While we have talked at length about the renditional qualities of a lens, we have yet to have a conversation about the output of digital cameras. A lens is as good as the output of its camera: it can display micro-contrast and depth rendition as much as its camera lets it do. To understand digital exposure and what improves the output of it, we must first look at the imaging system through the approach of the radio analogy.

Radio Analogy on Digital Exposure

Light is signal. This represents the tonality (colors, contrasts, details) of the subject. Its strength is defined by shutter speed and aperture.
The photosite is an antenna that receives the signal. The size of the photosite defines its native signal gain. The higher the native gain, the bigger is the gap between the peak of the gain and the noise floor over the same signal.
Photosites exist at various densities within the size of the camera sensor. Higher megapixel sensors has higher density and lower native gain.
The ISO defines the applied gain on the photosite so that it can receive a weaker signal. Increasing the gain raises the noise floor.
The Analog to Digital Converter (A/D converter) converts the gained signal into digital information. The quality of the conversion is influenced by Bit Depth.
The Signal to Noise Ratio firmware (SNR) separates the signal (the detail) from the noise (the noise) right before making the RAW file. If the converted gain is low, it will have a harder time figuring out the difference, therefore removing more signal.

Ideal digital exposure camera and moving forward into the future

The quality of the tonal gain matters for life-like image making. Tonal gain is NOT dynamic range. For a camera to record the maximum amount of micro-contrast and depth off a good lens, it requires:

Low photosite density for higher native gain: The current ideal photosite density is 12mp for the size of a fullframe sensor (Nikon D700 - 8.5 µm is ideal), but the minimum density is improving every year. Photosite designs are also improving but have a slower evolution. Native gain was once vital in order for the "dumber" SNR firmware to clearly see the difference between signal and noise.
An efficient A/D converter: An improving feature of cameras year by year as micro-processors evolve.
14bit or higher RAW recording: 14bit ensures a superior tonal gain over 12bit. It directly influences the camera’s ability to record the tonality of the scene. This mostly helps “low microns/high photosite density" cameras more than anything.
An efficient SNR firmware: An improving feature of cameras year by year as smarter algorithms are found to effectively reduce noise and keep more signal into the RAW file. (Nikon D750 - 5.9 microns could potentially be the “new” minimum)
Great electromagnetic shielding and internal cooling: Another influent of digital exposure are the electromagnetic interferences caused by uncooled electronic parts in a camera too compact. These affect the signal before it gets converted by adding noise if the sensor doesn't get good enough shielding from the heated parts.
Using a lens with great micro-contrast and depth rendition also helps... obviously.

What are those cameras?

This link compares the pixel pitch of various cameras. I encourage you to cross reference the rendition of those between 5.5 and 8.5 microns at 14bit with those of around 4 microns. Simply look at the flickr pool of each of them and witness their ability to extra depth and micro-contrast out of every scene regardless of lens (yes, even high-element-count ones). Here are some of cameras I consider to be tonal rich:

Full Frame Sensors Cameras

Nikon D750 (5.9 microns) - 2014 - borderline - 14 bit
Canon 6D (6.5 microns) - 2012 - 14 bit
Canon 1Dx (6.9 microns) - 2011 - 14 bit
Canon 5Dii (6.4 microns) - 2008 - 14 bit
Nikon D3/D3s/D700 (8.5 microns) - 2008 - 14bit
Canon 5D (8.1 microns) - 2005 - 12 bit

Crop Sensors Cameras

Nikon D300/D300s (5.5 microns) - 2008 - 14 bit
Canon 40D (5.7 microns) - 2007 - 14 bit
Nikon D200/D80/D40x/D60/D3000 (6.1 microns) - 2006 - 12 bit
Nikon D40/D50/D70/D70s (7.8 microns) - 2005 - 12 bit

The influences of pixel pitch on cameras’ tonality today

D700 (8.5 microns), D750 (5.9 microns), D800 (4.8 microns) cameras shot at F8 and compared at even histogram in Lightroom. Work RAW files available here

Here is a short list of results based on pixel pitch decisions happening in the photography gear industry:

Smartphone industry

#streetcorners 🐉

A photo posted by olivier martel savoie (@une_olive) on Feb 29, 2016 at 9:39am PST

The iPhone camera remains, even today, the cellphone camera with most life-like rendition because of its higher pixel pitch.
The HTC One attempted to push this theory in its Ultrapixel camera but had inferior A/D Converter and SNR firmware.
Sony Xperia Z smartphone cameras with 20.3mp fail every year to match the iPhone Camera due to the higher density of the sensor.
The Samsung Galaxy S7 drops down to 12mp from 16mp for higher gain.

Canon system

People still find the Canon 5d classic to render “organic” images.
The 5d3, with a pixel pitch nearly equivalent to its predecessor and a newer digic processor, displays higher tonality to the D800 to this day.
Canon 7D images are flatter than Canon 40D images.
Canon 1DX is well regarded as a “tonal monster”.
Canon 6D has “over the top” color saturation.

Nikon system

Many Nikon users change their workflow every time they buy a new Nikon camera due to the shifts in photosite density and processors.
Nikon D700/D3 are still workhorses of high value 8 years later after their creation. The D3s still sold used at premium prices.
D7000 raw files are much more flat than the D300s.
D750 regarded as a fullframe low-light god at its release.
D5 released at 20mp, 4 mp lower than the D750.

Film Cameras

Film grain density is lower than a digital sensor.
People find the results more life-like and genuine.
Photography students who shot with 35mm, 67 medium format or large format still prefer shooting film over digital today.

Compact and mirrorless cameras

Sony RX100ii produces highest image quality for 1inch sensor cameras.
Sony A7s/A7sii (11+7bit) cameras are said to have this high tonal “medium format” clean look thanks to higher pixel pitch.
Fuji X (14bit) cameras display quite pleasing "filmic yet muted" color science.
Ricoh GR keeps using 16mp APS-C sensor for two generations, but the Coolpix A and the upcoming Fuji X70 have better colors due to 14bit recording.
A7/A7ii, A7r/A7rii (11+7bit) cameras render images with "questionable" native white balance and muted colors. Users demanded the ability to record 14bit and a successful fix was provided.
No matter how good the lens is, M43 cameras of 16mp (12bit) and above produce very sharp images without micro-contrast leading to many like me claiming that m43 is flat. The Lumix GH1 was probably the very last “tonal rich” cameras of the sensor format.

Tonality matters, tonality is life-like

Hasselblad H4D-60... when you actually nail it.

Although digital sensors are also a game of balance between the native gain of the photosites and the efficiency of the image processors, the better tonal rendition of a low photosite density high gain sensor saves post-processing time and exploits the qualities of lenses much more than a high-resolution sensor of low gain. A lot of people enjoyed shooting film. There was something alive, soulful, genuine and true about it. Those emotions translate into strong tonality, life-like and depth. The transition to digital shocked many. The words sterile, clinical, cold and fake described such reactions. This translates into sharp, flat, detailed, commercial. While the lens industry tried to remove the “digital” in our pictures by removing chromatic aberrations or by providing us the opportunity to blur the background to separate subjects, the new lenses further enhanced the “digitalness” of photography. While the preset industry flourished as a promise to remove the “fake” from a digital exposure at various success, the increasing flatness of modern digital photography amplifies the idea of an underexposed pushed film look that attempts at creating contrast an sea of gray RAW files. I believe it is important to grasp a better understanding of digital exposure and acquire/demand a better camera for photography instead of a camera for bragging rights.

Addendum: Comparing 24mp FX sensor (5.9 microns) vs. 24mp DX sensor (3.9 microns) for depth and tonality. Same lens, F8.

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Digital Exposure and the Importance of Tonality