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11-20-2012, 05:39 AM   #1
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Sample quality variations in Pentax lenses

What's actually known about quality control of the recent Pentax lenses?

1) Reviews of some samples of the DA 40 and even the 77mm 1.9 have been quite poor. How many individual lenses of any type fall below expectations?

2) Why doesn't Pentax set higher production tolerances for their premium lenses?

3) Is buying second-hand lenses prone to disappointment because the bad samples get passed around from one photographer to another?

4) Has anyone had any success in getting Pentax to admit that a particular lens is below acceptable standards, and has anyone had a lens replaced?

5) Is Pentax better or worse than the other contemporary lens making companies? Are there examples of "best practice" where quality control is uniformly tight?

6) Was Pentax quality conrol of sample variation better in the past or is its history pretty constant?

I'm in the process of buying some lenses, looking at some of the Limited and FA series, and I just can't make the assumption that any random individual lens will be within the kind of quality standard of review lenses, or of the lenses that forum members have and have tested to be good examples. Lens buying looks like something of a lottery, not just for new lenses but for older ones too. I just bought two examples of the Super Takumar 55/2. One was terrible and the other was as sharp as a Leica 50/2 Summicron I have.

How do you deal with a situation like this?

11-20-2012, 06:33 AM   #2
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QuoteOriginally posted by les24preludes Quote
What's actually known about quality control of the recent Pentax lenses?

1) Reviews of some samples of the DA 40 and even the 77mm 1.9 have been quite poor. How many individual lenses of any type fall below expectations?

2) Why doesn't Pentax set higher production tolerances for their premium lenses?

3) Is buying second-hand lenses prone to disappointment because the bad samples get passed around from one photographer to another?

4) Has anyone had any success in getting Pentax to admit that a particular lens is below acceptable standards, and has anyone had a lens replaced?

5) Is Pentax better or worse than the other contemporary lens making companies? Are there examples of "best practice" where quality control is uniformly tight?

6) Was Pentax quality conrol of sample variation better in the past or is its history pretty constant?

I'm in the process of buying some lenses, looking at some of the Limited and FA series, and I just can't make the assumption that any random individual lens will be within the kind of quality standard of review lenses, or of the lenses that forum members have and have tested to be good examples. Lens buying looks like something of a lottery, not just for new lenses but for older ones too. I just bought two examples of the Super Takumar 55/2. One was terrible and the other was as sharp as a Leica 50/2 Summicron I have.

How do you deal with a situation like this?
Apples to Oranges here IMHO. New lenses are one issue and used, particularly old used, lenses are another entirely.

On the issue of your ST55/1.8s having variation - that is to be expected IMHO. They are tools. They have been used. In use tools get damaged, knocked around, etc. One of the lenses may be a hangar queen and the other a day-to-day shooter. There's no knowing with a 50+- year old lens.

As for BNIB lenses - yes, sample variation exists and can be a real PITA.
11-20-2012, 07:25 AM   #3
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On the subject of the Super Takumar 55mm f2 - this is the same lens as the 55mm f1.8 optically, and I read that it's just aperture restricted. Is it possible they restricted the aperture on lenses that were poorer wide open or is this not the case at all? I can't quite figure why they would make two versions of the same lens.
11-20-2012, 07:56 AM   #4
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Good Morning Les
I have the K mount version of the SMC PENTAX 1:2 55mm
At wide open, the 6 blades open beyond the bore, that is they are not able to influence to OOF areas at f/2

Also I have the Super Takumar service manual.
The differences between the 1:1.8 (Product 345-5) and the 1:2 (Product 345-6)
a different nameplate ring
a different diaphragm scale ring.
a different first lens retainer ring (item3)
a different 6th lens retainer ring ( item 8)
The 6 lenses are shown as common parts between the f/1.8 and f/2

The lens retainer rings form the bore diameter, so I assume the f/2 versions had smaller bores.

11-20-2012, 09:01 AM   #5
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QuoteOriginally posted by les24preludes Quote
5) Is Pentax better or worse than the other contemporary lens making companies? Are there examples of "best practice" where quality control is uniformly tight?
I think Pentax is in the same range as anyone else.

Best practices... ISO norms are probably the best bet, they do not ensure quality, but they do ensure repeatability of processes.

the thing is that Pentax does not offer warranty for any optical performances. They spec the focal length and aperture, and that's it basically. the rest is perceived and expected quality and performances, but on paper there is nothing of the sort.

I work for a telecomm T&M company. When we release a device, we spec things such as dynamic range, minimum laser output power, measurement range, etc. The spec sheets are quite extensive. for lenses, the spec sheets basically describe the hardware, not its performances. that,s a major difference.

QuoteOriginally posted by les24preludes Quote
1) Reviews of some samples of the DA 40 and even the 77mm 1.9 have been quite poor.
How so?
11-20-2012, 10:24 AM   #6
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QuoteOriginally posted by les24preludes Quote
On the subject of the Super Takumar 55mm f2 - this is the same lens as the 55mm f1.8 optically, and I read that it's just aperture restricted. Is it possible they restricted the aperture on lenses that were poorer wide open or is this not the case at all? I can't quite figure why they would make two versions of the same lens.
Weird marketing decision. Wombat describes the different parts. The f2 version is useful because it is exactly like stopping down the f1.8 lens a bit, except with a perfectly round aperture.

Quality wasn't perfect in the old days either (no photoshop here):

11-20-2012, 10:47 AM   #7
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QuoteOriginally posted by les24preludes Quote
On the subject of the Super Takumar 55mm f2 - this is the same lens as the 55mm f1.8 optically, and I read that it's just aperture restricted. Is it possible they restricted the aperture on lenses that were poorer wide open or is this not the case at all? I can't quite figure why they would make two versions of the same lens.
I own both of these lenses. The 55/2 came with the SP1000 camera I bought in the mid 70's and the 55/1.8 on a camera I found in a garage sale. The both look identical and both have excellent IQ. I doubt that they restricted the aperture. More likely, it's the same optically but assembled with a different (and cheaper) aperture mechanism and ring. I've heard all the stories for years. Personally, after using both, I think the f1.8 is the slightly better lens. There is a noticeable difference shooting wide open between the two on my K10D. I don't have the technical expertise to point out differences but my shots with the 1.8 just seem a little sharper and crisper. It could easily be the slightly brighter viewfinder helping me focus better and that is one of the big issues of the manual camera era that seems to be forgotten today. Fast lenses were highly valued because you could focus them easier. When you are manually focusing, f/1.4 was highly desired even if you never shot at that aperture. Next step lower in the price range was f/1.8 which was the most common among all the manufacturers and the budget SLR's came with an f/2 lens. As auto focusing cameras became the norm, the "fast" lenses became less common.
11-20-2012, 10:57 AM   #8
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QuoteOriginally posted by reeftool Quote
I own both of these lenses. The 55/2 came with the SP1000 camera I bought in the mid 70's and the 55/1.8 on a camera I found in a garage sale. The both look identical and both have excellent IQ. I doubt that they restricted the aperture. More likely, it's the same optically but assembled with a different (and cheaper) aperture mechanism and ring. I've heard all the stories for years. Personally, after using both, I think the f1.8 is the slightly better lens. There is a noticeable difference shooting wide open between the two on my K10D. I don't have the technical expertise to point out differences but my shots with the 1.8 just seem a little sharper and crisper. It could easily be the slightly brighter viewfinder helping me focus better and that is one of the big issues of the manual camera era that seems to be forgotten today. Fast lenses were highly valued because you could focus them easier. When you are manually focusing, f/1.4 was highly desired even if you never shot at that aperture. Next step lower in the price range was f/1.8 which was the most common among all the manufacturers and the budget SLR's came with an f/2 lens. As auto focusing cameras became the norm, the "fast" lenses became less common.
I thought the aperture restriction would be a snap-in ring that I could pop out, but it's not so easy. The slightly purple part here above the blades is what limits these lenses to f2. This is the SMC Takumar version. The part also holds the aperture blades in place so can't simply be removed. I could drill a bigger hole in it and allow f1.8, except mismarked, hard to sell, and I have three 55mm f1.8s already.



11-20-2012, 11:14 AM   #9
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QuoteOriginally posted by les24preludes Quote
5) Are there examples of "best practice" where quality control is uniformly tight?
The Zeiss ZK lenses come with an inspection slip, signed by an inspector.
11-20-2012, 11:22 AM   #10
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QuoteOriginally posted by reeftool Quote
It could easily be the slightly brighter viewfinder helping me focus better and that is one of the big issues of the manual camera era that seems to be forgotten today. Fast lenses were highly valued because you could focus them easier. When you are manually focusing, f/1.4 was highly desired even if you never shot at that aperture.
That's just as true today as it ever was, assuming the fast lens is sharp in the center wide open..

For example, the Zeiss ZK 85/1.4 is easier to focus manually than the Voigtlaender Apo-Lanthar 90/3.5.
11-20-2012, 11:28 AM   #11
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Yes, Dave, re Super Tak 55mm's, reading a bit further into the service manual, it looks like there was a later version of the f/2 ( product # 371 103)
which had all common parts, including lenses, with the later f/1.8's ( 371 and 371-101) except only the nameplate ring and the diaphragm turning ring had no interchangeability.

It looks like the earlier 345 versions had different bores, but the 371 versions had same parts, between the f/1.8 and the f/2

The manual does not show whether the glass was the same between the 345's and the 371's, however both had 6 elements
11-20-2012, 11:38 AM   #12
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QuoteOriginally posted by wombat2go Quote
It looks like the earlier 345 versions had different bores, but the 371 versions had same parts, between the f/1.8 and the f/2
Is there a way to tell the versions apart, without dismantling the lens?

Are serial number ranges known for the two versions?

Wide open, the entrance pupil of my 55/2 has a clearly visible restriction,
which might be caused by the kind of feature Just1More Dave showed.
11-20-2012, 11:50 AM   #13
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QuoteOriginally posted by les24preludes Quote
What's actually known about quality control of the recent Pentax lenses?

1) Reviews of some samples of the DA 40 and even the 77mm 1.9 have been quite poor. How many individual lenses of any type fall below expectations?

2) Why doesn't Pentax set higher production tolerances for their premium lenses?

3) Is buying second-hand lenses prone to disappointment because the bad samples get passed around from one photographer to another?

4) Has anyone had any success in getting Pentax to admit that a particular lens is below acceptable standards, and has anyone had a lens replaced?

5) Is Pentax better or worse than the other contemporary lens making companies? Are there examples of "best practice" where quality control is uniformly tight?

6) Was Pentax quality conrol of sample variation better in the past or is its history pretty constant?

I'm in the process of buying some lenses, looking at some of the Limited and FA series, and I just can't make the assumption that any random individual lens will be within the kind of quality standard of review lenses, or of the lenses that forum members have and have tested to be good examples. Lens buying looks like something of a lottery, not just for new lenses but for older ones too. I just bought two examples of the Super Takumar 55/2. One was terrible and the other was as sharp as a Leica 50/2 Summicron I have.

How do you deal with a situation like this?
I can't answer most of your questions. However, I think the following article from lensrentals.com gives a good indication of what might be expected from modern lenses in general, in terms of sample variation: LensRentals.com - Canon 24-70 Mk II Variation

As far as I know the only certain way to deal with the issue is to develop a relationship with a camera store that will allow you to test lenses and return ones that don't meet your expectations. Good luck on that one.

As others have pointed out, old lenses are a crapshoot because they have history. In my experience older Pentax lenses hold up better than most.

John
11-20-2012, 11:55 AM   #14
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QuoteOriginally posted by lytrytyr Quote
That's just as true today as it ever was, assuming the fast lens is sharp in the center wide open..

For example, the Zeiss ZK 85/1.4 is easier to focus manually than the Voigtlaender Apo-Lanthar 90/3.5.
Yes it is. I mentioned this because there are a lot of threads that talk endlessly about depth of field and bokeh but the biggest reason that fast lenses were so valued in the film days was much more practical. They are easier to focus.
11-20-2012, 12:20 PM - 1 Like   #15
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QuoteOriginally posted by lytrytyr Quote
Is there a way to tell the versions apart, without dismantling the lens?

Are serial number ranges known for the two versions?

Wide open, the entrance pupil of my 55/2 has a clearly visible restriction,
which might be caused by the kind of feature Just1More Dave showed.
Lyt:
The manual shows:
345 series:
Pre 1963 product numbers 345 ( 345 -2 was 1:1.8 and 345-3 was 1:2 )
the A/M ring was wide with a narrow finger tab had letter A on the left side and letter M on the right (Looking at the ring engraving),

Post October 1963 product numbers 345 ( 345 -5 was 1:1.8 and 345-6 was 1:2 )
the A/M ring was wide with a narrow finger tab had letter M on the left side and letter A on the right (Looking at the ring engraving),

(Both the diaphragm ring and the A/M ring directions were changed in Oct 1963)


371 series
Here I am not familiar enough because I only have K up lenses.
It looks like there were 4 versions
1:1.8
371 had the A/M tab with the letter A to the right of the tab
371101 had the A/M tab with the letters Auto to the right of the tab.

1:2
371102 had the A/M tab with the letter A to the right or the tab. The exploded diagram appears same as 371
371103 The photo does not show the letters near the A/M tab, and/but main part of the rear body was interchangeable with 371101 ( only)
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