6 Replies Latest reply: Sep 7, 2013 8:39 AM by 99jon RSS

    Size / quality of JPEG conversions

    JFletcher160

      Hope someone is able to help with this. I'm puzzled by the performance of the JPEG "save as" feature in PE11

       

      I was converting some RAW files taken on a Nikon J1, so starting with a file of about 10MB. I'd made some basic adjustments to white balance, exposure and saturation in PE11 but that was it. No more comlex editing, so no additional layers etc.

       

      PE11 creates DNG files of around 8MB from the initial Nikon RAW 10MB. On conversion (at maximum quality) the pictures all ended up around 1.4MB. (BTW, the J1's own JPEG conversion generates files approx 5MB big)

       

      A 1.4MB JPEG file size looks small and as I want to print some enlargements, I'm worried that the overall quality will suffer.

       

      By comparison, when I shoot files in RAW with my Nikon D3200, they are about 22MB per shot and PE11 converts these to JPEG of about 8MB each.

       

      I recognise that D3200 is starting with a larger RAW file than the J1 and that JPEG will compress based on its own algorithim but I thought that as PE11 was compressing the D3200  RAW:JPEG at 22:8 that the J1 should be compressing at around the same ratios, so a 10MB raw file should come out of PE11 as around 4MB in JPEG.

       

      I am pretty certain that I've not changed the conversion settings in PE11 and both the D3200 and J1 pictures were converted with JPEG options set to Image Option quality 12, maximum file size, baeline optmized.


      Any help really welcome.

      John

        • 1. Re: Size / quality of JPEG conversions
          dj_paige Community Member

          Hope someone is able to help with this. I'm puzzled by the performance of the JPEG "save as" feature in PE11

           

          I was converting some RAW files taken on a Nikon J1, so starting with a file of about 10MB. I'd made some basic adjustments to white balance, exposure and saturation in PE11 but that was it. No more comlex editing, so no additional layers etc.

           

          PE11 creates DNG files of around 8MB from the initial Nikon RAW 10MB. On conversion (at maximum quality) the pictures all ended up around 1.4MB. (BTW, the J1's own JPEG conversion generates files approx 5MB big)

           

          A 1.4MB JPEG file size looks small and as I want to print some enlargements, I'm worried that the overall quality will suffer.

          Trying to judge JPG photos by their file size is an exercize in futility, and will lead you to wrong conclusions.

           

          The JPG file size cannot tell you anything about the quality of the image.

           

          You simply need to assume that the JPG algorithm is doing the proper job, based upon the quality settings you chose. The whole point of the JPG compression algorithm is that you can compress the size of the file without losing much quality. Some photos are more compressible than others.

           

          So when you say a 1.4 MB JPG looks small ... you are making a mistake by judging the file quality by the file size. You have come to the wrong conclusion. If you had enough pixels to print an enlargement before the save to JPG, you have enough pixels to print an enlargement after the JPG conversion. You do NOT lose pixels when you save as a JPG.

           

          Lastly, your photos need to be judged by its megapixels, not by its megabytes. This will tell you if you have enough pixels to print at a given size.

           

          I recognise that D3200 is starting with a larger RAW file than the J1 and that JPEG will compress based on its own algorithim but I thought that as PE11 was compressing the D3200  RAW:JPEG at 22:8 that the J1 should be compressing at around the same ratios, so a 10MB raw file should come out of PE11 as around 4MB in JPEG.

          Based on my comments above, I disagree with this statement. You cannot determine the size of the JPG based upon the size of other JPGs.

          • 2. Re: Size / quality of JPEG conversions
            99jon Community Member

            If you are making print enlargements of any real size you want to be using your uncompressed originals. Either your NEFs or the more efficient raw DNG which is smaller because it does not contain the jpeg preview which displays on the camera LCD screen.

             

            If you need to send to a print lab save as an uncompressed tiff, but that will increase the file size.

             

            Having said all that I regularly use jpeg files for 8 x 10 prints at 300 ppi and the quality is excellent.

             

            http://www.photoshopessentials.com/essentials/jpeg-compression/

            • 3. Re: Size / quality of JPEG conversions
              dj_paige Community Member

              If you are making print enlargements of any real size you want to be using your uncompressed originals. Either your NEFs or the more efficient raw DNG which is smaller because it does not contain the jpeg preview which displays on the camera LCD screen.

               

              If you need to send to a print lab save as an uncompressed tiff, but that will increase the file size.

              I find myself disagreeing with your concerns about file size here. As I said earlier, it is not the file size which determines the quality of the image, and thus the quality of the print. It is the number of megapixels that matters, not the file size.

               

              However, I do agree that printing directly from NEFs or TIFs will eliminate any potential quality loss that would happen when you convert to JPG (but not becuase of the size of the file!) And I also agree that using JPGs for 8x10 prints works well if you have enough pixels in your image.

              • 4. Re: Size / quality of JPEG conversions
                99jon Community Member

                I never mentioned file size (except tiffs are generally larger and DNG smaller) , I was talking about print size.

                • 5. Re: Size / quality of JPEG conversions
                  dj_paige Community Member

                  Jon come on, you mentioned file size twice in the part I quoted. "more efficient raw DNG which is SMALLER" and "Uncompressed tiff, but that will increase the FILE size" — your words, my emphasis, your first two paragraphs were about file size and not print size

                  • 6. Re: Size / quality of JPEG conversions
                    99jon Community Member

                    OK but I essentially ignored differing jpeg sizes because each will be different depending on the tonal range of the image, even where the pixel resolution is identical. For Lossless formats size may make a difference e.g. if uploading to a photo lab.