Q: how do i find out the dpi of a an image on my i mac

MichelPM wrote:

 

You can't just change a low res 72 DPI image by just changing the DPI to 300 DPI.

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I'm assuming you intended to say "change a low res 72 DPI image to a higher res image...". Nobody said that.  The OP just want's to know how to make it so that his print company will accept the image file.  It would be a pretty primitive print company if they mandated that the dpi have a meaningful value in relation to print size the OP desires, but there are a few that work that way.  The fact that he mentioned CMYK increases that likelyhood a bit.

How to modify an image to make a large scale print from a low res image file is another subject but you've done a good introduction to the technique in a previous post.

Print scaling isn't hard or complicated, just basic math intensive.

The result is the same.

If the OP takes a low resolution image and just changes the DPI resolution number from 72 to 300 the image is still going to look crummy. Yeah, the print shop will take the file and images ibecause the file/s say they are 300 DPI, but its print quality will still be crap.

And yes, if you actually work in print, many print shops do their own pre-flighting of files they receive at pre-press (even after the client does their own pre-flighting of files) and if they spot any low res files, while they do not mandate the client fix them, they let the client know that the images they used in a project look of low quality resolution and allow the client a chance to either fix these before printing and send a new file or leave them alone.

This is why people involved with print graphics work together with printers instead of sending their files off to some Internet print site where there is no collaboration or communication. They just print the job as is.

MichelPM wrote:

 

The result is the same.

If the OP takes a low resolution image and just changes the DPI resolution number from 72 to 300 the image is still going to look crummy. Yeah, the print shop will take the file and images ibecause the file/s say they are 300 DPI, but its print quality will still be crap.

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It appears as if you're saying that the images produced by my Canon 5D Mark III are low resolution crap because the camera assigns a value of 72 dpi to the images.  I think not.  The only thing that defines the resolution of a printed image is the number of pixels in the image vs the size of the print.

Paul --

If your original graphic is a 72 dpi image, there's nothing you can do.  If you try to manulate it to a higher resolution, it will be a huge failure. 

If it's already 300 dpi, you're good to go. 

Graphic Converter is a great app, with outstanding customer service.  Another reasonably affordable app is Photoshop Elements.

~Bee wrote:

 

Paul --

 

If your original graphic is a 72 dpi image, there's nothing you can do.  If you try to manulate it to a higher resolution, it will be a huge failure. 

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Not necessarily true at all!  Changing the dpi has absolutely nothing to do with the quality of a digital image.

Take a look at this link:

http://www.rideau-info.com/photos/mythdpi.html

If you check the size of your 72 DPI camera images, their pixel dimensions are huge!

When you edit their size from 72 DPI to 300 DPI, the overall pixel dimensions shrink and you end up with a 300 DPi image at a certain, but smaller size. If you need that image at say a larger size than what the 300 DPI image is at, if only has be be say 25 percent larger than this, you might be able to get away with just resizing the image with no resampling. If the image needs to be bigger than this, to stay a 300 DPI, you need to resample the image up in increments to get to the dimensional size you need.

Not true with good image editing software and you know how to do this correctly.

Iif you do not believe me search the web or Photoshop forums about resizing and resampling low res images to a higher print resolution.

You will find what I am talking about as there a variations on the technique I describe and other ways to bring up the quality/resolution of low resolution images.

I Believe Graphic Converter can do these techniques, Pixelmator can do this, Photoshop Elements as well as full Photoshop, Corel Painter and Corel Graphics Suite can perform interpolated resampling of images.

It is how you use and implement this technique that makes all of the difference.

Of course, you have much more pixel information in the image, now.

But the resampling techniques are the same.

Message was edited by: MichelPM

Another cheap but good Photoshop alternative that works pretty much the way Photoshop works

Pixelmator

http://www.pixelmator.com/

Agree about Pixelmator - a bargain for what it does. And it's quick as well. The interface is not to everyone's liking, but you get used to it.

Paul,

If you keep using low res images and or need to fix/adjust DPI/resolution of whatever images you are using to go to print, you should invest a some decent image editing program.

Gimp is free and a good Photoshop alternative.

Pixelmator and Graphic Comverter are cheap and pretty powerful.

Pixelmator is a great Photoshop alternative that now has CMYK support (it didn't for a long time).

$40 for an image editor when compared to the costs of Full Adobe Photoshop is cheap!

About a tenth of the cost.

Adobe Photoshop Elements gets you 80%-85% of the features in Full Photoshop for less than $100.

A newcomer to image editing is Seashore and it's cheap, but it's a very basic image editor with limited feature set.

I needed at least 150 dpi. This website was very helpful!! http://convert.town/image-dpi.

To add to crh24's right on answer read this article: The Myth of DPI

I am tired of all the "circular" arguments and BS  and general crawp about image resoultion and this whole "DPI" issue.

I am a 20+ year Photoshop/Painter user and have scads of years and project experience with working the crawp, low res imagery and making them better quality images and I have used these very same techniques in my own artworks and projects that I am very, VERY particular about.

I know what I am talking about here and know what has to be done to get good quality images for any type of print scenario.

DPI term, in and of itself, doesn't matter, it's the amount of ACTUAL pixels and pixel data that is in an image that matters!!!

If there isn't enough pixel data in an image, it is going to look like garbage whenever, wherever you print it out.

If you take a normal, typical 72 dpi digital camera Jpeg image (NOT the RAW image format) from any consumer digital camera and print this out at its actual full size pixel dimensions, the image is going to look like garbage and very "blocky" and pixellated.

Change that image's dpi in any basic photo editor to any larger DPI value like 150, 225 or 300 DPI. the image is going to shrink down, the same pixel information compresses inwards and you get a smaller, but much sharper looking printed image.

This is how editing digital imagery works.

If you start off with a low DPI and/ or low pixel image that is NOT suitably clear when it prints out, the only way to get more pixel data into an image is to use multiple small incremental amounts of something called "digital interpolation" that adds additional pixels to an image by the software analysing the image's surrounding pixel data to make an educated "guess" to add the proper or approximate surrounding color pixels needed to increase the pixel data/resolution/density in a digital image.

If this interpolation method is done in small percentage increments (usually expressed in DPI), you can add pixel data to a low pixel image and, also, enlarge its size and create a much sharper, clearer, less pixellated, printable image that, if this method is done correctly and consistently can produce/create a very nice, final printed image from one that was total garbage when first printed out.

Is this a better explanation for everyone visiting this post? Hmmmm.....

<Edited by Host>

That sounds like a thorough explanation, thank you.
It, however, does not make a difference to me what the DPI of the photo is. Those are just one of the standards that the program I am trying to upload photos into requires. I have learned here that this requirement really doesn't make a difference, but a requirement for me nonetheless.

Cheers.