Pixel density - can the playing field be leveled???

Started Jun 6, 2009 | Discussions thread
ejmartin Veteran Member • Posts: 6,274
Why microlenses are a good idea

bushi wrote:

AHA! Gotcha. So please, somebody good with numbers (apparently there are many amongst us ;)), kindly do the math and tell me, taking into account the above hard evidence figures: if the camera manufacturers stop themselves from increasing that damn pixel count by all costs, and instead of "just" beating the previous generation sensor's already outstretched light capturing area , by advancing the sensor technology and increasing pixel's aperture, IF, instead , they use this newly developed technology to increase the light capturing area of the sensor, for the same MP count, how much (in percentage) more light capturing area would we have, on the same size sensor?

Not much, since pretty much all current small (ie digicam) sensors have 100% microlens coverage, which focusses the light that might have hit on the non-photosensitive area onto the photosensitive area. 100% coverage means that virtually all the light hitting the sensor gets directed onto photosensitive silicon.

I don't need the precise numbers (although it would be nice to have them), to know that this increase would have the positive impact on all of these:

  • higher ISO sensitivity

No, since just about all the light reaches the photosensitive area due to the microlenses.

  • better Dynamic Response

Yes, since photosite saturation occurs at a given number of photoelectrons per unit area. A larger active area means more photons can be captured before saturation occurs, increasing the high end of the dynamic range.

  • better S/N

Only if one increases the exposure to take advantage of the higher saturation level.

  • better "per-pixel" image quality

Insofar as there are fewer blown highlights for the same exposure as the smaller aperture photosite, due to the higher saturation level. Everything else (noise, SNR, etc) is pretty much the same for a given exposure, as I explained above.

All this fancy "noise" math (that I am starting to be a bit sick of, to be honest).

It wouldn't get repeated so much if it were more widely understood, and accepted as fact. People are going into it because it addresses the issue of what happens as pixel size is scaled, more so than the photosite aperture that you seem to be fixated on.

Sensors are not abstract sheets of paper, divided into pixels by infinitely thin lines.

They might as well be, due to the microlenses.


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