Banding with the E-M5 and the 20/1.7: A potential work-around

Started Oct 19, 2012 | Discussions thread
OP Anders W Forum Pro • Posts: 21,466
Re: PCB images

thinkfat wrote:

Anders W wrote:

thinkfat wrote:

Anders W wrote:

Thanks for that analysis! Looks very convincing from my untrained perspective.

Thanks. If only we could get the guys from ifixit.com into the game. Their experience in tear-down of electronic gadgets is outstanding.

Still, we have some elements in place to support the idea that maybe the power supply of the lens causes the banding. My next idea would be connecting an oscilloscope probe to the power supply contact of the lens mount. If there is any feedback of "dirt" from the lens into the camera, it might show up there.

BTW: My favorite hypothesis at this time would be the following: The voltage regulator in the lens (prior to being "warmed up") pollutes the voltage regulation in the camera. This in turn leads to voltage fluctuations in the on-sensor analog amplifier during the readout phase so that more gain is applied when reading out certain sensor rows than when reading out others. Hence we get banding. Does this sound like a credible explanation (in the absence of further information to the contrary)?

I'm thinking along the same line here. What baffles me is how a power supply meant to power a lens, should only be weakly protected against influence from that lens. Maybe it's a problem with the ground? It's quite tricky to isolate the grounds on a PCB against each others.

Yes. And one question that remains even if my hypothesis would turn out to be right is why the E-M5 voltage regulation and/or sensor is sensitive in this regard whereas other MFT bodies aren't. The problem appears only with the E-M5 and the 20. The lens works fine with other bodies and the body works fine with other lenses.

Another thought: does anyone remember any complaints in forums about disturbance of e.g. an EVF image while the focus motor of the "panacake" is moving?

Yes. I have seen that at times. And so have others. I don't think anyone has complained about in some more general way, however. The mentions I have seen are in discussions about the possible causes of the banding with this particular body-lens combo.

In general, the focus motor is one of the most common hypothetical culprits. The problem with the idea that the focus motor is responsible is that it isn't active during the readout phase. How then could it conceivably cause banding?

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