How can I tell what dpi any given .jpg is?
well, when i drag a jpg into a browser window it gives dimensions in the title bar. ymmv.
if you’re asking about how many dpi the file was saved at, i use photoshop. you could probably use gimp or any other free image program as well.
I know what the dimensions are, but someone wants these pictures in “72 dpi” and I can’t figure out how to see what the dpi is.
There is no such thing as DPI in a classic JPEG. In newer JPEGs, such as from digital cameras, there is an EXIF header that encodes some information, from which DPI can be calculated. But note that the numbers given are for all practical purposes meaningless and should be ignored. Too many people ascribe properties to a DPI number that really have no true physical basis.
Just stick with image size.
A JPG doesn’t have dpi. It has pixel dimensions, DPI don’t come into play until you print it. For instance, if you wanted to print a JPG in 300 dpi as 6" by 10", you would need at least 1800 by 3000 pixels.
yes, jpgs have a dpi as well. use gimp or photoshop.
Ah, here is the problem - it’s for a magazine. So really, since I don’t know what size they are going to print the photos, telling me 72 dpi is pretty useless, eh? I should just send big files?
The standard DPI for web .jpgs is 72. Printing requires 300/600/1200 DPI as a minimum. If the original image is only 72, “big files” is meaningless.
72 dpi sounds seriously low for a magazine - it’s more commonly used for screen display. I can’t see what harm it would do to send them the best picture you have, but maybe you should ask them - somehow it doesn’t seem right that a magazine would ask you for a picture in “72 dpi”.
ETA: Damn it, ninja’d for the second time in the same thread!
I guess I’d better get back to the girl that wants the photos and see what she was told and what they are actually going to do with them. Thanks guys tho - at least now I can quit looking for the dpi’s on these pics!
What do you mean “big files” is meaningless? “72 dpi” for a JPEG is meaningless. It can be a low res file. It can be a high res file. I can save my 36MP images as 72 dpi if I want to, and not lose any image data.
You answered your own rant. If the original image is of low resolution, chances are it’s not magazine quality. OTOH, if the original image is high resolution it could be used in print and easily used for the screen. A 36 MB image is meaningless without context.
dpi is only relevant along with a size. the same exact image can be:
5x7 300dpi
10x14 150dpi
20x28 75dpi
all 3 could be used for printing (depending on the size of the final image), all 3 would end up as the same size file on your hard drive.
if you were going to use the above image for the web, you’d probably save that image as a 72dpi version. if you were going to print that image you’d probably save it as a 300dpi version.
Rant? I’m confused what you’re talking about.
36MP (not megabyte) is not meaningless without context. In my case, it refers to 7360 x 4912 pixels. That tells you exactly what the resolution of the image is and how much information it contains. DPI is absolutely meaningless without context. It might contain 36 MP of infofmation. It might just be a 600x400 pixel file. You don’t know without more info.
FORGET THE DPI! What matters for print purposes is the number of pixels. If you give me an image that is 300 pixels across or more, I can print it quite well if the final image is about one inch or less. It matters not a bit what the DPI is!!
And who actually has a 72 dpi (or, actually, pixels per inch, PPI) display, anyway? My Dell is 109 ppi. My iPhone is something over 300 ppi.
Exactly! “DPI” is just a metadata tag, as has been mentioned.
Not to mention, jpg is lossy and not generally the best format for printing…
Sure. An LZW compressed TIFF or similar would be great, but a lot of places are fine with a high-quality JPEG. Almost all the newspaper images and a good portion of the news magazine images you see are JPEGs. Pretty much any photo you’ve seen that came off a wire is going to be a JPEG.
To keep it super simple.
Ask that person what size the image is to be printed at.
If it is say 3 inches by 5 inches then 72 DPI equals a (3 times 72) pixels by (5 times 72) pixels image.
Then again, if somebody is asking for a picture with 72 DPI resolution that right there is a hint they don’t quite understand this stuff either so its probably safest to figure out exactly what they want or need first. Or send them the highest quality (biggest file size) size you got and let them work it out from there.