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

Started Jun 6, 2009 | Discussions thread
Steen Bay Veteran Member • Posts: 7,418
Same result..

bushi wrote:
huh, I am replying to my own post, how bizarre

(n.t., some ppl apparently do not understand phrase "let's do not overcomplicate things", so I'll let myself start at this point again.)

Firstly, let's clarify things: I am referring to advanced P&S cameras, or so called "bridge" cameras rather than high end dSLRs. So the ever more crowded, small sensors might be considered as "more ambitious" or perhaps they just need different compromises to be made. Secondly, I have no expertise/practical knowledge of the DSLRs at all. So my points might not be valid at all for that second area, given different design challenges present there. But I am quite confident that my findings are correct for the "prosumer compact" area, and they are backed by careful inspection of the "best of breed" in the last couple of years.

So back to the point, in own "megapixel race supporters" words:

Daniel Browning (quoting Jay Turberville) wrote:

[Part 4 out of 6.]

Comparing the Sony ICX495AQN to ICX624, for example, pixel area shrunk from 4.84µm to 4.12µm, a decrease of 15%. But instead of losing 15% of the photoreceptive area, it actually increased by 7% (22% total):

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?

What the illustration shows is that reducing the pixel size from 2,2um to 2,03um in this case actually has increased the light capturing area ('aperture') of the sensor with 25,7%, since the same size sensor has 'room' for 17,5% more 2,03um pixels (than 2,2um pixels) and each 2,03um pixel has 7% larger photosensitive area. The designers could probably (with the newer technology) have increased the light capturing area of the 2,2um pixel with 25,7% instead (keeping the same pixel density), but the result would be the same in both cases, namely 25,7% larger light capturing area for the same sensor size.

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

  • better Dynamic Response

  • better S/N

  • better "per-pixel" image quality

All this fancy "noise" math (that I am starting to be a bit sick of, to be honest). Sensors are not abstract sheets of paper, divided into pixels by infinitely thin lines. So hypothetical divisions of the "sensor area" into more or less "pixels", and doing calculations based on this divisions is rubbish, unfortunately. We have circuitry an all that stuff on it (see above). It is like looking at the world through the sieve. More dense it is, less light it passes through, period (assuming the same wire thickness in my sieve analogy = the same sensor technology). If you have invented thinner wire (=new sensor technology), you don't necessarily need to make denser sieve (=more MP).

My last point: resolution is important. In some applications, it is crucial. But looking at 99% of my pictures taken to date, few things comes to my mind: you only need so much resolution. You will very rarely have the luxury of optimal lighting for all your razor-sharp pixels to shine. Opposite, you will very often find yourself in difficult lighting situations. When it happens, the only use of all your pixels will be to "clog your memory card", to quote one of DPReview folks, and he is quite right.

Not having more resolution will not ruin your shot, it will just constrain you from printing it larger (cropping it more). But low ISO sensitivity will ruin your shot, if you are not able to get fast enough shutter speed. High noise will ruin your shot, by eating all your image fine details. Blown highlights will ruin your shot. Low dynamic range will ruin your dynamic shot. And there is nothing you can do with all your high resolution pixels to compensate for all above.

Therefore, I strongly believe, that I would benefit from more versatile sensor, less densely populated, but having more light capturing area instead, rather than having very high resolution one. Perhaps it should be stated this way froim the very beginning, to avoid misunderstanding.

And perhaps if they were trying so hard to get there (I would dare to say "to the point"), instead of "how to put more MP on this tiny chip and still be able to call it a day", they would came up with some different approaches. Like Fuji's SuperCCD, Foveon, recent Sony's back-lighted sensor, etc. - much sooner.

(BTW. do you know if anybody have tried RGBW filter pattern, with one White (no color filter) subpixel instead of second green? That would allow for much more light passing for each four RGBW subpixels. Seems that it might do the trick with higher sensitivities.)

Better late than never, anyway.

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