9 Replies Latest reply on Nov 16, 2015 8:20 PM by Jao vdL

    Viewing the bit depth of an image file?

    ric80231

      Hi,

       

           I am surprised that I cannot find a means of determining the bit depth of an image in Lightroom. This would seem to be a fundamental piece of information a user of lightroom needs

       

      It arises because I have a number of old black and white photos to restore. I scanned them in with my Canon MP970  and as there were a lot of them I scanned them using Multiscan. This does not allow you to set the bit depth.

       

      When researching restoration of old photos I found recommendations that black and white photos should be scanned in in colour and with a bit depth of 16 bits, as this allows more editting before the image becomes obviously restored.

       

      Anyway now I have all these images with no idea what their bit depth is! How can I determine their bit depth? Or do I have to rescan them all.

       

       

             Sincerely Ric Evans

        • 1. Re: Viewing the bit depth of an image file?
          Jao vdL Adobe Community Professional & MVP

          I don't think this is possible in Lightroom. Jeffrey Friedl makes a Lightroom plugin that can show this: Jeffrey Friedl's Blog » Jeffrey’s “Metadata Viewer” Lightroom Plugin .

          That said, you shouldn't worry too much about this as most of that advice would have been for an old-fashioned destructive workflow. Not for a Lightroom-type workflow where such issues are less important as all edits occur in 16 bits and a very wide linear color space regardless of the source file. You will only notice problems with extremely heavy editing and you'll probably run into photographic limitations of the original technology (grain and such) before you run into bit depth issues. Also, if you do editing in Photoshop from these originals, Lightroom will generate a 16-bit RGB tiff from your original. I would not bother rescanning before you actually notice issues.

          • 2. Re: Viewing the bit depth of an image file?
            JimHess Adobe Community Professional & MVP

            You are correct. There is no provision to display bit depth in Lightroom. If you have Bridge you can get that information. But knowing the bit depth isn't really going to help you because you can't change it. Trying to change an 8-bit image to 16-bit will not gain you anything. The images that you scanned are what they are, and you can't change it. From my experience scanning, it probably wouldn't be worth the time to scan the images again just to change the bit depth. From what I have seen, the difference between 8-bit and 16-bit is marginal.

            • 3. Re: Viewing the bit depth of an image file?
              ric80231 Level 1

              Thank you for your comments.

               

              Knowing the bit depth is going to help because if it is 8 then, as you say, changing it would not provide a more complete image just an image with a greater bit depth. So I will have to rescan. My information is that the difference between 8 and 16 is not marginal. I freely admit I am not an expert, so I have to accept experts opinion and multiple sources tell me that 16 bit depth is better than 8 when restoring old images.

              • 4. Re: Viewing the bit depth of an image file?
                ric80231 Level 1

                I have found that it is possible to view the bit depth, under Windows 10, in File Explorer, the information is included under the Details tab of the image's Properties.

                • 5. Re: Viewing the bit depth of an image file?
                  JimHess Adobe Community Professional & MVP

                  I was given the task of scanning 40 years worth of departmental photos, nearly 12,000 slides, negatives and prints. We did a lot of experimenting as we started the project, and determined that 8-bit images provided sufficient quality. Unless you don't have a lot of images to rescan, I would carefully compare an image scanned at the two different bit rates. My project took 10 months of full-time work to complete.

                   

                  Don't misunderstand me. There is obviously nothing wrong with scanning in 16-bit mode. If you want to spend the extra time to do it, the more power to you.

                  • 6. Re: Viewing the bit depth of an image file?
                    Jao vdL Adobe Community Professional & MVP

                    You should distrust expert opinion in general and just see for yourself. Scan a file in 8 bit and 16 bits then edit in Lightroom. It is highly unlikely you'll see a difference except for really extreme editing and even in that case it is most likely due to the original media and scan quality. A lot of the advice you might have seen is based on a pure photoshop workflow where all edits are done in the original bit depth. Lightroom works fundamentally different and always works at high bit depth so that you do not get generational creep of limited precision calculations you would get in Photoshop at 8 bits and a lot of folks do not understand this.

                    • 7. Re: Viewing the bit depth of an image file?
                      ric80231 Level 1

                      Thank you both for your comments,

                       

                      JimHess, I'll bet those images you scanned for work, did not undergo very much further processing, but were just being archived. Understandably, in that case 8 bit is acceptable.

                       

                      Jao vdl, if distrusting expert opinion were universal, we would still be living in caves and trying to work out how to make fire. To put it another way, Isacc Newton wrote "We stand on the sholders of giants", by which he meant that we progress only by building on the knowledge of those who have gone before.  On a purely personal note, I do not have the time to conduct all the experiments required to establish which is best. Besides I only have about 250 or so images to scan and restore.

                       

                      16 bit seems like the way to go until it is disproved. Nothing that has been said has changed my opinion.

                      • 8. Re: Viewing the bit depth of an image file?
                        JimHess Adobe Community Professional & MVP

                        Richard Evans wrote:

                         

                        Thank you both for your comments,

                         

                        JimHess, I'll bet those images you scanned for work, did not undergo very much further processing, but were just being archived. Understandably, in that case 8 bit is acceptable.

                         

                        I suppose by your definition there wasn't much further processing. I was quickly correcting in Lightroom while the scanner was scanning, particularly slides and negatives where I could batch scan about 12 images at a time. However, the person who took the library of scanned images did some extensive work on some of them, and printed some large prints to display in the hallways of the department. I'm not trying to discourage you from doing whatever it is you feel that you need to do. If nothing else, you will have confidence that you produced the highest quality scanned images possible. And if you really plan to do extensive editing on those images, you might be right. I'm just saying that, for most of the work I have done, 8-bit TIF images have proven to be more than adequate. But then, I'm not trying to produce showpieces either.

                         

                        The only way you're going to know for sure is to compare for yourself. Take one of your images and scan it at both 8-bit and 16-bit and then process them to your heart's content. Then have someone else compare the two images to see if they can choose which one was the 16-bit. That might not be a challenge that you want to take because you might be surprised. Unless you have a very high end scanner, which could have an impact.

                        • 9. Re: Viewing the bit depth of an image file?
                          Jao vdL Adobe Community Professional & MVP

                          Just trying to save you some work. Photography is a field in which there is a lot of "expert" opinion that is simply dead wrong. Being a scientist by trade I generally take to experiment and question my assumptions. I scan a lot of images and have found that a high quality 8 bit file is generally a better choice than a poorly scanned 16-bit file. All things equal 16-bits is better, but only when the signal to noise ratio warrants it. This is often not true for many film scans where the noise in the scanner is higher than the low bits in a gamma-corrected file.