A basic camera question

[mirrodie]

A friend for mine jsut bought a 30 D and asked me a question I never realy thought about.

the camera takes 8.2 mega pixel sized images.. But when he is looking at his images once uploaded to the computer, why doesn't it show the file as 8 MP large (he shoots in large jpeg, not raw)?

The file thumbnail shows it is usually as 1.81 megabytes large.

I never thought about it. I know I am thinking in a linear fashion but what are he and I misinterpreting?

[Derf]

A Jpeg is a compressed file...just becasue there are 8 million pixels does not equate to storage space of 8mb. 1 pixel can be .2 bites in size or 5 bites or 1 bite.

In your head, you thing 1 megabite and 1 pixel are the same, 2 different things....

You can save an image FULL 8megapixel resolution and can have 3 different image sizes....(CAN BE ALOT MORE)

1.7mb High compression Fine JPEG mode
3.3mb low compression JPEG mode
19mb RAW

the difference is the compression of the picture that make the storage size. I can make a picture any size literally in MB, but that will not change the ammount of pixels in the actual photo, just the quality of the photo itself.

Hope I did not confuse you more!

[Matt Molnar]

Yes, what Fred said.

Megapixels is a measure only of the number of pixels (in millions) that a sensor can capture.

1 megapixel = 1 million pixels

RAW files on a given camera should be the same file size every time. The file size of JPEGs, however, will vary depending on the detail of the picture.