let's go back to the rice analogy.

when you're looking at rice cookers, does it make sense to ask if a particular rice cooker can cook rice in half-cup servings?

what matters is the maximum capacity of the cooker itself, or how much rice you've made this particular time.  it is only when the rice is actually dished out that the "grains of rice per person" affects how many people you can serve out of the amount of rice you have cooked.

when you're looking at digital image creation tools (digital cameras or various rendering applications), it doesn't make sense to ask if it can create images at various "pixels per inch" -- what matters is the number of pixels that you capture or render.

just like the number of servings you'll get out of your rice cooker, it is only when the image is printed that the pixels per inch required by the printer (grains of rice per serving) tells you how many inches you'll get (number of servings) out of the number of pixels you have captured or rendered (amount of rice you have cooked).

in dvlenk6's example, a huge pot of rice has been cooked.  in the first case, we've served up 300 people with a tiny amount of rice each and they're all unsatisfied (printing 30 inches by 15 inches at low quality).  in the other case, we've served up 100 people with a reasonable amount of rice each (printing 10 inches by 7.5 inches at high quality).  in both cases, it's the same amount of rice!

it's highly unlikely that a digital camera will include a "pixels per inch" setting any more than a rice cooker will include a "grains of rice per serving" setting, except perhaps as a convenience to the end user.  far more important is the maximum capacity of the device - the total number of pixels it can capture or render, or the total amount of rice it can cook.

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