More leaked specs on the Nikon D850 – and it could be something of an imaging revolution for Nikon users after all.

Screen grab of the Nikon Italy page that was live for about 5 hours yesterday, click to view full size.

According to the leaked specifications, the camera will be fitted with a back lit sensor and gapless micro lens technology.

If this is true, then all the scathing I gave the Nikon D850 specs last week may need to be ‘dialled down’ a bit – the one thing this camera will NOT BE (again,if the tech leak is true) is a pumped up FX version of the D500.

What is a back lit sensor?

You can regard all Bayer pattern CMOS sensors in your dslr and mirrorless cameras as front lit.

Light leaves the rear element of your lens and strikes the sensor, passing through the micro lenses first, then a wiring/connectivity layer, and finally it strikes the photo diodes/photosites.

Front lit (left) and Back lit (right) sensor layout.

Light can scatter within that wiring layer, and the distance between the micro lenses and the photo diodes effectively narrows their viewing angle.

Having the photo diodes directly behind the micro lenses removes the scattering potential, and increases the diode viewing angle – a bit like putting your eye closer to a key hole – you see more.

A back lit tech sensor may well have a 50% or larger diode/photosite ‘view angle’ than its front lit counter part with the same mega pixel count.  Couple that with new micro lens technology to remove the interstitial gaps, and there is a lot of potential for increased performance in terms of:

• Native gain/light gathering during the exposure
• Increased Dynamic Range over the Nikon D810
• Increased Dynamic Range over the Nikon D500
• Increased high ISO performance over both the D500 and D810
• Dare I say it, lower diffraction values?  Surely the Circle of Confusion has got to increase in size – I don’t know for certain but it would definitely be interesting to find out.

Back lit/backside illuminated/BSI CMOS sensor tech is out there already – the Sony A7R2 springs to mind.

At the begining of this post I said the D850 could be something of an imaging revolution for Nikon users – and I meant it.

It’ll be the first Nikon FX DSLR (as far as I’m aware!) to be fitted with BSI tech, but if they screw up the ADC/SNR side of things like they did with the D5, then it’ll amount to NOT A LOT.

If however, Nikon do a good job of converting the analogue output of this sensor to a digital file, then we could say that no Nikon FX digital camera has ever been capable of delivering the potential benefits of the D850.

But we are still waiting for the official release of the specs so who knows…!

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