Mass Hysteria Poll (K-7 blur)

Started Oct 12, 2010 | Discussions thread
Real Engineer
Regular MemberPosts: 368
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Re: Mike, please try again
In reply to MightyMike, Oct 13, 2010

OK, you're either not understanding what is happening or I'm not making it clear enough.

The SR is unstable at longer focal lengths. Plain and simple.
These are the reasons:

Buzzing from an SR system is resonance caused by positive feedback.

It is NOT a normal mode of operation. It is a direct result of too much gain and time delays resulting in what should be negative feedback being made in to positive feedback.
Think of an amplifier and a microphone going into feedback ringing.
What are your options to correct this?
1) Turn the volume down. This is lowering the gain.
2) Create a phase change. This turns positive feedback into negative feedback.

When you take a picture the feedback is just beginning and will slowly raise till its that buzzing you yourself felt. The CPU will detect this and take corrective measures using most likely (1) above.
Then the system becomes stable again.

So far all well and good.

Now, lets not use liveview and take a normal picture instead.

Lets start at a 1sec exposure.
What we will observe is buzzing through most of the exposure.
The photo is rubbish.

Lets shorten the shutter time.
What we observe is less buzzing.
Photo is still rubbish.

Lower it more.

You will get to a point where you cannot feel it or hear it but your photo's will show it.

You'll observe double exposure type images.

This is a fault. It is caused by having too high a gain setting initially.
It is not normal operation.
Most importantly it is easily fixed in firmware.

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