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Question How to calculate at what dpi to print?
- Thread starter Tuanny
- Start date
You need to learn about pixels vs DPI and how it all works. Frankly, it confuses too many people. It's 101 stuff. It's stuff you should know before entering the field or learn within your first few days.
1. DPI doesn't exist in the digital world. It's only pixels. Also a lesser discussed part of digital artwork is quality. I can easily provide stupid high res artwork but it might look like absolute garbage.
2. DPI in the digital world is basically a scaling factor stored in the meta data. It's also used as information provided if you want to turn something that is digital to something physical (printing). To prove this, open up Photoshop and make a new document that size. Now change the DPI from 100 to 300. Notice how the file size doesn't change. The only thing that changes is the canvas size. Now take either of those files and bring it into Illustrator and reduce the size 1/3 or increase it 3x. Notice how the DPI corresponds? Like I said, it's a scaling factor.
3. In this example, your ratios are different, but ignoring that, your 5000x3000 image when scaled to 100" high, would be 30dpi. This will likely appear pretty pixelated and crappy unless you res-up the image. That low DPI figure is essentially telling you it's a low resolution image.
4. DPI when printing is a completely different subject. It boils down to the quality of the print. High DPI = more detailed print as it's putting more droplets of ink per inch. You could also say it's higher ink density, but that can be semi controversial.
So big picture you need to look at two different things. The first is the digital quality. Is the image a good enough quality image for the size I want to print? The next question is how high of a quality print is necessary for the application.
Either way, you should really know the basics if you want to be in the digital art / printing field. This is 101 stuff.
1. DPI doesn't exist in the digital world. It's only pixels. Also a lesser discussed part of digital artwork is quality. I can easily provide stupid high res artwork but it might look like absolute garbage.
2. DPI in the digital world is basically a scaling factor stored in the meta data. It's also used as information provided if you want to turn something that is digital to something physical (printing). To prove this, open up Photoshop and make a new document that size. Now change the DPI from 100 to 300. Notice how the file size doesn't change. The only thing that changes is the canvas size. Now take either of those files and bring it into Illustrator and reduce the size 1/3 or increase it 3x. Notice how the DPI corresponds? Like I said, it's a scaling factor.
3. In this example, your ratios are different, but ignoring that, your 5000x3000 image when scaled to 100" high, would be 30dpi. This will likely appear pretty pixelated and crappy unless you res-up the image. That low DPI figure is essentially telling you it's a low resolution image.
4. DPI when printing is a completely different subject. It boils down to the quality of the print. High DPI = more detailed print as it's putting more droplets of ink per inch. You could also say it's higher ink density, but that can be semi controversial.
So big picture you need to look at two different things. The first is the digital quality. Is the image a good enough quality image for the size I want to print? The next question is how high of a quality print is necessary for the application.
Either way, you should really know the basics if you want to be in the digital art / printing field. This is 101 stuff.
ColorCrest
All around shop helper.
I've sent you a message.
ColorCrest
All around shop helper.
Well, seems the OP came to the right place.
bob
It's better to have two hands than one glove.
Rule of thumb: Print at least 4 times the image resolution. This yields at least a 4x4 matrix for every image pixel and gives approximately 4^16 printer color choices per. Usually, this comes down to printing 150ppi images at 720dpi. Printing a 300ppi image at ~1200dpi is silly, the most human eyes have a hard time discerning 1 part in 100. No one can see 1 part in 150.
Annette Asberg
New Member
But if the print has just one color which it does not say in the post then you can go with a low DPI and low passes and that will work perfectly
Most of the time it corresponds to the distance something is going to be viewed from.
But the biggest issue is file type - is it a raster file or vector?
A vector will always come out at the highest resolution possible - you just need to decide how far away it's going to be viewed from. Closer = higher printing dpi required, so say a map would need the highest quality, whilst a billboard could get away with much less.
When it comes to raster files you add file dpi into the mix.
For something close you need 300dpi in the image file - file size will always increase as the dpi increases as long as the canvas size stays the same. You can get some pretty big files
Simply changing just the dpi doesn't work, as the canvas size will change as well (dots per inch, so the lower the dpi the larger the canvas) , you need to ensure that the canvas size is fixed.
Then, another issue is quality - unless the raster file is large enough, no matter what you change the dpi to, the quality will still be rubbish.
Rule of thumb is - file needs to be 300dpi at canvas size, printing dpi is down to how far away you're going to view it from.
But the biggest issue is file type - is it a raster file or vector?
A vector will always come out at the highest resolution possible - you just need to decide how far away it's going to be viewed from. Closer = higher printing dpi required, so say a map would need the highest quality, whilst a billboard could get away with much less.
When it comes to raster files you add file dpi into the mix.
For something close you need 300dpi in the image file - file size will always increase as the dpi increases as long as the canvas size stays the same. You can get some pretty big files
Simply changing just the dpi doesn't work, as the canvas size will change as well (dots per inch, so the lower the dpi the larger the canvas) , you need to ensure that the canvas size is fixed.
Then, another issue is quality - unless the raster file is large enough, no matter what you change the dpi to, the quality will still be rubbish.
Rule of thumb is - file needs to be 300dpi at canvas size, printing dpi is down to how far away you're going to view it from.
newparade
New Member
Seems that a forum named Signs101 would be an appropriate place to ask, then.
Pratik Shah
Web to print software
I think this doc will helps you. check out : https://www.iprintfromhome.com/mso/understandingdpi.pdf
DAVID MARSHALL
New Member
That rule of 300dpi for offset work was based on laziness and ignorance. The correct formula for determining correct resolution for offset printing is line screen in lines per inch multiplied by the square root of 2. If you do the math, unless you are trying to print banknotes, this is way short of 300dpi. In the olden days, computer power and storage were both expensive so you tended not to be wasteful with file sizes. The 300dpi number came about with tyros with Macintoshes making pretty designs without understand production processes. Sadly, nothing seems to have changed. Paul Brainerd, founder of Aldus is famously quoted as saying "With the power of desktop publishing, anyone without any artistic or technical talent can produce ugly paper more economically than ever before."
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