How does shooting low-light photos in ProRAW technically allow for greater flexibility in recovering underexposed shadow detail compared to standard JPEG files?

Shooting low-light photos in ProRAW technically allows for greater flexibility in recovering underexposed shadow detail compared to standard JPEG files primarily due to differences in data capture, bit depth, and processing. ProRAW, a computational RAW format from Apple, combines the benefits of multi-frame image processing, like Deep Fusion and Smart HDR, with the extensive data retention of a traditional RAW file. A RAW file, in general, is the unprocessed, uncompressed data directly from the camera's image sensor, functioning like a digital negative. ProRAW captures this raw sensor data with a significantly higher bit depth, typically 10-bit or 12-bit, compared to a standard JPEG file which is always 8-bit. Bit depth refers to the number of discrete tonal values available for each color channel (red, green, blue). An 8-bit image has 256 possible levels per channel, resulting in about 16.7 million total colors. A 10-bit image has 1,024 levels per channel, equating to over 1 billion colors, while a 12-bit image has 4,096 levels, or over 68 billion colors. This vastly greater number of tonal steps in ProRAW means it captures and retains a much wider dynamic range, which is the difference between the lightest and darkest areas a camera can record. In underexposed shadow areas, this higher bit depth preserves subtle gradations of tone and color that would be indistinguishable and lost in an 8-bit JPEG. When brightening these shadows in post-processing, ProRAW's abundant tonal data allows for smoother transitions and prevents issues like color banding (visible steps in a gradient) or posterization (loss of smooth transitions leading to blocky color areas). Additionally, ProRAW preserves the image data with minimal destructive processing. While ProRAW leverages computational photography, the adjustments for noise reduction, sharpening, and tone mapping applied by these systems are stored non-destructively or applied in a way that allows the user significant control over them later. This means the user can apply their preferred noise reduction and sharpening algorithms in editing software without inheriting the camera's potentially aggressive or sub-optimal default processing that might have already flattened or destroyed fine detail in shadows in a JPEG. Conversely, a JPEG file is a highly compressed (lossy compression means data is permanently discarded), processed, and finished image. All white balance, sharpening, noise reduction, and tone curve adjustments are "baked in" irreversibly by the camera's internal image processor. The limited 8-bit depth, combined with lossy compression and fixed processing, means that much of the subtle shadow detail is irrevocably lost or merged into uniform dark blocks. Attempting to brighten underexposed shadows in a JPEG file typically reveals severe image noise, banding, and a lack of smooth detail because the necessary data was discarded during the initial compression and processing.