How to choose between a colour camera and a mono camera
A mono camera has no colour-filter array, so the same pixels resolve pinholes, register, and fine type more clearly. Only a colour camera shows a wrong ink colour. A Bayer filter makes real resolution lower than the pixel count. For both, use mono for defects and a separate colour measurement.
A mono camera has no colour-filter array, so the same pixels resolve pinholes, register, and fine type more clearly. A colour camera is what shows a wrong ink colour. A Bayer filter makes a colour camera’s real resolution lower than its pixel count. When you need both defects and colour, the usual split is mono for defects and a separate colour measurement, not one colour camera asked to do both at the top of its resolution.
Not every pixel is usable
Neighbouring pixels on a colour camera look at different colours, and a real colour point uses several of them. So a colour camera and a mono camera both labelled 0.05 mm are not equal: the mono camera separates a small hole more clearly. If you use a colour camera to catch a 0.1 mm pinhole, recalculate from the resolution after the colour filter. Do not use the sensor’s total pixel count.
A mono camera sees a wrong colour only as lighter or darker. It does not see cyan printed as magenta. That check is either a colour camera on a defined area or a spectro on the solid. Do not issue a colour difference from a mono grey-level difference.
How to pair them
| What you mainly need to catch | Camera | Do not expect it to |
|---|---|---|
| Pinholes, fine type, register | Mono | Issue a colour difference |
| A wrong ink colour | Colour, or a spectro | Treat the nameplate pixel as fine-defect resolution |
| Both | Mono plus colour measurement | One colour camera at the highest resolution for both |
Check at a job change
- Run the smallest defect sample and see which of mono and colour alarms steadily.
- A colour requirement is a separate solid measurement. Do not read Delta E out of the colour frame.
- The resolution written on the ticket is the size you measured as separable, not the nameplate pixel count.
