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03-12-2008, 06:03 PM   #1
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DPI Question on Pentax K10d

I recently purchased a K10d with the hopes of renewing my photography hobby. It's been about 8 years since I last used an SLR and a lot has changed with the digital SLRs. So please bear with me because I might not come across as too savvy.

My question is this. I recently travelled to Morocco for an amazing trip. When I got home and uploaded my shots, it looks like ALL of the pictures are set at 72dpi. I had some 8 x 10 prints made and they mostly look awful. I didn't realize until after I had these prints made that the resolution was so low. All of the pictures were shot at either RAW or JPEG set at 10 megapixels.

I need some advice on how I can change the dpi to get higher quality photos for printing?

Thanks!

03-14-2008, 09:40 PM   #2
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QuoteOriginally posted by slb5342 Quote
I recently purchased a K10d with the hopes of renewing my photography hobby. It's been about 8 years since I last used an SLR and a lot has changed with the digital SLRs. So please bear with me because I might not come across as too savvy.

My question is this. I recently travelled to Morocco for an amazing trip. When I got home and uploaded my shots, it looks like ALL of the pictures are set at 72dpi. I had some 8 x 10 prints made and they mostly look awful. I didn't realize until after I had these prints made that the resolution was so low. All of the pictures were shot at either RAW or JPEG set at 10 megapixels.

I need some advice on how I can change the dpi to get higher quality photos for printing?

Thanks!
72 dpi is the standard web/screen resolution. If you still have the originals, reopen them in your post processing software, and convert the jpegs at 300 dpi to a new file name and use that file for printing. If you uploaded them to a web source (Picassa comes to mind) they will be converted to 72 dpi.
03-14-2008, 10:14 PM   #3
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Something is amiss here; 10Mp (around 3900x2600) at 72dpi = 4.5ft x 3ft !!
Your print wasn't that size, so it wasn't printed at 72dpi.

If you ordered 8x10 print the print program would scale 3900x2600 to best fit, so roughly ~300-400dpi. The 72dpi info was ignored. In other words changing 72dpi in the pic file to a higher number won't change anything in its 8x10 print.

Last edited by Kguru; 03-14-2008 at 10:20 PM.
03-14-2008, 11:12 PM   #4
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20x32" (51x76cm) prints are great from 10MP photos, so something went very wrong.

03-15-2008, 02:51 AM   #5
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The DPI info of a JPEG file really shows absolutely nothing. It's the pixels that count. I can change the DPI to 1 or to 10 000 and unless I actually resize the image (by converting it to less megapixels) the quality does not change. Did you do any post processing of your images and if yes, was one part of it any kind of resizing ?
03-15-2008, 03:35 AM   #6
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i have played only a bit with the whole setup..

what i can tell you is there are two major elements to printing the photos...

DPI and PPI....
dots per inch and pixels per inch

when printing both play an important part i am led to believe...
03-15-2008, 04:50 AM   #7
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Just to clarify a bit - there are two "kinds" of DPI (or to be more accurate PPI, but that's another story) that you can see.
First - most JPEG files from digital cameras have some DPI value set in their EXIF data. K10D JPEG files have all 72. This value means practically nothing. If you shot at 10MP then you have 3872 x 2592 pixels and no DPI value in there will take them away from you.
Second - if you print an image, then the printer distributes those pixels evenly across paper. Let's assume that those 3872 pixels of the longer image side will form the 10 inch side of a print. Then you can calculate how many pixels there will be in every inch. 3872 divided by 10 = approximately 387 pixels per inch (that is called PPI, but I suspect we are all actually talking about PPI not DPI here so ... ). Now this calculated value does have a meaning. It shows what quality print you will have. If the value is high you will get a good quality print.
So to get a better print you need to either increase the number of pixels (camera with more megapixels) or decrease the print size.
So what I'm trying to say here is that you should find out how many pixels the image you uploaded for printing has. If it was really printed at 72DPI then the image size should be (72 x 10 ) x (72 x 8) = 720 x 576. That's a really small picture, only suitable for viewing on a computer. For printing the image size should be the actual size you get from camera (minus cropping of course).
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