14 Replies Latest reply on May 25, 2010 7:20 AM by Noel Carboni

    Any Advantages to convert Canon 5D raw from 8bit to 16?

    LucianP Level 1

      My digital camera (Canon 5D) shoots at 8bit in raw. I'm wondering if there is an advantage to converting that to 16 bits when I'm in Adobe raw and moving it to photoshop? For example if I'm doing things like burning and dodging etc will the extra bits mean smoother gradations or is that because my original is 8bits, bumping it to 16 won't make a difference?  Any thoughts?  Thanks, Lucian

        • 1. Re: Any Advantages to convert Canon 5D raw from 8bit to 16?
          dorin_nicolaescu Level 5

          How do you know your camera is shooting 8-bit raw?

          • 2. Re: Any Advantages to convert Canon 5D raw from 8bit to 16?
            JimGoshorn Level 2

            The original 5D captured 12 bit images and the new 5D captures 14 bit images. When you process through ACR, you can select the output file bit depth by clicking the text indicating color space, bit depth, dimensions and ppi at the bottom of the ACR window.

             

            I have always set my output to be ProPhoto 16 bits.

             

            Jim

            • 3. Re: Any Advantages to convert Canon 5D raw from 8bit to 16?
              LucianP Level 1

              Thanks Jim. I didn't realize that it shot at 14bits. I assumed that Camera Raw brought them in at the original camera settings. When I open mine in Camera Raw, it say 8 bits. You'd think they would open it in the default settings.

              I'll try ProPhoto again, but in the past, I've had weird color coming from it, though I can't remember if it was after I converted it to another profile or not. Anyway, thanks for the quick answer!

              • 4. Re: Any Advantages to convert Canon 5D raw from 8bit to 16?
                Bill_Janes Level 2

                LucianP wrote:

                 

                My digital camera (Canon 5D) shoots at 8bit in raw. I'm wondering if there is an advantage to converting that to 16 bits when I'm in Adobe raw and moving it to photoshop? For example if I'm doing things like burning and dodging etc will the extra bits mean smoother gradations or is that because my original is 8bits, bumping it to 16 won't make a difference?  Any thoughts?  Thanks, Lucian

                 

                Like most older dSLRs, according to the specs listed on DPReview, your 5D raw files have a bit depth of 12 bits. Some newer dSLRs have a bit depth of 14 bits, but few have sufficient dynamic range to make full use of the 14 bits and the extra bits are mainly quantifying noise. Photoshop in 16 bit mode actually uses 15 bits and the 12 bits of the camera raw file are padded with an extra 3 bits. The 12 bit raw file is linear (gamma = 1) and has 4096 levels, but when you render into an 8 bit space the number of levels is reduced to 249 rather than the full 256 levels that you would expect (see Bruce Lindbloom's levels calculaltor). If you do a lot of editing in post, rendering into 16 bits will maintain 4096 levels, which will give you more flexibility.

                 

                http://www.dpreview.com/reviews/canoneos5d/page2.asp

                • 5. Re: Any Advantages to convert Canon 5D raw from 8bit to 16?
                  LucianP Level 1

                  I have the newer 5D so in fact it does shoot at 14bits or something close to that. Thanks everyone, I've learned quite a bit here today.

                  • 6. Re: Any Advantages to convert Canon 5D raw from 8bit to 16?
                    Bill_Janes Level 2

                    LucianP wrote:

                     

                    I have the newer 5D so in fact it does shoot at 14bits or something close to that. Thanks everyone, I've learned quite a bit here today.

                     

                    The newer Canons have excellent signal:noise, but whether or not 14 bit is that much superior to 12 bit is questionable. With my Nikon D3, I usually shoot in 14 bit mode, but there is likely little advantage over the 12 bit mode with this camera. Interested readers should look at an excellent essay on the subject by Emil Martenic:

                     

                    http://theory.uchicago.edu/~ejm/pix/20d/tests/noise/index.html

                    • 7. Re: Any Advantages to convert Canon 5D raw from 8bit to 16?
                      Yammer Level 4

                      Or you can do like I did, and shoot the same subject in manual at 12 and 14 bits, and see for yourself! I could see the difference. It was subtle, but there was a difference.

                      • 8. Re: Any Advantages to convert Canon 5D raw from 8bit to 16?
                        Bill_Janes Level 2

                        Yammer P wrote:

                         

                        Or you can do like I did, and shoot the same subject in manual at 12 and 14 bits, and see for yourself! I could see the difference. It was subtle, but there was a difference.

                        It's always best to perform your own tests. With my D3 I can see very little if any difference between 12 and 14 bits. In Bill Claff's dynamic range collaboration (to which I contributed), he determined a dynamic range of 9.01 stops for 12 bit raw and 8.97 stops for 14 bit files for the Nikon D3 (Photographic   DR based on CoC corrected SNR of 20). IOW, no difference. What differences did you note in your own tests?

                         

                        http://home.comcast.net/~nikond70/Investigations/Sensor_Characteristics.htm

                        • 9. Re: Any Advantages to convert Canon 5D raw from 8bit to 16?
                          Yammer Level 4

                          I just set-up in my back garden on a sunny day, and photographed my house. There was strong sun and shade. 90% of the photos looked identical, but, where the side of the house was in shade I could see slightly more detail, and the noise was less 'lumpy'. I used a bit of shadow fill to bring out the detail, and the 14bit image easily looked better.

                           

                          I don't often shoot at 6fps, so I leave it set to 14bit, just in case it comes in handy.

                          • 10. Re: Any Advantages to convert Canon 5D raw from 8bit to 16?
                            Bill_Janes Level 2

                            Yammer P wrote:

                             

                            I just set-up in my back garden on a sunny day, and photographed my house. There was strong sun and shade. 90% of the photos looked identical, but, where the side of the house was in shade I could see slightly more detail, and the noise was less 'lumpy'. I used a bit of shadow fill to bring out the detail, and the 14bit image easily looked better.

                            That is interesting. Could you post some cropped images to show the differences?

                            • 11. Re: Any Advantages to convert Canon 5D raw from 8bit to 16?
                              dorin_nicolaescu Level 5

                              In Bill Claff's dynamic range collaboration (to which I contributed), he determined a dynamic range of 9.01 stops for 12 bit raw and 8.97 stops for 14 bit files for the Nikon D3

                              I thought DR is the difference between the darkest and lightest a camera can capture, while the Bit Depth is the number of gradations in between. So how can bit depth affect the DR?

                              • 12. Re: Any Advantages to convert Canon 5D raw from 8bit to 16?
                                Yammer Level 4

                                > Could you post some cropped images to show the differences?

                                 

                                I can't find the images, and I suspect that I deleted them (it's the sort of thing I would do). I'll do a fresh set soon.

                                • 13. Re: Any Advantages to convert Canon 5D raw from 8bit to 16?
                                  Bill_Janes Level 2

                                  dorin_nicolaescu wrote:

                                   

                                  In Bill Claff's dynamic range collaboration (to which I contributed), he determined a dynamic range of 9.01 stops for 12 bit raw and 8.97 stops for 14 bit files for the Nikon D3

                                  I thought DR is the difference between the darkest and lightest a camera can capture, while the Bit Depth is the number of gradations in between. So how can bit depth affect the DR?

                                  That is a good question. With a linearly encoded raw file, bit depth sets an absolute limit on the dynamic range. With a bit depth of 12, the brightest part of an image would have a pixel value of 4095 and the darkest part would have a pixel value of 1, giving a DR of 4095:1 or 12 f/stops. With a 14 bit sensor, the maximal DR would be 14 stops. Furthermore, the theoretical signal:noise of an ADC (analog to digital converter) is related to the bit depth. See Widipedia and Roger Clark for details.

                                   

                                   

                                  http://en.wikipedia.org/wiki/Quantization_error

                                  http://www.clarkvision.com/articles/digital.sensor.performance.summary/#dynamic_range

                                  • 14. Re: Any Advantages to convert Canon 5D raw from 8bit to 16?
                                    Noel Carboni Level 7

                                    Something I didn't see really well stated here:

                                     

                                    YOU select the bit depth and color space of the converted output (and the settings become the defaults for the next conversion).

                                     

                                    These settings have essentially NOTHING to do with the camera's capabilities, they have EVERYTHING to do with what you're going to use the converted output for.

                                     

                                    Reason:

                                     

                                    You select this depth based on what you may be planning to do with the image.  If you like what you see in the conversion and you're immediately going to save the image as a JPEG with no further editing, you have no real reason to convert to anything other then sRGB and 8 bit depth.

                                     

                                    If, however, you're going to edit the thing for hours you should consider converting it to 16 bit color depth.

                                     

                                    Lastly, Camera Raw tends to clip highlights and blacks when converted into anything but ProPhoto RGB (the profile with the widest gamut), so if you do have very bright or dark subject material, you might want to choose ProPhoto RGB.  This "feature" (the clipping when other profiles are used) is a pet peeve of mine and I plan to make a separate thread about it.

                                     

                                    -Noel