Learn the concepts of bit depth in raster images.
Bit depth specifies how much color information is available for each pixel in an image. More bits of information per pixel result in more available colors and more accurate color representation in an image, thereby affecting the image size. Simply put, the file size of an image increases with bit depth because more color information is stored per pixel in an image having higher bit depth.
RGB images with 8‑bits per channel (Bits/Channel or bpc) are sometimes called 24‑bit images (8 bits x 3 channels = 24 bits of data for each pixel). In addition to 8 Bits/Channel images, Photoshop can also work with images that contain 16 or 32 Bits/Channel.. Images with 32 Bits/Channel are also known as high dynamic range (HDR) images.
To convert your bit preference, do any of the following:
To convert between 8 Bits/Channel and 16 Bits/Channel, choose Image > Mode > 16 Bits/Channel or 8 Bits/Channel.
To convert from 8 or 16 Bits/Channel to 32 Bits/Channel, choose Image > Mode > 32 Bits/Channel.
Photoshop provides the following support for working with 16 Bits/Channel images:
To take advantage of certain Photoshop features, such as some filters, you can convert a 16 Bits/Channel image to an 8 Bits/Channel image. It’s best to do a Save As and convert a copy of the image file so the original file retains the full 16 Bits/Channel image data.