Osai wrote:
Images are measured in PPI not DPI
Printing is done in DPI not PPI
Here your talking semantics DPI and PPI are basically the same thing PPI pixel per inch is usually used when referring to pixels on a display screen which is actually made up of 3 dots or sub pixels R G B. Appends have been made that claimed there is just pixels its all or nothing. That there is no such thing as a partial pixel. Well actually there is and the author of the disk program spin right demonstrated how these sub-pixels could be used to make text look much better on screen. Today Microsoft calls this technology Clear Type which can be set in the displays properties for LCDs. Pixels on a CRT are also composed of three dots but the geometry of a CRT is not perfect like on LCD so clear type does not work on CRT. Prints Resolution is measured in DPI dots per inch. In reality when it comes to printers a Dot is actually and area the size of which is defined by how many of there are in an inch. Like on display this dot is not a single blob of ink. Instead the dots are filled by many droplets of ink which are deposited from many small ink-jet nozzles.
Resampling changes the number of pixels in an image...IF......you keep the actual size of the image the same.
"Resampling changes the number of pixels in an image" Stop right there that what resampling is.... The size of the image is simply the product of number of pixels you have and the size of a pixel. The size of a pixel is measured in DPI one dot = one pixel.
DPI is a printing function, not an image function. You can print a 300 PPI image at 1440 DPI and have a great image.
Paper does not have pixels.
DPI is a resolution measurements what is confusing people here is that there are two resolutions being discussed here. One the resolution of the Print Image. The second resolution being discussed is the printers resolution. Printers can be set for different Print qualities. Like My Epson 4800 can be set to 720dpi, or 1440dpi or 2880dpi with high quality paper. When ink hits paper some bloom occurs if you lay down too much ink on low quality paper it becomes saturated runs just a big mess. Ink-jet printers use their high dpi resolution to fill in the lower resolution image pixels.
Here your talking semantics DPI and PPI are basically the same thing PPI pixel per inch is usually used when referring to pixels on a display screen which is actually made up of 3 dots or sub pixels R G B.
Osai is correct in terms of practical discussion of the tools we have. Attempting to use PPI and DPI interchangeably leads to endless confusion because our tools do not use them as though they were "basically the same thing."
Our common image tools use pixels as the unit of management, our print tools use dots as the unit of management, and they are not the same as they are used.
If dpi and ppi were the same, then when Photoshop says the image has a resolution of 300 ppi at 8x10 and the printer says it's going to print at 1440 dpi, which is lying to us?
If dpi and ppi were the same, and I change to 200 ppi at 8x10 in Photoshop but the printer still says 1440 dpi, what have I changed?
With the tools we have, ppi and dpi refer to two different concepts. When we read articles about setting "image resolution" in Photoshop and other editors, those articles are refering to pixels in the image, not dots of the printer. There is no reference anywhere in Photoshop of dpi...that's in the printer driver.
Saying dpi and ppi are only semantically different is like saying inches and grams are only semantically different.
Image resolution use which ever three letters term you want I don't care.
Printer resolution user what ever term you want I don't care.
These resolutions are not the same no mater what terms are used.
The Printer uses one of its higher resolution modes to produce the lower resolution image by painting the image's dots or pixels what ever term you want to use. The printers resolution and the image resolution are not the same that is what I have been trying to get across.
They are both just terms use as units of measurement for resolution for sharpness often used interchangeably.
An image has some resolution. The printer that has produced it has a higher resolution then the images. A printer has to have a higher resolution the the images it produces because it has to lay down several droplets of ink to produce the required color for most pixels or dots what ever term you want. If a printer has 2880 dpi as its highest resolution I don't think it could produce an image with a resolution of 2880 ppi or dpi. It would not matter much for you would need a microscope to check on this I don't know about you but I don't view images through a microscope.
I'm sure I could find something you wrote and take a sniplet from it out of context too. What I wrote was and still is
"DPI is a resolution measurements what is confusing people here is that there are two resolutions being discussed here. One the resolution of the Print Image. The second resolution being discussed is the printers resolution. Printers can be set for different Print qualities. Like My Epson 4800 can be set to 720dpi, or 1440dpi or 2880dpi with high quality paper. When ink hits paper some bloom occurs if you lay down too much ink on low quality paper it becomes saturated runs just a big mess. Ink-jet printers use their high dpi resolution to fill in the lower resolution image pixels.
"
The meaning of "DPI and PPI are basically the same thing" was my way of saying the are used interchangeably.
You guys went waaay off topic here
I use dpi and ppi interchangeably, because it does not matter to me, we all know what we are talking about.
Since there were two different opinions on my original question, I will ask again:
is it necessary to follow those certain dpi values ( 360, 480,...) or at least try to stay close to them, or can I - if needed - go right in between, say 311.5 dpi in order to fill the sheet (as an example)?
RDKirk wrote:
[If dpi and ppi were the same, then when Photoshop says the image has a resolution of 300 ppi at 8x10 and the printer says it's going to print at 1440 dpi, which is lying to us?
If dpi and ppi were the same, and I change to 200 ppi at 8x10 in Photoshop but the printer still says 1440 dpi, what have I changed?
I'll answer this now. To change a 8x10 300ppi image into a 8x10 a 200ppi image you reduced the image and file size by 4,000,000 pixels. A image 8" by 10" at 300ppi is an image 2400 pixels by 3000 pixels total pixel count 7,200,000 pixels. An image 8x10 at 200ppi 1600 pixels by 2000 pixels a total of 3,200,000 pixels 4,000,000 pixels less the 300ppi image if the files were uncompress tiff 8bit color you reduced the file size by 12Mbytes. If 16 Bit color you reduced the file size be 24Mbytes.
Both of the image will easily print on a 1440 dpi printer. The images will look a like unless held very close to the eye. It is hard for the human eye to resolve beyond 200ppi at a distance.
cencored wrote:
You guys went waaay off topic here
I use dpi and ppi interchangeably, because it does not matter to me, we all know what we are talking about.
Since there were two different opinions on my original question, I will ask again:
is it necessary to follow those certain dpi values ( 360, 480,...) or at least try to stay close to them, or can I - if needed - go right in between, say 311.5 dpi in order to fill the sheet (as an example)?
No it is not necessary to follow those certain dpi values in image files. Printers use their resolution capabilities to fill in/paint. the images pixels what ever number of pixel per inch there are. The whole inch is always filled in. The only difference is the size of a pixels. When you fill in the inch with 200 pixels you paint with bigger pixel then when you fill the inch with 300 pixels per inch sized pixels.
Don't take my words or anyones word as dogma. There is a lot of incorrect information on the web and a lot of people who know it all. All of whom have good intentions. Some of us may be jerks use your own intelligence to place us where you think we belong.
There are many good Web site also http://www.drycreekphoto.com/ has lots of information
Digital Imaging Resources for Photographers by Photographers
One of the best is http://www.luminous-landscape.com/ don't miss reading their understanding series if you want to learn how thing work.
Yes I hang out on LL quite frequently and also watched many of their videos.
However that question came anyway.
Osai, as far as I remember you two had a discussion about the differences in dpi and ppi, so that is actually off topic and I don't realy care who is right and who isn't.
Please - if you don't mind, could you please let me know your point on my original question?
is it necessary to follow those certain dpi values ( 360, 480,...) or at least try to stay close to them, or can I - if needed - go right in between, say 311.5 dpi in order to fill the sheet (as an example)?
The reason you're asking that question is because you're not clear that there is a difference with the tools you're using between ppi and dpi.
You want the pixel resolution of the print to be too small for the eye to distinguish at the viewing distance you intend for that print. If the print is going to be viewed at reading distance, that should be in the range of 280 to 300 or so (you can go lower if the viewing distance will be greater, but it doesn't matter too closely).
You want to size your image with your editor so that at approximately 300 ppi, the image is the size you want it. This may require interpolation (resampling)--the editor will do that automatically by default.
Going above 300 ppi is pretty much a waste of resources, unless you expect your viewers to take a loupe to your print. A healthy eye can't resolve any better than 300 dpi at reading distance.
Note that none of this has anything to do with the dpi of the printer driver. It's better to leave that alone, because only the printer manufacturer or a very good profiler can do better at figuring out how to lay 1/1440-inch dots to fill out a 1/300-inch pixel.
cencored wrote:
I will ask again:
is it necessary to follow those certain dpi values ( 360, 480,...) or at least try to stay close to them, or can I - if needed - go right in between, say 311.5 dpi in order to fill the sheet (as an example)?
2 quotes from Jeff Schewe's comments:
"If you need a specific size, set it and let the PPI resolution fall where it may. Don't resample just to hit some some number! Then sharpen for that resolution."
"If your image is between 180-480 ppi, don't resample. Use the native resolution and resize to fit the paper."
I'm not trying to start a war I'm trying to help you to understand this digital mountain. Maybe Osai will be satisfied with this
PPI & DPI
PPI (Pixels per Inch) and DPI (Dots per Inch) are frequently used interchangeably in this industry, by pros and amateurs alike. While wrong, this isn't a huge problem since we usually know what we're talking about. To be absolutely correct it's worth noting that scanners, digital cameras and screens are all measured in PPI while printers are measured in DPI. Just so you know I know the difference.
As pointed out this thread is not that anyway.
RDKirk last append is quite good I would take exception to some of his numbers believe I'm entitled to my own opinions there. My eyes are most likely much older then his. While the human I can resolve to his 280 - 300 range I don't know if mine can. I have printed many a picture below 280 DPI like in the 190-200 DPI and in my hand with my eyes they look fine. Viewing distance plays a big role. When I print 16"x24" images I do so at 200DPI.
While one get no benefit from printing above 300 DPI I also do that. The reason I do is I do not want to resample my images down in size for some time in the future I may want to make a larger print and I don't want to have to up-sample at that time. IMO the only extra resource you use is some storage space.. You don't use more paper and the area you cover with ink is the same. When I print my cameras images 4x6 they print at 584DPI a non issue for me.
Once had an image printed on canvas 6' wide 8' high at only 100 DPI hung on stage it looked great from the audience.. To me 100DPI sounded to low I was skeptical. The amount I had to up-sample made me even more so. You see I was ask for a jpeg sRGB image the would print 6' x 8' @ 100 DPI so I obliged gave the organizer what he asked for. My Cameras are a 8.2 Mpixel Canons they capture 2:3 aspect ratio images 2336 x 3504 pixels. After cropping the image to the required 3:4 aspect ratio I was down to 2336 x 3115 pixels what started out 8 mega pixels was down to 7 mega pixels I had to up-sample this to 7200 x 9600 that is 69 Mega-pixels. I thought the was asking too much from Photoshop's Bi-cubic Smoother Interpolation. I was amazed when I saw the print. The subject matter was a 6'x8' oil painting of a man. The artiest style did not put much detail in the image. Yet when the artiest saw the print she could not believe the detail in her signature on the print. The event was a charitable one at the end of it the Artiest and the model signed the print and it was auctioned off it brought in over a thousand dollars. The buyer may just needed a tax write off but I can tell they took the print.
1.) Your Image needs to have the same aspect ratio as the paper if you want no borders.
2.) Don't Resample your image use your Cameras original Pixels.
3.) Let the DPI fall where it need be.
If you are doing your own printing from Photoshop there are a few things you need to do. This particular write up is geared to CS3. There was a big print interface change made in CS3 Adobe consolidated all that it could into a single dialog menu File>Print.
First be aware that both Photoshop and your printers device drivers are capable of doing Color Management. You do not want both doing it that is called double profiling if done your print will not look good.
In the Print Dialog First select the printer you will be printing with in the middle section. Then click on the page setup button. This will take you to that printers device driver settings. Here set the Paper its orientation and borderless if you want no borders. Use the advance mode button to turn off the device drivers color management and set the print quality the click OK and then OK again to get out of the device settings.
Next the right side of Photoshop CS3 Print Dialog. The top pull-down menu can be Output or Color management. I'm not going to address output just Color Management. Color Management print Radio button Document; Color Handling Photoshop Manages Colors. Printer Profile always double check setting in CS3 print dialogs. There were bugs in it and one of the thing that sometime occurs is old setting seem to be refreshed sometimes. Adobe has been working to fix these. I still thing there may be one or two hiding.
Photoshop can soft proof your image and its Print and the Print dialog preview will show how your image when you check the middle section box Match Print Colors. There can be a big difference between how the image looks on your screen and printer. If you know the print setup while your editing your image. You can use men View Proof Setup>Custom and select you printer/paper profile. You can then short cuts Ctrl+Y and Ctrl+Shift+Y to toggle soft proof and gamma warning. If there is a big difference you can usually get the closer by adding adjustment layers. Brightness and contrast and a second one Hue and saturation. To be able to make a judgment call before you add these layers. First dupe the document. Use menu windows arrange Tile the two image horizontally on screen and also to match the zoom and location. Your not doing to save the dupe it just there as a reference. Switch tho you document and use Ctrl+Y to soft proof the colors. You can now see both views. Add the adjustment layers and try to match the print view to your screen view.
Here are two screen capture of Photoshop's Dialog for a test file that shows the difference between the Screen view and the printer view. Its not that the screen is better then the printer it the other way around. Photoshop uses you screens default ICC color profile when it renders/displays and image. Soft proof view tries to render the image on screen how it will look printed by using your display's ICC profile; your printers ICC profile and the color space the image is being edited in. The test file was created with Photoshop's gradient tool in a ProPhotoRGB mode many of the colors are outside my printers color gamut.
Now to get your image into the same aspect ratio as your paper and set its DPI to fill you paper without resampling could be done with an action. It is possible to create an action that would crop your image from the center point regardless what it current aspect is an maintain its orientation landscape or portrait to your paper's aspect ratio and set the correct DPI. Now before someone chimes in that you can not use logic in any action let me write an action can record the use of a script and scripts can use logic. So it is possible to write simple scripts the could be used when you create actions to enable the actions to use logic. The Crop and set DPI action would need two simple scripts to accomplish its task. The action would just need four steps:
1.) Use script select center to papers aspect ratio.
2.) Menu Image>Crop
3.) Menu Select>Deselect
4.) Use script set Image DPI so that the image long side equals the papers long side length.
Its snowing today here in New York and its my 67 birthday and I feel good today so here are the two scripts. You can see by changing one variable in the select script you can carte a script for any aspect ratio you need. The same is true of the long side script.
// validate that a document is open
if (documents.length < 1) {
alert("No Open Document!");
return;
}
// prepare the ruler
var defaultRulerUnits = preferences.rulerUnits;
preferences.rulerUnits = Units.PIXELS;
var height = activeDocument.height.value;
var width = activeDocument.width.value;
if (height>width) {
// Portraits
originalAspectRatio = height/width;
if (originalAspectRatio < aspectRatio) {
// Current aspect ratio less trim width
x1 = 0;
y1 = 0;
x2 = Math.round(height/aspectRatio);
y2 = height;
if (origin == "CENTER") {
x1 = Math.round(width-x2)/2;
x2 += Math.round(width-x2)/2;
}
} else {
// Current aspect not less trim height
x1 = 0;
y1 = 0;
x2 = width;
y2= Math.round(width*aspectRatio);
if (origin == "CENTER") {
y1 = Math.round(height-y2)/2;
y2 += Math.round(height-y2)/2;
}
}
} else {
// Landscapes including square
originalAspectRatio = width/height
if (originalAspectRatio < aspectRatio) {
// Current aspect ratio less trim height
x1 = 0;
y1 = 0;
x2 = width;
y2 = Math.round(width / aspectRatio);
if (origin == "CENTER") {
y1 = Math.round(height-y2)/2;
y2 += Math.round(height-y2)/2;
}
} else {
// Current aspect not less trim width
x1 = 0;
y1 = 0;
x2= Math.round(height*aspectRatio);
y2 = height;
if (origin == "CENTER") {
x1 = Math.round(width-x2)/2;
x2 += Math.round(width-x2)/2;
}
}
}
// Set Marquee Selection Top Left and Bottom Right corners (X1, y1, x2, y2);
var selRegion = Array(Array(x1,y1),Array(x1,y2),Array(x2,y2),Array(x2,y1));
app.activeDocument.selection.select(selRegion);
// restore the ruler to whatever unit it was in
preferences.rulerUnits = defaultRulerUnits;
