Expeed - Nikon D300 Complete Manual

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When the exposure is complete and a signal is received by

the sensor from the camera's main electronics, these electrons

are moved through column-parallel analog-to-digital

converters on the sensor, which includes a series of gain and

noise suppression techniques, before it reaches the external

circuitry (the stuff Nikon calls EXPEED; see next). These

converters have a relatively simple job, which is to count the

number of electrons they see from each photosite and convert

that into 12-bit or 14-bit digital values that are then passed on

to the rest of the camera's circuitry.

For a fuller discussion of how sensors work, see

http://www.bythom.com/ccds.htm.

EXPEED

As part of the D300 (and D3) introduction, Nikon finally got

around to giving a name to the digital imaging system internal

to their cameras.

On a digital camera, there are a handful of digital parts that

are involved in the imaging. First, we have the imaging sensor

(see "The D300 Sensor" on page <48>). Either the sensor has

on-board ADC (analog-to-digital conversion) or external ADC.

(The D300 has an on-board ADC.) From there the image data

goes to a memory buffer where it is looked at by a custom

ASIC chip that handles interpreting the data. After processing,

the data ends up back in the memory buffer (where the

imaging ASIC may continue to work with it). Finally, when

the memory buffer contains a finished image file, that file is

moved to the camera's storage card.

Thom Hogan's Complete Guide to the Nikon D300