What are megapixels?
One megapixel is equal to one million pixels in an image. You can easily calculate the megapixels of your camera by looking at the width and height of the image in pixels. For example, if I click an image using my Canon 5D Mark III, I get an image of 5760 × 3840px. So by multiplying 5760 by 3840 pixels, we get 22,118,400 pixels which mean that the image that I clicked has 22.1 megapixels.
How many pixels do you actually need?
The requirement of megapixels depends on the final use of the image clicked by you. There are three major ways you can use your images after clicking them from your camera:
- View it on your monitor
If you click images just to view them on your monitor, you hardly need a high megapixel camera. Suppose you own a 19-inch 1920×1080 resolution monitor, all you would need is a 2-megapixel camera to view the images clearly.
So even if you would be cropping your images a bit after clicking them, you can use a 5-6 megapixel camera to view images without any compromise in display quality.
Upload on social media
If your end use of clicking images from your camera is to upload them on social media platforms such as Facebook and Instagram, all you need is a 2-megapixel camera. But why?
No matter how high-resolution your image is, Facebook and Instagram would downsize them to their respective maximum resolution.
Facebook – Ideal image resolution
Square image: 2048 x 2048 pixels
Horizontal image: 2048 x (as per the image ratio) pixels
Vertical image: (as per the image ratio) x 2048 px
To upload any image on Facebook, be it in square, horizontal or vertical proportion, you only need a 0.2-megapixel file. Even if you try uploading a 4000 x 4000 pixel image, it would automatically be downsized to 2048 x 2048 pixels if you are uploading with the high-resolution option checked.
Instagram – Ideal image resolution
Square image: 1080 x 1080 pixels (maximum)
Horizontal image: 1080 x 566 pixels (maximum)
Vertical image: 1080 x 1350 pixels (maximum)
If you upload any high-resolution image on Instagram, be aware of that fact that the image will be compressed into the respective maximum proportion as mentioned above. So if you upload a 4000×4000 pixels image, it will be downsized to 1080 x 1080 pixels.
If you plan to print your images, you need to make sure that the megapixel count is good enough for the size of the print. If your image has fewer megapixels, the final print would lack sharpness. To get the best quality prints, you should make sure that you consider 300 dpi range.
As you can see in the table shown above, if you want to get a photo printed in 8×10″ an 8-megapixel camera would be good enough for you.
Similarly, if you wish to get a big print of 20×24″ then you will have to use a medium format camera or a DSLR which can click images having more than 43.2 megapixels.
Different print sizes would require respective megapixels in order to get clear print quality. You can get the prints at 200 dpi or even 150 dpi, but then you might have to compromise on the quality. The more the dpi, the better would be the print quality and the image would appear much clear even while standing close to the print.
It is a simple math, just multiply the print size by dpi and you will get the image dimensions you would require for that particular print size. For 8×10″ print at 200 dpi, you would need an image of 1600(8″x200 dpi) x 2000(10″x200 dpi) pixels. Now multiply the dimensions (1600×2000 pixels) and you will get the required megapixels for the print, which would be 3,200,000 pixels = 3.2 megapixels.
Reasons why more pixels are better
You must have heard that one should always buy a camera with higher megapixels. Well, partially it is true if the end use of your photographs would be either of these:
As I have mentioned above, if you wish to get large prints you need to make sure that you are using a camera which has a sensor capable of required megapixels. If your camera fails to meet the megapixel requirement, you would end up getting prints which would lack clarity and would appear substandard.
So if you are planning to take up some commercial assignments and your asks you to deliver images with are to be printed at 20×24″ canvas (300 dpi), you would definitely require a camera with at least 43.2 megapixels. If your client is happy with a print at 200 dpi, you would still need a 19.2-megapixel camera.
There are times when you have to crop your image in order to make it look more pleasing and catchy, which is not at all a wrong practice. But as you crop your image, you are actually cropping out the pixel from your image.
Keeping this fact in mind, you need to make sure that either you frame your photo in such a manner that you do not have to crop it too much or you are using a camera with high megapixels.
More megapixels are required if you crop and image and then wish the same to be printed on a large canvas. So if you are using a camera with less megapixels, try and frame the scene which does not require much cropping afterwards.
Digital zoom is basically when you zoom using your digital camera, and not the lens. If you use a digital camera which offers digital zoom, you would end up losing pixels as you increase the zoom range.
While using the digital zoom, your camera is actually cropping the frame and allowing you to capture selected portion. If you zoom 50% using your camera, you are actually cropping the image by 50% and thus losing the pixels.
So it is advisable to avoid using digital zoom and try and get closer to your subject, if possible. If not, then you need to get a digital camera with high megapixels so that you can manage to get a decent amount of pixels in your image.
Why more pixels can be bad for your photos
We have all seen camera manufacturers emphasizing on the fact that they have a sensor with much more megapixels that their competitors, but that always does not benefit you as a photographer.
I have come across many people who choose their digital camera solely on the basis of the number of megapixels it has. Well, before you become a victim of this marketing myth be sure to do some research and find out the sensor size and the pixel size of the camera.
Affect low light performance
Assuming that the sensor size is the same, manufacturers are adding the number of pixels in order to attract budding photographers. But ideally, the pixel size is getting smaller and smaller as more pixels are being added on a sensor which is of the same size.
The issue with the small sized pixel is that each pixel will store less light as compared to a bigger sized pixel. The ‘A’ sensor with 16-megapixel will receive the same light as the ‘B’ sensor with 8 megapixels, but each pixel within the sensor ‘A’ will receive comparatively less light that each pixel within the sensor ‘B’.
Assume that there are two rooms of the same size, in the room ‘A’ you can fit 100 big buckets and in the room ‘B’ you can fit 400 small buckets. If you have to fill 100 litres of water in each room, every single bucket in the room ‘A’ would collect 1 litre of water whereas the one in room ‘B’ would collect only 0.25 litre. Similarly, when you add more pixel to the sensor of the standard size, the amount of light retained by each pixel reduces.