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03-07-2015, 04:54 AM   #1
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Interval Shooting Epic fail

Original Q.
01 Lens.
Set JPEG high quality @ 2Mp (1920x1280)
Turn off SR
Turn off sensor clean
Set on solid table tripod.
Set white lamp over subject (sprouting wheat)
Camera on MF.
Focus lens on subject.
Set for 300 images 5 minutes apart.
Start shooting now.
25hours later
Check images and I discover that the photos started going out of focus at number 14....

WTF!!!!!!
Nothing was disturbed or knocked. The only movement was the sprouting wheat.
The tripod column was locked tight, so it wasn't slowly sinking...
The focal length for each of the 300 photos is 8.5mm (fixed of course) - this makes no sense at all!!

Why would it go out of focus?

One thing, I do notice that on startup the SR mechanism shakes the image, even with SR turned off. This happens for every capture during interval shooting, but would not account for the lens to go so far out of focus.
This makes the Pentax Q completely useless for time lapse. I was hoping to give it a single purpose, but now I don't even feel it's worth keeping

Has anyone else come across this anomaly??

Below are copies of the first and last image in the 300 shot sequence.

---------- Post added 03-07-15 at 10:11 PM ----------

All I can think of it the IBIS movement on startup is enough of a shake to move the focus ring a little each time.

Attached Images
View Picture EXIF
PENTAX Q  Photo 
View Picture EXIF
PENTAX Q  Photo 

Last edited by Steve.Ledger; 03-07-2015 at 05:03 AM.
03-07-2015, 05:21 AM   #2
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I'm just throwing out some ideas here:
a) zoom or focus creep, due to weight or temperature changes, or even shutter, mirror slap (ok, not on the Q), aperture blade movement or shaking from the button press itself
b) filter or optics fogging up due to temperature changes or moisture, but that would cause a general blur without changing focus
c) even someone walking past the tripod can shake it and cause motion blur, especially with a small, light camera and tripod. You can add weight to the tripod to add stability and reduce shake.


b) and c) are probably not the problem in this case. If its a), you can enable focus clamp (some lenses have this feature, locks focus in place, especially macro lenses where this is critical) or buy one of those rubber bands that is supposed to help. I never tried those, but they might help. Or just improvise and DIY

Last edited by Na Horuk; 03-07-2015 at 05:35 AM.
03-07-2015, 05:33 AM   #3
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I use bits of masking tape to hold focus and focal length when shooting long exposures - that's K-3 with any of my lenses.
03-07-2015, 05:35 AM   #4
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Thanks for reading.
No zoom, prime lens - Pentax 01 Standard Prime..

Thing is I did two short runs (few hours) before the 25 hour marathon. Each time they were fine.
No temperature changes, it's hot day and night here in the tropics right now, besides the focus started to drift (noticeably) at image 14, but would have started earlier.
14 images 5min apart = 70 minutes.

It's too late to try again now as the wheat has sprouted. Will need to wait until another time.
It's very disappointing not to be able to rely on a camera for what is essentially a very simple task.

03-07-2015, 05:57 AM   #5
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but you created quite a nice bokeh... (it's always good to find something positive)
03-07-2015, 06:02 AM   #6
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Interesting.
Try it again with exact same setup, same tripod, table, etc (any subject) but use bits of masking tape to mark the lens settings.
See what happens.
03-07-2015, 06:13 AM   #7
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I'd say firmware bug. The lens is completely camera controlled - focus ring movement doesn't actually do anything, it just tells the camera the focus ring moved. On the other hand focus is reset every time the lens is powered on, and the camera can then optionally move the focus back to a saved position (which you can select to do or not in the settings). On timelapse it would be aming to do this for sure, but it might fail. Once it fails I guess is saves the new position, and all your lates photos are wrong.

Another possible explanation for not getting the focus quite the same every time would be it signals the lens motor a fixed number of times (instead of until it actually reaches the desired position). This I would still count as a firmware bug, but maybe something you can work around. If it's the lens motor you'd need to fix the lens, but maybe it's the signaling, and cleaning the contacts would help.
03-07-2015, 06:47 AM   #8
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QuoteOriginally posted by Na Horuk Quote
a) zoom or focus creep, due to weight or temperature changes, or even shutter, mirror slap (ok, not on the Q), aperture blade movement or shaking from the button press itself
This is my guess. The 01 may be a tiny, light lens with internal focus, but if it was pointing down there is still a possibility of the lens elements slowly moving downward with gravity. Yes, it is focus-by-wire (the front focus ring only tells the camera electronics to move the focusing elements, so taping this down will do nothing in AF or MF), but there are still moving parts inside that lens with a necessarily small amount of resistance to motion.

Speaking of which, the 01 has an internal leaf shutter, so maybe that's jostling the focus with each shot. Perhaps try again with the custom function to only use the electronic shutter? Otherwise, do you have a toy lens (like the 05) that you *can* tape the focus down with?


Last edited by panoguy; 03-07-2015 at 06:54 AM.
03-07-2015, 07:07 AM   #9
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Oh yes, I didn't know the 01's focus ring doesn't actually connect to the lens internals mechanically. So taping it down might not fix the problem. Can you please tell us whether the camera was tilted, or horizontal? If it was in a normal, horizontal position, then gravity wouldn't have a big effect and that would indicate a firmware, camera problem.
I only have experience with long exposures with K-mount (K-01, K-r) which are more mechanical beasts. Would be interesting if any other forum members would try a Q with 01 setup for long exposures. Anyone else into sprouting?
03-07-2015, 07:38 AM   #10
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This will be an interesting mystery to follow as it doesn't really make sense. It would be interesting if you contacted Pentax to see what the got to say about it.
03-07-2015, 09:00 AM   #11
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Hmmm, I've done a couple of interval shoots with the Q although not with that lens and had no problems. I guess I would ask what was the difference between the test shoots and the failure. Since the problem started about shot 14 then surely it would have shown up in the tests.
03-07-2015, 02:45 PM   #12
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Thanks for all the responses

QuoteOriginally posted by roberrl Quote
Hmmm, I've done a couple of interval shoots with the Q although not with that lens and had no problems. I guess I would ask what was the difference between the test shoots and the failure. Since the problem started about shot 14 then surely it would have shown up in the tests.
No difference at all, identical setup. The camera is pointing down, positioned above the sprouting wheat.
Focus position not set in memory settings, so I will enable this next time.
It's a hell of a thing to run tests seeing as you need to wait so long before checking results.
It bothers me a lot that the IBIS shakes around on startup though. Seems there's no way to prevent this.

Last edited by Steve.Ledger; 03-07-2015 at 02:53 PM.
03-07-2015, 11:20 PM   #13
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Have done some time lapse with original Q, #03 fisheye lens with 3D printed focus lock, and tripod. No focus change. Pretty sure SR is turned off when intervalometer is used. Will have to try the #01. Interesting mystery.
thanks
barondla
03-07-2015, 11:30 PM   #14
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I set SR to off to be certain, but the IBIS plate still wiggles on each startup. You can see it on the LCD each time..
03-08-2015, 12:42 AM   #15
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QuoteOriginally posted by Steve.Ledger Quote
I set SR to off to be certain, but the IBIS plate still wiggles on each startup. You can see it on the LCD each time..
Well, that's kinda unavoidable isn't it? The SR is off when the camera is off, and the sensor just sits there. When you turn the camera on, it centers the sensor.
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