Can I use DPI as a print-protection method?

Marc Sabatella · 04-21-2009, 02:58 PM

Originally posted by graphicgr8s

How big is a pixel?

How big do you want it to be?

Damn Brit · 04-21-2009, 03:53 PM

Originally posted by Marc Sabatella

How big do you want it to be?

Well there are physical limitations at the moment Marc, depending on the sensor used. But obviously technology will push those limitations over time. And the shape of them is important too. I think the largest a pixel can be is going to be a little smaller than the largest sensor available.

jeffkrol · 04-21-2009, 03:57 PM

graphicgr8s · 04-21-2009, 07:10 PM

Originally posted by Marc Sabatella

How big do you want it to be?

1/300"

10char

Alfisti · 04-21-2009, 07:51 PM

The usual people spouting the usual misinformation. The DPI figure DOES count in this instance. If you provide a 300 DPI file that is set to say 4 x 6 inches then they can print it. If you provide a 50 DPI file at 4x6 inches then they are gonna struggle.

Some here will say that this is essentially just re-sizing and there was no need to change the DPI, just change the image size. This is correct to a point but then you're sending a very small image to a client and they will twig as to what you are doing. Send a large photo with low DPI and most clients will have NFI why it prints badly.

graphicgr8s · 04-21-2009, 08:25 PM

Originally posted by Marc Sabatella

Changing the *actual* dpi does this. Changing the meaningless number stored in the EXIF does nothing of the sort. In fact, it does nothing of *any* sprt - it does nothing at all. It's as relevant to the discussion as changing the file-modified date. That won't *really* make the picture go back (or forward) in time any more than chanigng the EXIF resolution figure will change the *actual* resolution of any printed image. The actual resolution is number of pixels divided by size in inches - very literally, pixels per inch. Nonumber stored in any EXIF will ever change this. The only way to change to resolution of an image to be printed at a given size is to actually change the number of pixels. You can't divide 3000 by 10 and ever get anything but 300. If you want something other than a 300dpi image in a 10" print, you're going to need something other that 3000 pixels.

If it makes you feel better call it ppi instead of dpi. It is still 1/3 of the equation. You can say it doesn't matter but it is still part of the equation. Semantics is all.

Marc Sabatella · 04-21-2009, 09:28 PM

Originally posted by Alfisti

The usual people spouting the usual misinformation. The DPI figure DOES count in this instance. If you provide a 300 DPI file that is set to say 4 x 6 inches then they can print it. If you provide a 50 DPI file at 4x6 inches then they are gonna struggle.

That's looking a it backwards. A image doesn't have dpi nor does it have a size in inches. All it has are pixels. The other two parameters - size and dpi - are determined when you go to print, and are not - cannot *possibly* be - attributes of the images. An images has a certain number number of pixels. It does not *have* a resolution in dpi. That's not misinformation, it's the nature of digital imaging.

So sure, you could say you have an image that is "a 300 dpi file that is set to 4x6 inches" - but that's an extremely roundabout and technically inaccurate way of saying it has 1200x1800 pixels.

Wheatfield · 04-21-2009, 09:32 PM

Originally posted by Alfisti

The usual people spouting the usual misinformation. The DPI figure DOES count in this instance. If you provide a 300 DPI file that is set to say 4 x 6 inches then they can print it. If you provide a 50 DPI file at 4x6 inches then they are gonna struggle.

Some here will say that this is essentially just re-sizing and there was no need to change the DPI, just change the image size. This is correct to a point but then you're sending a very small image to a client and they will twig as to what you are doing. Send a large photo with low DPI and most clients will have NFI why it prints badly.

So far, I haven't read anything on this thread that would count as misinformation. Perhaps you'd care to point out who you are talking about and what information you think is incorrect rather than blathering.

Marc Sabatella · 04-21-2009, 09:34 PM

Originally posted by graphicgr8s

If it makes you feel better call it ppi instead of dpi. It is still 1/3 of the equation. You can say it doesn't matter but it is still part of the equation. Semantics is all.

Yes, the *real* resolution of the printed image is part of the equation. The number stored in the EXIF is *not*.

As I said above, an image does not have a resolution in dpi (or ppi). It does not, cannot, will not ever. That's a meaningless as saying a car has a speed in MPH. The car doesn't have a speed until you drive it, and the image doesn't have a resolution in dpi or ppi until you print it. Saying that file X is 300dpi and file Y is 72dpi is completely and utter nonsense - no file has a resolution in dpi, because a pixel doesn't have a size until you print it, and then the size of the pixel will be a size of print / #pixels.

One of these days I'll think of a clear way to explain this that will finally convince people. Today, apparently, is still not that day.

Wheatfield · 04-21-2009, 10:09 PM

Originally posted by Marc Sabatella

Yes, the *real* resolution of the printed image is part of the equation. The number stored in the EXIF is *not*.

As I said above, an image does not have a resolution in dpi (or ppi). It does not, cannot, will not ever. That's a meaningless as saying a car has a speed in MPH. The car doesn't have a speed until you drive it, and the image doesn't have a resolution in dpi or ppi until you print it. Saying that file X is 300dpi and file Y is 72dpi is completely and utter nonsense - no file has a resolution in dpi, because a pixel doesn't have a size until you print it, and then the size of the pixel will be a size of print / #pixels.

One of these days I'll think of a clear way to explain this that will finally convince people. Today, apparently, is still not that day.

I get it, if that makes you happy.

HGMonaro · 04-21-2009, 10:51 PM

Originally posted by Wheatfield

I get it, if that makes you happy.

me too!

debbie · 04-22-2009, 12:01 AM

Originally posted by graphicgr8s

If it makes you feel better call it ppi instead of dpi. It is still 1/3 of the equation. You can say it doesn't matter but it is still part of the equation. Semantics is all.

I dont agree, X*Y in pixels is the only part of the equation. Then you can use this information to make it understandable in the physical world.

Except for layout software, the computer will not display images with different dpi tags in different sizes. Simple as that...
And if you print them, the first thing you do is to make clear that it fits the paper its going to be printed on.

jeffkrol · 04-22-2009, 06:17 AM

Originally posted by Marc Sabatella

That's looking a it backwards. A image doesn't have dpi nor does it have a size in inches. All it has are pixels. The other two parameters - size and dpi - are determined when you go to print, and are not - cannot *possibly* be - attributes of the images. An images has a certain number number of pixels. It does not *have* a resolution in dpi. That's not misinformation, it's the nature of digital imaging.

So sure, you could say you have an image that is "a 300 dpi file that is set to 4x6 inches" - but that's an extremely roundabout and technically inaccurate way of saying it has 1200x1800 pixels.

Actually it seems to me that an image has a starting size ie 14mp's contained in a 24x16mm frame. So each "pixel" starts off at 6 (2, 5, 9 ect)microns (forgive the sweeping generalities and pretend the software has interpolated each sensel into one "color"). From there you enlarge (shrink) or multiply (divide) to "FIT" the container of your choice at a density of your choice...
As long as uprezing (downrezing) isn't done the "tag" is meaningless until you give it meaning.....
of course an image printed at "native" size would be exactly the size of the sensor minus dead space at an extremely high "ppi" (198 pixels per mm or 5029 ppi)
Roughly... I think.......
Old printer stats.....
Canon's new print head features Micro-Nozzles capable of delivering consistent 2pl droplets with ultimate dot placement and giving a true resolution of 4800 x 1200 dpi. At 10 microns in diameter, the individual nozzles are about 40% smaller than the closest competitor's

BBear · 04-22-2009, 06:25 AM

Originally posted by Marc Sabatella

That's looking a it backwards. A image doesn't have dpi nor does it have a size in inches. All it has are pixels. The other two parameters - size and dpi - are determined when you go to print, and are not - cannot *possibly* be - attributes of the images. An images has a certain number number of pixels. It does not *have* a resolution in dpi. That's not misinformation, it's the nature of digital imaging.

Originally posted by Alfisti

The usual people spouting the usual misinformation. The DPI figure DOES count in this instance. If you provide a 300 DPI file that is set to say 4 x 6 inches then they can print it. If you provide a 50 DPI file at 4x6 inches then they are gonna struggle.

Obviously I have no idea what the final word is!

The thing is, why when I am exporting in LightRoom I have the option to choose DPI and canvas size at the same time, if apparently it is redundant?

jeffkrol · 04-22-2009, 06:57 AM

Originally posted by BBear

The thing is, why when I am exporting in LightRoom I have the option to choose DPI and canvas size at the same time, if apparently it is redundant?

No , not correct..... Choosing dpi and allowing the software to create a container to fit is non-destructive. Choosing both will modify (unless lucky

) the file itself...

04-21-2009, 03:57 PM	#33
jeffkrol Veteran Member Join Date: Sep 2006 Location: Wisconsin USA Photos: Gallery Posts: 8,434	1 inch = 18 pixels...

04-21-2009, 09:32 PM	#38
Wheatfield Moderator Join Date: Apr 2008 Location: The wheatfields of Canada Posts: 15,986	Originally posted by Alfisti The usual people spouting the usual misinformation. The DPI figure DOES count in this instance. If you provide a 300 DPI file that is set to say 4 x 6 inches then they can print it. If you provide a 50 DPI file at 4x6 inches then they are gonna struggle. Some here will say that this is essentially just re-sizing and there was no need to change the DPI, just change the image size. This is correct to a point but then you're sending a very small image to a client and they will twig as to what you are doing. Send a large photo with low DPI and most clients will have NFI why it prints badly. So far, I haven't read anything on this thread that would count as misinformation. Perhaps you'd care to point out who you are talking about and what information you think is incorrect rather than blathering. Last edited by Wheatfield; 04-21-2009 at 10:07 PM. Reason: So Gary wouldn't have to brig me again.

04-22-2009, 06:17 AM	#43
jeffkrol Veteran Member Join Date: Sep 2006 Location: Wisconsin USA Photos: Gallery Posts: 8,434	Splitting a large hair Originally posted by Marc Sabatella That's looking a it backwards. A image doesn't have dpi nor does it have a size in inches. All it has are pixels. The other two parameters - size and dpi - are determined when you go to print, and are not - cannot possibly be - attributes of the images. An images has a certain number number of pixels. It does not have a resolution in dpi. That's not misinformation, it's the nature of digital imaging. So sure, you could say you have an image that is "a 300 dpi file that is set to 4x6 inches" - but that's an extremely roundabout and technically inaccurate way of saying it has 1200x1800 pixels. Actually it seems to me that an image has a starting size ie 14mp's contained in a 24x16mm frame. So each "pixel" starts off at 6 (2, 5, 9 ect)microns (forgive the sweeping generalities and pretend the software has interpolated each sensel into one "color"). From there you enlarge (shrink) or multiply (divide) to "FIT" the container of your choice at a density of your choice... As long as uprezing (downrezing) isn't done the "tag" is meaningless until you give it meaning..... of course an image printed at "native" size would be exactly the size of the sensor minus dead space at an extremely high "ppi" (198 pixels per mm or 5029 ppi) Roughly... I think....... Old printer stats..... Canon's new print head features Micro-Nozzles capable of delivering consistent 2pl droplets with ultimate dot placement and giving a true resolution of 4800 x 1200 dpi. At 10 microns in diameter, the individual nozzles are about 40% smaller than the closest competitor's

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04-21-2009, 02:58 PM	#31
Marc Sabatella Veteran Member Join Date: Sep 2006 Location: Denver, CO Photos: Gallery Posts: 10,685	Originally posted by graphicgr8s How big is a pixel? How big do you want it to be?

04-21-2009, 03:53 PM	#32
Damn Brit Guest	Originally posted by Marc Sabatella How big do you want it to be? Well there are physical limitations at the moment Marc, depending on the sensor used. But obviously technology will push those limitations over time. And the shape of them is important too. I think the largest a pixel can be is going to be a little smaller than the largest sensor available.

04-21-2009, 07:10 PM	#34
graphicgr8s Guest	Originally posted by Marc Sabatella How big do you want it to be? 1/300" 10char

04-21-2009, 07:51 PM	#35
Alfisti Veteran Member Join Date: Mar 2007 Location: Toronto (for now) Posts: 1,748	The usual people spouting the usual misinformation. The DPI figure DOES count in this instance. If you provide a 300 DPI file that is set to say 4 x 6 inches then they can print it. If you provide a 50 DPI file at 4x6 inches then they are gonna struggle. Some here will say that this is essentially just re-sizing and there was no need to change the DPI, just change the image size. This is correct to a point but then you're sending a very small image to a client and they will twig as to what you are doing. Send a large photo with low DPI and most clients will have NFI why it prints badly.

04-21-2009, 08:25 PM	#36
graphicgr8s Guest	Originally posted by Marc Sabatella Changing the actual dpi does this. Changing the meaningless number stored in the EXIF does nothing of the sort. In fact, it does nothing of any sprt - it does nothing at all. It's as relevant to the discussion as changing the file-modified date. That won't really make the picture go back (or forward) in time any more than chanigng the EXIF resolution figure will change the actual resolution of any printed image. The actual resolution is number of pixels divided by size in inches - very literally, pixels per inch. Nonumber stored in any EXIF will ever change this. The only way to change to resolution of an image to be printed at a given size is to actually change the number of pixels. You can't divide 3000 by 10 and ever get anything but 300. If you want something other than a 300dpi image in a 10" print, you're going to need something other that 3000 pixels. If it makes you feel better call it ppi instead of dpi. It is still 1/3 of the equation. You can say it doesn't matter but it is still part of the equation. Semantics is all.

04-21-2009, 09:28 PM	#37
Marc Sabatella Veteran Member Join Date: Sep 2006 Location: Denver, CO Photos: Gallery Posts: 10,685	Originally posted by Alfisti The usual people spouting the usual misinformation. The DPI figure DOES count in this instance. If you provide a 300 DPI file that is set to say 4 x 6 inches then they can print it. If you provide a 50 DPI file at 4x6 inches then they are gonna struggle. That's looking a it backwards. A image doesn't have dpi nor does it have a size in inches. All it has are pixels. The other two parameters - size and dpi - are determined when you go to print, and are not - cannot possibly be - attributes of the images. An images has a certain number number of pixels. It does not have a resolution in dpi. That's not misinformation, it's the nature of digital imaging. So sure, you could say you have an image that is "a 300 dpi file that is set to 4x6 inches" - but that's an extremely roundabout and technically inaccurate way of saying it has 1200x1800 pixels.

04-21-2009, 09:34 PM	#39
Marc Sabatella Veteran Member Join Date: Sep 2006 Location: Denver, CO Photos: Gallery Posts: 10,685	Originally posted by graphicgr8s If it makes you feel better call it ppi instead of dpi. It is still 1/3 of the equation. You can say it doesn't matter but it is still part of the equation. Semantics is all. Yes, the real resolution of the printed image is part of the equation. The number stored in the EXIF is not. As I said above, an image does not have a resolution in dpi (or ppi). It does not, cannot, will not ever. That's a meaningless as saying a car has a speed in MPH. The car doesn't have a speed until you drive it, and the image doesn't have a resolution in dpi or ppi until you print it. Saying that file X is 300dpi and file Y is 72dpi is completely and utter nonsense - no file has a resolution in dpi, because a pixel doesn't have a size until you print it, and then the size of the pixel will be a size of print / #pixels. One of these days I'll think of a clear way to explain this that will finally convince people. Today, apparently, is still not that day.

04-21-2009, 10:09 PM	#40
Wheatfield Moderator Join Date: Apr 2008 Location: The wheatfields of Canada Posts: 15,986	Originally posted by Marc Sabatella Yes, the real resolution of the printed image is part of the equation. The number stored in the EXIF is not. As I said above, an image does not have a resolution in dpi (or ppi). It does not, cannot, will not ever. That's a meaningless as saying a car has a speed in MPH. The car doesn't have a speed until you drive it, and the image doesn't have a resolution in dpi or ppi until you print it. Saying that file X is 300dpi and file Y is 72dpi is completely and utter nonsense - no file has a resolution in dpi, because a pixel doesn't have a size until you print it, and then the size of the pixel will be a size of print / #pixels. One of these days I'll think of a clear way to explain this that will finally convince people. Today, apparently, is still not that day. I get it, if that makes you happy.

04-21-2009, 10:51 PM	#41
HGMonaro Veteran Member Join Date: Apr 2007 Location: Melb. Aust Posts: 840	Originally posted by Wheatfield I get it, if that makes you happy. me too!

04-22-2009, 12:01 AM	#42
debbie Senior Member Join Date: May 2008 Location: stockholm Photos: Albums Posts: 111	Originally posted by graphicgr8s If it makes you feel better call it ppi instead of dpi. It is still 1/3 of the equation. You can say it doesn't matter but it is still part of the equation. Semantics is all. I dont agree, X*Y in pixels is the only part of the equation. Then you can use this information to make it understandable in the physical world. Except for layout software, the computer will not display images with different dpi tags in different sizes. Simple as that... And if you print them, the first thing you do is to make clear that it fits the paper its going to be printed on.

04-22-2009, 06:25 AM	#44
BBear Veteran Member Join Date: Mar 2008 Location: CT / NY Photos: Gallery Posts: 822 Original Poster	Originally posted by Marc Sabatella That's looking a it backwards. A image doesn't have dpi nor does it have a size in inches. All it has are pixels. The other two parameters - size and dpi - are determined when you go to print, and are not - cannot possibly be - attributes of the images. An images has a certain number number of pixels. It does not have a resolution in dpi. That's not misinformation, it's the nature of digital imaging. Originally posted by Alfisti The usual people spouting the usual misinformation. The DPI figure DOES count in this instance. If you provide a 300 DPI file that is set to say 4 x 6 inches then they can print it. If you provide a 50 DPI file at 4x6 inches then they are gonna struggle. Obviously I have no idea what the final word is! The thing is, why when I am exporting in LightRoom I have the option to choose DPI and canvas size at the same time, if apparently it is redundant?

04-22-2009, 06:57 AM	#45
jeffkrol Veteran Member Join Date: Sep 2006 Location: Wisconsin USA Photos: Gallery Posts: 8,434	Originally posted by BBear The thing is, why when I am exporting in LightRoom I have the option to choose DPI and canvas size at the same time, if apparently it is redundant? No , not correct..... Choosing dpi and allowing the software to create a container to fit is non-destructive. Choosing both will modify (unless lucky ) the file itself...