ISP: the processor that turns a camera signal into a photo

An image signal processor (ISP) is a dedicated block in the system-on-chip that turns raw data from the camera sensor into a finished photo or video: it removes noise and sets colours, white balance, exposure and sharpness.

The ISP "develops" the raw camera signal into a good photo

In plain words

The camera sensor is like a photographer who brings you a pile of undeveloped film. On its own the film is dull and grainy. The ISP is like the technician in a photo lab who, in milliseconds, develops it, adjusts the colours, removes the grain and prints a beautiful photo. A good technician can pull a decent shot even from average film.

How it works

The sensor captures light, but each pixel sees only one colour.
The ISP reconstructs full colour for every pixel (demosaicing).
It removes noise and corrects exposure and white balance.
It adds sharpness, corrects lens distortion and processes HDR.
Together with the NPU it handles night mode, portrait blur and video stabilisation.

What image processing does

Where you'll see it

Every smartphone, tablet and camera has an ISP. Manufacturers highlight it in chip descriptions (Spectra from Qualcomm, Imagiq from MediaTek). Some brands add their own separate image processing chips.

Does it matter when buying

Yes, and it explains why a 50 MP phone sometimes takes worse photos than a 12 MP one: processing matters as much as the sensor. I suggest looking at real photos and videos from the phone, not just the megapixels. A good ISP is especially noticeable in 4K video and night shots.

Myths

Myth: Photo quality depends only on megapixels. Reality: The sensor, lens and processing (ISP and AI) matter just as much.
Myth: The ISP and NPU are the same thing. Reality: The ISP processes the camera signal; the NPU runs neural networks. They work together.

FAQ

Can I turn off ISP processing?

Partly - shooting in RAW gives you less processed data.

Why do phones with the same sensor take different photos?

Because of different ISPs, algorithms and manufacturer tuning.

Does the ISP affect video?

Yes, it processes every frame - from noise reduction to stabilisation.