Physical vs. electronic light systems

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bob5050 Senior Member • Posts: 1,862
Physical vs. electronic light systems

Marba made this interesting claim in another thread, and I thought I'd pull it out because the issue is much larger than the simple OVF vs. EVF contest:

MarBa wrote:

The trend is clear. Electronics is and will be better than human eyes.

source :

Prejudice: I made a living in tech--as a software developer and development manager/director, so the general proposition that electronic systems always win isn't a particularly controversial one to me: of course they do.

But it's not always simple: the more pointed inquiry is that of what we need as a technical foundation in order for an EVF to be, not just "as good as" but actually better than an OVF. At what point, that is, must the Pentax OVF lose? There's more involved ther than frame refresh rate.

Let's take just one factor: dynamic range. The problem here is that the physical limitation of the OVF is, indeed,  the human eye, just as Marba wrote. And the human visual system is continually adjusting its 'ISO' for its own purposes. I can see both the moon and the mountains not because I have greater DR, but because I'm seeing each part of the scene at different sensitivity levels.

So one of the first things we have to deal with here is that EVF limitations are not actually EVF issues: what DR can the main sensor record?

The model approach here, I'd propose, is audio Dolby(c)  processing, because auditory DR presents exactly the same issue as light intensity: the recording medium is inherently unable to record the full dynamic range that the ear can hear: sounds too quiet are overwhelmed by noise that the mind filters out but become part of the recording, while sounds too loud cause distortion. We can see the immediate similarities to our problems with recording light.

Dolby(c) encoding responds to this, essentially, by compressing the volume spectrum: low sounds are recorded louder than they actually are, and louder sounds muffled, leaving a recording that preserves all information about relative volume, while confining the recording to levels that the recording medium can handle. Then, in playback, the lows can again be suppressed, and the highs amplified, because speakers (good ones), are capable of reproducing that fuller range. The listening experience can have as much DR as the actual performance, and be, in fact, cleaner then the actual performance.

What this implies that camera makers need to do is to

  1. develop a sensor that can actually compress (or said in our terms, exhibit a cell-by-cell context-sensitive ISO characteristic), thereby avoiding signal/detail loss in the dark areas, and burnout in the bright. And also
  2. develop a screen or display device that can actually cover the re-expanded DR that the sensor encoded.

When those are achieved, the OVFs time will indeed be over, and Pentax will have to look for another feature to sell. I'll be able to see though the EVF the same DR that the world presents--and to know that that DR is preserved in my photos.


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