Photo size question.

Discussion in 'Photography Beginners' Forum' started by KPak1984, Sep 29, 2008.

  1. KPak1984

    KPak1984 TPF Noob!

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    Hello everyone! I wanted to know if I'm supposed to be changing the sizes of my photos? For instance, I will take a photo and the size will be 3168 X 2376. When I photoshop it, am I supposed to be changing the size smaller? Keeping photos the original size will take up lots of room in the computer will it not? Am I supposed to edit and keep original size? I'm a bit confused.

    thank you
    Kim-
     
  2. tirediron

    tirediron Watch the Birdy! Staff Member Supporting Member

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    There are a whole bunch of factors involved here which I'll get to in a moment, but let me start off by saying that unless storage space is absolutely critical, never, ever, ever, and I do mean never mess with your original images. If you're shooting in .jpg, then make a copy of them and work with that. If you're shooting RAW, make your initial adjustments, save as .tif or .jpg and work from there.

    Anyway, to get into this a little more deeply, "image size" has a number of different meanings. First off there's the size in memory which is what I think you're concerned about. If you're shooting .jpg, a 6mp camera will generally turn in best quality .jpgs that are about 3-5 Mb in size and a 12mp camera will produce 6-8Mb large/fine .jpgs. RAW files are significantly larger (20+Mb for a 12Mp camera) but contain much more information, and allow you greater lattitude in your post-processing.

    Display dimensions (That's the 3168x2376 you mentioned in your post) have little relation to size in memory, but everything to do with the size the image is displayed at on your computer or printed at. That dimension rempresents the number of pixels in the image, that is, it was taken with a camera whose sensor has a sensor 3,168 pixels wide, and 2,376 pixels high.

    There are two different, and often confused (and somewhat interchangable) units of measurement that relate to display size. One is Pixels Per Inch (PPI) and the other is Dots Per Inch (DPI). PPI relates to how the image is displayed on your computer screen and DPI to how the quality of a printed image. Typically .jpg images are interpreted as 75PPI, while photo-quality printing is done at 300DPI (although you can go as low as 240DPI and get acceptable results) which is why an image that prints out at say 8x10 will appear huge on your monitor.

    So, assuming that all makes sense, here's what I do: I download all of my RAW images (I always shoot RAW) to my hard drive, go through and weed out any immediate dogs. Then I go through a second time and mark all those that I think are worth post-processing. Now I fire up my RAW handler and do my initial corrections on each image and save it as a .tif file in a separate directory. Now I run the tif files through PhotoShop and the first step I make is to crop them to whatever printed size I want (usually 8x10 or 5x7) do any other corrections and save as a .jpg in a third directory. When I crop the images, that will change their dimensions (and to a limited extent their file size). Assuming that I want an 8x10 at 300DPI, the final image size will be 2400x3000 (8x300=2400...).

    Hope that helps.

    Just my $00.02 worth - your milage may vary.

    ~John
     
  3. KPak1984

    KPak1984 TPF Noob!

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    So since i shoot in .jpg i should edit w. photoshop and keep the original size, but if i want to print a hard copy then i should shrink the document size in photoshop to 8X10 , 5X7 etc?
     
  4. tirediron

    tirediron Watch the Birdy! Staff Member Supporting Member

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    Always keep an original, untouched copy of your image and edit a copy, yes.

    Don't think of cropping as shrinking your image, but rather as assigning a final size to it. You may have to remove almost nothing from an image to produce an 8x10 print. You can also print the entire image as a 4x5. In that case, rather than 300 DPI, it might five or six hundred DPI; more is better to a point. Once you've cropped an image to it's final size, that information will be written into the image header, and it should print correctly from nearly any standard image-editing application.

    The best way to understand this is to play with it. Open an image in PhotoShop, select the crop tool (The one that looks like two 'L's), enter dimensions you might want to print the image at, and move the crop guides around with your mouse to see how it works. Experiment with different dimensions so that you get an idea of how the different print sizes affect your image.
     
  5. djacobox372

    djacobox372 No longer a newbie, moving up!

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    Storage space is cheap these days, a typical computer hard drive could hold over 100,000 high resolution photos before space is even a concern.
     
  6. mrodgers

    mrodgers No longer a newbie, moving up!

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    Stating something is cheap is a giant pet peeve of mine. Inexpensiveness and expensiveness are directly related to the individual.

    And not everyone uses a computer strictly for photography. Many have music, videos, many different programs, games, etc on their computers. Believe it or not, I had to do some extensive cleaning on my computer because when I reached about 3000 images from my camera, I ran out of space on my 330 GB worth of hard drive space.
     

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