So the question is: If I take the same picture with a 4 mp camera, a 6 mp camera and an 8 mp camera, then re-size all the pics down to 640x480 and post them here, would anyone be able to tell the difference or does the re-sizing negate the increased megapixels?

what i do know:

any time you resize a jpg, it re-compresses and loses a little bit more information. if you had a raw image from a 8mp and resized it, it shouldn't lose anything.

That's what I was wondering. Thanks Dood!.

The reason I asked, is because I have a 6 mp camera and got a new 10.2 mp camera for Father's Day and was wondering if one would even be able to tell the difference once I've re-sized to post here. I suppose I could take a pic with both and post them up and try to see that way.

Yep, Ld00d's right - there should be no difference in quality at all. Megapixels are just a measure of how big the photo can be taken. But when reduced, all shots should be almost identical in terms of quality.

However, if you're looking for the best quality, I'd recommend uploading to a 3rd party photo site. I saw much better quality and size from other's photos when they were using sites like Photobucket (which resizes the photos for you) and linking the shots over to their posts. When I uploaded to the DT gallery my shots lost color quality and crispness. Now that I use Photobucket, things are looking much better.

Cool. Thanks for the info. I always use a third party site to resize to post here--much faster and easier.

The optics of the camera will make a bigger difference in quality than the megapixels.

_________________
There's a lot of shame on a road bike. -- evdog

Meaning...?? I know nothing about cameras.

I use irfanview to resize pictures. its easy

Quality of sensor, metering and software has much to do with the quality of the image, too. These criteria are where our cell phone cameras actually and expectedly fall short, before we even get to the low-quality, dirty lenses on them.

What's that new 10.2? I bet it takes better photos than yer cell phone.

As the others have stated, the megapixel rating is not as important as the quality of the lense, the CCD and software.

As mentioned, the quality of the light going to the sensor is primary to image quality at max resolution (megapixel for camera speak). Any time you reduce the image size from an original file, the graphic editing program has more information to define what the resized image should look like. Often Times slightly out of focus images in the native (full) resolution of the camera will look crystal sharp once you resize down to 640x480 or even 1024x768. Sensors are important as well but they can only record what the lens lets through.