How to change PPI permanently in ps when cropping

Discussion in 'Digital Darkroom' started by mars c, Dec 13, 2006.

  1. Please dont hate me if similar questions were asked before. But I need
    answers that are easy to understand.

    When Choosing crop proportion in ps cs2 the ppi is 300, of course you can
    change it to 1000 in the resulotion box. but when you choose another
    proportion, it reverts back to 300 PPI.

    1st question. How do we change the 300ppi to 1000ppi in the multiple choice
    menu? So that it would say the FF:

    4x6 1000ppi
    5x3 1000ppi
    5x4 1000ppi
    8x10 1000ppi

    instead of 300ppi when choosing between proportions.

    2nd question. when editing an image w/out cropping or resizing , the file size
    shrinks a litle, after saving. How do you make it to not reduce the file size?

    Thank you.
  2. Mars,

    Not sure exactly what you're asking or why. When you camera captures an image the pixel count is determined by your sensor. So a typical 6 megapixel sensor is 2000 by 3000 pixels. This is a "permanent" characteristic of that file unless you crop out some of the pixels. The size of the final image as a print or on your monitor is determined by the pixels per inch you choose to output the image so at 300ppi the image would be 10 inches wide (3000/300). So ppi is like changing the volume on your stereo. It is not a characteristic of the image file but of your output medium.

    Now why in the world would you want an image at 1000ppi? most people can't tell the difference below 240ppi without examining a print at close range with a magnifying loupe, and certainly nothing above 360ppi.

    The reason your file gets smaller with saving is that you're saving as a jpeg and with each save, you get another round of jpeg compression and image degradation. Save as a PSD of TIFF and this won't happen.

  3. .

    Hi Mars C,

    Hate? Yes, there's much anguish over simple (and complex) questions here at - we lend our energies in the oddest ways, eh? Sorry if anyone's been aggressive with your before.

    May I redirect your inquiry? May I suggest that you NEVER set ppi? Clear the box, erase it, and merely crop existing pixels and enjoy them. Otherwise, when cropping AND resetting ppi, Photoshop throws away or invents additional pixels to make the cropped area "fit" your chosen ppi. Why? Is it your intention to throw away image data or invent non-image data? Or is it your intention to crop?

    Finally, remember that file sizes depend on file formats. I imagine you are using JPG? If so, that's an OUTPUT or PUBLISHING file format, NOT an editing or archive file format, so save as PSD or TIF. However, PSD and TIF can also change size even though they may not throw away image data because they can also store non-image data, such as layer information and other meta data, and if layers get flattened or meta data comes or goes, then PSD and TIF file sizes will change. This is innocent, BUT I also recommend that you NEVER save OVER an existing file, rather, save with a new name. I save as, for example, pict1015a.tif, then pict1015b.tif, and on a next edit, pict1015c.tif, or even add information, such as pict1015b-crop-600x300.tif and so on. That way I always have my original image capture to revisit and try, try, try again, especially next year and the years ahead when I hope to be much smarter at all this!

    Let us know if this is helpful, and keep asking those questions as you figure this all out today and on, and on! Enjoy!

    -- Click! Peter Blaise, Minolta Rokkor Alpha DiMage Photographer
  4. I don't know what you're talking about. The resolution you set for the cropping tool stays at whatever value you choose, even if you change the dimensions of the crop. The Image/Image Size dialog box allows you to change the size without altering the number of pixels (resample off), or change the size (and number of pixels) without changing the resolution (resampling on).

    The file may change size slightly since TIFF and PSD files contain other information besides image which may vary. Saving as a JPEG involves compression, which varies between applications and the amount of detail in the image.

    Contrary to Peter's advice, it is OK to set the resolution when cropping when the intent is to print to an exact size. In general, you want to have a resolution appropriate for the output device, and at least 300 ppi for printing. The type of resampling (e.g., bicubic) is set in Photoshop Edit/Preferences/General.
  5. .

    Yes, some people are confident of making multiple decisions in a single stroke when editing image files, especially when they either have an unscathed master backup or consider their resources disposable and or easily duplicatable. However, these two conditions are neither necessarily compatible, nor are they givens for everyone.

    I consider each task sacrosanct unto itself. I make printing decisions when printing, and cropping decisions when cropping. I do not presume that cropping is ALWAYS and ONLY a printing decision. I may also use a particular crop for web, email, a business card, envelope, greeting card, full page print, or many other uses. So, rather then including a final printing decision in my initial cropping decision, I separate them and address them separately as appropriate.

    Hey, some people make printing decisions during capture, I suppose. Me? I'm always repurposing images, so I make scant few dead-ending decisions along the way. Someone else may be happy to finish and be done with a single purpose for an image, and they may be happy to kill it dead when done, and later only revisit and deal with repurposing it if absolutely necessary, and consider that requirement a rarity. Fine. We each pick our poison as appropriate for our own skills and resources.

    Back at ya, though, Mars c, why 1000ppi?

    -- Click! Peter Blaise, Minolta Rokkor Alpha DiMage Photographer
  6. Thank you,

    The 1000 ppi is just an example, Cause somtimes I crop the image very lightly and I'm not sure if I loose some resulotion or not.

    Example: In the default crop setting of 4x6, there is 4x300,6x300 I get 2.16 mega pixels, but I only cropped out roughly 1 or 2 MP in a 10MP image, coming from a 10MP camera.

    My confusions and questions are,

    How can I make the PS to not do that? since I only threw away 2mp from a 10mp image, I should be left with a 8mp image, not the default 1600x 1200 res. from the 4x6 300ppi crop setting , when I left the ppi at the default setting.

    And also , How can the default 300ppi crop setting be change to a desired value?
  7. BTW, when I'm cropping at 4x6, I'm thinking of printing at 8x12 not 4x6. since there is no 8x12 setting.
  8. I just did some work just now, and my problem is solved by blanking out the 300ppi box, I didnt loose nor gain any res. When I tested cropping in the whoile image by doing that.

    Thank you for your time :)
  9. Mars c,
    What do you mean "there is no 8x12 setting"? You can enter any numbers you wish into the width and height boxes, including 8 and 12 inches.

    There's no need to wax philosophical about "making decisions". If you have a solid reason to do (or not to do) something, state it without the generalities. Moving forward, after backing up the original (usually NEF) file, I create a master TIFF image file, leveled, curved, color corrected and spotted for dust. If it needs to be cropped for composition or printing, that is the last step, for which a copy is made. That step usually includes resampling appropriate to the intended size (in one step), followed by sharpening then saving the results as a JPEG.

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