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visunique
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Image Size Change

Oct 3, 2009 9:35 AM

I need to know why when I open a raw downloaded jpg image (directly from my camera... I have done absolutely nothing with it) the image size in photoshop reads:

 

Pixel Dimensions 7.97 M

width 2048 pixels

height 1360 pixels

 

Document size

Width 28.444 inches

Height 18.889 inches

Resolution 73 pixels/inch

 

BUT

 

When I open it again in Camera Raw and then click open image (in Photoshop) then save it as a psd it changes (without me changing it) to

 

Document size

Width 8.53 inches

Height 5.667 inches

Resolution 240 pixels/inch

 

And... is this going to matter when I want to enlarge the photo for printing??? Because, I know, logically, going from a larger size to a smaller size will not destroy the quality of a photo but going from a smaller (in this case 8.53 x 5.667 to say 18 x 24) I am afraid will change the image quality tremendously.

 
Replies
  • Currently Being Moderated
    Oct 3, 2009 10:06 PM   in reply to visunique

    You have nothing to worry about. Camera Raw does not change the pixels in an image. It is a non destructive editor. When you have camera raw open look at the bottom center of the window for what looks like a URL link. Click on that and the properties will open. From here you can specify what ppi to use when it send the file to photoshop. As you will see for the size it will show only one size. For a raw or dng file the size can display muliple sizes but it does not save over top of a raw or dng file.

    For a jpg file, camera raw will save over the jpg file, but all changes are meta data. Therefore any program that does not recognize the meta data will not see the changes.

     

    Now for your concern and about damaging the file - The ppi is a multiplier for determining the final size of the print when you send it to the printer. It does not effect the pixels of the image it self because camera raw won't allow it.

     

    Lets say you wanted to print an image at 300 ppi, and the resolution of your image is 1600x1200. Take the 1600 and divide it by 300 then take the 1200 and divide that by 300 and that will tell you that it will print at 6" x 4". In this instance sense camera raw will not change the amount of pixels then that means when you change the ppi the physical size in inches will change or if you change the size then the ppi will change to accomodate the pixels of that image.

     

    I hope the above makes sense...

     
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  • Currently Being Moderated
    Oct 4, 2009 6:09 PM   in reply to visunique

    Its best to leave the settings at their defaults.  If you were to select any of the sizes above default it would generate a pixelated image, but the original image is untouched.

     

    At 2048 x 1360 it will create a 6.82" x 4.52" image printed at 300ppi. This is the only time when camera will change the pixels when you specify a pixel value from that list. But that is for a new image only and does not effect the raw image.

     

    Looks like I was wrong about pixel size in the previous post. Apparently I check a jpg that was not from a camera. I assumed all jpg displayed only one size . But I check one from a camera and it does show a list. But that list is for exporting to photoshop so a new file is generate at that size, leaving the original jpg untouched. I appologize for that I should have double checked.

     
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  • Currently Being Moderated
    Oct 4, 2009 9:34 PM   in reply to visunique

    I didn't see the last part of your post. 300ppi should more than suffice for any print that is held at a comfortable arms length (about as far away as you normally look at a photo) The further away the photo will be the lower the ppi can be as the eye can not see the pixels as easy. You can get away with a lower ppi at arms length but it will be more noticable and will look pixelated.

     

    If you find the quality is still no there especially if you plan on printing at larger sizes, you may want to think about a higher MP camera.

     
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  • Currently Being Moderated
    Oct 5, 2009 3:06 PM   in reply to visunique

    You are mixing apples and oranges here. At first you talk about pixel count for the JPG, but then you leave that off for the raw file.

     

    2048x1360 pixels at 72 ppi and 8.53 x 5.667 inches at 240 ppi are the same thing.

     

    Only the pixel dimentions matter. At 72 ppi that equals 28.444x18.889 inches. If you change the dpi to 240 the print size changes to 8.53x5.667. But the image is the same (no pixels are changed). If you change the ppi to 300 (without resampling the image) your print size will change to 6.827x4.533 inches.

     

    By changing the PPI setting you are telling your printing software to place the pixels further apart or closer together. This won't matter while you are in Photoshop, but will matter if you place your file into a page layout program like InDesign.

     

    John

     
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  • Currently Being Moderated
    Oct 5, 2009 3:14 PM   in reply to visunique

    Which particular 6mp camera are you using?

     

    Are you working with raw files? Or are you opening a JPG in Camera Raw?

     

    If raw, the 6mp camera should default to around 3072x2040 pixels, not 2048x1360 (which is only around 3 megapixels). If you are working in JPG, make sure the camera is set to its maximum file size and quality. From what you are saying, it sounds like the camera is set to only record at 3mp instead of 6 when working in JPG mode.

     

    John

     
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  • Currently Being Moderated
    Oct 5, 2009 3:17 PM   in reply to Silkrooster

    A 6mp image at 300 dpi should be 3072x2048 pixels, and will give a print at 10.24x6.827 inches. The numbers in your post (2048x1360) would indicate a 3mp image.

     

    John

     
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  • Currently Being Moderated
    Oct 5, 2009 7:21 PM   in reply to John Cornicello

    Good explanation.

    What I think is most confusing to many people is that what you say seems

    counterintuitive.

    One would expect more ppi for a 28.444x18.889 inch image than for one that

    is 8.53x5.667 inches.

     

    CC

     
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  • Currently Being Moderated
    Oct 5, 2009 11:04 PM   in reply to adobe2418

    Its actually the opposite. PPI stands for pixels per inch. Since the pixels of the image is fixed the number of pixels within one inch must decrease in order for the physical size of the print to increase.

     
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  • Currently Being Moderated
    Oct 6, 2009 10:23 AM   in reply to adobe2418

    Try thinking about the image as if it was a balloon with dots on it. If you blow it up a little bit the dots are all close together and may form an image. As you blow it up more you still have the same number of dots on the balloon, but as it expands they move further apart and become less recognizable.

     

    In the case of the print, you have the same number of pixels in both prints, but in the larger one they are expanded and lose quality.

     

    So, yes, one would expect there to be more pixels per inch in a larger image IF both images had the same quality. But the larger one is going to be of lesser quality because the number of pixels available is a fixed quantity.

     

    John

     
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  • Currently Being Moderated
    Dec 20, 2009 3:34 PM   in reply to visunique
    I am not sure I am "getting it" as it sounds like tbe greater the resolution the smaller the print size and if that is so then logic tells me that if I wanted to enlarge the image (when it seems to turn my larger image automatically to say 4x6 300 DPI) it would come out pixelated.

    If you opened either image in PS, and chose Image>Image Size, making sure that Resample Image was unchecked, you'd see the Resolution go up, as you drop those large dimensions (in inches) down. Try it, and observe. Just open both, and change either the dimension, or the Resolution.

     

    Good luck,

     

    Hunt

     
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  • Currently Being Moderated
    Dec 20, 2009 3:45 PM   in reply to Bill Hunt

    Here's an example: I scan my 4 x 5 transparencies at 1000 ppi. If I open the resulting files in Photoshop, I see 4" x 5" x 1000 ppi (Resolution). If I uncheck Resample Image and choose 72 ppi, I get an image that is 69.444" x 55.556".

     

    Some programs make the assumption that the user will want to view the resultant image on a computer monitor, hence the default 72 ppi. Other programs assume that the user will likely want to go to print, where the Resolution will really matter, and might default to, say 300 ppi. With that, I'd get 16.667" x 13.333" x 300 ppi. Does that make sense?

     

    Good luck,

     

    Hunt

     

    PS - now stick that image into Video, where ppi/dpi do not matter, and you will only want to consider the pixel x pixel dimension.

     
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    Jun 23, 2010 11:43 PM   in reply to John Cornicello

    Hi John,

     

    I need to know that, why camera raw dose change the image sizes? I don't want to change the image size, I want only the colour correction with camera raw.

     

    Saqib

     
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  • John_Cornicello_home
    787 posts
    Mar 31, 2003
    Currently Being Moderated
    Jun 24, 2010 8:48 AM   in reply to Saqibze

    Camera raw doesn't change the size of the file unless you tell it to via the workflow options under the preview (it looks like a hyperlink listing the color space, bit depth, and size). And even then, it only changes the size of the file that opens into Photoshop. The original raw file is not changed at all.

     
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  • Currently Being Moderated
    Jun 30, 2011 7:54 PM   in reply to John_Cornicello_home

    wow. thanks I have similar problem and this thread answered it perfectly.

     
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  • Currently Being Moderated
    Apr 18, 2011 8:07 PM   in reply to visunique

    Hi friends

    We know that your problem is very short cut solve them.so your camera raw dose change the image sizes? I don't want to change the image size, so I want only the colour correction with camera raw.so image size change it.

     

    Thanks

     
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