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04-30-2012, 05:33 AM   #1
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Image Resolution and DPI

I did a job for a company last week and they gave me a reminder that "next time i do work for them, make sure the camera settings are set to dpi of 300" so that when the image goes to print they can have the best resolution possible. where is this setting in the menu?

04-30-2012, 05:38 AM   #2
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Camera's output a resolution. DPI settings for print are defined at the printer. You would set the DPI at your printer software.
04-30-2012, 06:34 AM   #3
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If you shot RAW, the DPI settings are configured on your RAW processing software, for example, in Lightroom, you would go to Edit --> Preferences --> External Editing and there you can set the output DPI of your files when you send them to Photoshop or other image editors, or in the "Export..." dialog in the Image Sizing section you can set the resolucion as well.
Please note that the camera creates a fixed number of pixels, so by changing the DPI all you are changing is how large the image will print (esencially you are telling it how many pixels it should print in an inch), so let's say you have an image that is 10x16" at 240 DPI, it would become an 8x12" at 300 DPI as long as you don't resample the image (interpolate new pixels from surrounding pixels), resampling the image will lead to image degradation. Any designer worth the title should know this and it is absurd they request 300 DPI as long as you are giving them the highest resolution (megapixel count) that your camera can output.
04-30-2012, 06:35 AM   #4
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DPI is what is called a tag, and is a pretty meaningless one until, as Jim mentioned, it's time to go to print. It isn't something you can set in the camera menu, IIRC, the Pentax assigned tag is 72.
What you need to do is set the tag in your image editor. In Photoshop it is image/image size, and use the sub window to reset the DPI. There is a radio button for resampling the image, make sure it is unchecked.
The formula for printer output is DPI x Image size (in inches) = the number of pixels required to make the image.
The company you did the work for is clueless, all that matters is that you submit enough pixels for them to do whatever it is that they need to do, but you will run into this sort of ignorance frequently.
Take your full res files, and as part of your post processing, set the tag to 300 (don't resample, to make sure you don't make more pixels), and then save the file.
Don't bother trying to explain it to them, the likelihood of them understanding is faint, the likelihood of them wanting to understand is fainter.

04-30-2012, 08:57 AM   #5
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Actually to call it DPI is wrong because it looks at the Pixels not the Dots the printer make so it's PPI not DPI
But who cares right?

btw the DPI setting is also meaningless with printing, if you say the photo needs to fit the paper it automaticly scales the photo regardless wht DPI you have set it.
So it's only an idication of the resolution of the print.
IF you've a photo with 1000pixels wide and you print it on a paper 10 inch wide you got 100dpi
If you print it 1 inch wide you got 1000dpi, so as you can see it's the resolution of the file that matters not the dpi setting.

Next time just make it an insane number say 24000 DPI saying that you really max the quality this time

Last edited by Anvh; 04-30-2012 at 09:03 AM.
04-30-2012, 09:14 AM   #6
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QuoteOriginally posted by Deiberson Quote
so that when the image goes to print
When you/they say "goes to print" you/they actually mean REAL printing? Real printing as meaning "goes to press"? If this is the case then absolutely they need the art in 300+, doesn't really matter if they are printing to a printer but if this is press ready stuff than that is a totally different ballgame...
04-30-2012, 10:11 AM   #7
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QuoteOriginally posted by joe.penn Quote
If this is the case then absolutely they need the art in 300+
Sure, if you are designing and ad or something in photoshop, you want to send the final art to press at the real print size and 300 DPI, but the camera will always output a fixed number of pixels, so 100 DPI o 1000 DPI makes no diference, in fact when you place the photo into your design it will present the image in the size it would print according to the pixel count and DPI setting of your document.
04-30-2012, 10:17 AM   #8
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QuoteOriginally posted by joe.penn Quote
When you/they say "goes to print" you/they actually mean REAL printing? Real printing as meaning "goes to press"? If this is the case then absolutely they need the art in 300+, doesn't really matter if they are printing to a printer but if this is press ready stuff than that is a totally different ballgame...
But surely they also fit the image to the size of the paper right?

And if it's use in the magazine then the software certainly is sart enough to make everything the resolution you want before sending it to the printer.
Also of they change the size of the photo in the magazine then it doesn't matter you deliver it in 100 or 300 DPI since they are actually changing the DPI by doing this anyway.

04-30-2012, 10:27 AM   #9
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QuoteOriginally posted by joe.penn Quote
If this is the case then absolutely they need the art in 300+
Actually when we get this far that you total prepare the image for printing then you need to have:
- colour-space of the printer + paper
- native DPI of the printer
- print size (+viewing distance)

Only then you can really get a good file that can go directly into the printer.

Last edited by Anvh; 04-30-2012 at 10:58 AM.
04-30-2012, 10:42 AM   #10
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QuoteOriginally posted by Anvh Quote
And if it's use in the magazine then the software certainly is sart enough to make everything the resolution you want before sending it to the printer. Also of they change the size of the photo in the magazine then it doesn't matter you deliver it in 100 or 300 DPI since they are actually changing the DPI by doing this anyway.
For one section of our magazine that I work on, our art departments asks us to get images at 4-5 inches in size at 300 DPI. What they don't want is 4-5 inches in size at a lower DPI, nor do they want someone taking a much bigger image and rescaling it without adjusting the DPI accordingly. So DPI on its own may not matter, but once you start getting closer to the final image size, it does matter.

What your printer said didn't make sense - it isn't the camera that is fixing the DPI - it has its own maximum resolution. But what @jase36 and @Wheatfield said gets at what you do need to worry about. Once you process the image to a particular size you need to worry about it. And if you are just sending them a RAW file, the printers ought to be able to figure out how to resize things appropriately.
04-30-2012, 10:52 AM   #11
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QuoteOriginally posted by joe.penn Quote
When you/they say "goes to print" you/they actually mean REAL printing?
real printing.....used for some kind of case study. it had to be printed at a dpi of 300. when i was asked.....i din't really know what to say, i thought it was a camera setting which is why i started the thread. i didn't do the post processing. the graphic designer asked me about it.
04-30-2012, 10:56 AM   #12
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@MSL
But they give you the image size in inches and the DPI, that mean smaller files that fit perfectly inside the magazine with the right quality so that makes a lot of senses.

However like you say complaining about the DPI while you deliver full resolution photo is ridiculous.

So the company either needs to say how much the pixel resolution must be or give physical dimensions and the DPI, either way the result is the same.
04-30-2012, 11:45 AM   #13
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Most photographic printers ask for a 300dpi, which is simply a density of the 'dots/pixels' in a square inch of area. As others have mentioned, this is simply reassigned in your PP program under the image resize option, not on your camera, and then you'd have no problem with your printer. There are a couple of guides available that give us an idea of how many dpi are needed for various forms of print jobs: Welcome to Fabness - Create stunning multi piece canvas prints using your own image or select from our Art Market. Room Preview lets you see your canvas on the wall before you buy!, How Big Can I Print | Size of Canvas Prints, Canvas Art, Photos Canvas

And another useful resource on dpi is here: Display, Printing, DPI and PPI - photo.net
04-30-2012, 11:54 AM   #14
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QuoteOriginally posted by Anvh Quote
But surely they also fit the image to the size of the paper right?

And if it's use in the magazine then the software certainly is sart enough to make everything the resolution you want before sending it to the printer.
Also of they change the size of the photo in the magazine then it doesn't matter you deliver it in 100 or 300 DPI since they are actually changing the DPI by doing this anyway.
Well, no (to the bold'ed quoted question, see the image below when fitted to the paper/ad block). I was in Printing and Publishing (the real stuff, you and your kids have probably seen some of the stuff we did for NASA and also various fill in press works for Discovery Communications, NOAA, Smithsonian and Library of congress) for about 12 years, did everything from hard labor on a 48" 6-Color Heidelberg Lithograph Press to assistant production manager, very hard work and probably the hardest work I have ever did - I was an underpaid 80 hour a week worker in at the time what was the only occupation that had a higher divorce rate than law enforcement . Back to the sizing, in short, you can't drop in a 72dpi photo on a spread designed for a 300dpi layout. The image would in return look like this after printed:

Left: Sized at 300dpi - placed in advertisement at actual size
Right: Sized at 72dpi - image had to be stretched to size to fit the ad space




QuoteOriginally posted by Deiberson Quote
real printing.....used for some kind of case study. it had to be printed at a dpi of 300. when i was asked.....i din't really know what to say, i thought it was a camera setting which is why i started the thread. i didn't do the post processing. the graphic designer asked me about it.
Printing at 300dpi can be done for any type of press work although it is pretty high for newsprint and some offset magazine/catalog printing. Almost all legitimate full color upper end publications require a minimum of artwork to be supplied at 300dpi (and that's minimum), back in the day we used to get some artwork that was scanned on high end drum scanners at resolutions upward of 1000dpi which translated to massive file sizes, kind of sucked to because it took forever to rip them off of the zip drives...
04-30-2012, 08:58 PM   #15
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The 300 dpi is basically 2x a 150 line screen used in offset lithography. This is common for photographic reproduction in magazines.

Example...if you are doing an 8.5 x 11" full bleed (8.75" x 11.25"), your Photoshop file would need to be 2625 x 3375 pixels. You can test this yourself by creating a new file in PS of the required linear dimensions at 300 dpi.

The bare minimum resolution for a photo going to offset litho is 1.4x the line screen, so 300 dpi could actually work for a finer screen. However, the 2x rule of thumb is used much more often, so you may encounter a situation where they need 2x of a finer screen, eg, 175 line, which would mean your photo should be 350 dpi.
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