Everything You Need to Know About Megapixels

[Hardware Secrets Team]

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Title: Everything You Need to Know About Megapixels
URL: http://www.hardwaresecrets.com/article/647

Here is a snippet:
"At the beginning of the age of digital cameras, it was all about the number of megapixels. A 2-megapixel camera was better than a 1-megapixel camera and a 3-megapixel camera was better than a 2-megapi..."

Comments on this article are welcome.

Best regards,
Hardware Secrets Team
http://www.hardwaresecrets.com

[Olle P]

Good article, especially page three!

There are a few more factors I'd like to add:

1. Screen view.
In addition to the image adaptation for printing as described on page three, there are also images you might take just for viewing on your computer or even just to publish on web sites.
These are best of adjusted in size (pixel wise) to fit the monitor if viewed on screen, or even smaller, if published on the web.

2. Image sensors.
As mentioned in the article all cameras have image sensors with rows of elements (sensor pixels).

- It is the number of sensor pixels that is presented with the camera data, not the number of pixels in the highest resolution image possible to take with the camera.

- The sensor pixels are usually arranged in a honeycomb pattern.

- The vast majority of cameras use sensor pixels that each are sensitive to one colour component only; red, blue or green. The typical distribution is to have every other row of pixels sensitive to green, and in the other rows blue and red pixels alternate. Therefore the number of pixels sensitive to for example red is only 1/4 of the given camera "resolution".

- When you take a picture with the camera set to highest resolution, the colour of an individual pixel is defined by the nearest sensor pixel, plus data from the surrounding pixels. Since most sensor pixels are sensitive to green it's my experience that pictures taken at maximum resolution will be greenish.

- When you take pictures using reduced resolution more sensor pixels fit within each image pixel, so the colour will better represent reality. When the full image contain 1/4 as many pixels as the sensor all image pixels will cover two green, one blue and one red sensor pixel, and have near optimal colour representation.

3. Digital zoom.
This is, from an image quality point of view, a nearly useless feature.
What it does is to exclude the outer parts of the sensor and create the image based on information from fewer sensor pixels.
If you take an image using maximum optical zoom, maximum resolution and highest quality setting, and then crop it in the post production, you will get the same or better result.
I can think of two conditions when digital zoom is useful:
- When the "target" is so small that you can't see it in the viewfinder without the digital zoom.
- When the camera memory is so low that you must use a setting below maximum resolution and quality. With digital zoom the image is "cropped" before being damaged by JPEG-compression.

Personally I have a 10 MP camera (Nikon Coolpix P5000), with which I use a standard setting of 3 MP images (2048x1536) at highest quality.(Unfortunately the camera can't use any other file format than JPEG. I'd rather use TIFF or RAW to avoid compression artefacts altogether.)
With these settings I get good colours while still being able to crop and/or resample the images to fit snugly within my monitor's 1680x1050 resolution.

Cheers
Olle

[Gabriel Torres]

Thanks for your addition, it was really apreciatted.

Cheers,
Gabriel

[hemo200]

there is a mistake in the article
1 Megapixel == 2^20 not 2^30

[Gabriel Torres]

Ops, fixed, thanks!