details (e.g., buildings, trees, etc)?

Photos of your headphone setup with LCD2/3 are also welcome.
07-30-2013, 12:43 AM   #15
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There's no way to know from these shots. All they show is that the K5 is reasonable at high isos.

Outdoors in daylight with a tripod and a clearly selected point of focus...
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