Effectively, this is a next-generation step into computational photography. With quad pixels, you can easily see how the iPhone 14 Pro generated 12MP images from a 48MP sensor. It’s grade school division: 48 ÷ 4 = 12. But there is no 24MP sensor in the 15 Pro main camera. The Photonic Engine takes several images from the sensor for each photo, including a 48MP one for detail, and a 12MP quad-pixel one for low-light and noise reduction, then computationally fuses them together to produce a single 24MP image. Apple is having its cake and eating it too, merging the benefits of a sensor with many small pixels with the benefits of a sensor with fewer large pixels. You don’t need to know that this is happening, you just get more detail in your photos from the main camera.