What are Megapixels?

A question I'm often asked is "how many megapixels should I get?". Many camera salesmen present megapixels as if they are the single most important thing in your camera and sell equipment on the basis that one camera has more megapixels than the others.

In truth, megapixels shouldn't worry you at all. All modern cameras and even cameras ten years old, have more than enough megapixels for most people needs. As I've said in previous blogs, the lens, sensor; ISO, shutter speed and F number ranges are more important.

First off, let us understand what a pixel is. The name is an abbreviated version of picture element. Pictures is shortened to pics and then to pix and the first two letters of element is added. The picture element referred to is the little dots that make up an image in your camera, print, monitor, etc. These dots are tiny and so tightly packed together that the look like one continuous image and can't be seen individually, with the human eye.

So, for example, when you print an image at 300 pixels per inch or dots per inch, you have 300 pixels or dots for every inch (PPI) along the side.  A print 10 inches by 8 inches, at 300 PPI has 10 by 300 pixels on the long side, in other words, 3000 pixels and 8 by 300 pixels on the short side, 2400 pixels in total.

To find out how many pixels are in the image as a whole, simply multiply 3000 by 2400, that gives you 7,200,000 pixels. A megapixel is one million pixels, so it is 7.2 Megapixels.

---

A print at 300 PPI is a high resolution image. In high resolution printing it is recommended to use between 240 and 350 PPI. This standard is used for magazines, books and wall prints. If you choose to print at 240 PPI you will only need 4.6 Megapixels. 

There is also the option to use low resolution printing. Posters, for example, are printed at low resolution. This would require resolutions of 25 PPI and up. Obviously, you will need even less megapixels for one of these images. So for example, if you want to print your image at the standard poster size of 36 by 24 inches and use 50 PPI, you will have 36 by 50 pixels on the long side and 24 by 50 pixels on the short side or 1,800 by 1,200 or  2,160,000 pixels. That is less than 2.2 Megapixels.

---

​So far, I've written about printing but suppose you only want to display your images on a computer or smart phone screen. What do you need then? The resolution of a screen is 72 PPI. There is no point in using a higher resolution, as it will slow down you display, while it works out how to show the higher resolution, removing pixels and trying to get an accurate representation of the image, at the same time.

If you are sharing your images by email, 72 PPI is also the resolution that you will use. The gives the best representation of your images on the receiver's monitor or screen. If you're sharing images for printing, you will need to send one to match the requirements, as laid out above but usually, they are for viewing only.

Let us suppose that you are sending an image to fit the screen at the other end and the screen is 1,300 pixels by 800 pixels. That makes the screen 1,040,000 pixels or just over 1 Megapixel. If you want to know what the dimensions of the image should be in inches, simply divide the 1,300 and 800 by 72, giving you 18 inches by 11.1 inches at 72 PPI, in landscape format.

If you are posting your images on a website, there will be maximum dimensions you have to stick with. For this site the maximum is 500 pixels by 300 pixels or  150,000 pixels.  That's 0.15 Megapixels.

---

So, as you can see, we've come across no circumstances where you require more than 8 Megapixel in normal use. If you have an 8 Megapixel camera and you want to print a large, high resolution image, that requires 16 Megapixels, for example, there are ways of solving that problem without investing in a new camera. There are plug-ins for editing programmes that will sort that out for you easily and at low cost.

The simple answer to the question "how many Megapixels should I get?" is that it doesn't matter. All cameras on the market have more than enough Megapixels to do even professional photographers.

Scientific cameras require much higher resolution and there's a race on to be the first with the next level of high resolution. To the best of my knowledge 185 Megapixels is the highest resolution available at the moment but there are talks of a 240 Megapixel camera coming out soon.

It's a bit like motor manufacturers producing cars that can go at 380 KPH, when the speed limits in all countries are 120 KPH or lower.

In a way, all of the extra pixels are in fact a waste. They take longer to process, require more storage space and end up being dumped at the final stage of processing.

---

Until next time, enjoy your photography, take good care of yourselves and those you love and keep shooting. If you have any questions or comments, please feel free to contact me, by leaving a comment or emailing [email protected]

Bye bye,
​Eddie

Eddie Guiry Photography, 085 1531498 or 069 69381, email [email protected] Facebook - Eddie Guiry Photography, Viewbug -
http://www.viewbug.com/member/eddie2#/eddie2/followers  500px -
​https://500px.com/eddieguiry

---