Avoiding the confusion DPI and PPI - they are not the same, a guide for editing images and printing

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Keith Cooper

Keith Cooper

6 ай бұрын

Although sometimes used interchangeably DPI and PPI are not the same thing. A guide for editing images and printing them.
When does it matter - do camera images have a PPI?
The written guide to this is at:
www.northlight-images.co.uk/d...
For a full index of all my videos, see:
www.northlight-images.co.uk/k...
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Пікірлер: 60
@KeithCooper
@KeithCooper 6 ай бұрын
The written guide to this is at: www.northlight-images.co.uk/driver-settings-and-print-detail/
@Stefan-oc9bo
@Stefan-oc9bo 6 ай бұрын
Thank you for this clear explanation. It sometimes surprises me how PPI and DPI are confused. On the other hand, I had the same problem in the beginning, but luckily I know and understand it correctly now. And of course a happy new year for you and your family.
@KeithCooper
@KeithCooper 6 ай бұрын
Glad it was helpful! - And all the best to you!
@charlessweeney2061
@charlessweeney2061 6 ай бұрын
Excellent information, Keith! I always wondered why printers had much higher dots per inch than than the pixels per inch of the image. My mistake was: Thinking a pixel and a dot were the same size! So multiple printer dots are used to print one image pixel. Got it!
@KeithCooper
@KeithCooper 6 ай бұрын
Thanks - I know some thing it doesn't really matter, but I've seen the confusion cause problems for people looking to make prints....
@ColzoArt
@ColzoArt 6 ай бұрын
Happy new year! This is such a helpful video again, Keith! Shall be sharing this. With some digital painter friends as the same principles apply in terms of DPI / PPI
@KeithCooper
@KeithCooper 6 ай бұрын
Happy new year! - glad it was of interest
@giuseppevella4368
@giuseppevella4368 6 ай бұрын
Bravo Keith e Buon Anno!
@KeithCooper
@KeithCooper 6 ай бұрын
Thanks, and to you too!
@fransschmitz2628
@fransschmitz2628 2 ай бұрын
great explanation! Thx Keith!
@KeithCooper
@KeithCooper 2 ай бұрын
Thanks!
@lynsmith1096
@lynsmith1096 6 ай бұрын
Good video Keith and Happy New Year.
@KeithCooper
@KeithCooper 6 ай бұрын
Thanks!
@randyblack2124
@randyblack2124 6 ай бұрын
Thanks Keith, very helpfull. I recently bought a P5000 and am very happy with the color and B & W that I'm getting from it. Now I am trying to learn about proper sharpening and upscaling. This shoud be a great place to start. Thanks again
@KeithCooper
@KeithCooper 6 ай бұрын
Thanks - I've several videos looking at making large prints which might be of interest? See also www.northlight-images.co.uk/printing-low-megapixel-images/
@cnicolo
@cnicolo 6 ай бұрын
Thank you Keith very interesting. Happy new year 🎊
@KeithCooper
@KeithCooper 6 ай бұрын
Thanks - and to you too
@tmartin6717
@tmartin6717 6 ай бұрын
Thanks, your written guide was most helpful as I just purchased an Epson 8550. I also appreciate your scientific approach as you investigate camera and printer performance details.
@KeithCooper
@KeithCooper 6 ай бұрын
Thanks - glad it's of help
@frstesiste7670
@frstesiste7670 6 ай бұрын
Really good point IMO to try to determine the knowledge level of people to be able to provide help. I run into the problem all the time, both with photo and computers that someone don't understand what they are asking.
@KeithCooper
@KeithCooper 6 ай бұрын
I have a series of 'non-specific' questions which help inform me without [I hope] any criticism of the person asking ;-)
@henkhenk4357
@henkhenk4357 6 ай бұрын
Thank you !
@KeithCooper
@KeithCooper 6 ай бұрын
Glad it was of interest!
@mb-moose
@mb-moose 6 ай бұрын
I'm looking forward to the piano video series😂. Happy new year
@KeithCooper
@KeithCooper 6 ай бұрын
Thanks ... However, a cooking one is far more likely ;-) Does remind me that I need to book a tuning!
@jpdj2715
@jpdj2715 6 ай бұрын
Pixels for resolution, and dots of ink for gradation. I became consciously aware of that late in the digital day. There must be an optimisation problem in there, though, that Keith you are more aware of than I am. And you may have figured it out already. If we leave the "per inch" out, I would distinguish 3 scenarios in the frame of an image: (1) we have more pixels than dots, (2) they are equal, (3) we have more dots than pixels. As you say, the printer will place colours over each other in order to mix towards the colour described in the pixel. Between pixels and dots at some point we have an alignment issue between pixels and dots (but at a level probably too small for the naked eye). Also, as dots can be placed over each other, we need to distinguish two things: the amount of dot-coordinates versus the amount of dots of ink placed on those dot coordinates. If a dot in location [x,y] needs only precisely light grey, then that one dot location gets one squirt of light grey. But a dot coordinate that must become greyish yellow may get a grey dot with a yellow dot over it. In that sense, DPI may be "dot coordinates" per inch. I know Keith, you know all this better than I do - this is communication: you say something (video) to me, I say a similar thing back in my words and we think we understand each other (or not). For example, I am inclined to avoid (1), but in smaller prints that's impossible. The question here is, what software, where, makes the calculations and image analysis needed because of the mismatch. Does it happen in the printer layer? In the printer's print engine? There must be some image processing involved. And then we should wonder, what impact this has on the image's quality (detail sharpness, gradation, absence of added digital artefacts). I don't have the answer. It may be trivial.
@KeithCooper
@KeithCooper 6 ай бұрын
Yes - actual ink dots are utterly irrelevant in most instances - 'dpi' settings are just numbers set by printer head/transport/ink design. Even this means vastly less than it once did as dithering and ink mix involves increasingly more complex maths and can involve using adjacent pixels to give 'hints' in dot placement. This aspect will improve with hardware and software developments. Take variable dot sizes [and shapes] and different approaches to UCR/GCR for example. This is a function spread through driver, firmware and hardware, so once again defining specific numbers is more to give relative numbers than have any actual meaning. Some people like numbers - even when you tell them they are meaningless ;-) Try this PDF for a little 'light background reading' on the subject ;-) :-) library.imaging.org/ei/articles/35/15/COLOR-208 Your question is addressed rather more in the written article - you'll note that the article has links for similar tests on other printers. This video comes with a much stronger 'READ THE WRITTEN ARTICLE' notice than many ;-) :-) Just one other thing to consider... the algorithms controlling ink dot placement are highly proprietary. So perhaps just as well the details matter very little for actual high quality printing? My approach is to look closely at prints - with a known image. This guides my practical choices. Knowing I've done this testing allows me to remove it from the 'something to be concerned about' list. Any attempted calculations [IMHO] might be of curiosity/practice to those with the maths background, but of precious little actual relevance to making great prints ;-)
@jpdj2715
@jpdj2715 6 ай бұрын
@@KeithCooper - sincere thanks, Keith
@shallowman231
@shallowman231 5 ай бұрын
Hello keith what printer would you suggest for casual photos,i want to try raw editing thanks.
@KeithCooper
@KeithCooper 5 ай бұрын
Epson P20000 www.northlight-images.co.uk/epson-sc-p20000-printer-review/ You didn't specify size or budget ;-) ET-8550 is popular, see www.northlight-images.co.uk/epson-et-8550-printer-review/
@shallowman231
@shallowman231 5 ай бұрын
Oh sorry keith yes i have been watching your reviews on the et8550 i will have a look at them thank you for your quick reply.@@KeithCooper
@user-dk5xy1dr6u
@user-dk5xy1dr6u 4 ай бұрын
Hi. If printing an image that is 6496 px x 4640px for example on 5x7 paper that would be 928 ppi. Thats more then needed and if it is more than my printer can handle is it better to downsize it in photoshop or just let the printer software downsize it. I have canon pro 200 and canon professional print and layout.. I usually send all my pixels from photoshop to ppl and do the settings there regardless of if the resolution box in the image size box says if 72 or something else. .the image has its pixels no matter what. I usually upscale in some photo software Am i doing it wrong?
@KeithCooper
@KeithCooper 4 ай бұрын
My detailed tests suggest that here is nothing wrong with sending more resolution than needed See here for a look at what I do: www.northlight-images.co.uk/best-canon-pro-200-driver-settings/
@user-dk5xy1dr6u
@user-dk5xy1dr6u 4 ай бұрын
@@KeithCooper Thanks for the answer. I have learnd a lot from your articels and videos. My understanding is that in the example with the fenceposts showing in 600 ppi and not in the 300 ppi the printer had little to do with it they got lost in the downsizing of the image . Am I understanding it right.
@KeithCooper
@KeithCooper 4 ай бұрын
Yes - the lower res image doesn't have the detail. The higher res image does, so hence it's worth sending more detail than 300. The article addresses the question "Is it a waste of time sending more detail to the printer" and the answer to that is no, it is not a waste of time. So, to your original question - it is not 'more than the printer can handle'
@thomaseriksson6256
@thomaseriksson6256 6 ай бұрын
Thank you. I recognize parts of this video from your earlier videos. There will be allot of work for me when I start printing. I have 12Mpix and 16 Mpix that I use for wildlife, 36 Mpix and 45 Mpix, that I use for woodland, cameras. I aim to print A2 and I think I need some good AI program for noise reducing, Topaz Labs DeNoise AI, and a good pixel upscaling , Gpixel AI, program from 12 Mpix to 34 Mpix for A2 print.
@KeithCooper
@KeithCooper 6 ай бұрын
Glad it was of interest - yes, I've addressed aspects of this in several articles and videos, but I do get asked quite often.
@thomaseriksson6256
@thomaseriksson6256 6 ай бұрын
@@KeithCooper I need to read your articles
@davidmilisock5200
@davidmilisock5200 6 ай бұрын
You will be best served by taking a high pixel count image, assign it several different resolutions and physical sizes, saving each version as its own file, then test print it to your different mediums. I found the some media setting allowed me to use 100 DPI (per physical inch) others required 200 DPI. This can save you print time when your media works with lower resolution images.
@thomaseriksson6256
@thomaseriksson6256 6 ай бұрын
@@davidmilisock5200 Thank you for the feedback. I Try that when I get a printer in 2-3 year. I currently learning to use the D800E and then the D850. I will try a printer serice this year.
@davidmilisock5200
@davidmilisock5200 6 ай бұрын
@@thomaseriksson6256 most output providers today are rather poor in their communications. You'll need to ask them what file formats they prefer, JPG is not bad but once you save your work as JPG do not reopen the JPG file edit and save, the quality will deteriorate. You'll also need to ask what color space they prefer, I will not use a provider who uses sRGB. You'll also need to know what resolution is required (at print size)
@dunnymonster
@dunnymonster 6 ай бұрын
Indeed Keith, DPI/PPI often gets used interchangeably as if both are essentially describing the same thing. You often hear people say things like, oh the maximum you can print " X " resolution image is 13" x 19" ( or whatever ) just because they believe the amount of pixels per inch must equal the number of dots per inch when printing. Of course you can print a 2MP image 20ft x 14ft should you wish all be it the amount of translational pixel data in the image itself will limit how close you can view the final result. The printer driver cannot create data that wasn't there in the first place no matter how many dots it lays down per inch. Here is where viewing distance is making the defining difference. There is technically no reason you couldn't print a 20ft billboard at 300dpi if you so wished but what would be the point if you can achieve the same visual outcome printing at vastly less, say 20dpi given it will be viewed from 30ft away anyway. I do agree however that as it stands today there is no reason why you should set a specific dpi at all. Just send the maximum image resolution to the printer and let it's driver calculate the DPI based on its own capability. If it chooses 1500dpi then that's fine whether the final print is being viewed very close or far away, I don't think you can have " too many " dots per inch ultimately, unless doing so uses vastly more ink or takes so long to print that it has a negative impact on workflow. This is not to suggest that there shouldn't be some level of consideration when choosing a specific dpi when printing. For example I just leave mine set to 300dpi for everything from 4 x 6" prints to much larger 13" x 19" prints and get satisfactory results. If I were printing vastly larger knowing my prints would be viewed much further away I might be inclined to reduce the DPI but I generally stick to 300dpi as a general rule. I've let my printer choose the DPI of some of my small 4 x 6 prints and it often chooses a crazy high dpi of 1000+ depending on the pixel resolution of my image. I personally can't see any real world difference between a 4 x 6 ( 45MP image ) print at 1000dpi over the same print at 300dpi anyway even close up! This is why I set my print output to 300dpi and leave it. I'd suggest others do the same and stop fretting over the whole dpi/ppi thing. 😋
@KeithCooper
@KeithCooper 6 ай бұрын
Nope - I've seen far too many problems and issues to go along with that. Using dpi for everything is simply wrong... ;-)
@dunnymonster
@dunnymonster 6 ай бұрын
@@KeithCooper I print out of Lightroom. There is a box in the print dialog which you can put a tick in which allows you to specify a dpi setting ( in my case set to 300dpi ). Would you suggest I untick this box and just send the file to the print driver for it to work out the dpi instead? I have experimented with this before and found no visual improvement ( maybe I'd need a loupe to notice ) on my actual prints but maybe it's because I don't print super huge?
@KeithCooper
@KeithCooper 6 ай бұрын
The issue is that the lightroom setting is setting PPI not dpi - dpi is set by the printer driver quality level [for inkjet] However, I've not tested LR printing for some time, so couldn't say what is optimal in this. I'm hoping to cover this when I've all my new editing systems set up. The sending of higher PPI data to a printer driver is what's discussed in the linked article and depends on the actual printer used. This video is primarily about the use of the PPI and DPI terminology ;-) I still get it wrong sometimes...
@20centurymodern
@20centurymodern 6 ай бұрын
The PPI doesnt matter when viewing on screen, you can make it 1 or a million PPI and the photo on screen will he the same. How is a photo and its relative size to screen measured? Is rhis measured on terms like 1080p or 4k?
@KeithCooper
@KeithCooper 6 ай бұрын
Depends on the editor and how it scales the image Screens have a native ppi However images are usually displayed as a direct scaling between image pixels and screen pixels, so the physical size of an image depends on the size of the screen as well as the number of pixels
@20centurymodern
@20centurymodern 6 ай бұрын
@@KeithCooper ah ok…so the ppi has nothing to do with how big or small it appears on a screen - it’s still related to the actual megapixel dimensions of the photograph?
@KeithCooper
@KeithCooper 6 ай бұрын
Yes, for screens.
@brightboxstudio
@brightboxstudio 6 ай бұрын
The math is rather straightforward. If you have a 4K screen, it’s probably 3840 x 2160 px. Now all you have to do is look at the width and height of your image in pixels. If your image is 1920 x 1080 px, then naturally, it will occupy half the width and half the height of that display. Because the image’s 1920 px is half of the display’s 3840 px. Now, what ppi is that on screen? If viewed at 1:1 magnification (one image pixel to one display pixel), then the image ppi equals the display dpi. So, what is the display dpi? Just use the usual formula: Take the width of the display in pixels, divide it by the width in inches, and you will naturally get pixels (dots) per inch. The typical dpi value of a 27” 4K display is around 163 ppi, depending on the actual width of the display area in inches. Keep in mind that this is all relative to the magnification of the image. If you magnify the image to 200%, then the resolution of the image preview drops by half (same number of pixels now covering twice the original distance), so in the above example the image on screen becomes roughly 81 ppi.
@DCockey
@DCockey 6 ай бұрын
The prevelance of "PPI" being used when there is no associated physical size is both amusing and confusing. What is the meaning of PPI for an image which will be projected to an arbitrary, or shown on monitors/screens of assorted sizes? Of course it is meaningless. The overall number of pixels in each direction is what matters in those instances. The confusion appears to be embeded. An Adobe web page about PPI says: "Does higher PPI mean better quality? Yes, a higher PPI generally correlates with better quality, as the image will have a higher pixel density. However, you’ll also need to take into account the full number of pixels in the image to understand its resolution entirely." Agghhhh! When I export/save a file without resizing as a JPEG, TIFF, etc the PPI I select has no influence on the resolution. At least the last sentence is a weak attempt to clear thing up. On the other hand I've discussed this topic with folks who cannot comprehend the idea of resolution without an associated physical size.
@KeithCooper
@KeithCooper 6 ай бұрын
Yes - it's a regular source of confusion The other area I've seen commonly misunderstood is 'aspect ratio...
@cameraprepper7938
@cameraprepper7938 6 ай бұрын
So to easier understand, dpi is for an area and ppi is for a line.
@KeithCooper
@KeithCooper 6 ай бұрын
No, not really, both are one dimensional. Areas would be dots per square inch and pixels per square inch Pixels are usually square but not necessarily so. Dots are dots of whatever shape they are Sometimes horizontal resolution may not be the same as vertical, but the DPI and PPI are still linear measures
@cameraprepper7938
@cameraprepper7938 6 ай бұрын
@@KeithCooper So dpi is the analog count printed on paper ? and the ppi the digital count on a screen ?
@KeithCooper
@KeithCooper 6 ай бұрын
Only in inkjet printing. It is a whole number, so there is no 'analogue' about it really... DPI tells you nothing of the shape or size of the dot [they can overlap in printing]. Dots could, for example, apply to screens, where each pixel could be made of three coloured dots. The uncertainty is loved by marketing departments who can refer to viewfinders and camera screens by their number of dots - bigger numbers must be better when selling stuff ;-) Have a read of the article - I've lots of specific examples there
@cameraprepper7938
@cameraprepper7938 6 ай бұрын
@@KeithCooper No, it will confuse more than enlightening in a very short and simple way.
@KeithCooper
@KeithCooper 6 ай бұрын
I cannot help much more then - I spend vastly more time writing an article like that than any video. Short, simple and wrong is too easy an outcome for a topic like this...
@davidmilisock5200
@davidmilisock5200 6 ай бұрын
This is the only time I've heard the truth in a video about images, they have no physical dimensions until you assign a resolution. It's just simple! The other BS you hear is that resolution does not matter on the web. Of course resolution matters, some displays are 96 DPI and others are 200 DPI so the same pixel count displays on screens with these specifications at radically different physical sizes.
@KeithCooper
@KeithCooper 6 ай бұрын
Thanks!
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