From a review on an Indian tech website:
"As for the photos, the overall image quality is below average. Photos shot in daylight came out bright but fell short on detail with murky textures. Shooting subjects in broad daylight led to blown-out highlights, both on the subject and in the background. The same applies to the Portrait mode when using both the front and rear cameras. The rear camera, just like the Realme C25, boosts colour saturation when shooting a human subject in Auto mode. This does not happen when shooting inanimate objects
As expected, post sunset, photos get murkier with detail taking a big hit. Most low-light photos ended up looking like paintings, and the dedicated Night mode did not help improve things either, in my experience. Photos shot in the Night mode came out blurry, with oversaturated colours. They also lacked depth and looked flat. Auto-focus speeds take a hit at night too, and you will need a bit of patience, even if you tap to focus when shooting darker scenes. Selfies shot in low light were packed with noise and lacked any sense of depth.
The 2-megapixel macro camera captured shots that looked a bit too dramatic with excessive contrast and odd-looking colours. Shots taken with the main camera looked a lot better, with good sharpness and colours that were closer to the real thing.
Video recorded in daylight is satisfactory but not usable if shot in low light. Videos shot at 1080p 30fps showcased blown-out highlights in brighter areas of the frame. There's no sort of stabilisation, which makes videos shot when walking really shaky"
Or, to put it another way 'you get (or don't get) what you pay for (or don't pay for, as the case may be' with most smartphones:
https://gadgets.ndtv.com/mobiles/reviews/realme-c21-review-price-in-india-specs-performance-camera-battery-life-2456525