Why EVF will never replace OVF for me

Started 11 months ago | Discussions thread
nigelht
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Re: Non-destructive read or image stacking?
In reply to Erik Magnuson, 11 months ago

Erik Magnuson wrote:

nigelht wrote:

Every 1/24th of a second (or whatever desired refresh rate) I can show the image produced by integrating over the prior 10 seconds of time.

This requires that you can do a non-destructive read of the pixel voltages. I did not think contemporary sensors could do this.

I don't know what the current sensors do but you can build CMOS sensors with non-destructive read.

There is some conjecture that Nikon is using that to get 14 bit resolution while using a 12-bit ADC.  Either there is a non-destructive read capability in the sensor and Canon does this as part of their noise reduction process.

Or it's all fancy software processing.  I don't have any definitive citations that state either way.  Just some astro forum conjecture.

The olympus OMD "live time" long exposure feature can kinda sorta do this. [5][6] Since you can get up to 24 previews then for a 12 second exposure you can get a preview every half second. It's not a constant refresh but it's a more useful feature the way it's done. I wish more cameras could do this.

Given the timings involved, I suspect Olympus is basically doing in-camera image stacking, i.e. every 0.5s the sensor is read (and reset) and the values are simply added added together to update the display or the cumulative exposure. If they could do an actual non-destructive read, then there would be no need to restrict the time of the updates to 0.5s.

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Erik

That seems a likely possibility.  That would explain why they limit the number of previews as readout noise would all get added together.  Although if they had non-destructive reads that's probably true as well.

Hmmm.  Dunno.

I didn't see an interview of an oly engineer that explains how they do this but perhaps its in Japanese or something or they simply don't want to talk about it.  I'd figure that a Canon or Nikon engineer could guess how its done anyway.

It's a very cool feature that I would probably use once a year (July 4th).  Maybe twice if I wanted to do some long exposure flowing water pics or night time traffic pics somewhere.

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