Nikon Electronic Shutter

First published on: Friday, 26 August 2011

You probably remember the good old days of the D70, D70S, D50 and D40 where we had flash sync speeds of 1/500 sec, something no other competing camera offered.

To achieve sync speeds this high, Nikon had to use a hybrid electronic / mechanical shutter solution.

If you’re wondering why Nikon doesn’t implement this capability in their newer digital SLR cameras, Joseph Wisniewski has the answer:

An electronic shutter requires the sensor to be equipped with what is commonly called “snap shutter” circuitry. Basically, this is a second set of diodes, as big as the light gathering photodiodes, but shielded under a dark cover, and some additional switches. To shoot, the photodiodes are cleared of charge, exposure starts, and at the end of exposure, the charge in the diodes is transferred over to the shielded storage part of the cell. The cell is already full of stuff, so the only way to make space for this extra circuitry is to cut the size of the photodiode in half. Which cuts dynamic range and low light, high ISO performance.

A second problem is that with a full mechanical shutter, photodiodes are in the dark most of the time and only exposed to light during the actual exposure, so protecting the sensor from overloads (which cause charge to “spill” across the chip and create lines or blobs of light) is fairly easy. But look at that D40 you mentioned. The mechanical shutter is slow, 1/90 sec to open or close. So for a 1/2000 sec “sunny day fast lens” exposure, the chip is blasted with light for a full 1/90 sec while the shutter gets opened, 22 times as much light as hits it during the actual exposure. That means blooming is 22 times harder to control. I had a D70 for a short while, and like the D40, you saw a lot of blooming. Sunsets were a disaster, interior architecture had streaks coming off light fixtures, etc.

Joseph Braun mentioned that the cheaper shutters sync faster. That’s why, because in the cameras that had actual 1/90 sec sync, Nikon made the decision to give up dynamic range and increase blooming to raise sync to 1/500 sec. That’s why the last pro bodies with electronic shutter were 8 years ago, Nikon D1 and Canon 1D.

It’s the old “you don’t get something for nothing” scenario all over again. Most photographers would prefer a camera with a sensor that has high dynamic range, low noise, and no blooming rather than one that offered high flash sync speeds.


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