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Beginner how to get A high DPI
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Ignore the DPI setting on the file - it has no meaning, value or use. It can only confuse you and will never help you. A file that says it's 72dpi will print at 300dpi at one prints size, and a file that says its 300dpi will print at 72dpi at another print size. Ignore the dpi value in the file properties.
If you want to print at 6"x4" you need a file 1800x1200 pixels (6" x 300dpi - 1800 pixels), for 12"x8" you need 3600x2400 pixels, etc. Look at the pixel dimensions of the image, not the dpi value.
If you want to print at 6"x4" you need a file 1800x1200 pixels (6" x 300dpi - 1800 pixels), for 12"x8" you need 3600x2400 pixels, etc. Look at the pixel dimensions of the image, not the dpi value.
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Either your camera or an image editor is setting the DPI filed to 72dpi, a common default. That parameter in the EXIF data is taken seriously by some printing software, but generally speaking is just an advisory parameter of no significance. Note that it's DPI, dots per inch, most definitely not PPI, picked per inch, which some confuse it with. Printers make up colours from their ink colours not by mixing them but by placing a cluster of dots of their ink colours so close together that the eye mixes them. For example, a blue dot and yellow dot in close proximity looks green. So DPI is actually much larger than PPI, and depends on the technology of the specific model of printer,how many inks it has, how large a pixle of mixed dots is, what size it's dots are,etc..
My camera puts 72 DPI into my image file EXIF data. Sometimes a customer or printer complains that my large high resolution 24MP image isn't large and detailed enough and requests a 300dpi high resolution version. I don't bother arguing with them. I just edit the file I sent them to contain 300 DPI in the EXIF data and give them back exactly the same file. Makes them happy and saves argument.
To change your DPI you simply need to change that field in your JPEG image EXIF data. If you're lucky your editor will have an option allowing you to do that. If not, you'll have to use another editor which does, or one of the utilities which allows you to edit EXIF data.
My camera puts 72 DPI into my image file EXIF data. Sometimes a customer or printer complains that my large high resolution 24MP image isn't large and detailed enough and requests a 300dpi high resolution version. I don't bother arguing with them. I just edit the file I sent them to contain 300 DPI in the EXIF data and give them back exactly the same file. Makes them happy and saves argument.
To change your DPI you simply need to change that field in your JPEG image EXIF data. If you're lucky your editor will have an option allowing you to do that. If not, you'll have to use another editor which does, or one of the utilities which allows you to edit EXIF data.
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But for simplicity, all of the most popular online printers equate PPI with DPI. When they say they want 300DPI what they really want is at least 300PPI - very clear when you look at the minimum pixel dimensions they list in their guidelines, e.g. DCSL - http://dscolourlabs.co.uk/about/Technical_Support
And PPI is easier to work with in the abstract - 300PPI is plenty for all general purpose printing.
The worst for this are the picture desk monkeys with local newspapers.
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That's because he has no idea what he's talking about. He's not alone, read through this thread it's a common misunderstanding.
big soft moose
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hes talking out of his arse , assuming you picture was actually 14MP (ie that you didn't set the camera to significant reduce the file size) then it will easily print to any reasonable poster size,
14MP is 4228 x 3216 pixels , so in theory at 300 ppi you'd be looking at a 8x10 inch pic (or there abouts) while at 200 dpi you'd be looking at 16 x21 , however if you wanted bigger than that you could easily interpolate in PP , or use a lower PPi as posters aren't meant to be viewed close up anyway... I once had a 6MP image printed to A02 and it looked fine on the wall (at the intended viewing distance)
incidentally if you really want to present a file as a higher DPI (because you have an audience who doesnt understand it) its easy to change the DPI setting in photoshop , the file dimensions will just alter accordingly (make sure you don't have 'constrain proportions' sellected)
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Matt
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for work, one of our suppliers insists that we send 300dpi artwork, we are printing up to 3m wide, so for that kind of size it would be necessary to have a higher pixel density to get the size, or could they get a good print at 72dpi?
I think that is unfair, he probably knows what he is talking about but just doesn't want any guesswork in the process. As you state, for a larger images it probably requires interpolation to get the the resolution required by his printer. A simple change of the exif data does nothing to change that. You suggest using a lower DPI for posters but the printer probably cannot do this - he still needs to upscale it (either manually or automatically by the printer) to meet the print size, the printer cannot just print bigger dots..........
Surely it is better that the customer does that interpolation? If the printer does it then the customer has no control over the algorithm (and hence output quality) used. Plus it prevents any confusion over output sizes. If image exif states a 10x8 at 300dpi is that a mistake or did the job sheet mistakenly ask for it to be printed at 21x16? No chance of errors if the image is correct to start with
I realise there are different ways of doing things, and that DPI is generally ignored for home printing, but I just wanted to put a different side to this.
big soft moose
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the DPI of the actual file is a red herring - your printer needs sufficient pixels to be 300DPI at 3M wide, however if the file was 72 DPI and about 12 M wide and 4 times as high ( ICBA to do the exact maths) the number of pixels would be the same and they could simply resize the file.
a seperate issue is that 3M prints aren't mean to be viewed close up so you can get away with a lower pixel density than you would on a small print, 72Dpi would still be too few but you could probably get away with 150
big soft moose
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I think that is unfair, he probably knows what he is talking about but just doesn't want any guesswork in the process. As you state, for a larger images it probably requires interpolation to get the the resolution required by his printer. A simple change of the exif data does nothing to change that. You suggest using a lower DPI for posters but the printer probably cannot do this - he still needs to upscale it (either manually or automatically by the printer) to meet the print size, the printer cannot just print bigger dots..........
Surely it is better that the customer does that interpolation? If the printer does it then the customer has no control over the algorithm (and hence output quality) used. Plus it prevents any confusion over output sizes. If image exif states a 10x8 at 300dpi is that a mistake or did the job sheet mistakenly ask for it to be printed at 21x16? No chance of errors if the image is correct to start with
I realise there are different ways of doing things, and that DPI is generally ignored for home printing, but I just wanted to put a different side to this.
The printer can easily use a lower DPI as the idea is not to print bigger dots, but that at a greater viewing distance your eyes fill in the detail. and while it may sound unfair hes definitely talking out of his arse if he says you can't print a poster /large print from a 14MP file (given my previous comment about printing A02 from 6mp )
Perhaps some confusion with the term "printer" in my post. The printing device will print at a specific resolution (normally), if the the image resolution is not enough for the required print size then it needs upscaling/interpolating. I think we both agree on that. The only question is who does that upscaling. The customer, the guy running the print shop or the printing devices software?
The way I see it, the print guy is not saying you cannot print a large print from a 14MP, he is saying it is not of high enough resolution to print without interpolation and hence reduction in quality. As you said, whether that quality loss is important depends on viewing distances etc. I am pretty sure anyone running a commercial print shop will know that an image can be interpolated, he will also know that this will lose quality so he doesn't want to be the one to do it in case the customer kicks up a stink because it wasn't what he was expecting.
I hope that clarifies what I was trying to say.
big soft moose
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you can print a poster sized print from a 14MP file without interpolation.
tbh I suspect that this isnt the issue at hand - my money would be on the OP having somehow reduced the resolution of his file during PP and despatch to the printer (some email programs do it automatcally) meaning that the file the printer has would be significantly less than 14MP
tbh I suspect that this isnt the issue at hand - my money would be on the OP having somehow reduced the resolution of his file during PP and despatch to the printer (some email programs do it automatcally) meaning that the file the printer has would be significantly less than 14MP
Sorry, can you explain this to me? Are you talking about a print process that does not have fixed native resolution? (ie not your average ink jet or similar)
big soft moose
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Most commercial printing services can print at more than one resolution - the one i use can accept files at 300, 200 or 150 dpi - and as i said earlier 14MP at 200 dpi is 20 inches by 16 and that resolution is fine for display on a wall where you arent going to examine it up close
Got you, I think I see what you are getting at now. They are still fixed resolutions though. Possibly they use different machines for the different resolutions or possibly they having fixed interpolation for the non-native resolutions. However, either way, they are still stating a fixed dpi which allows them to control the image quality at a certain level and hence avoid any customer confusion
No argument with that, personally I have printed a 5MP image at A2 and it hangs in my stairwell. There are lots of things wrong with it but lack of resolution is not one of them!
but that wasn't really what I was getting at, I don't think it is about what is possible, it is about what commercial printers want to received to avoid confusion and errors in the process. Hence (getting back on topic.....), I do think it is important for photographers to understand the relationship between dpi, resolution and canvas size and be able to put their images in the size a print service asks for.
Just my opinion though
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The confusion tends to come from people thinking that the DPI / PPI of a file has anything to do with the resolution.
A 3000 pixel wide image, set at 72PPI in the file, but printed 10" wide, is 300PPI.
PPI only really matters as a setting if you're defining the physical dimensions of an image on export, rather than the number of pixels.
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Just to add one little thing into the mix here...
The DPI setting in an application like Photoshop can be important when working with fonts, even if the work stays purely in electronic format. Because font sizes can be expressed in point sizes, which relate directly to physical print, the same font size will produce different sized text if the DPI figure is changed. For example, if two send you images of identical pixel dimensions, and tell you to add a caption using 36pt font, the results will not be the same unless the two images have the same DPI setting.
The DPI setting in an application like Photoshop can be important when working with fonts, even if the work stays purely in electronic format. Because font sizes can be expressed in point sizes, which relate directly to physical print, the same font size will produce different sized text if the DPI figure is changed. For example, if two send you images of identical pixel dimensions, and tell you to add a caption using 36pt font, the results will not be the same unless the two images have the same DPI setting.
sk66
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AFAIK, no lab changes the printer resolution to match the file's PPI. In fact, many/most commercial printers use RGB laser ("photographic") heads w/ light sensitive (silver halide) paper. For instance, the lab I use prints medium size prints (up to 20x30) on a Durst Theta which has a resolution of 254dpi... this never changes. I could send them one pixel and have them print it at 8x10 and it will be printed at 254dpi. What they *want* is an image with the same resolution as the printer for maximum IQ.
It's all about "matching the dots." A lens projects dots, recorded by dots on a sensor, to be projected/printed by dots (screen/printer)... whichever has the fewest dots/ will be the limiting factor in resolution (and very often it's the lens/aperture).
FWIW, most monitors have a resolution of not more than 100dpi (and if they do, they are probably being run lower)... have you ever thought "my monitor doesn't have enough resolution for this image?" No? Then any image that looks good on your monitor will look good printed at *any size* as long as it is viewed from a corresponding distance.
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sk66
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Depends on what's being printed (how much detail is actually in the artwork) and how closely/critically it is going to be viewed. Fact is, *if* an image is viewed in it's entirety (i.e. from a distance where it fills ~ 45* diagonal FOV) somewhere around 12-14mp is equivalent to the maximum resolution the human eye can resolve (for any size print).