9 Replies Latest reply on Aug 26, 2012 1:05 PM by conroy

    CS5 - Photo Saving and File Size

    cnitski Level 1

      Recently I've noticed, when uploading some photo's to my web site that the file size is rather small.  I know that cropping, processing, and saving to jpeg results in file size reduction.

       

      So ... I did a test.  I took one photo shot in the raw format (the file size was about 21 mp).  I then took it into Photoshop CS5 and just saved it as a jpeg ... and the file size went to 9.9 mp.  I found that to be a questionable reduction.

       

      My image size details of the test photo is:

       

      Pixel Dimenstions:

      5616 px x 3744 px

       

      Document Size:

      18.72 x 12.48 and 300 px Resolution

       

      All of the following are checked:

      Scale Style

      Constrain Proportions

      Resize Image

       

      I have selected:

       

      Bicubic (best for smooth gradients)

       

      I saved the photo at the highest quality setting of 12

       

      So the Question:  Is this test reduction normal or am I doing something wrong with my "save as" settings

        • 1. Re: CS5 - Photo Saving and File Size
          Curt Y Level 7

          There is no set percentage of compression, it depends on the image content.  If there are layers jpeg will not save so that in itself will reduce size.  Some web options even strip out metadata.    So are you thinking that is too much or too little compression?

           

          I do know that there can be significant differences in saving at image quality 9 or 10 and at 12.  Try it and see what you get.  For what is the correct compression it depends on the end use.  For web use maybe all you need is 5.

          • 2. Re: CS5 - Photo Saving and File Size
            Mylenium Most Valuable Participant

            JPEG is a format based on a lossy compression and as Curt said, there os a ton of things to consider and results will hugely vary not only on your settings but also on the image content. So far I see nothing wrong with teh results you get. In fact for web use it's still a pretty "fat" file and there may be additional processing on the server to reduce file size further.

             

            Mylenium

            • 3. Re: CS5 - Photo Saving and File Size
              conroy Level 5

              Did you mean MB (megabytes) where you wrote MP (which suggests megapixels)? The width times height of the image comes to about 21 megapixels and it could coincidentally come from a 21 megabyte RAW file due to lossless compression of the RAW. It doesn't sound unusual for JPEG Quality 12 to consume 10 MB for a 21 MP image.

               

              Try converting the original RAW to JPEG quality 8, too. It could get your Web file down to a couple of MB yet appear virtually indistinguishable from the original.

              • 4. Re: CS5 - Photo Saving and File Size
                Noel Carboni Level 8

                When you open up the JPEG, does it look to you as good as the master file you saved it from?  If so, there's no problem. 

                 

                I suggest you experiment with various settings, including extreme values, to see the size and visible quality changes, so that you'll get a feel for what settings meet your personal quality goals.

                 

                The others have mentioned why.there are size differences.

                 

                -Noel

                • 5. Re: CS5 - Photo Saving and File Size
                  cnitski Level 1

                  Yes yes - I typed too fast.  It is MB.  not Pixels.  The picture does look as good in the jpeg format as processed in Photoshop "before" saving.  I left this out of my original post - I am not concerned with savings as a jpeg to the web, I want the largest and best file size for  "printing".

                  • 6. Re: CS5 - Photo Saving and File Size
                    Curt Y Level 7

                    If you want the best quality image from a raw image you need to save in TIFF or PNG.  They are both lossless while jpeg is lossy, meaning everytime you save you loose quality.

                    • 7. Re: CS5 - Photo Saving and File Size
                      cnitski Level 1

                      Thanks - I am aware of the file extensions and the TIFF / PNG.  I'd really like to know if anyone sees anything wrong with my "save" settings for jpeg.  I've done some research and it seems that I should uncheck the "resample image".  Any comments on this ? ? ?

                      • 8. Re: CS5 - Photo Saving and File Size
                        Noel Carboni Level 8

                        There's nothing wrong with saving a JPEG for printing.  Many print houses encourage it.

                         

                        I always just use File - Save As, then select JPEG.  Save for Web isn't intended for saving large images for printing.  Problem solved - no resample question with File - Save As.

                         

                        -Noel

                        • 9. Re: CS5 - Photo Saving and File Size
                          conroy Level 5

                          Resample is only applicable when an image is being resized. If you are saving at the original size then ignore the resample option.