Perseverance rover cameras

[cube]

Hello everyone, I have a few questions about the photos and camera of perseverance:
I wonder why with the Mastcam camera there is always a black and white photo and a color photo of the same place? and why only the black and white photo has a kind of grid? (is this to indicate the location of the pixels)

When we look at a photo taken by the Navcam we can see that it has about 1.2 megapixels on the other hand when I go to wikipedia it is indicated that the Navcam have 20 megapixels what can explain this difference? Is it the sensor that has 20 megapixels but is underused and the optics only release photos at 1.2 megapixels?

Thank you!

[ccdengr]

I wonder why with the Mastcam camera there is always a black and white photo and a color photo of the same place? and why only the black and white photo has a kind of grid?
When we look at a photo taken by the Navcam we can see that it has about 1.2 megapixels on the other hand when I go to wikipedia it is indicated that the Navcam have 20 megapixels what can explain this difference?

The Mastcam has a Bayer pattern sensor and the grayscale images are uninterpolated.  https://en.wikipedia.org/wiki/Bayer_filter

The Navcams have summing and subsampling modes and usually don't take images at the full resolution of the sensor.  https://link.springer.com/article/10.1007/s11214-020-00765-9