Photoshop Question

Discussion in 'Photography Beginners' Forum' started by blu_billiken, Jan 27, 2010.

  1. blu_billiken

    blu_billiken TPF Noob!

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    I have CS2 and sometimes when i finish editing an image it gets re sized. My images are around 8 mega pixels but after editing they sometimes turn out 5 or even 3 mega pixels. I am not cropping them just some minor color correction and such. Am i saving them in a compressed format?
     
  2. KmH

    KmH Helping photographers learn to fish Supporting Member

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    What you're describing is what happens with a lossy image file format like JPEG. How much image file compression occurs depends on the quality level the image is saved at.

    A JPEG gets compressed, to one degree or another, everytime it's saved.

    Save a JPEG enough times and you'll start to see a degredation of image quality.
     
  3. Dwig

    Dwig TPF Noob!

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    Unless you are using the Crop Tool, the Image Size dialog, or the Canvas Size dialog your images are not being "resized". What you are likely seeing is variations is either the compression level when saving or the compression efficiency.

    The file size of an image saved in a compressed format will vary depending on the compression setting if that particular format's compression method allows for it. JPEG is one format that uses a compression method that does. In Photoshop, and other Adobe products, the compression level is adjusted with the "quality" sliders in the Save dialogs. The higher the "quality" the less compression and the larger the file.

    The other thing that impacts the file size with most compressed formats, JPEG in particular, is the level of detail and color variance in the image. Some images (e.g. a purely black and white image with no grey and large blank areas of either black and white) compress very efficiently. Others (e.g. nothing but fine detail like a sharp image with nothing but leaves and grass) don't compress well. Its quite possible that editing a file and resaving at the same compression level could alter the efficency of the compression resulting in either larger or smaller files. A typical example would be an outdoor portrait where the original has a lot of DOF making the backround sharp and detailed. If your edits were to blur the background the resulting save, even using the same compression "quality" would likely result in a smaller file. Your edits would have to be substantial to produce a major change.

    You do state that the file changes in terms of "mega pixels". If true, this would not be the size listed in a file dialog as the size of the file, that would be megabytes, but the result of multiplying the width of the image in pixels by the height of the image in pixels. If the number of megapixels is actually changing then you are incorrect in stating that you are not cropping or resizing the images.
     
  4. Higgs Boson

    Higgs Boson TPF Noob!

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    So what is a better format to save as that doesn't lose quality every time and is still widely enough read that people can still view it?
     
  5. Montana

    Montana TPF Noob!

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    I save to Tiff. Then when I need to send a JPEG out to be printed or posted to the web I make one from the TIFF file.
     
  6. KmH

    KmH Helping photographers learn to fish Supporting Member

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    Any format.

    As I said above, if the image is a JPEG, you make a copy of the original and work with the copy. The original doesn't get saved again just because you opened the file and made a copy of it. Opening and closing a file is not a save.

    Many think it's best to capture an image as a RAW data file.

    JPEG is a lossy image file format.

    If you have a 10 MP camera and capture photo's as JPEG's, you never see nearly 80% of the data your camera's image sensor captured.

    What was a 30MP file (10 MP/Red, 10MP/Green, 10MP/Blue, RGB) is now a file of about 7 or 8 MP. 22 MP got tossed out in the conversion to a JPEG.

    The advantage to a lot of shooters though, is that in the conversion process automatic image editing was done: Contrast, saturation, sharpening were all adjusted and the image is ready to print.

    JPEG is a ready to print format, sort of. You have to consider all those editing adjustments were done based on what a committee of camera engineers thought would look good. :D
     
  7. blu_billiken

    blu_billiken TPF Noob!

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    thanks all, that helps. now i just need to upgrade my cs2 to a version that handles raw images
     
  8. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    CS2 handles RAW files just fine. If you can't open your RAW files, then you need to upgrade the part of Photoshop that deal with RAW...it's called Adobe Camera RAW and you can download the latest version from Adobe.com.

    Alternatively, you can use the software that came with your camera, to convert the RAW files into TIFF or JPEG etc., then open that file for further editing in Photoshop.

    Another option would be to use Adobe's free RAW to DNG converter, which converts the RAW files into DNG format, which can be opened in Photoshop.

    Yet another options would be to get a program like Lightroom.
     

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