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11-17-2017, 08:32 AM - 1 Like   #16
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QuoteOriginally posted by Paul the Sunman Quote
I've only seen it with the DFA 28-105. Not even the minuscule DA 40 seems to produce it, though my testing hasn't been extensive.
Interesting!

I wonder if it's not just the low mass of the DFA 28-105 but also some internal elements of the lens that are prone to vibration. If mirror shock causes the AF group of elements or one of the zoom-groups of elements to move laterally even a tiny amount, it could induce a significant shift it the image.

11-17-2017, 09:59 AM   #17
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I'm the OP and just remembered that I also have evidence of the issue from the August solar eclipse. I was using the K-1, Sigma 50-500 at 500mm, and a tracking mount. SR and lens OS were turned off because of the tracking. I took multiple brackets and had some sharp photos, and some obviously blurred with a ghost image. A friend with a Nikon D800 and a different lens experienced similar issues for the eclipse.

We discussed doing tests under controlled conditions but haven't had an opportunity to follow through.
11-17-2017, 10:12 AM - 1 Like   #18
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QuoteOriginally posted by gaweidert Quote
I personally think the sensor moves a bit as it as a resonant frequency is hit during the exposure cycle
I did a test by mounting my DA* 300mm and placing it and the camera on my granite kitchen worktop. Pressing down while taking some test pictures. No shutter induced blur at all. When the same combination is on a tripod shutter shock blur is evident.

I dont think the sensor is the issue
11-17-2017, 02:14 PM   #19
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I had this problems not with the 28-105 but with the 50 macro f 2,8,SR activated and between 60 and 200 th all the images blurred!The 28-105 is much more stable but not perfect in the high end.One of many reasons to switch to K1 from a Nikon 800 E was this issue,with the Nik tripod ,mirror up to expect have a sharp photo,the SR helps a lot at 8th to 30 th were most are ok!

11-18-2017, 11:30 PM   #20
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Still a mystery why the problem is centered on 28-105. Pity, because this is a very good lens esp for travel. Lately I'm seeing more blur at 1/200 while 6 months ago that was a safe shutter speed. One thing for sure, Pentax chose not to respond as I've reported this so many times through the distributor. They solved other problems on my K-1 quickly, just not this vibration issue.

Now my K-1 will most likely stay in the cabinet as I'd shoot more with 5DSr. Avoiding 1/60-1/200 and shooting a heavy DSLR the same way as shooting with a smartphone is beyond me....
11-19-2017, 12:28 AM   #21
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I may have been the first to report this issue on PF. I have learned to live with it. It only seems to be an issue for me with the DFA 28-105, and only between about 1/100-1/200 s. So I have switched from using mostly P mode and now TAv is my standard. I avoid the troublesome shutter speed range almost automatically, and have had no further problem. Even in the offending range, it doesn't always occur.
11-19-2017, 01:31 PM   #22
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SR somehow mitigates the issue, although does not recover full sharpness potential. Nikon D800E had the issue, Nikon improved it in the D810 used a different kind of shutter. K1 is probably half way between D800E and D810.

---------- Post added 19-11-17 at 21:34 ----------

QuoteOriginally posted by scopedude Quote
They solved other problems on my K-1 quickly, just not this vibration issue.
The "fix" according to Ricoh was adding EFCS via firmware upgrade.
11-22-2017, 01:52 AM - 1 Like   #23
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Pentax distributor lent me a grip and a 24-70/2.8 today. I have tested them and my 28-105 repeatedly, using VF, LV, back to VF, LV and so on. I observed the RAWs and found out:

K-1. Grip, DFA 28-105, 1/125s, 28mm

The grip doesn't help. The sharpness difference is clearly noticeable among the LV shots and VF shots.

K-1 (no grip), DFA 24-70/2.8, 1/125s, 24mm

The shutter shock does affect this setup - to a lesser degree - but still I didn't miss how sharp the LV shots are. Micro contrast and edge sharpness are better with the LV shots.

I'll do some more test tomorrow, though I don't expect anything different but just to make sure before I report this to Pentax distributor. Maybe my unit is among the worst affected by the shutter shock, so if there is no response again from Pentax, I see no options other than selling the body...

Just my 0.02

11-22-2017, 07:49 AM - 1 Like   #24
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Before you sell the body, you might want to test the likely replacement -- the replacement may be no better to your eye that what you have.
11-23-2017, 07:27 AM   #25
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Same here with K-1 and FA24-90 at 1/200 when focal length is in the 24-35 range. SR mitigates the effect.
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