Sensor and Shutter: The Two Vital Organs of Your Camera

It happens all the time: a buyer carefully checks the shutter, sees a reassuringly low number like 20,000 frames, hands over the money, gets home… and at the first evening portrait shoot, a bright red or blue dot appears right in the most conspicuous spot!

Those are dead or hot pixels on the sensor. With age and heavy use, their number inevitably grows.

The Right Way to Shoot Two Test Frames in One Minute

Test 1: Finding Dead (White/Colored) Pixels on a Dark Background

1. Put the body cap on the lens (or cover the mount with a rear cap).
2. Switch to Manual mode M, set ISO 800 and a shutter speed of 1/2 second.
3. Take one raw (.NEF) frame. Open it on your phone or PC at 100% zoom. Any persistently glowing bright dots on a black background are hot pixels.

Test 2: Finding Dark ("Stuck") Pixels on a Bright Background

Shoot a white wall or sheet of paper at f/8 and ISO 100. If you see black dots, determine whether they're dust on the lens filter or burned-out sensels.

Does Nikon Have In-Body Pixel Remapping?

Yes! On modern Nikon bodies (particularly the Z-series mirrorless and later D850/D780 DSLRs) the menu includes a Pixel Mapping function. The processor masks a dead pixel by interpolating from neighboring working photosites. On older DSLRs like the D700 or D90, pixel remapping was only possible via service software at a repair shop.

Sensor Defect Assessment Table

Defect Type	How It Appears in Photos	Service Solution
Dead Pixel	Always white or black dot at any ISO	Pixel remapping (software concealment)
Hot Pixel	Red/blue dot at high ISO and long exposures	Normal for a warm sensor (eliminated by noise reduction)
Dust Spot	Blurry gray circle visible at f/16 – f/22	Standard wet sensor cleaning