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x 300 dpi ) X (6 inches x 300 dpi ) for a total of 1200x1800 or 2,160,000 dots (Pixels). Now, referring to our Greek prefixes, we know that a MEGA pixel is a million pixels, so to make a 4x6 print where our eye cannot see the dots we will require a camera with 2.1 Mega dots err pixels.

Now, 2.1 Mp in today's cameras is pretty easy to obtain. There are cell phones with better resolution than that on the market. What can I really do with my new 8 mega pixel camera?

If you look at the specs some where in the manual, or more likely on the manufacturers website, you will find that your 8 mega pixel camera probably has a sensor with a ratio of resolution around 3264 X 2448. (this will vary between manufacturers). Using the reverse of the process above we will divide these numbers to see how large of a print we can achieve from this camera. 3264 / 300 = 10.88 inches, and 2448 / 300 = 8.16. So, using our eyes as the limiting factor, we see that an 8 mega pixel camera can give us a print about 8 x 10.

Before you go attack your camera salesman that sold you the camera promising poster sized prints, please realize that these figures are for non edited images, and for 300 dpi images, which are considered "art prints". With software, using interpolation (various types, depending on software) you can increase the size of the image, keeping relative quality up to 7 fold with some software. This would bring your print a 56x70 inch print, far larger than a movie poster. The draw back to this is that the file size increase exponentially, as does the cost of the software and plug-ins.

Now lets talk about viewing versus printing.

Remember that our eye can see 300 dpi? Well our computer screen can't. In most cases computer screens can display 72 dpi. Some higher end ones are up to the 96 dpi realm. For ease lets say that the figure is 100 dpi. (Photographers don't like to complicate the math if we don't have to). So if we are wanting to display a 4x6 image in an email to grandma, we can see that our previous 4x6 at 300 dpi will be far to large, resulting on a computer screen as three times (at least) the size, making it a down scrolling 12x18 inch image! Toning it down by saving it (depending on software) as a 4x6 at 100 dpi will result in a much easier to view image, as well as a smaller and quicker to upload image.

Now you should have a grasp on what resolution is and how much you really need, depending on your shooting and printing habits. There are many more aspects to imaging that will effect your final outcome however. Please stay tuned to view more on why your point and shoot camera doesn't ever seem to get the same results as your friends fancy SLR camera.

Thanks for playing along.

Learn more about this author, Thomas Howard Elliot.
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