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02-20-2013, 10:11 AM   #1
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FA31 MIJ and AIV are Optically Different - Front Element Coating

Can someone explain why my two copies of FA31 have different coatings on their respective front elements.

I recently came into possession of a fine MIJ copy with none of the wobble lens hood issue. It is a later production model with green lining inside front cover. When shined with LED light, the MIJ copy exhibits a dark blueish hue with a little pink in the reflection, where as the AIV copy exhibits a more greenish hue. I have not had the chance to field test the MIJ version yet. But the difference in reflection suggests that there was coating change when Pentax moved the production from Japan to Vietnam.

Does the blue hue means the coating contain lead? What's the implication? Does this mean MIJ copy is physically different from AIV copy?

02-20-2013, 10:20 AM   #2
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I'm guessing the AIV copy is newer and might have a newer coating? My DA lenses all have a green hue whereas my old M50/1.7 has a bunch of different colors (blue, orange, pink). So the coating on your AIV is probably similar to the one used on DA lenses.

Actually, I picked up a 2nd copy of an M50/1.7 for cheap, and it looked different from my original. It had more blue while the original was more orange. Lenses seem to perform identically, though.
02-20-2013, 11:29 AM   #3
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Were the lighting conditions exactly the same? I mean, exactly?

It might be that Pentax made some adjustments to their coatings along the way, but the real test is performed when you take a picture.
02-20-2013, 11:35 AM   #4
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Lighting was exactly the same. Preliminary test pictures do look slightly different, more akin to the difference between old and new versions of FA43 that has been posted elsewhere on the web. I will need more time to examine the difference and my preference.

02-20-2013, 11:46 AM   #5
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The 31 has been in production since 2001 - that's a long time for a lens. Over that time we know that Pentax has changed their coatings and introduced some additional technologies. Is there anyway from the serials to know when the lenses were produced during the 12 year period?
02-20-2013, 12:27 PM   #6
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QuoteOriginally posted by Docrwm Quote
The 31 has been in production since 2001 - that's a long time for a lens. Over that time we know that Pentax has changed their coatings and introduced some additional technologies. Is there anyway from the serials to know when the lenses were produced during the 12 year period?
As far as my investigation goes - there is absolutely no connection between lens serial number and the date of manufacture. Sad
02-20-2013, 02:03 PM   #7
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QuoteOriginally posted by Apapukas Quote
there is absolutely no connection between lens serial number and the date of manufacture.
I think there was some intention with the serial database here
to try and collect enough data to make a rough connection,
but I'm not sure how successful that is.

SMC Pentax-FA 31mm F1.8 AL Limited Serial Numbers - Pentax Serial Number Database - PentaxForums.com

The 002xxxx look like MIJ,
and most of the 003xxxx look like AIV.
0034139 is MIJ, though.

@MikeSF, is yours AIV?
02-20-2013, 02:18 PM   #8
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QuoteOriginally posted by lytrytyr Quote
I think there was some intention with the serial database here
to try and collect enough data to make a rough connection,
but I'm not sure how successful that is.

SMC Pentax-FA 31mm F1.8 AL Limited Serial Numbers - Pentax Serial Number Database - PentaxForums.com

The 002xxxx look like MIJ,
and most of the 003xxxx look like AIV.
0034139 is MIJ, though.

@MikeSF, is yours AIV?
Serial database contains information about purchase date, not the date of manufacture.
I looked through the serials but it doesn't make any sense to me. I guess you have to be that guy from "Beautiful mind" to see the meaning or something in those numbers


Last edited by Apapukas; 02-20-2013 at 02:27 PM.
02-20-2013, 02:34 PM   #9
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I like how Seiko does their serial numbers for watches. You put the movement model number and the serial number into a database and you can find out the month and year of assembly for nearly any watch they have made over the past 40-50 years. Something like that would not be too hard to do and would have some benefits for QC and maintenance issues down the road.
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