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11-26-2010, 10:57 PM   #1
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Mirror cycling on optical preview, stopped-down movie recording

This may be a silly question, but why does the mirror go up and down on exiting optical preview?

I've also noticed this behavior when using an aperture other than the maximum when in movie mode. Specifically, the mirror cycles when recording starts and when recording ends, except when shooting wide open. Does stopping down require cycling the mirror?

--DragonLord


Last edited by bwDraco; 05-15-2012 at 11:38 AM.
11-27-2010, 12:07 AM   #2
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Isn't it so that you can look through the VF and preview your image?

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11-27-2010, 08:58 AM   #3
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When the Green Button is assigned to Optical Preview, pressing and holding it will cause the lens to stop down to the set aperture, darkening the viewfinder and displaying the depth of field for the set aperture. However, upon releasing the button, the mirror will cycle. Why can't the camera simply reset the aperture without cycling the mirror?

--DragonLord
11-27-2010, 09:12 AM   #4
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This is similar to the mirror up/down quirk on green button metering with an M-lens (k-x). No apparent need for that either. Maybe the firmware routine is shared with exposure?

11-27-2010, 09:18 AM   #5
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QuoteOriginally posted by jolepp Quote
This is similar to the mirror up/down quirk on green button metering with an M-lens (k-x). No apparent need for that either. Maybe the firmware routine is shared with exposure?
I feel that this is a hardware limitation, but correct me if I'm wrong. Why is this necessary?

--DragonLord
11-27-2010, 09:54 AM   #6
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QuoteOriginally posted by DragonLord Quote
I feel that this is a hardware limitation, but correct me if I'm wrong. Why is this necessary?

--DragonLord
I have wondered about that myself :-) Just speculation about firmware above: the idea is that they might already have had subroutine(s) used for exposure that could be conveniently used for green button metering and optical preview that also happened to raise the mirror.
09-11-2011, 10:57 PM   #7
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QuoteOriginally posted by DragonLord Quote
I feel that this is a hardware limitation, but correct me if I'm wrong. Why is this necessary?

--DragonLord
Have no idea, but maybe the whole shutter mechanism is designed differently enough from film cameras that the shutter/mirror mechanics need to be reset after doing this? And for some reason, it's not required if the aperture is set wide open? Does this happen on all Pentax digital SLRs?

You may be right.
09-12-2011, 04:13 AM   #8
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QuoteOriginally posted by DragonLord Quote
This may be a silly question, but why does the mirror go up and down on exiting optical preview?
The K-5 doesn't behave as you describe.
It won't touch the mirror in all operations you describe.

Of course, if you have electronic preview (rather than the default optical one), the mirror must move to unblock the sensor. This is pretty clear though and I guess isn't what you meant.

What you hear is the shutter and the shutter must move because otherwise, the sensor won't receive light

After an exposure, the shutter must close and then, both curtains must rewind and then, the shutter must open again. That's almost as loud as the K-5's silent mirror.

Lesser bodies (K-r etc.) have a traditional mirror-box where shutter-rewind and mirror-down are mechanically linked. So, what you describe may apply to the K-r and if it so, it is indeed a hardware limitation the K-5 wouldn't have.

09-12-2011, 06:14 AM   #9
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QuoteOriginally posted by falconeye Quote
The K-5 doesn't behave as you describe.
It won't touch the mirror in all operations you describe.
Does this mean that if you pull the optical preview lever on the K-5, the mirror will not cycle on releasing the lever?

On my K-r, the mirror actually cycles with the viewfinder blacking out momentarily when I let go of the Green button for optical preview.

If possible, can someone post a YouTube video comparing the K-5 or K-7 and the K-r or K-x in optical preview?

--DragonLord

Last edited by bwDraco; 09-12-2011 at 06:28 AM.
09-12-2011, 06:43 AM   #10
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QuoteOriginally posted by DragonLord Quote
Does this mean that if you pull the optical preview lever on the K-5, the mirror will not cycle on releasing the lever?
I said so and say it again: yes.

Optical preview (which is a third stop in the ON-OFF lever) activates the aperture motor to engage and release the aperture. The aperture motor is rather silent (much more than a mirror) but it isn't unaudible. There is no black out of course.

On a K-5, the green button can't be configured to optical preview which has it has its own lever.

QuoteOriginally posted by DragonLord Quote
On my K-r, the mirror actually cycles with the viewfinder blacking out momentarily when I let go of the Green button for optical preview.
The K-r has no aperture motor (the little bump in the K-5 body on the right side (left if you look onto the lens) of the mirror box.

Therefore, it needs a second source to pull the aperture spring back. It is all part of a single mechanics which rewinds the shutter curtains, rewinds the mirror and pushes the mount's aperture lever. The K-7/5 needed to get an entirely new mirror box (new dampened mirror, new shutter, new aperture motor) to separate functions.

QuoteOriginally posted by DragonLord Quote
If possible, can someone post a YouTube video comparing the K-5 or K-7 and the K-r or K-x in optical preview?
Or you simply believe me ...
09-12-2011, 06:50 AM   #11
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Sorry, Falk. I understand. That also explains the extra bump at 10 o'clock around the lens mount. Thanks.

--DragonLord
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