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).

Similar Messages

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.

Halftones and dpi for screen printing

I am creating a halftone effect on a black and white picture for screen printing, using photoshop. I know about where to place my LPI, however, Im not sure where I should put my DPI. If anyone can help with some advice, I would appreciate it. I was also curious if i should some how put it illustrator, and vectorize it, or just print transparencies straight from photoshop.
Thanks

There's no need to go to Illustrator with the photo. You can print from Photoshop using the 1-bit halftone. The thing that you have to keep in mind is not so much DPI ( which is an output resolution ), but the actual screen mesh used for the actual screen printing. You also have to figure "screen angles" into the matrix because the screen angles are affected by not only the grament material, but the screen mesh, too. So, I would recommend contacting the printer and finding out what screen frequency ( LPi / lines per inch ) will work best on the type of garment you are planning to print-on and ask the printer what mesh they plan to use for your job. I've seen 35 LPi halftones; I've also seen 65 LPi halftones. The finer the screen mesh, the higher the LPi. Tell the printer you have a 2-color job printing halftones and you need to know what LPi and what angles to use for color #1, and color #2. Then, you can input that information into the separation halftone files in Photoshop. Remember to discuss the garment type ( thread count ) and the mesh of the screen. If the printer is good and knows what they are doing, they will give you everything you need to know. If they do not, they'll refuse the job.

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

Is there a formula to show the ratio of ppi to dpi terminology?

I am preparing activity pages for a Pictorial Directory. Adobe Photoshop Elements only gives me the ppi. The company is asking for all pages to be 300 dpi.
They requested all pages to be 8.75 x 11.25. Does that automatically translate into 300 dpi?

Yes, do what they mean and not what they say . In fact a very small percentage of people saying dpi actually mean dpi, most mean ppi.
PPI is pixels per inch. Pixel stands for the smallest Picture Element. Pixels exist in digital files and pixels is also used for describing resolution of LCD displays where it means the smallest LCD picture elements (cells) of the screens. Pixels also can be used for the number of pixels camera sensors can produce.
DPI is dots per inch and is mostly used for smallest ink drop (dot) a printer is set to print. DPI can also be used for the samples of scanners and for describing the CRT monitors' resolution because the technology used for CRT monitors is more like printing dots than using fixed size cells as is the case with LCD screens, although when LCDs appeared on the market people started to use the term pixels for CRTs and some people used dots meaning LCD pixels and probably from there also meaning the same for pixels in digital files.

How do i set dpi for picture printing in photoshop elements 4

how do i set dpi for pictures to print using photoshop elements 4 . . . thank you. i do not mean resolution but the dpi asnd if i can't then what version would be able to do it . . .

You can set that under Image>Resize>Image Size and uncheck Resample Image and enter the Resolution
http://planetphotoshop.com/explaining-image-resolution-and-view-print-size.html
http://graphicssoft.about.com/od/photoshop/l/bllps502x6.htm

DPI reduced when printing a picture

In Photoshop Elements 9 when I print a 4x6 picture it redcues the DPI due to photo size. It also is reducing the clarity of the picture. How do I get it not do this?

Please provide more information:
Go to Image>resize>image size
Post W & H in inches, resolution in px/in
Is this a picture from your camera or from the web?
Are you telling the printer in a dialog to crop or to resize?
Are you printing from Editor or from Organizer?
If printing from Editor (preferred way), what are the settings in the print dialog?

Wide-format printer discussion group?

Hi,
I know this is the Photoshop Forum and I'm hoping this group can refer me to a discussion of wide-format printers either here, or another site.
I'm looking at purchasing the Canon Imageprograf ipf5100 or 6100. I've read a lot or reviews of the printers in this category. I'm looking for the thoughts of experienced users, what the day to day issues are, and are they happy with the Canon product. Do they wish they had gotten Epson or HP?
Thanks in advance.
Craig Cheatham

I have a Canon iPF9000. You couldn't get me to go back to Epson. The Canons just work and with the PS plugin for printing you don't have to worry about all the Apple/Adobe Printer/Driver silliness. The plugin lets you print 60,000 x 60,000 pixels.
You might want to consider the iPF 6200 as that I believe has the hard drive in it. After having a printer with a HD in it I would never go back to one that doesn't.
If your also printing from Indesign there is a "Fast Graphic Process" selection that uses a different path/process than what Apple uses and does not introduce the monitor profile into the print flow.

Help! My 300 dpi images are printing low quality!

I've purchased print-ready images (300 dpi) from an extremely well-known stockphoto website to use in a brochure I'm creating. On the brochure cover (which is 8.5" x 5.5"), I have placed 14 of these print-ready images. (FYI-all of these print-ready images are pictures of people smiling while doing various activities.)
As you can imagine, I have had to reduce the scale of each of these print-ready images to approximately 1" x 0.7" to fit on the page. The layout itself looks really nice, but when I attempt to create a .pdf using the "Print Booklet" option, all of my images look horrible! I've also attempted to create a .pdf using the "Export" function and selecting "Press Quality" and my images are slightly better, but still look horrible!
I have also re-scaled the images in Photoshop (leaving them at 300 dpi) and created a .tiff file, but no matter what I do (and I've been wrestling with this single problem for DAYS), I can't get these images to actually appear clearly on a printed page. When I forwarded my brochure (in .indd, .pdf, and .eps formats) to a professional printing company, they came back to me telling me to use print-ready images.
I've been working with print-ready images for well over a year and have sent multiple jobs to professional printers and this is the first time I've ever had a problem with images looking like they aren't print-ready. Could it be that you can only reduce the size of an image so much? Has anybody had this problem before???
Thanks in advance for your input!

Thanks for the comments thus far! I forgot to mention that all of my images are .jpegs (300dpi).
I've reviewed my "Print Booklet" settings and under my "Images- Send Data," I have "All" selected as opposed to "Optimized Subsampling." My Effective Resolution is also set at 300 dpi.
I'm still working, and am open to more suggestions.
Thanks!

Ebook cover ppi and dpi help please

Hello,
I am working on an ebook cover. It seems that I have come across different numbers for recommended sizes. When using Photoshop Elements, I have the choiced of pixels or inches. Then ppi.
I created a cover at 300 ppi. I have read that it should be 72 dpi. Are the two numbers related? How do I make an image at 72 dpi in Photoshop Elements?
I am new to all of this.
Thank you

Use Image --> Resize --> Image Size
Type 72 into the resolution box.

300 DPI images for print?

Hi All,
I'd like to create a promotional leaflet for my activity, where I want to place the picture of the discounted products I'm selling.
what is the minimum resolution I need to (professionally) print them? I understand that images found on the internet can't be used (as they are 72dpi and they would appear pixelated etc.)
I've tried to look at the websites of the companies that produce those products, but couldn't find any high resolution one.
Any suggestions (apart from asking them directly for images, that would take a lot of time?)
thanks,
Patrick

easily controllable color management
True, but in my opion spot 'colour' should not be supported as it it in fact not a colour specification in the first place. Typically, a spot 'colour' is represented as a name callout in the page description and the in separations process the CTP plane/imagesetter plate is rendered with whatever density is defined, but there is no concept of the colour as determined in a device independent colour model.
Colors may or may not be in cmyk.
You mean colourants, not colours. The colourants will be as in the file placed into Pages, or as defined the (limited) colourant controls in Pages. The colours will be as defined in the ICC source colour space embedded in files placed into Pages, and if none is embedded then as assigned by the system level service for the placed colourant model.
tests showed too much ink being laid down
The ink limiting is independent of system level services and is solely dependent on the TRCs and LUTs in the ICC destination colour space either embedded as PDF/X-3 OutputIntent or selected in the driver-level interface. The ink limiting that is part and parcel of the ICC PRTR Printer profile has asymmetric ink limiting internally (e.g. a higher ink limit for Relative Colourimetric than for Perceptual or Saturation) or if the driver is set up to use the wrong ICC PRTR Printer profile as in using a profile with a high ink limit for a coated substrate when in fact an uncoated substrate that should have a low ink limit is loaded into the printing system.
If you use the big commercial applications like Quark XPress and Adobe's Creative Suite they do not use Apple's print engine and completely bypass the issue.
Precisely the same problems with ink limiting will occur in Adobe InDesign (any version) and QuarkXPress (any version) if the user selects the incorrect ICC PRTR Printer profile for the current configuration of the printing system, or if the user selects a correct ICC PRTR Printer profile that internally has a problem such as asymmetric ink limiting even if it should have symmetric ink limiting across the internal tables.
Otherwise, it is correct that Adobe InDesign and QuarkXPress have commands to control transparency flattening for PDF/X-3 such that spline illustration, spline composition, and pixel photography can be interactively processed. The system level service in Apple Mac OS X is a meat cleaver and not a surgeon's scalpel, but in the midterm and longterm transparency flattening should be transferred from the designer to the RIP operator who is the one who controls the configuration of the rasterisation rendering. However, the RIP developers will then compete as to the 'application intelligence' for transparency flattening, and since they will do it differently there will for the indefinite future always be an option to control flattening as well at the designer's desk as at the RIP, with complications consequent on either scenario.
/hh
/hh

Saving to 300 dpi but when I reopen it is back to 240 dpi

I am doing this in image size but the changes are not staying when I reopen. What am I doing wrong?
Thank you
Melissa

Hi Melissa.
In the beginning, there are pixels. Period. Not pixels per anything. The number of pixels you start with is determined by your camera. If my camera sensor array is 3000 pixels by 2000 pixels, it is a 6 megapixel camera. The resolution, or pixels per inch, is an arbitrary assignment of those pixels when rendered.
Doing simple math, our 6 mp image will display at 41.66 inches by 27.77 inches on a 72 ppi computer image screen. If you assign it 300 ppi for printing, it will size out at 10x6.66 inches. But the point is, image size is a mathematical calculation base strictly on the number of pixels and the assigned ppi. Assuming you have unchecked Resample Image, which is highly recommended. In general, you don't want to resample your image. You don't want to create new pixels or throw away pixels, which is what resampling does. Unless your printer has indicated otherwise, 300 ppi is a suitable output resolution for most print work.
This is where dpi or dots per inch comes in. It is a printer specification. The printer will convert the ppi to dpi, according to its own logic. And as Kurt said, this is highly variable. But the 300 ppi rule of thumb is based on the way this conversion is made. 300 ppi converts gracefully from ppi to dpi for most print situations. This would include your clients printing from the CD to their own home printer.
Surprisingly, many pro printers aren't clear about the relationship between total pixels, ppi, and dpi. They aren't photographers. So they ask for a print specification, dpi. Not realizing all you can specify is the ppi.
Below, Resample Image is unchecked, as recommended. Changes made in the Document Size box will not change anything in the Pixel Dimensions box. This is good. Any changes made in the Document Size box does not change pixels. It assigns them a dimension. Changes made here will not change the way the image appears at Actual Pixels on your screen, because they are displayed at screen resolution (usually 72 or 96) no matter what ppi you have assigned. Changes in the Document Size box are nothing more than a set of calculations, and have no effect on the image at all. Until it it printed. Then the printer will take these calculations use them to do it's own, converting the assigned ppi to its native dpi. Or something like that.
You are not the first one to be confused by this. And may be more confused after my explanation. But there's tons of info about this on the web. Some of it makes sense. Good luck.
Peace,
Lee

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

PPI/DPI setting... why do you want it?

I occasionally see requests for a PPI/DPI setting in Aperture and I just noticed a request for the same in the discussion about Adobe's Lightroom. I've posted comments about why a PPI/DPI setting is not needed, so I'm curious to see if maybe I'm missing something and I'd like to hear some feedback on the subject to help educate myself and others along the way. If my examples aren't exactly clear and seem confusing, perhaps someone else can explain what I'm saying in a much more elegant and easier understood way.
Here's a copy of my original post about the subject. I've added a few other examples for further clarification on pixel dimensions in relationship to output.
"An output ppi/dpi setting is not necessary and not relevant and here's why...
Remember, were talking about pixels here, not inches. Pixel dimensions are all that matter when it comes to sizes in digital photography.
So when you export an file from Aperture and want something different from the built-in presets, choose "Edit" from the "Export Preset" pop-up in the Export dialog box. You can then add your own settings based upon the output pixel dimensions you would like to have.
For instance, if you need an 8 x 10 inch image, then take whatever ppi/dpi you would like and times it by those dimensions. A common standard for the web is 72ppi, so your pixel dimensions for an 8 x 10 inch image will be 576 pixels x 720 pixels. A common standard for printing is 300dpi, so then an 8 x 10 inch image will need to be 2400 pixels x 3000 pixels.
Hence, say you have a 2400 pixel x 3000 pixel file, it would equal...
- 8 x 10 inches @ 300 ppi
- 33.333 x 41.667 inches @ 72ppi
- 4 x 5 inches @ 600ppi
- 10 x 12.5 inches @ 240ppi
- 2400 x 3000 inches @ 1ppi
All the above listed dimensions will give you the exact same perfect 8 x 10 inch print from a 300dpi printer. In fact, whatever the dpi of the printer, each of the above listed dimensions will print the same size on the same printer.
Say you gave your favorite printer a file that another image editing application (Photoshop perhaps) says is 33.333 x 41.667 inches @ 72dpi or any of the other combinations I listed above. Well most printers are set to print at 300dpi, so it would output perfectly as an 8 x 10 inch print. If the printer was set to print at 360dpi, then you would have a perfect 6.667 x 8.333 inch print.
Again, if you need an 8 x 10 inch print and the printer prints at 300dpi, then you need a 2400 x 3000 pixel file, if you need a 16 x 20 inch print, and the printer prints at 300dpi, then you need a 4800 x 6000 pixel file. If the printer prints a 240dpi, then an 8 x 10 inch print would need to be 1920 pixels x 2400 pixels and a 16 x 20 inch print would need to be 3840 pixels x 4800 pixels.
So, you see, it doesn't matter what you ppi/dpi is, it can be anything you want it to be. The only thing you need to know is what you want your pixel dimensions to be and choose those based upon what your output device is."
-Robert
PowerMac G5 Quad 2.5Ghz Mac OS X (10.4.3) 4.5GB RAM, Nvidia 7800 GT, 600GB RAID

Many of my clients have come to expect me to ftp
their images cropped, sized and sharpened for final
reproduction. They say they get much better results
when I handle all of that. I'm billing by the hour
for Photoshop type work, so it has become a profit
center, and I find that when left to the printer to
sharpen files, and oft times even the designer, they
do not do such a great job.
So, the ability to export at a given size and ppi is
a feature that does not seem at all unreasonable.
Telling my clients that their requests for files at
300ppi are unreasonable is unreasonable. It is not
befitting of a "professional" program to ask us
constantly to do workarounds for such commonly
expected capabilities. But it is, like so many
other "we know best" features, the Aperture way.
David,
I completely understand your point and I really do believe that it would be very simple to add a function like this to both Aperture and Lightroom. It's not like such a common setting is a complete mystery to software developers or anyone associated with the commercial arts industry. So, in light of the fact that Adobe, the king of the commercial art software industry leaves a simple common function such as this out of their application also, one has to ask, why?
I really don't believe for one second that Apple just dropped the ball and didn't include this function just because some believe they rushed a product to market. That just doesn't make any sense. How could you not include what is considered to be such an important function by so many out of an application. Nope, I don't buy it, I truly believe it's not include it on purpose.
So again, I ask why?
I keep having to rethink about what is just "photographic". Remove myself from the business of running my studio. Forget about what a photographer needs in order to run their business, I myself use Photoshop, Bridge, InDesign, Illustrator, GoLive, Quark, QuickBooks, many times a week if not everyday. I need all these things and much more in order to conduct business, but business isn't "photographic". Business is business.
Photoshop is an absolutely wonderful application, but it doesn't do "photography" very well. This is where both Aperture and Lightroom come in. They both ask, what is "photographic" and then only do that.
And again, I keep coming back to the fact that the ability to control DPI/PPI settings is a pre-press function only, it's not a photographic function, never has been and never will be. It maybe a common function that a photography studio may need, but it has absolutely nothing to do with photography. It's strictly pre-press.
With both these new products that Apple and Adobe have offered the photographer, I think they're really trying to drive home the point that they want us "Photographers" to really re-think how we've done things in the digital realm all these past years. They want to help us be "Photographers" not just businesspersons that need to run a multi-function commercial art business.
-Robert

How can I view resolution in DPI and not PPI?

Hi all,
Under Bridge>view content as list, I got a column of Resolution but the mesurement are ppi and not dpi and i need to see the dpi.
Anyone knows where can i set it?
thanks..
shlomit

Shlomit,
Strictly speaking, images do not have dpi (ever), only ppi. Images are made of pixels, not dots.
Dpi refers to prints.
However, in everyday use, the terms are loosely used interchangeably. They work out to exactly the same thing (same numbers), but ppi is the correct terminlogy.
See: http://www.scantips.com/basics01.html
DPI, PPI, SPI - What's in a name?
Printer ink dots and image pixels are very different concepts, but both use the term dpi in their own way (dots per inch).
Inkjet printer dpi ratings refer to printer ink dots (the four colors of ink), which is NOT AT ALL the same thing as image pixels. These are such different concepts that some people think we should reserve the term dpi for those inkjet ink dots, and reserve use of ppi only for image pixels. Not a bad plan, except that this view fails to recognize real world usage.
We may hear scanning resolution called spi (Samples Per Inch), and that is indeed what it is. We often hear image resolution called ppi (Pixels Per Inch), and that is indeed what it is. The spi and ppi terms are correct. But historical and common usage has always said dpi for image resolution, meaning pixels per inch, and fully interchangeable with ppi. Pixels are conceptually a kind of colored dot too, and resolution has always been called dpi, for years before we had inkjet printers. Dpi is just jargon perhaps, but it is a fact of life. Scanners and scanner ratings say dpi too, meaning pixels per inch (see dialog pictures here, here, here, and here). I habitually always say dpi myself, but I did try to switch to ppi in the book version.
We may use the term of our own preference, but we need to understand it both ways. Some photo editor programs have switched to saying ppi now, which has much to be said for it. But others have not switched, so insisting on conformity for others to only say ppi will necessarily encounter much frustration, because the real world simply isn't that way, and obviously is not ready to switch yet.
My point here is that we must understand it both ways, because we will see it both ways, often, in the real world.
It's easy, not a problem - the idea of printing digital images is always about pixels per inch, so when the context pertains to images instead of printers, all of these terms, spi, ppi, and dpi, are exactly the same equivalent concept - they all mean pixels per inch.
There is no problem understanding any use of dpi if you know the context. It always means the only thing it can possibly mean. If the context pertains to images or printing pixels, dpi means "pixels per inch". If the context pertains to inkjet printer ratings, dpi means "ink dots per inch". There is no other meaning possible. This should be clear and no big deal - the English language is full of multiple context definitions.

PPI VS. DPI in verbal printing discussion

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