how do I find the dpi of an iPhoto?

The photos in iPhoto do not have dpi assigned. They are just a matrix of pixels and have a pixel width and pixel height.

When you export a photos from iPhoto it will create an image file that may have dpi assigned. You can see the dpi values when you open the exported photo in Preview and open the Inspector from the Tools menu. For example, this photo has been exported with 180 dpi. But more important than the dpi is the pixel size. It will tell you the quality of the photo.

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

The question was the dpi of a photo in iPhoto. iPhoto photos do not yet have physical dimensions in inches or cm, because they have not yet been rendered and printed or displayed - they are waiting in limbo to be rendered as an image. Without dimensions in cm or inches there are no dots or pixels per inch and so dpi has no meaning for the iPhoto photos. The pixel width and pixel height of a digital photo in iPhoto could result in any dpi value, depending on which size the photo will be displayed on the screen.

When iPhoto exports any photo, it will set the metadata tag 180 dpi Height and 180 dpi Width; but that is only a polite indication how the pixel width and pixel height could be mapped to the display or printing paper.

Obviously there are no inches or square inches in a digital photo on disk - those only come when you print or display the image which is why there is no DPI (Dots - or pixels - per inch) for a digital photo

The simple answer to how many DPI a printed image has is to use third grade math - per is another word for divided by - divide the Dots (pixels) in the digital image by the inches in the printed image (a 1800 x 1200 pixel image printed as a 6" x 4" image would be 300 DPI - 1800/6 = 300 )

LN

- I am downloading the free test now.

The Preview.app is coming free with any Mac and will show you the dpi of any digital photo that has a dpi tag, like shown in my screenshot.

You don't need to buy an expensive program to show you dpi tags.

But that does not change anything about the fact that photos in iPhoto do not have a dpi tag, only when thy are exported.

Your photo has a width of 1936 pixels and a height of 2592 pixels.

300dpi means - you need 300 pixels per inch.

So, so if you want a resolution of 300 dpi you can display your photo with a width of 1936 / 300 = 6.45 inches and a height of 2592 / 300 = 8.64 inches.

Your photo has not enough pixels for the desired print size. Te pixelsize is slightly too small.

You could try the online image enlarger to invent a few more pixels without making the photo blurry:

Online Image Enlarger

Drop the pic in Preview.

Click "Tools" up there.

Then "Adjust Size".

At the right of Width and Height, select "inches".

In the box "Width", type in " 8 ".

In the box "Resolution", type " 300 ", with "pixels/inch" selected

Check "Scale proportionally"

Check "Resample Image"

Click OK.

Now click "File" up there, then "Save as" ( this will let you keep your original image untouched ).

Add "M" at the end of the name.

Choose destination "Desktop",

format : "jpeg"

quality : " maximum"

Click "Save"

The "new" pic will now be on the Desktop.

You can not

to have an 8" x 9" photo print at 300 DPI the photos must be 2400x2700 Pixels minimum - the maximum size yours can be printed at 300 DPI is 6.4533" x 8.64"

You can enlarge the pixel dimensions using some software but it will reduce the final quality - it would be better to use the photos you have and print it giving you a better final quality - printed as an 8"x9" image your photos will be 242 DPI x 288 DPI - visually to most people it will be indistinguishable from a 2400x2700 image being printed

LN

Yes, Preview can create a version of the image file with more pixels by resampling. But the resulting image will not have a better resolution than the original image. It will just have more, redundant pixels, need more storage, and the edges will be a bit blurry. The link to the online image enlarger I posted will allow to use advanced software that increases the pixel size while preserving the sharpness of the edges, without increasing the noise - quite magic. But it will take a lot of trial and error to get decent results.

and the basic answer is that you can not make a silk purse out of a sow's ear- if a photo does not have enough information you can not fix that - you can make it bigger but at best the quality will be the same as the original and most likely of less quality - there is not way to add dots that do not exist except to make them up guessing at what they might look like so there is no way to increase the pixel size of a photos once it has been taken without losing quality

LN

Denison,

to see by yourself and compare the original with the new 300 dpi version :

1-click on the Preview icon , then on the word "Preview", then "Preferences", "General", then check "Open each file in its own window"

2-back in iPhoto, export both pics to your desktop ( "IMG 2589" and "IMG 2589M" )

3-on desktop, double-click each pic: they will open in Preview, each in its own window.

You can then adjust each window to its half of the screen, and compare the photos , zoom in on details of each pic separately with the + and – signs up there in each one's tool bar.

This document will help explain dpi: The Myth of DPI

You need a program that will give you the resolution in DPI. Try Graphic Converter.