DPI or PPI

Hello Adobe,
In Photoshop, under Image > Image Size, the resolution is labelled ppi, pixels per inch. This is correct.
In Bridge, with metadata showing, the label says dpi. This is not correct.
Could we fix this?
Mike Witherell in Washington DC

Thanks for you feedback. You wish has been granted. Check out the free beta of Bridge CS3 (http://labs.adobe.com/technologies/photoshopcs3/)
Cheers,
Arno.
Bridge Engineering Manager, Adobe.

Similar Messages

DPI vs PPI - a definitive answer?

I've looked back at some previous discussions of the DPI setting in Aperture, and I've also read some online explanations of DPI vs PPI. Apparently software applications sometimes confuse the two, and I suspect that this is the case with Aperture but I haven't seen this definitely specified. Photography competitions that ask for high-res files often ask that you use 300 PPI (not DPI); but previous discussions of Aperture suggest that the DPI option (there isn't a PPI option) should be set to 300 for high-res exports. In other words, Aperture seems to refer to DPI when it should be referring to PPI. Is this correct?

LondonDave wrote:
Photography competitions that ask for high-res files often ask that you use 300 PPI (not DPI); but previous discussions of Aperture suggest that the DPI option (there isn't a PPI option) should be set to 300 for high-res exports.
PPI and DPI are often incorrectly used interchangeably but most of the time the improper usage does not hurt anything. However IMO we should ourselves endeavor to use the terms properly. Aperture uses the dpi term correctly because it is referring to an output device.
Much of the time "photography competitions" are just stealing your image one way or another, so the image spec is just to get it into the form they want to harvest. <OK I am a cynic...>
When the contest spec is making sense usually it is just specifying linear size (inches or centimeters) x ppi (like 300 ppi) to achieve consistent linear pixel dimensions, which are what really matter. So if they want to harvest what would be typical 8x10 print quality image files they specify 8" x 10" at 300 ppi: the important net result is that every contestant provides a (8x300) x (10x300) = 2400 pixels x 3000 pixels file.
Or they could specify 24" x 30" at 100 ppi: net result (24x100) x (30x100) = 2400 pixels x 3000 pixels file.
Or maybe it is a size-righteous competition, in which size as viewed matters. After all, we all know some pix show well small while others demand large presentation. In that case they may only specify the ppi. The photog determines the presentation size. E.g. 300 ppi is specified and one wants to present at 4" x 4" it would be a 1200 pixels by 1200 pixels image submission.
-Allen

DPI and PPI in Aperture 'Export' and 'Print' windows

Hi,
As mentioned in an earlier post, I just bought an Epson 3880 printer and some Epson Hot Press paper, so now I have to pay attention to PPI (term used for displays) and DPI (term used for printers).
In Aperture however, files being exported require DPI specs(!), while files being printed require that we specify PPI specs. How is that?
Also, my Epson manual indicates that I can print at 5 distinct "DPI" settings, from 180 to 2880. My Aperture Print window, however, only offers 3 options with 360 "PPI" as the highest (considered Draft quality by Epson - if "DPI"), plus a 4th referred to as Custom.
Also, I have a note jotted down a while back that says: "1440 dpi for most papers with 240 dpi files, at 2880 if 360" - whatever that meant 6 months ago at an Epson 3880 seminar, before I got the printer.
Can you guys sort this out for me? Please?
Thanks a lot,
Raphael

I'm not at my studio. My current driver is 8.x. The newest driver is 9.33. My remarks here may not fit with your more current version of the driver (but that would surprise me — the printer came out about 4 years ago, iirc).
The profiles are not, afaik, included with the driver, at least when you download it from Epson's site.
There are two profiles for each Epson Fine Art paper — one at 1440 and one at 2880. You should try each with every kind of print you make, and determine which is better. IME, _for my needs_, 2880 was never worse. I use the 2880 profiles.
The profile is selected from the "Color Profile" drop-down at the top of the "Rendering" section of Aperture's "Print" dialog.
(Set "Render Intent" to "Perceptual" for, in general, photographs or anything with smoothly graduated changes in color. Set "Render Intent" to "Relative Colorimetric" for, in general, graphics or anything with smooth areas of constant color and sharp transitions between areas of color. Generally, if "Render Intent" is "Perceptual", check "Black Point Compensation"; otherwise uncheck it.)
Leave "Print Resolution" at "Auto". I know of no reason to ever change this. (I don't, in fact, know what this control does, and have never changed it.)
When you click "Print" in Aperture's "Print" dialog, a short dialog opens asking you if you want to save any changes you made to your Preset. I always save my changes. Prints often need to be immediately remade — all transitions of data from electronic to physical media are problematic — and I like to return to my Preset ready to print the same Image(s) again.
When that dialog closes, the OS print dialog opens. Your 3880 printer should already be selected in the "Printer" drop-down. You need to create and should save an OS Preset for your paper. Note that on the "Color Matching" page (this dialog has pages, not tabs; direct complaints to Cupertino), all (two) options should be grayed-out. This indicates that Aperture is handling color matching, which is what you want (for best prints and anything approaching a color-calibrated workflow). On the "Paper Handling" page, the "Destination Paper Size" drop-down is grayed-out, but should show you the selection you made in the Aperture Print dialog. The "Printer Settings" page has two tabs. On the "Basic" tab, in the "Media Type" drop-down, select your paper ("Fine Art Paper ▹ Hot Press [Bright or Natural])*. The "Ink" drop-down should be grayed-out, but show "Matte". Matte is proper selection for Hot Press [Bright or Natural]. This dialog knows this from your color profile selection in the Aperture Print dialog. Chose "16-bit" output and any other options your want (you can experiment; I find no difference). I ignore the warning about print quality at the bottom area — this has never been an issue. On the "Advanced" tab of the "Printer Settings" page, it should tell you that "Epson Driver Color Management is Off". That's what you want. You want Aperture to manage the color.
Save your OS print dialog Preset. Use it every time you print to the same paper.
*If you cannot select your paper, you have not selected the correct paper size in the "Printer" section of Aperture's Print dialog. Note that the "Paper Size" selection includes not only the paper size, but also whether the feed is by sheet-feeder or manual, and whether or not the print is borderless. (I didn't design this; I assume there are reasons to have shoe-horned these options into the "Paper Size" selection.
This is all tricky on top of being actually complex and next to being new. It takes everyone time and mistakes (read: ink and paper) to canalize a flow that works for producing the prints they want. I hope this gets you there a little faster. Report back with what doesn't work.
—Kirby.

DPI or PPI during cropping?

Is there a way to get a readout of the PPI or DPI in real time during cropping?
Regards,
David

"Set one of them that you prefer to either cropped dimensions or megapixels."
Yes, that shows the info I often need to see when cropping, but shouldn't there be something approaching instant feedback showing latest cropped dimensions (as in Photoshop)? On my Mac G4 1.47GHz (dual processor with 2 Gb RAM), LR seems to require approx 10 seconds before updating the info display to show current cropped dimensions. Is this typical? That's painfully slow feedback and makes cropping to a fixed pixel dimension a very tedious process.
Phil

How do I change the Bridge settings in CS4 from displaying ppi to displaying dpi

I want to see the dpi, not ppi. Is it possible to change this, and if so, how?

Jamie Voetsch wrote:
> You [...] are just wasting my time in here.
When you consider learning a waste of time then it explains your lack of understanding.
Jamie further wrote:
> First of all it does make sense
> because CS2 displays DPI not PPI.
> I've switched back to CS2 because of this.
Maybe the label in the dialog box on the screen says 'dpi.' But the numbers displayed actually are ppi. There's a reason why they changed the label in later Photoshop versions. To stick with CS2
i for this reason only
is just plain foolish.
What you really want
i is
ppi anyway, not dpi. And exactly that's what you're getting---in CS2, CS3, and CS4 ... or any image-processing software.
Jamie further wrote:
> Being a stock illustrator and photographer, you have to submit
> images at 300 dpi so I have to see that setting, which CS2 does
> in Bridge you idiots.
The idiots are the stock agency managers asking for digital images submitted at 300 dpi. That's just plain impossible. And requiring submissions at 300 ppi does not make any sense either because that's just a meaningless number in the image file's metadata. Whether the ppi number in the metadata is 72, 240, or 300 will make
i absolutely no difference
to the actual image. Got it? Absolutely no difference at all.
Except it will make a clueless stock agency manager happy. So do enter '300' into the ppi metadata field; that sure is a lot easier than to educate a fool. But do not think that the 'DPI' vs 'PPI' labelling in Photoshop's or Bridge's user interface would make any difference. It doesn't.
-- Olaf

Dpi / ppi distiller

Hey
I have a postscriptfile from InDesign that I want to make into a PDF by opening it in distiller. It contains highresolution photos, vectors and text. Usually I export to PDFs with 300 ppi. Different sources claim that the plotter can plot the accuracy of respectively 200, 300 or, maximum, 600 ppi
My question is; wath dpi(not ppi) should I choose in distillers adope pdf settings?
300? 2400? neither of those?
I have tried to look dpi/ppi up myself, but the information is so contradicting.
I hope someone can help me!

Probably not Distiller Server. If not, I recommend the Acrobat Windows
forum (it's Acrobat Distiller, and comes with Acrobat). There are
several places where dpi/ppi is mentioned in the Distiller settings,
so when you post be sure to say which one you mean.
Aandi Inston

PPI VS. DPI in verbal printing discussion

Hi,
I was wondering If I could get a professional opinion on how DPI and PPI should be conversed with a print vendor?
This would include screen printing and offset printing.
Also, for years when I talk with a designer, I always asked to save as 300 DPI…not 300 PPI thats just the language I have been used to.
Can someone please give me an endepth explaniation of the two choices and which is more common to use.
Personally I think DPI is the more current to use.
Thanks…please advise,
JB

They are used interchangably (unfortunately) and if they ask for 300 DPI then you can be confident that they mean 300 PPI.
However, this doesn't make it correct: there are no "dots" in a digital image, never have been and never will be. There are only pixels. PPI is the correct unit of measurement, and that's only if you know the print size; the actual resolution of a digital image is the total number of pixels, for example 1500px by 850px -- until you determine the output size there is no PPI measurement. Of course you need to know the output size in order to give them 300 PPI; scanning an image @ 300 PPI and then enlarging it 200% in your layour will give you an effective resolution of 150 PPI.
DPI refers to output resolution of a device such as a printer, imagesetter, platesetter, etc. It does not refer to linescreen (that would be lines per inch, or LPI).
The best way to avoid confusion in any discussion is to use proper terminology (and teach and encourage others to do the same).

PPI or DPI?

When a printer says they need 150 DPI, is that the same as 150 PPI for my images in InDesign? And if not, how do I figure out the DPI?

DPI and PPI are not the same thing though most people use them interchangeably. I suspect that’s the case here.
Bob

(New slant on) Printing at 1200 dpi from inDesign CS5 to a Xerox colour laser.

I print calendars magazines and stuff like that.
If I use Photoshop CS3~CS5 I can print a 600 dpi photograph to my Postscript 3 enabled Xerox 1200 dpi laser and get quite good appearance of the photo. Even better if I use a 1200 dpi image in the first place but when I use inDesign CS4~CS5 I can't print to the Xerox at anything over 600 dpi. Sure I can place a 1200 dpi image in the document but it still prints at a resolution that looks suspiciously like 300 dpi and the option to print at 1200 dpi is not available to me. I've filled the xerox to capacity with RAM and have a hard drive in it to store popular documents on.
I've explored many ways some associates and posters to these forums have suggested but I still can't get the quality of print from inDesign that I get from Photoshop (or for that matter a popular page layout program from Canada).
The perplexing thing I have yet to find the answer to is:
Commercial printing presses print at 2400 dpi. (let's not confuse the issue here with lpi screens) inDesign is supposedly a professional level program, you'd think would be capable of delivering 2400 dpi output if commercial presses use that resolution. If this is so... Can anyone tell me please how to make inDesign output 2400 or even 1200 dpi?
I've tried distilling the document to a PDF and using pure postscript to no avail. If the printer did not accept 1200 dpi images from Photoshop, I might be tempted to believe it was a printer issue but I'm satisfied it is not. I might point out that I also have an old Minolta (Postscript 3) colour laser too. It produces better quality output than the Xerox but at a huge cost of consumables. I also recognise the Xerox is a LED laser and not the ideal choice for image reproduction but still quite good enough (from Photoshop) for the work it is doing.
Thanks in advance

"John... You seem to be knowledgable in the area of RIPs and platemaking so here's a question you might care to answer. Suppose my platemaker can make a plate at 5080 dpi. (Forget the screening pitch for now) how do send an inDesign document to the platemaker at 5080 dpi resolution? For that matter how do I send any device a document at more than 600 dpi using inDesign? Answer that and you've answered my original question."
ID's "Print Presets" for Postscript output are based on the RIP's PPD. Since I do not have a RIP connected to my current workstation, the preset defaults to 'device independent'. The only setting for resolution is the transparency flattener which can be set to "High Resolution". You should be able to use the Xerox's RIP PPD in the "Print Presets" under File > Print Presets; where the output resolution should be able to be established. My hunch is, you may have to settle for "High Resolution" and the RIP will output the highest resolution available in the Xerox machine ( if there are no options for resolution in the presets ).
"The only way I can import an indesign PDF into a my pagesetter is to interpolate the images to 1200 ppi seperately from the text and line art which can be 300 dpi or ppi without showing discernable difference. Perhaps your reply in this area was regarding text, not images?"
No. This is backwards. Text and line art is set at output resolution ( i.e., 2540dpi ). You would definitely see a different between 300dpi vs. 2540dpi, especially in small text and the smoothness of lines. Adobe has a Postscript formula for output resolution. I quote from their Print Publishing Guide "The maximum number of grays that most output devices can produce is 256." Their Postscript formula is ( output resolution ÷ screen ruling )2 [ squared ] + 1 = shades of Gray. So, typical offset imagesetter = 2540dpi ÷ 150lpi = 17 x 17 = 289 + 1 = 290 levels of gray. More than enough to generate smooth blends. In short, lasers ( or, in your case, LEDs ) typically cannot generate enough resolution to produce what you want. Which is 1200ppi image resolution(?). 1/1200 LED is about half of what you need for the resolutions you're looking for.
The long and short of it is this. InDesign is capable of setting its resolution as "High" for raster setting ( i.e., transparency flattener ). I agree with you it is frustrating that you cannot set the output res anywhere in ID. I believe that is because it ( the resolution ) is left up to either the RIP or the Print Driver ).
"The perplexing thing I have yet to find the answer to is:
Commercial printing presses print at 2400 dpi. (let's not confuse the issue here with lpi screens)"
No. The standard is 5080dpi; 2540dpi is minimum ( see my Postscript levels of Gray formula above. When I prepare an ID file for offset printing, I first have to determine the print vendor's RIP LPi. This number determines image resolution which, typically is referred to as 2x the LPi. LPi is ( or should be ) determined by the press itself, the paper, and the inks. Desktop lasers are totally different. InDesign does the user a favor by defaulting to device independent so that multiple file do not have to be generated for proofing. Adobe leaves the print resolutions up to the output device.

Resolution of 600 DPI and Illustrator

Someone would like a small 1 inch by 1 inch logo for invoices at 600 DPI. However I understand that illustrator doesnt work in DPI or PPI since it's vector. Would I have to transfer the small image over to photoshop. I did try and save a 1 inch by 1 inch logo at 600 PPI, however when I saved the image it was no longer 1 inch by 1 inch. It had increased significantly in size regardless of what file format I saved the image as.
I would really appreciate help in this matter as Im unsure how to proceed.
Thanks

Its confusing to say the least!
Here's a universal truth that will help aleviate the confusion:
Think about this term: Pixels Per Inch.
Per Inch. You have some things (pixels). A given number of them occupy a given distance (an inch).
How do you do that? By scaling the things (pixels) so that a desired number of them fit within a given distance (inch).
Per Inch is just a scaling value. Understand and remember that universal truth, and it will clear up alot of the confusion.
Once a raster image is saved, it contains a fixed number of pixels. In order to draw a given number of the image's pixels within a measured distance, the raster image has to be scaled. Change the scale of the image, and you change the number of its pixels which occupy a measured distance.
Now be aware of these universal truths (aka facts):
Raster image file formats are different. Some formats record in the file the intended scaling value (if one is provided) that is in effect when the file is saved. Others don't.
Programs which export raster images are different. Some programs write the scaling value into the raster image file (if the raster image format supports that). Others don't.
Programs which import raster images are different. Some programs pay attention to the stored scaling value (if any). Others ignore it.
Someone would like a small 1 inch by 1 inch logo...
First issue: Is the logo square? Is the design's height equal to its width?
...for invoices...
This suggests that "someone" intends to import the raster image into some program used for invoices. That could be any of a kazillion different programs, from Word to Excel, to FileMaker Pro, to QuickBooks, to....you name it (but you didn't). You always need to know your customers' intended usage and be at least somewhat familiar with the target software's capabilities regarding importing artwork.
...at 600 DPI....
This suggests that "someone" wants a raster image with a color depth of 1-bit. That means a raster image in which each pixel can be either black or white, and nothing else. This is suggested because that is a commonly-used scale factor for 1-bit raster images that are intended for use in common programs like office applications which have very limited graphics import capability, and because it is the most common hardware resolution of most office laser printers. In other words, 1-bit raster images scaled to 600 PPI is a kind of "lowest common denominator" for commonplace office environments.
But the above suggestion is based on the assumption that "someone" knows what he/she is talking about, which is never a safe assumption. If the image is of any color depth higher than 1-bit, then 600 PPI is ridiculous. In other words, if the image file contains any pixels of any color at all, then 600 PPI is absurd for use as an invoice imprint. This is because any higher color-depth image will have to be halftone screened by the printer in order to render it with any decent-looking fidelity. That means rendering the image as a grid of variable-size dots. But the printer cannot actually print variable-size dots. It only prints fixed-size printer spots. To render variable-size halftone dots, it "fakes it" by "building them up" out of its fixed-size printer spots.
Moreover, even if the logo (the actual design) contains nothing but black and white, but you save the raster image file at a higher color-depth anyway, then 600 PPI is still just as ridiculous. Grayscale, RGB, and CMYK raster images are saved with a color depth of 8 bits per pixel per channel. When the printing device receives an 8-bit image, it is going to try to screen it (print it as halftone dots). That means that the printer will not use one printer spot for each pixel, but several. So there is no reason to provide as many image pixels as printer spots that the printing device can physically print in one inch--unless the image is not going to be rendered by halftone (or stochastic) screening (i.e.; a 1-bit image).
However I understand that illustrator doesnt work in DPI or PPI since it's vector.
But Illustrator's raster export filters do indeed work in PPI, because they are exporting raster images, which are nothing but pixels. In order to export a raster-based rendering of the vector-based artwork (which is all a raster image is), Illustrator has to write some number of pixels into the raster image file.
Your vector-based path is a mathematical description of a curve. In order to render it as a raster image file, or even to print it on a printer, or even to display it on your computer monitor as you work in Illustrator, it has to be rendered as pixels. In effect, your vector-based paths are "overlaid" onto a grid of pixels. The pixels which land inside the path are turned on. The pixels ouside the path are turned off. This is basically what occurs when a vector path is printed, when a vector path is exported to a raster image, or even on-the-fly while you view your vector paths on your monitor.
That's what vector-based paths are: Mathematical instructions to determine which squares of a raster grid to turn on.
In other words, all vector-based artwork is eventually rasterized; it's just a question of when. The scaleability advantage of vector graphics does not derive from the myth that it does not involve raster-based imaging; it derives from the fact that the rasterization is postponed until output time.
In still other words, all your vector-based artwork is going to be overlaid onto a raster grid, the squares of that grid will be colored accordingly, and that finished raster image is all anyone is ever going to see of your vector-based formulae. It's just that which grid is to be overlaid is left undetermined until the "overlay" is performed.
So when you export your vector-based artwork to a rastter-based image format, that's what you're doing: You're telling Illustrator to overlay the vector paths onto a particular raster-based grid (so many rows, so many columns of pixels, at some scale).
That's the difference between vector-based artwork and raster-based artwork: A raster image is a pre-determined rectangular grid of a fixed number of color values. A vector graphic is a set of mathematically-described shapes which can be overlaid onto any rectangular grid, so that the number of color values is dependent upon the particular grid used, be it the grid of your monitor's pixels, the grid of a printer's spots, or the grid of a raster image file that you export.
Would I have to transfer the small image over to photoshop.
No, you can export directly from Illustrator to any of several common raster formats.
I did try and save a 1 inch by 1 inch logo at 600 PPI, however when I saved the image it was no longer 1 inch by 1 inch. It had increased significantly in size regardless of what file format I saved the image as.
It "had significantly increased in size" where? When viewed in what program?
When this occurs, the raster image is simply not being scaled so that its pixels measure 1/600th of an inch. As explained above, some raster image formats do not record the scaling value. Even if the raster image file does record the intended scaling value, some programs into which you import the raster image will ignore it.
So since you can't really control whether the scaling factor is going to be ignored, to meet the stated requirements (600 PPI when scaled to 1 inch), you simply need to concern yourself with providing the correct number of pixels and it's up to the recipient's software to scale them to the desired measure.
For example, if your vector-based artwork measures 1 inch according to Illustrator's rulers, then export the raster image at 600 PPI. If your vector-baed artwork measures 2 inches according to Illustrator's rulers, then export a raster image at 300 PPI, and you'll be exporting the same number of pixels. You can either do the math, or you can simply export a raster image by specifying the desired number of pixels directly.
But do not forget to consider the question of color-depth. 600 PPI at final rendering scale is not necessary for anything other than a 1-bit image.
If the logo in question consists of nothing but a single solid color:
In Illustrator, scale it to 1 inch.
Do not color it. Use only solid black and white fills and strokes. No grayscale. No graduated fills, strokes.
Export it to a raster image format at 600 pixels (in the measured direction), with a color depth of 1-bit. You can do this by either specifying the nubmer of pixels, or by specifying the scale factor, 600 PPI. Understand, this means using a raster image format which supports 1-bit (for example, TIFF) and which the recipient's program can import. (Most common office productivity programs can import TIFF.)
When the recipient imports it into his invoice program, if it appears enlarged, it just means his program is ignoring the embedded scale factor. He can just scale it to 1" and it will then be 600 PPI.
The above scenario is common. A typical 600 SPI (printer Spots Per Inch) laser printer will turn on one of its printer spots for each black pixel in the image, thereby rendering the image as accurately as it can.
But even if the logo contains no graduated tones, and you apply some color to it (the recipient's logo spec color, for example), then you'll have to export it to a higher color depth in order to include that color. Even if you export it as grayscale, you will still be exporting 8-bit color values for each pixel. In that case, it may look fine on the recipient's monitor, but when he prints it, the printer will have to screen the image in order to render it using halftone dots which, again, are larger than actual printer spots.
The same applies, even if you use only solid black in the design but still export it to a higher color depth (grayscale, RGB, or CMYK) raster image. The recipient's printer is going to recognize the incoming raster image as 8-bits of data per pixel and assume that it has to halftone it; so again, it will not be printing one printer spot for each image pixel.
All this is why Illustrator's so-called "Save For Microsoft Office" feature is really nothing but another interface for its PNG export filter. Many AI users (mostly beginners) want to do the impossible: export their Illustrator drawings to something that ordinary office programs can import, display, and print with fidelity.
But that's really a pipe-dream. Office applications don't understand the kind of vector-based curve math which Illustrator (and all similar programs) generate. So the Save For Office interface resorts to a raster image export.
Office users don't understand the caveats and limitations of CMYK color mode, lossy JPEG compression, or color depth and don't want to have to muck with them. They just want something that they can plop into their word processing, spreadsheet, and presentation programs and have it "look good" on screen and when printed on their low-resolution office inkjets and laser printers.
Too many Illustrator users also don't want to have to think about color depth.
So the Save For Office interface defaults to RGB PNG, turns off transparency (even though PNG supports it) because some specific Microsoft Office apps before a particular version have a problem with it, and does not present the user with much in the way of other PNG-capable options (such as 1-bit grayscale).
Why am I bringing this up? To point out that Adobe's own default and explicit "recommended" export for office-type programs is an 8-bit RGB format which, again, obviates the appropriateness of 600 PPI. In RGB, 300 ppi provides more than enough pixels for the office-using recipient to scale the image to 400% without evident pixelation because even 150 PPI is higher than the screen ruling of most office printers.
So 600 PPI at the actual final on-page scale is sensible for simple office uses like ploping a black logo onto a form like an invoice that is goingto be printed in one ink (or toner) assuming 1-bit color depth; but not otherwise.
JET

Changing dpi changes resolution

Does changing the dpi of an image change the resolution of the image without changing the size?
I have an image that is 300 dpi that I need to enlarge 400% changing the dpi to 75.
I don't think manually changing the dpi to 600 will actually change the clarity of the image when enlarged 400%.
Is that correct?
Thanks
Cindy

First, DPI (dots per inch) is different to PPI (pixels per inch) despite the terms very often being wrongly interchanged. Photoshop works with pixels, not printer output dots.
http://www.google.com/search?q=dpi+v+ppi
Changing resolution with "Resample" enabled will result in changed pixels, but no change in the physical size (inches/cm/etc.) of the document.
Changing resolution with "Resample" disabled will result in unchanged pixels, but there will be a change to the physical size of the document.
You will not increase the clarity of an image by enlarging it.
The best way to learn what happens is to try things and observe the results.

Placing Images and PPI issues

Hello, I am new to InDesign.. I am a digital artist who has only used PS in the past, so I'm used to manipulating images however I like concerning PPI, DPI, and pixels. I am now creating an app for ipad use and created the background images for the pages in PS. Now, I'm placing them into ID. When I do that, no matter what I have the file saved as, it converts the image to a different ppi.
When I created the images in PS, I used the standard ipad resolution (262px) and dimensions. When I created the ID file, I used the standard ipad dimensions and the ppi is obviously much lower, at 72?
Is there a way to set the ID resolution, or do I need to create my documents with only 72ppi? This doesn't seem like it would give the best image viewing available on the ipad.
Thank you!

InDesign respects the original size and resolution of images, as long as you keep them at 100% of the original size. When they are at 100%, the "Actual ppi" and "Effective ppi" fields of the Info panel display the same value. In your specific case, the Info panel needs to show "262" in both fields. If not, it means that the respective image is scaled. To verify its scale, click the image using the Direct Selection Tool (the "white arrow" one) and look at the percentage fields in the Control Panel. (By the way, the resolution of the retina iPads is 264 ppi, not 262.)
When importing an image, the easiest way to assure that it will be placed at 100% is simply clicking the loaded cursor instead of dragging it. Give it a try.
But bear in mind that this "ppi" issue only matters for print publications. For tablet apps, what is important is the number of pixels; the resolution is irrelevant. For retina iPads, you need to use twice the size you use in a standard screen iPad. So, if you want a full-page image in an old iPad, the image dimensions must be 1024 by 768 pixels. If you want the same image in full screen on a retina iPad, create it with 2048 by 1536 pixels. You'll get a better explanation here: http://www.planetquark.com/2012/03/14/132-ppi-72-dpi-264-ppi-what-image-resolution-should- you-use-the-for-new-ipad/#.UhdbsLwWFL8

Why can't I save a re-sized image in the new size and new dpi? This just started happening 2 days ago.

I haven't been here before.
For some crazy reason when I try to save a re-sized image with a different dpi, PS6 indicates I have saved it.
But if I go to re-open the same image, its in a different (but proportional) size and its original dpi.
I also have PS3 and if I open the re-sized image in PS3, it opens in the correct new size and the new dpi!!
What's wrong with my PS6??

Thanks but I don't think you understood the question so I'll be specific.
I took an 8x12 image at 300 dpi (not ppi) and enlarged it to 20x30 at 240 dpi.
I then did a "save as" for this larger size and it seemed to save properly.
I closed the image.
When I re-opened the image in PS6 it opened as 16.667x25 at 300 dpi, not the saved 20x30 at 240 dpi.
That shouldn't happen.
When I opened the same image in PS3 it opened as 20x30 at 240 dpi the way I saved it.
So my question was why isn't PS6 opening the image as it was saved?
I hope this is clearer.
Thanks.

DPI & PIXELS/ INCHES OR CENTIMETERS

Hi guys , I am new to illustrator and photoshop I don't have the DPI on my Illustrator and photoshop I only have Pixels/inches and centimeters, How can I have a good resolution equal to 300 DPI that is required for my project?

It depends on what you mean by "Project". The issue is resolution at your output size using a particular output device. Get your hands on an excellent reference book titled: Adobe's Print Publishing Guide. Output requirements, resolution, document raster setting, etc. are all covered and should be an easy read. Get used to the proper terminology. DPi = output resolution ( i.e., 5080 dpi ). PPi = image resolution ( i.e., 300 ppi @ 100% final size ). Adobe does a fairly decent job illustrating halftone screening and its relationship with "Shades of Gray" formulae. This is difficult for the typical user to get their head around. For instance, the Shades of Gray formula reads like this...
Output Reolution divided by screen ruling > squared + 1 = Shades of Gray ( 256 )
Once you understand the background gymnastics going on in the formula, it becomes easier to understand what resolution will be required for your "Project". Most inkjet printers output using 72 lines per inch stochastic screening. So, most people assume that 144 ppi is only required for output at 100%. There are many many variables involved. There are also consumers who believe offset presses use 150 lies per inch ( referred to screen ruling above ) halftone screens and, therefore, require 300 ppi image resolution ( just multiply the halftone screening 2x ). Another element is output resolution which, if you follow the formula, would need to be 5080 dpi in order to render ( output ) a 150 line screen. Sorry to get so technical. The main point is establishing final output size and to create an image resolution that is appropriate for a particular output scenario. Each "Project" is different, but should be pre-established before the document is produced. That means communicating with whoever is going to output the file before you design the "Project".
So, let's say your "Project" is an 8.5x11" vertical flyer that needs a background image @ 8.75x11.25" vertical ( bleed size ). You talked to the printer and they plan to use a 133lpi screen ruling based on a uncoated sheet. Newr Illustrator applications only require you to set the output resolution in the Print dialogs and give you a selection of low - medium - high which is also the document's raster setting choices. You know that the printer will need an image resolution of 266 ppi based on the lpi output screen ruling ( 133 x 2 = 266 ) at 100%. In brief, document raster res setting shoukld be "High" ( 300ppi ). Note: output resolution is independent and you should not have to set it in Illustrator. Many versions back, you could manually set it in the Document Setup dialogs. May direct-to-plate imaging technologies wil assume a 5080 dpi output resolution at the print vendor's facilities.
Class dismissed.

Export jpeg ppi

Whenever I export a RAW file to jpeg, the resulting ppi is 72 irrespective of what I set in the export dialogue. Further, the constraint to maximum size is disregarded. Exporting to psd format performs as expected. Using LR 1.1 with Vista.

A search on 72dpi might not work, try just dpi.
The dpi setting can be ignored. Only applies if you are actually printing and even then, from what I have read, dpi is calculated, the critical info being file size in pixels and desired print size. PPI would be the more correct term but that would be ignored too since resolution cannot be a factor in screen display of images, only pixel dimensions are used.
In any event it appears to me that LR (and other Adobe products) are confusing the issue by including resolution settings (dpi is definitely wrong since it is strictly a printing term) for images that are being resized for email or any other form of screen display. Only pixel dimensions count for screen display - 800x600, 1600x1200, etc. Monitors do not have variable resolution and they display images in pixel dimensions only - dpi (or ppi) settings are ignored.

DPI or PPI

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