Maybe I am denser than I thought but I recently saw a request for photographs that were 10 megapixels or better. What is the difference between megapixels and resolution?
Megapixels tell you the physical size of the file produced by the sensor. It's not necessarily an indication of how much detail the sensor can resolve, although the two are generally correlated.
Resolution is indicated in line-pairs-per-mm and is usually measured using a resolution chart that has black/white lines in various densities. This information is not usually provided by manufacturers but can be found in some detailed reviews.
Generally speaking, when comparing sensors of similar technology and physical size, more megapixels usually means more resolution but this doesn't always hold true when comparing different sizes/technologies (e.g. an 8-megapixel SLR sensor will likely resolve more detail than a 10 megapixel point-and-shoot sensor).
Resolution of the resulting file depends not only on the resolution of the sensor, but also on the resolution of the lens, so things get even more complicated.
To keep things simple, most people use megapixel count as a general indicator of resolution, despite these caveats (kinda like most people estimate computer performance by the processor clock speed).
Guy
Thanks for the response; however, with your answer causes another question comes to mind. I remember the line resolution from Photo 101 classes many years ago. But today in Photoshop the resolution is pixels per square inch; how does that relate to the megapixel in digital?
Mike, there's no relation. The resolutions in ppi is used for printing only. For example, if you have a file with a physical size of 6000x3000 pixels (i.e. 18 megapixels) and you print it at 300ppi, your print will be 20"x10". If you print the same file, with no interpolation, at 200ppi, the print will be 30"x15" (with less detail).
To clarify, Guy, it will have exactly the same amount of overall detail, but less detail per inch.
And in general, even though it may not be quite correct, most people use resolution to mean the amount of detail involved, whether that's a pixel measurement (physical size), or line pair measurement, or just a general off-the-cuff detail assessment. In fact, a lot of people would say that, for instance, 10 Megapixels is the resolution of the camera.
Discussion
4 repliesThanks,
Resolution is indicated in line-pairs-per-mm and is usually measured using a resolution chart that has black/white lines in various densities. This information is not usually provided by manufacturers but can be found in some detailed reviews.
Generally speaking, when comparing sensors of similar technology and physical size, more megapixels usually means more resolution but this doesn't always hold true when comparing different sizes/technologies (e.g. an 8-megapixel SLR sensor will likely resolve more detail than a 10 megapixel point-and-shoot sensor).
Resolution of the resulting file depends not only on the resolution of the sensor, but also on the resolution of the lens, so things get even more complicated.
To keep things simple, most people use megapixel count as a general indicator of resolution, despite these caveats (kinda like most people estimate computer performance by the processor clock speed).
Guy
Thanks for the response; however, with your answer causes another question comes to mind. I remember the line resolution from Photo 101 classes many years ago. But today in Photoshop the resolution is pixels per square inch; how does that relate to the megapixel in digital?
Guy
And in general, even though it may not be quite correct, most people use resolution to mean the amount of detail involved, whether that's a pixel measurement (physical size), or line pair measurement, or just a general off-the-cuff detail assessment. In fact, a lot of people would say that, for instance, 10 Megapixels is the resolution of the camera.