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01-15-2017, 04:24 PM   #61
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QuoteOriginally posted by erosenbe Quote
I think when you mount an FF lens on a crop body, you are in some sense magnifying a portion of the glass (image circle), which can magnify the achilles heel of the lens.

Perhaps you are encountering this to some extent with your tests.

I have the old Tamron 70-200 f/2.8. It is reasonably sharp, but definitely soft from f/2.8-f/4 at 135mm-200mm, and especially at close focusing distance. The weakness is a bit less pronounced on my K1 than on my crops.

Tony Northrup relayed a story of a guy who bought Canon FF 24-70 f2.8s and had a poor go with them on crop bodies, sending them in to Canon service, who found nothing. He switched to FF and had much better performance with the exact same lens copies.

Just food for thought.
Interesting thoughts,

One thing I should have done is tried a K1 with it to see how it would perform. I have a friend nearby with a K1, I wished I would have done that, just to see if they behave better on that body.

---------- Post added 01-16-2017 at 07:30 AM ----------

QuoteOriginally posted by Kunzite Quote
No, you're not.
The K-1's pixel density is similar to that of a K-5 series camera, and lower than that of a K-3. If we're talking pixel peeping, a K-1 won't stress a lens (in the center) any more than a K-5IIs.
I agree about the magnification, so with the pixel density being higher on my K3 than the K1?
6.66 MP/cm² on K3
4.24 MP/cm² on K1
It would be trying to get more detail out of the cropped portion of the glass than the K1 would be. Right?

That is also something I never thought about.


Last edited by randee; 01-15-2017 at 04:39 PM. Reason: edited for clarity,
01-15-2017, 04:31 PM   #62
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Randee:

I have the D FA 70-200 which I use with my K1.

I previously purchased it early last year in anticipation of getting a K1. I used the lens with my K3. I almost always order from Amazon and did here, as well. I went through two copies, and sent back both, because the D FA 70-200 on the K3 had issues very similar to yours. I had focus accuracy problems and it also was not as good as my Sigma 70-200 (the latest version for Pentax before Sigma stopped making the lens in the Pentax mount--which was a very good lens). And, I had made sure to update the firmware for the K3 to make sure it functioned with the D FA 70-200.

Fast forward to me getting the K1 last summer. I purchased again the D FA 70-200 and I love the lens and it works amazingly well with my K1.

My unscientific conclusion is that the lens simply does not work well with the K3, or at least it is susceptible to not working well, since I assume other K3 owners may be happy with their copy of the lens.

I sold my Sigma and now use the D FA 70-200 as my main zoom when photographing MMA and BJJ events.
01-15-2017, 04:32 PM   #63
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QuoteOriginally posted by randee Quote
I agree about the magnification, but wouldn't the pixel density be higher on my K3 than the K1?
This is what I said.
01-15-2017, 04:37 PM   #64
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QuoteOriginally posted by Kunzite Quote
This is what I said.
Yes, my comment sounded confusing, but I was agreeing with you.
Just saying that it would be like trying to get more detail out of the same physical portion of the glass.
Some some sort of sharpness issues might be highlighted with the K3 vs the K1, correct?

Thanks for the input!

---------- Post added 01-16-2017 at 07:44 AM ----------

QuoteOriginally posted by sbh Quote
I've been following this discussion and there are some good thoughts. Now I just got a 70-200 myself and I think I got a bad copy, unfortunately it's not what I expected.
SBH,

That's very interesting. Is that the K3 or K1 or ??

See on my copy it seemed like every once in a while I could get a sharp shot. So I kept thinking it wasn't the glass, it was the AF or IS or something else I was doing.

Looks like you got a nice test chart, and some testing going. Are you comparing it to the 100mm Macro D FA 2.8?
What is your distance to the test chart.

Very interested to hear more about your situation.

Thanks for posting!

01-15-2017, 04:56 PM   #65
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QuoteOriginally posted by randee Quote
Yes, my comment sounded confusing, but I was agreeing with you.
Just saying that it would be like trying to get more detail out of the same physical portion of the glass.
Some some sort of sharpness issues might be highlighted with the K3 vs the K1, correct?
You might better observe such issues when pixel peeping with higher density sensors, yes. However, this is a bit tricky - increasing the pixel density will get you less sharp pixels, but more detail in the final image. So in the end, would you really observe an issue?
01-15-2017, 05:00 PM   #66
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QuoteOriginally posted by candgpics Quote
Randee:

I have the D FA 70-200 which I use with my K1.

I previously purchased it early last year in anticipation of getting a K1. I used the lens with my K3. I almost always order from Amazon and did here, as well. I went through two copies, and sent back both, because the D FA 70-200 on the K3 had issues very similar to yours. I had focus accuracy problems and it also was not as good as my Sigma 70-200 (the latest version for Pentax before Sigma stopped making the lens in the Pentax mount--which was a very good lens). And, I had made sure to update the firmware for the K3 to make sure it functioned with the D FA 70-200.

Fast forward to me getting the K1 last summer. I purchased again the D FA 70-200 and I love the lens and it works amazingly well with my K1.

My unscientific conclusion is that the lens simply does not work well with the K3, or at least it is susceptible to not working well, since I assume other K3 owners may be happy with their copy of the lens.

I sold my Sigma and now use the D FA 70-200 as my main zoom when photographing MMA and BJJ events.
Wow! That is very interesting!

Very good information to know, but also very disappointing.
I wonder if Pentax has anything to say about this?
Might be able to have a firmware fix that could resolve the issue.
01-15-2017, 05:41 PM   #67
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QuoteOriginally posted by randee Quote
Wow! That is very interesting!

Very good information to know, but also very disappointing.
I wonder if Pentax has anything to say about this?
Might be able to have a firmware fix that could resolve the issue.
Others have used the K-3 without issue.

Kenspo was an early tester with his concert photography, if you remember.



01-15-2017, 05:51 PM   #68
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It is the K-1. Yes, I compared it to the 100mm macro since it is the only FF lens I have in that focal range. I didn't plan to do that chart testing but I wondered whether his was normal. Re-tested several times to be sure. Distance was approx. 2.8m (9’ 2¼”). Long distance tests gave similar results (1000m / 1100 yards) but not as severe.

I tested the 100mm macro, DA* 60-250, DFA 24-70, DA*55, FA43, DA 17-70 and the old ones 35-70 and 35-80. The 70-200 and FA43 are new and supposed to replace my 60-250 and DA-55. The 100mm outperforms all of them at f/2.8 and f/4.

The 70-200 seems strange. The top left quarter is awful. Bottom left and top right are similar unacceptable. They start to get ok at f/8. But the bottom right is actually always sharp. I used the center as focus point. Also the focus ring behaves strange. When I overshoot the focus point and reverse the rotation, the focus doesn't reverse immediately but keeps going in the original direction for a tiny bit before following the new direction. Maybe some mechanics are off. Idk.
01-15-2017, 05:56 PM   #69
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Trying to find some sample pictures with K-3 at f2.8, I ran across this:
QuoteQuote:
Focusing can be a little bit hit or miss, so extra care may need to be taken to ensure focus is accurate, especially at fast apertures
Pentax HD PENTAX-D FA* 70-200mm f/2.8 ED DC AW Review


---------- Post added 01-16-2017 at 09:13 AM ----------

QuoteOriginally posted by clackers Quote
Others have used the K-3 without issue.

Kenspo was an early tester with his concert photography, if you remember.
Or I remember Kenspo,
I appreciate his input.

Ya, it's still a mystery or quite possibly in my head.
01-15-2017, 06:46 PM   #70
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I haven't tried the DFA 70-200 but I had a similar problem with the DA 18-135 years ago. On my K20D it would "smear" the lower corners, on some shots more than others. Then I got a K3 and it worked fine.
01-15-2017, 06:47 PM   #71
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I'm sending mine back tomorrow and hope to get a replacement that is better.

---------- Post added 01-16-17 at 02:50 AM ----------

QuoteOriginally posted by Skewed Quote
I haven't tried the DFA 70-200 but I had a similar problem with the DA 18-135 years ago. On my K20D it would "smear" the lower corners, on some shots more than others. Then I got a K3 and it worked fine.
Interesting, sounds familiar.
01-15-2017, 07:41 PM - 1 Like   #72
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QuoteOriginally posted by sbh Quote
I'm sending mine back tomorrow and hope to get a replacement that is better
And send the next one back too, if it's decentred.

We pay a lot for these products, we're entitled to do this.

Digitalis is on his fourth copy of the Sigma 8-16mm, now he's happy.

01-15-2017, 08:29 PM   #73
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QuoteOriginally posted by clackers Quote
And send the next one back too, if it's decentred.

We pay a lot for these products, we're entitled to do this.

Digitalis is on his fourth copy of the Sigma 8-16mm, now he's happy.
Wow, 4th copy. That's very interesting. You see videos of employees in white suits and gloves testing lenses in a laboratory setting. Thinking there is computer aided lens testing and aligning processes to get these lenses perfect. Hard to believe there could be that much of a variance in lenses. I wonder what the percentage of "good copies" to "bad copies" there are?

I would think that at this price point there would be some rigorous quality assurance practices for the Pentax 70-200mm.
01-15-2017, 09:23 PM   #74
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I would make sure to use "Spot" AF Area mode (center point), have ample light, and a sensible Aperture if I was testing the lens.
01-15-2017, 10:22 PM   #75
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QuoteOriginally posted by randee Quote
Wow, 4th copy. That's very interesting. You see videos of employees in white suits and gloves testing lenses in a laboratory setting. Thinking there is computer aided lens testing and aligning processes to get these lenses perfect. Hard to believe there could be that much of a variance in lenses. I wonder what the percentage of "good copies" to "bad copies" there are?

I would think that at this price point there would be some rigorous quality assurance practices for the Pentax 70-200mm.
Read Roger Cicala for sample variation. All companies, all lenses suffer from it ... his rental firm can gather stats.

Even Canon L series glass.

Instead of studiously checking each piece, clearly all the makers are happy enough to cut time/wages during manufacture and let a certain percentage return.

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