How do I find the dpi of my photo I need at least 300 dpi

I know you guys love to argue but the OPs question is how to change the DPI of a photo and you can not do that because it is the answer to a calculation - it is not a setting and even though there is a setting (as I explained) changing it has nothing to do in any way with the DPI of the image - that is a mathematical calculation -- changing the setting is like changing the acreage on on a Plot plan - it does not change the acreage of the plot nor does changing the home square footage printed on a set of house plans change the actual square footage of the house- the house is still what it it and the DPI (remember it is Dots Per Inch) on the image is what it is no matter what the setting says

Unless people understand this they are likely to get poor or unpredictable results - if they send a photo that is going to be printed at a size making it 50 DPI thinking tha t because they changed this meaningless field to 300 they are going to get bad results where as if they understand that they can not set the DPI then they will get good results again the OP's questions is only about the DPI of the finished image - noting to do with irrelevant settings that have no effect on the actual results of printing the photo

How do I find the dpi of my photo I need at least 300 dpi

The answer to their question is to do the math - thee is no setting to accomplish what they want and if someone mistakenly tells them there is it is a disservice to the OP

LN

DPI is a simple third grade math equation - Dots Per Inch - or pixels divided by inches

So get info on the photos and see the pixel dimensions and divide by the size of the print in inches

a 2400 pixel x 3000 pixel photo to be printed 8 inches by 10 inches would be 300 DPI (2400/8 by 3000/10 -- equals 300 DPI)

DPI is not a setting - it is simply a mathematical answer - http://www.rideau-info.com/photos/mythdpi.html

LN

You have to export the original (file->export->export unmodified) to the desktop and look at it with Preview, the info pane will show you the dpi.

But as Larry alluded to, you can have an publishable 100 x 200 pixel image at 300 dpi, or a perfectly publishable (at 8x10 inches) 2400 x 3000 pixel image set to 72 dpi.

with Preview, the info pane will show you the dpi.

Not at all - it shows the contents of the irrelevant, meaningless DPI field - DPI is simply not a setting, it is the answer to a calculation and the results of that calculation are the DPI of the printed image no matter what the DPI field contains

If you have a 80 x 100 pixel image with the DPI filed set to 300 that you print as an 8 inch by 10 inch image the print will not be 300 DPI - it will be 10 DPi and crapy

You can put any number you want in the DPI field and the DPi of the print will always be the mathematical result of a third grade arithmetic problem dividing pixels by inches - it will not have anything at all to do with the irrelevant digits in the DPI field

LN

You know I know that the dpi field is just a number, but it is a number that some folks care about and some software (I am looking at you Photoshop!) seems to care about.

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I'd have to agree, there are a number of applications that use the dpi setting. Preview itself is one, you can choose to view images at 1:1 or use the DPI setting to determine the size they will display on screen at. Many publishing apps will also use the DPI setting to determine the initial size of an image when dropped into a document.

I think the thing here is that there is no inherent need to provide anyone your photos with any particular DPI setting since it can easily be changed, however just because the setting doesn't actually matter doesn't mean there isn't one.

We understand your point and what you are trying to say, but you are plain wrong, changing the DPI setting changes the way the photo will behave when opened or imported into other applications. You can change the DPI setting to avoid having to do any of the math as you put it.

You are doing the OP a dis-service because you have a thing about DPI and are only telling them half a story.

No you are wrong and obviously you do not even understand the question - it only changes the DPI setting which has no effect on the actual DPI of the printed photos which is the OPs question - a photos that prints at 100 DPI will print at 100 DPI no matter that the EXIF/IPTC DPI setting says - a 800x1000 image printed as an 8 " x 10 " photos will only be 100 DPI no matter what the setting is - it is meaningless as far a the actually DPI of a printed image is just writing a new acreage on a plot plan is meaningless as to the actual size of the plot - that, like DPI, is the answer to a math problem

You are answering a totally different question that has no relevance to this question and your constant arguing will confuse the OP and future readers

LN

... it only changes the DPI setting which has no effect on the actual DPI of the printed photos

You seem to be assuming the OP wants to print photos

You are answering a totally different question

It's you that's answering your own question, the OP just asks how they find the DPI, you have decided why they want to find it and have told them just the bit that you want to.

You left out two very important words: "to publish". We don't know what that means. If some clueless publishing house is requiring that the dpi field be set to 300 dpi, than I answered the question correctly.

I need at least 300 dpi to publish. Thanks

You need two things - a photo with a pixel size large enough for the desired print size, as Larry described. To print the photo at 12 x 9 inches it should have 3600x2700 pixels.

And if your publisher insists on an embedded dpi tag of at least 300 dpi you need to save the photo from an application that allows to set the dpi tag.Preview can show the dpi tag , but not set it. Aperture and has a preset to modify the dpi for the desired print size.

I believe preview can set the DPI tag, the adjust size option has a resolution setting which appears to do this.

I believe my son uses it regularly for two reasons.

He's the marketing manager at a local restaurant and often is involved in preparing literature and also working with the publishers who also prepare the companies literature on occasions.

The publisher (or rather the person working at the publisher, who is a friend of the owner of the restaurant and possibly in training) who should really know better, asks for photos at 300 dpi, my son understands what Larry is saying about DPI, but there is no point in arguing with these people and changing the DPI setting keeps everything sweet.

However, when my son puts together publications himself he uses preview to change the DPI of each photo to 300 dpi before importing it into his publication software. The publication software imports the image at a size which is dependent on the DPI setting. This makes life much simpler for my son since he now knows when he resizes the photo to his desired size, if he has to enlarge it, it's no good. On the other hand if he has to make it smaller he knows it's 300 dpi or greater and is acceptable for publication.

Being able to set a DPI is certainly not an irrelevance for my son.

but there is no point in arguing with these people and changing the DPI setting keeps everything sweet.

Very true! We have seen many contributions in the Aperture forum asking for help to set the dpi tag for a photo correctly, so it will be accepted for a competition or publication. I think Keith Barkley has been referring to these kinds of requirements in his post as well.

I believe preview can set the DPI tag, the adjust size option has a resolution setting which appears to do this.

Right. 😊 I forgot about Tools > Adjust size, sorry, because I always use Aperture's Export presets to ensure the requested dpi settings.