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150 dpi to 300 dpi conversion

Posted on 1999-01-04
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Last Modified: 2008-03-06
I have an aerial photo that is 150 dpi. How can I convert this to 300?  I know at I will not get extra information from the image but I need the higher resolution for a CAD program
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Question by:entretec
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by:Mirkwood
ID: 1113528
Who not loaded it in PaintShopPro or Photoshop and use the stretch function to increase the size
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Author Comment

by:entretec
ID: 1113529
I don't think that will increase the resolution, just the size of the image will get bigger.
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by:Mirkwood
ID: 1113530
Yes, but DPI is more or less a scan or print property. So either you have scanned on 150 DPI or you print to 150DPI. If you scan on 150DPI and print on 300DPI you have to double the height and width of the picture.
The picture will now be printed in the same size as it was scanned.
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Osiris010898 earned 100 total points
ID: 1113531
Photoshop:
go to menu "image" - select "image size", check "constrain proportions" and  "reasample image" type in 300 dpi in the "resolution:" box. Press OK.
Your 150 dpi image is now 300 dpi.
You will most likely have  pixelation. You can't go up in resolution/dimesions w/out  image deterioration.

To clean it up: (not promising  a great image)
Apply a small amount/s of Guassian Blur filter over entire image.  This will hopefully reduce pixelation in image. Use "curves" or "Levels" to increase contrast.  Use Unsharp Mask filter with a low pixel radius, thus sharpening image even more.You will have to experiment with settings between these filters.

Don't expect a great image after  you've gone up in resolution via image size,you lose image quality no matter what. But I've done this a few times on images scanned at low resolution and the images were "acceptable", and it didn't look too bad in final print.
If possible re-scan image at 300 dpi at the final image dimension. Or rescan at 150 dpi and double the image dimension.


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LVL 2

Expert Comment

by:Osiris010898
ID: 1113532
Photoshop:
go to menu "image" - select "image size", check "constrain proportions" and  "reasample image" type in 300 dpi in the "resolution:" box. Press OK.
Your 150 dpi image is now 300 dpi.
You will most likely have  pixelation. You can't go up in resolution/dimesions w/out  image deterioration.

To clean it up: (not promising  a great image)
Apply a small amount/s of Guassian Blur filter over entire image.  This will hopefully reduce pixelation in image. Use "curves" or "Levels" to increase contrast.  Use Unsharp Mask filter with a low pixel radius, thus sharpening image even more.You will have to experiment with settings between these filters.

Don't expect a great image after  you've gone up in resolution via image size,you lose image quality no matter what. But I've done this a few times on images scanned at low resolution and the images were "acceptable", and it didn't look too bad in final print.
If possible re-scan image at 300 dpi at the final image dimension. Or rescan at 150 dpi and double the image dimension.


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