These are images from Orion's navigation cameras. They're great for getting your bearings, but they're not the top tier surface imaging cameras such as those used on the LRO.

>I don't believe Nasa installed a camera with a fixed aperture, completely non-adjustable

If you want something for figuring out your vehicle's orientation and position in space, that's exactly what you want. Now, I agree that the cameras onboard aren't the best, but this is a technology demonstrator mission, not a "lets map the moon in 12K sharp quality" mission.