Today’s Question: Continuing with the discussion of 8-bit and 16-bit, for images captured at 8-bit, is there any advantage to converting them to 16-bit TIFF files for editing and then printing to photo paper?
Tim’s Quick Answer: While the potential benefits of converting an 8-bit per channel capture to 16-bit per channel mode would be minimal, I still consider it a best practice, especially in the context of converting a JPEG image to a non-compressed format for editing.
More Detail: There are theoretical benefits to converting an 8-bit per channel image, but from a practical standpoint the benefits are relatively minimal. However, considering there’s a good chance that an 8-bit capture is also a capture that used JPEG or other image compression, converting to another file format (such as TIFF) can help preserve image quality. I consider it a best practice to convert to 16-bits per channel as part of that process. Just keep in mind that the file size for a 16-bit per channel image will be double the file size for the same image in an 8-bit per channel file.
If you consider the numbers involved, converting an image from 8-bits per channel to 16-bits per channel sure sounds like a good thing. After all, you go from an image with just under 16.8 million possible colors to an image that has the potential to contain more than 281 trillion possible colors! But the image still only contains fewer than 16.8 million colors, even if it has greater potential.
As you apply adjustments to an image, the changes in pixel values can cause the total number of colors represented in the image to increase. That, in turn, can help lead to slightly smoother gradations of tone and color. But what you’re really gaining is a reduced risk of posterization, which is the loss of smooth gradations of tone and color.
As noted above, there is also a slight benefit to converting a JPEG capture to a non-compressed format (such as TIFF, even with ZIP or LZW compression since they are lossless). The primary benefit here is that you are avoiding the additional degradation in image quality caused by repeatedly saving (and therefore compression) the image as additional changes are applied.
To be sure, converting an image from 8-bit to 16-bit per channel mode is not going to provide such a significant benefit that you would be able to tell the difference. Similarly, the compounding effect of JPEG compression being applied multiple times is not something you’d likely be able to make out without zooming in to the pixel level. But I still consider it a best practice to save images in a format without lossy compression, in the 16-bit per channel mode, and in a format that supports layers if you’ll be working in Photoshop.
