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Author Topic: The EOS 1D X Sensor Demystified...  (Read 14599 times)


  • EOS 5D Mark IV
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Re: The EOS 1D X Sensor Demystified...
« Reply #15 on: October 20, 2011, 10:24:32 PM »
Larger pixels giving more Dynamic Range is not a myth just an oversimplified statement because there is more to it than just pixel size.  It is true when those other things are equal.  DR is the ratio of the largest signal to the lowest signal that can be measured .  That ratio can be expressed as a simple ratio, stops/EV, or dB.

The maximum signal is the most electrons that can be stored in the photosite (one electron is release for each photon absorbed).  This is also referred to as saturation value or full-well capacity.  Note that it's the size of the photosite that matters... the area of each pixel that is sensitive to light which in the past I believe has been as low as 30% but in recent years was up to about 50%.  This is called the fill-factor 

The lowest signal is taken as the noise floor.. which is the read noise at whatever ISO your using.  Most CMOS sensors up until the most recent generation actually had higher read noise at ISO 100 but the Sony sensor used in the D7000 greatly improved on this and the read noise is fairly constant with ISO settings.

The Sony also has much higher full-well capacity even though the pixels are smaller.  This is most likely because they were able to increase the fill-factor... i.e.  a higher percentage of the pixel area is used for the photosite.  In other words, even though the pixels are smaller the photosites are larger (higher max signal).  Combined with the lower read-noise at ISO 100 (lower noise floor) the ratio of largest to smaller signal is much larger giving the very high 13.9 stops of DR.

Hopefully, we'll see these advances in the 1DX sensor as well but there are many other tradeoffs in designing a sensor to optimize for speed, heat, minimizing blooming (current leakage), etc. that the Sony sensor may have sacrificed... I don't know that's the case just stating the possibility.

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Re: The EOS 1D X Sensor Demystified...
« Reply #15 on: October 20, 2011, 10:24:32 PM »


  • EOS M5
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Re: The EOS 1D X Sensor Demystified...
« Reply #16 on: October 21, 2011, 01:58:10 AM »
According to dxo labs the 1dsIII has about 12 stops of dynamic range, the Nikon d3x has an amazing 13.7 both at iso 100. If its near 14 stops like the Nikon flagship with low noise that would be amazing for wedding and landscape photographers.

I believe even Nikon's 16 MP APS-C cameras like the D7000 achieve 13.9 eV of dynamic range (so much for all the myths about larger pixel size giving wider dynamic range), beating out their very own venerated 12 MP FF D3s which has 12 eV of dynamic range. Canon's Archille's heel really lies in their sensor electronics. We'll wait for real world tests to see if they have overcome this.

Dxomark's dynamic range measurement is actually quite useless and confuses many. What they measure is the mathematical/engineering type of dynamic range, how small a signal can be until it is equal size as the noise. That is not the same as saying that shadows 13.9 stops down are usable to the photographers, when the signal is equally large as the noise there is not a usable picture! The measurement does not say anything about how much dynamic range that is useful in a picture, well only that it is considerably less than 13.9 stops. Typical usable range in a good digital camera is around 7 stops if I remember correctly -- the reason why it so much smaller than the measured dynamic range is that you must have much more signal than noise in your shadows for a picture to be pleasing.

It is better to look at their SNR 18% measurement, which shows how much noise there is in parts that are not insanely dark, and there you can see for example that the 5D mk2 has less noise than D7000, despite that its "dynamic range" is only 11.9.

But then there's another factor -- pattern noise -- which Canon happens to have problem with, meaning that you can see a pattern in the noise. This is not measured by DxOmark, but does reduce the useful dynamic range, because most people really don't want to push the shadows such that you start seeing noise pattern. Noise that is totally random is much more pleasing to the eye.

And there's yet another factor -- auto exposure -- if you let the camera expose the picture itself it may play it safe and leave space at the top to avoid clip highlights, or it may push the histogram as far to the right as it can. If I remember correctly the D7000 autoexposure exposes much farther to the right than for example 7D. This means that D7000 will seem to have more dynamic range than it actually has. When you expose manually you can max out the sensor as you like.

In all, useful dynamic range is subjective and need to be tested, it is not easily measured.


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Re: The EOS 1D X Sensor Demystified...
« Reply #17 on: October 21, 2011, 12:50:56 PM »
I am surprised and more than a little disappointed that the new D1X sensor does not seem to provide an extended dynamic range.  Surely this is something that would be a winner for Canon!

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Re: The EOS 1D X Sensor Demystified...
« Reply #17 on: October 21, 2011, 12:50:56 PM »