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Converting 300 dpi into 72 dpi with more resolution

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Russell Lasson
Converting 300 dpi into 72 dpi with more resolution
on May 2, 2008 at 7:21:45 pm

If I have pictures scanned at 300 dpi, can I convert them to be 72 dpi and have a larger resolution (image size)? If so, how?

Thanks,

-Russ

Russell Lasson
Kaleidoscope Pictures
Provo, UT


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Richard Harrington
Re: Converting 300 dpi into 72 dpi with more resolution
on May 3, 2008 at 2:39:37 am

Wht are you trying to do...

if its video.. 72 ppi is meanongless (all ppi is)

pixels per inch (not dots) only matters for print.


You can always change image size... and uncheck the resample box.... but again for video or multimedia.... doesn't matter

Richard M. Harrington, PMP

Author: Photoshop for Video, Understanding Adobe Photoshop, and ATS:iWork


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Russell Lasson
Re: Converting 300 dpi into 72 dpi with more resolution
on May 3, 2008 at 4:05:21 am

[Richard Harrington] "You can always change image size... and uncheck the resample box.... but again for video or multimedia.... doesn't matter"

I have a image that was scanned at 300dpi. Because the image was so small, the resolution ended up only being something like 200 pixels x 200 pixels.

So my question is, can I use the extra dots per inch to scale the image without losing quality by setting the image to 72dpi and scaling the image. So would the resulting image would be something like 400x400. If I uncheck the resample box, does this work and not loose quality?

Otherwise, the extra dpi is useless because video is the equivalent of 72 dpi and I still only have an image that is 200x200 pixels. I guess my real question is if I'm scanning an image that is only 1"x1", how to I scan it so I end up with something like 1200x1200 pixels at 72dpi and not 200x200 pixels at 2400dpi? (the math is probably way off, but you get the idea.

I'm trying to write this so it makes sense, but I'm not sure if it's worked yet. Let me know if I'm still not being clear and I'll try to explain it a different way.

Thanks,

-Russ

Russell Lasson
Kaleidoscope Pictures
Provo, UT


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Richard Harrington
Re: Converting 300 dpi into 72 dpi with more resolution
on May 3, 2008 at 6:42:54 pm

Stop talking in PPI...

Set your scanner to total pixels....



If you scanned a one inch sqaure at 300 ppi
it woudl be 300 pixels across... changing the PPI setting will only change how it prints on a physcial page and does not give you any more info.

STRONGLY encourage you to dig into Photoshop for Video or Understanding Adobe Photoshop.... you need to fill in some foundations to make your life easier,

Richard M. Harrington, PMP

Author: Photoshop for Video, Understanding Adobe Photoshop, and ATS:iWork


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Emily Carmichael
Re: Converting 300 dpi into 72 dpi with more resolution
on May 9, 2008 at 11:41:45 pm

Russell, the simple answer is this:

Go to Image Size.

Look where it says "Width:" under "Pixel Dimensions" (the very first number field in the dialogue box.) This shows how many pixels wide your image is. Remember this number.

Make sure "constrain proportions" is selected.

Where it says "Resolution: 300 [pixels/inch]" erase the 300 and type 72.

You will notice the top of the dialogue box says something like "Pixel dimensions: 38 KB (was 1.4 MB)." This is because Photoshop is planning to throw away extra pixel information to match the smaller print resolution, which is not what you want.

You will also notice that that under Pixel Dimensions the Width and Height have changed.

Just erase the new Width, and type the very first Width you saw in the box.

Now the top should say "Pixel Dimensions: 1.4 MB" --the exact same file size it was when you opened it. It does not matter if "resample image" is checked or not, as the image is not being resized.
_____

So you haven't changed the file at all, just the metadata that says what size to print the image. Some applications do read this metadata so it can be important, (for example when importing PNGs into Flash--for some crazy reason) but most do not.





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