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04-21-2009, 06:32 AM   #1
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Can I use DPI as a print-protection method?

Whenever I do jpg conversions, I have the option to change the DPI I(which I usually set to 300).

Whenever sending photos to clients, I set the DPI to 50, believing (possibly wrong) that the client won't be able to print the photos.


Now, is there a way to easily revert the photo back to 300 DPI and print it or not? I am curious how effective this method is to prevent them for printing the sample shots....



Not sure if important, but usually I submit these samples at 1600x1200 pixels, in order to fit their full screen.


thanks for any clarifications!

04-21-2009, 06:58 AM   #2
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BBear, the DPI setting in the file has absolutely no effect on the quality of the printed photo. It exists only as a convenience for people using desktop publishing software, and little else. It says, in effect, "If you decide to print this picture, I recommend printing it at 50 dpi." It can be overridden with no effort.

On the other hand, the pixel dimensions if your photos do affect the print quality. At 1600x1200, your photos can be printed at a size of 4x6 inches with good quality, and not much larger.

If you want to keep people from printing even at that size, submit your photos even smaller, perhaps 1024 pixels wide.
04-21-2009, 07:12 AM   #3
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QuoteOriginally posted by Jim Royal Quote
BBear, the DPI setting in the file has absolutely no effect on the quality of the printed photo. It exists only as a convenience for people using desktop publishing software, and little else. It says, in effect, "If you decide to print this picture, I recommend printing it at 50 dpi." It can be overridden with no effort.

On the other hand, the pixel dimensions if your photos do affect the print quality. At 1600x1200, your photos can be printed at a size of 4x6 inches with good quality, and not much larger.

If you want to keep people from printing even at that size, submit your photos even smaller, perhaps 1024 pixels wide.
Actually w/ one interpolation (2X pixel count) you can make a pretty decent 8X10 out of it...
600 x 800 @ 72 dpi seems to break down faster as you size up.
BBear :
1600x 1200 @ 50 dpi = 32 X 24 inch image, at 100dpi = 16 x 12 inch image, at 200dpi = 8x6, ect
It's probably best to destructively resample down..... 1 orig copy, 1 "thumbnail" so to speak.....
04-21-2009, 07:37 AM   #4
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QuoteOriginally posted by jeffkrol Quote
Actually w/ one interpolation (2X pixel count) you can make a pretty decent 8X10 out of it...
600 x 800 @ 72 dpi seems to break down faster as you size up.
BBear :
1600x 1200 @ 50 dpi = 32 X 24 inch image, at 100dpi = 16 x 12 inch image, at 200dpi = 8x6, ect
It's probably best to destructively resample down..... 1 orig copy, 1 "thumbnail" so to speak.....
I've seen some pretty decent 4x6 prints made from files not much larger than VGA (640 x 480).
I'd recomment to anyone that is handing out files to try the following experiment:
Take a file and size it to what your lab wants for a poof sized print. This will be in the 1200 x 1800 pixel range for a photographic printer (Fuji prints at 300 dpi, Noritsu prints at 320).
Now start downsizing the files in 25% increments, doing a save with a modified filename after each downsize.
Keep the filemanes simple and short so that you can flip the print and see which file is which from the back printing.
Keep doing this until you have files ranging from 1200x1800 down to perhaps 300 x 450, and send the whole lot off to your local minilab.
At this point, you will know first hand just how small a file has to be before a usable print can be taken from it.
I think you'll be shocked by how good the interpolation of minilab printers, especially Noritsu, is at making files that are too small look pretty good.

04-21-2009, 08:16 AM   #5
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QuoteOriginally posted by Jim Royal Quote
BBear, the DPI setting in the file has absolutely no effect on the quality of the printed photo. It exists only as a convenience for people using desktop publishing software, and little else. It says, in effect, "If you decide to print this picture, I recommend printing it at 50 dpi." It can be overridden with no effort.

On the other hand, the pixel dimensions if your photos do affect the print quality. At 1600x1200, your photos can be printed at a size of 4x6 inches with good quality, and not much larger.

If you want to keep people from printing even at that size, submit your photos even smaller, perhaps 1024 pixels wide.
Are you for real? Of course it matters. If you want to protect your work save it as a pdf and put a watermark that only shows when printed.
04-21-2009, 08:23 AM   #6
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QuoteOriginally posted by graphicgr8s Quote
Are you for real? Of course it matters. If you want to protect your work save it as a pdf and put a watermark that only shows when printed.
Good advice regarding the PDF, and if you are really smart, you can put a no printing allowed into the security of the file.
The DPI tag, however, really does have no bearing whatsoever on final output quality, the physical pixel dimensions of the file are what's important, not whether the file is tagged as 72dpi or 240 dpi or whatever.
04-21-2009, 09:06 AM   #7
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QuoteOriginally posted by graphicgr8s Quote
Are you for real? Of course it matters. If you want to protect your work save it as a pdf and put a watermark that only shows when printed.
QuoteOriginally posted by Wheatfield Quote
Good advice regarding the PDF, and if you are really smart, you can put a no printing allowed into the security of the file.

Very interesting alternative!! And I even have Acrobat Professional already in my desktop. Very good tip.. i'll use that for proofs.... BUt it doesnt solve all the issues...


.... the thing is, some times the final product IS web-usable jpgs but NOT printable (i want them to come back to me for prints).

The PDF does not work in this case, because they wouldnt be able to use the PDF in their websites...


So I guess the real question is: what is a safe pixel size for webdisplay and not for printing?
04-21-2009, 09:59 AM   #8
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QuoteOriginally posted by BBear Quote



So I guess the real question is: what is a safe pixel size for webdisplay and not for printing?
Unfortunately, smaller than what is usable for web viewing.
However, all is not necessarily lost.
You can watermark your photos, though this lowers their usefulness for web viewing.
You can compress the heck out of them so that they'll show artifacting when printed, you can use browser tags to force the browser to resize the images to larger than what is actually on the server.
Both of these will have a detrimental effect on their presentation quality on the web.

While it isn't difficult to overcome right click limiting, you'd be surprised by the number of people who just aren't savy enough to know how to do it. It will stop the casual thief.

You could also look into page encryption with tools such as HTML Guardian:
Encrypt HTML source, Javascript, ASP. Protect links & images. HTML encryption
or HTML Protector:
HTML Protection Tool - Encrypt HTML Source Code and Disable Right Click
though this implies that you are writing the code for the page, not just submitting content.

04-21-2009, 09:59 AM   #9
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QuoteOriginally posted by BBear Quote
Very interesting alternative!! And I even have Acrobat Professional already in my desktop. Very good tip.. i'll use that for proofs.... BUt it doesnt solve all the issues...


.... the thing is, some times the final product IS web-usable jpgs but NOT printable (i want them to come back to me for prints).

The PDF does not work in this case, because they wouldnt be able to use the PDF in their websites...


So I guess the real question is: what is a safe pixel size for webdisplay and not for printing?

If you give them a 100 dpi file at the size they are going to use when you try printing it it will look like crap but still will be okay on the web.

The thing to remember is to always think finished size.
04-21-2009, 10:01 AM   #10
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QuoteOriginally posted by graphicgr8s Quote
If you give them a 100 dpi file at the size they are going to use when you try printing it it will look like crap but still will be okay on the web.
The DPI values does not matter (and is meaningless without a print format), only the pixel dimensions.
04-21-2009, 10:05 AM   #11
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QuoteOriginally posted by RBellavance Quote
The DPI values does not matter (and is meaningless without a print format), only the pixel dimensions.
It actually isn't meaningless since he's worried about someone printing it. You do a save as and try printing it. It looks like garbage if it's 100 dpi/ppi at the finished size.
04-21-2009, 10:10 AM   #12
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QuoteOriginally posted by graphicgr8s Quote
Are you for real? Of course it matters.
Yes, I'm for real. The DPI value embedded in the file has no effect whatsoever unless you let it.

QuoteOriginally posted by graphicgr8s Quote
If you want to protect your work save it as a pdf and put a watermark that only shows when printed.
This is an excellent idea so long as the the images are not being used for placement purposes. If they are, then a multi-page PDF is an inconvenience.
04-21-2009, 10:13 AM   #13
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QuoteOriginally posted by BBear Quote
So I guess the real question is: what is a safe pixel size for webdisplay and not for printing?
It depends on who you are dealing with, and how then intend to use the photos, but 800-1000 pixels on the long side should be just fine.
04-21-2009, 10:36 AM   #14
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QuoteOriginally posted by Jim Royal Quote
Yes, I'm for real. The DPI value embedded in the file has no effect whatsoever unless you let it.
Well if I take an image that's 8" x 10" and 72 ppi/dpi and print it on my Xerox Doc 12 it will without a doubt not look like an 8 x 10 300 ppi/dpi image printed on the same machine. I can tell you which one will look good and which will not before I ever hit the print button.
04-21-2009, 10:52 AM   #15
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QuoteOriginally posted by graphicgr8s Quote
It actually isn't meaningless since he's worried about someone printing it. You do a save as and try printing it. It looks like garbage if it's 100 dpi/ppi at the finished size.
I see where you are coming from, my tendency is to forget about the DPI tag unless I am sizing a file to a specific print (finished) size.
For web use, the finished size is pretty hard to determine, since it will vary tremendously depending on how much real estate the screen has.

For example, a 4x6 inch file at 100 dpi is going to be huge on a 600x800 screen, a nice size on a 1024x768 screen and positively diminutive on a 1200x1920 screen, even though they are exactly the same file.
This is why for web use, I tend to just go with actual pixel dimensions and forget about the ppi/dpi tag.
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