I wasn’t sure what you meant by the “pixels themselves smaller”. Except for the meta data, the image file itself is unchanged. Printing programs can ignore the meta data or it can be over ridden for printing.
Right.
You are saying “take these pixels (which are now 5.5mils) and make them into 3.3mil pixels.” Since nothing else about the pixels changes, no information is lost doing this.
DPI = Dots per inch = Pixels per inch.
300 DPI = 300 pixels per every horizontal and vertical inch.
If you want to print something 10" x 10" @ 300 DPI, that’s 300 (pixels) times 10 = 3000 pixels across and 3000 pixels down, giving you an image area of 9 million pixels (9 Mega Pixels).
Apply the same math to any dimension. DPI needs to be in relationship with the inches (or whatever unit) you plan on printing it out in.
I think we’re in violent agreement and just using different terminology. My concern would be confusing people into thinking that the pixel has a size to begin with - it only has size in relation to printing. Before you print, IMO, it’s easier to just deal in dimensions (1200 pixels by 1600 pixels). I never think of an image file having DPI, that’s reserved for prints.
Unless the author can specify the photos, or the editor is telling the author, we will publish photos as full- half- quarter-page or whatever, it does not matter.
I assume what they are actually doing in a round-about way, is saying “if you send us a picture 1200x900, the biggest we will print it in the article is 4"x3” large."
A 1200x900 pixel image, printed out at 300 DPI, will be 4" x 3" on the printed page.
A 1200x900 pixel image, printed out at 100 DPI, will be 12" x 9" on the printed page…
It’ll be bigger than the 300 DPI image, of course, but the quality of the image will start to look pixelated and less crisp (as you’re effectively printing the pixels larger).
You can print a 1200x900 pixel image at 1 DPI and have a 1,200" x 900" billboard, but each and every pixel will be printed 1" square in size.
But basically the magazine is saying we want 300dpi.
I assume what they are really saying is ‘we will publish no worse resolution than 300dpi’, i.e. if you give us 1200x900 the biggest it will be printed is 4x3 inches. If you want 8x10, give us no worse than 2400x3000 (7.2Mp).
Correct.
The OP will have to open it in Photoshop or something and determine the pixel dimensions. He hasn’t done that.
OP: If it’s going to print, you should convert it to cmyk (I know), as an image straight from your cam will be in an rgb format. Although, they’ll probably just convert it for you if you’re having them lay it out.
Sounds like they’re just covering their ass in regards to resolution, so in case it prints and is all fuzzy or pixelated, they can say “we told you the requirements.” Magazines can be pretty passive-aggressive like that.
Yeah, what they mean is “I want this at 300dpi (at final print size).” They never say that last part, so it causes confusion.
Is that still true? I would’ve thought it depends on what method the printing company uses. Printing at the equivalent of Kinkos or on your own laser or inkjet printer doesn’t require CMYK.
Thanks for this explanation and MD2000 also for the info. After starting this thread, and reading all the posts, I find it rather amusing at the divergence of opinion.
I thought “dpi” was archaic and now I am convinced of it. 
An image printing out to a laser or inkjet will convert on the fly, either from the software you’re using to output from, or using some conversion presets in the printer driver.
However, if it’s going to separate for a 4-color press, converting to cmyk gets a bit more particular, what with dot gain, ink densities, etc., especially when it comes to printing rich blacks. But yeh, now-a-days I’m sure it’s all done on the Magazine’s end, since they know what inks, paper and equipment they’re running.
Not archaic, just a holdover term from the analog days. DPI refers to the dot density of halftones on the press side of things, which are still very much universal for process printing.
Just think of it as PPI (pixels per inch), and you’ll be fine.
One pixel = One dot.
It’s really very simple. (30 years in the art/printing biz is speaking)
If the magazine prints a 2 inch wide image, they want 2 x 300 dots or pixels to play with as a minimum.
It doesn’t matter how many pixels or dots your image is per inch. It doesn’t matter how many inches your image is. It only matters how many dots you have. And dot’s the truth. 
I see a lot of people dancing around the answer, but not really spelling it out.
Take the size of the painting as it is supposed to appear in the magazine (use other, similar paintings as a guide). Multiply the dimensions, in inches, by 300. Your paintings need to be at at least (or exactly, if the requirements are rather strict,) the resolution, in pixels.
And, for the pedants, add “digital representation of” every time you see “painting.”
Missed your other question. Yes, they are incorrect in using “dots per inch” (DPI): they should technically be using “pixels per inch” (PPI), because, depending on the printing method, DPI and PPI do not have to be the same thing. For example, a 300 PPI image should be printed at at least 2400 DPI on a standard home inkjet printer. Why? Because said inkjets are only capable of producing dots of 9 colors, as each color is either on or off, meaning there’s only cyan, magenta, yellow, blue (cyan + magenta), red (magenta + yellow), green (yellow + cyan), gray (cyan + magenta + yellow), black, and white (all colors off). In contrast, a 300 DPI image, which is usually 24-bit), has 16,777,216 colors. Having a total of 64 dots (2400/300 = 8 in each dimension) per pixel helps even this out. I’m sure a mathematician could get the exact equivalent.
Magazines are usually printed in a different way that makes it even harder to talk about their true DPI, as each color is printed at a different angle. Hence why you can assume that a magazine using DPI really means PPI. Well, that and that you have no real control of how many actual dots they will use.
No he doesn’t need to do anything that sophisticated.
OP, assuming you are using windows, all you need to do is go into Explorer and right click on the file and choose properties, and then look under the summary tab. There you will find all the jpg metadata, usually including pixel dimensions, printing dimensions, date picture taken, camera type, yada, yada…
Well, all that does (at least on Win XP) is show me the size of the image in megabytes. I can see that in Explorer without clicking on properties. Am I missing something?
I’m using XP Pro right now. Are you looking under the summary tab? You have to go to the summary tab specifically. Properties will open on the general tab.
Windows XP right click the icon for the picture and select properties, then the details tab - you will find dpi listed there.