megapixels

Can anyone tell me the equation to work out if I crop a 8.2MP image down to 50% of it's original size how many pixels will be left.

logic say 4.1 but I thought I read somewhere that it doesn't work like that.

Thanks in advance for your answers.

My 40D produces 3888 x 2592 pixels That is 10,077,696 pixels.

Taking the image to 50% means you half the height and the width so 4x reduction and size is 1944 x 1296 or 2,519,424 (2.5Mp)

To halve the No of pixels you should crop only one side by half

On an 8.2 MP camera...we can use the 30D for this example... The pixels work out like this...

3507 pixels on long end
2338 onshort end

3507 x 2338 = 8,199,366 Pixels or 8.2 MP

If you crop out 50% of the pixels on both the long and short end:

1754 pixels on the long end
1169 pixels on the short end

1754 x 1169 = 2,050,426 pixels or 2.1 MP roughly

If you were to just crop half of the picture:

1754 Pixels
2338 Pixels

1754 x 2338 = 4,100,852 pixels or 4.1 MP

Does that help at all??

MK

ICee wrote in post #7226778
Can anyone tell me the equation to work out if I crop a 8.2MP image down to 50% of it's original size how many pixels will be left.

logic say 4.1 but I thought I read somewhere that it doesn't work like that.

Thanks in advance for your answers.

If the 50% crop is based on diagnal length, you should end up with 1/4 of the pixels, 2.05 MP.

Oops, I did not see last post. Go with 12Mnkys.

Thanks guys that's what I was trying to get.

Cheers.

No problem! Good Luck!