Monday, March 29, 2010

Megapixel Myth

High megapixel value equates to better quality? Megapixel = quality?

If you search for "megapixel myth" on a search engine, you'll find many websites on this subject. In fact, there's an entire website dedicated to this. But most of these websites are text only, and full of technical jargons. Therefore, I decided to bust the myth with photos and simple language.

The devices I used to perform the comparison are Canon SD940 IS (a.k.a. Canon IXUS 120 in Asia and Europe) and the camera on the Nexus One phone. Canon has 12 MPs, set to 5 MPs during testing; Nexus is 5 MP.

Canon SD940 IS (IXUS 120)Nexus One
Canon SD940 IS (IXUS 120)Nexus One

Below are two photos taken by the two cameras at the same spot, almost at the same time:

↓Canon SD940 IS (IXUS 120)↓
↑Canon SD940 IS (IXUS 120)↑

↓Nexus One↓
↑Nexus One↑

When reduced to this small, both look great. But if you view them at their original size, that is using each pixel on your screen to display one pixel from the photos, we get these results:

↓Canon SD940 IS (IXUS 120), 100%↓
↑Canon SD940 IS (IXUS 120), 100%↑

↓Nexus One, 100%↓
↑Nexus One, 100%↑

Obviously, Canon the real camera has much better quality. If enlarged at 300%, the contrast is even greater:

↓Canon SD940 IS (IXUS 120), 300%↓
↑Canon SD940 IS (IXUS 120), 300%↑

↓Nexus One, 300%↓
↑Nexus One, 300%↑

Due to the web page layout, I cannot give you a more comprehensive comparison within the text. So I provide this side-by-side comparison. Click to enlarge and see the side-by-side:

I was very forgiving to the Nexus One by testing under broad daylight. The result would be catastrophic if under low light:

↓Canon SD940 IS (IXUS 120), hand held, no flash↓
↑Canon SD940 IS (IXUS 120), hand held, no flash↑

↓Nexus One, hand held, the output would be the same with or without flash↓
↑Nexus One, hand held, the output would be the same with or without flash↑

You might be asking, "if MP doesn't mean quality, what does it mean?" It measures the size of the photo. It is the number of dots that make up the photo. A 5 MP photo is composed by 5 million dots. When a camera takes a photo, the following happens
  • Light ray shoots off from the object
  • These light rays enter the camera's lens
  • Lens causes refraction or reflection
  • After refraction, the light arrives at the sensor
  • You can imagine that a 5 MP camera has 5 million units of sensors, where each one must determine how much red, green, and blue is hitting itself

If the lens is bad, the number of MPs of the sensor is irrelevant because the sensor is behind the lens. If you want image quality, the basic requirements are
  1. Good lens, no faulty refraction
  2. High MP value
  3. The photosensor must be accurate about the color and brightness

Therefore, high MP value is a necessary condition, but not the only condition. If you want to learn about the image quality, the only way is to judge from sample images from an objective web site.

How many MPs are enough? It depends on your ultimate output.
  • Viewed on a 19" screen → 1.3 MPs
  • 4×6" print (10×15 cm) → 2.2 MPs
  • Viewed on a 26" screen → 2.3 MPs
  • A4 size print (29.7×21 cm) → 8.4 MPs
  • 40×30 cm print →16.7 MPs

If a camera cannot be judged by a simplified number, can you judge a person by number? Can you evaluate a student by a standardized test score? Can you say how "achieved" a person is by his or her salary?