Why is my picture overexposed?

Setup: Canon XT, 28-70mm, w/ tripod.

I was at a local nature trail and tried to slow the shutter speed to capture waterfalls in a cotton appearance. I've done it successfully once before using 0.3" (different waterfall however), but this time the picture looked over exposed regardless. Why couldn't I obtain a more cotton affect?

This is the picture, and below are the specs
http://www.flickr.com/​photos/8250417@N03/543​144590/

Tv(Shutter Speed)
0.3Sec.
Av(Aperture Value)
F22
Metering Modes
Centerweighted average metering
Exposure Compensation
0
ISO Speed
100
Lens
28-70mm
Focal Length
28.0 mm
Image size
3456 x 2304
Image Quality
RAW
Flash
Off
White Balance
Cloudy
AF mode
One-Shot AF


Here is the second take with a faster shutter speed, but it's still not the cotton look I was looking for, but it looks better.
http://www.flickr.com/​photos/8250417@N03/543​266189/

Tv(Shutter Speed)
1/25Sec.
Av(Aperture Value)
F22
Metering Modes
Centerweighted average metering
Exposure Compensation
0
ISO Speed
100
Lens
28-70mm
Focal Length
28.0 mm
Image size
3456 x 2304
Image Quality
RAW
Flash
Off
White Balance
Cloudy
AF mode
One-Shot AF

One possibility was the scene may have been too bright for a slower-shutter speed. Once you've closed down the aperture all the way (higher f-stop) and lowered your ISO (100) as you did... the only other ways to get slower shutter speed in some scenes is by using a polarizer to drop by another f-stop or so... or you'd need to use Neutral density filters to block the overall amount of light entering your lens.

As for the first photo the shutter speed is a bit too long.
aecond one it bit of an improvement should have gone a litttle more higher shutter speed.say about 1/100 to1/ 250 sec
first of all I think part of the problem is based on the white balance is in cloudy mode.
if you have DPP reload the picture and see if you can change the white balance mode.
say to landscape? and mabye do a few more tweaks.
give it a try
If you have DPP version 3 then it would be great. or what ever program you use for PP
other wise maybe invest in some good ND filter set.
wait for other to give there input.

Sunshine is too bright for 0.3 seconds and f/22. 1/50 and f/22 would be about right for full sun. Your lens simply couldn't stop down enough to avoid overexposure with a shutter speed that long. If you used Tv mode, the aperture value in the viewfinder would have been blinking. It's important to keep an eye on that.

A polarizer would give you maybe a couple stops and allow perhaps 1/12. To get slower shutter speeds in sunshine you'll need a neutral density filter of more than 2 stops.

Or trying early in the morning or late in the afternoon when it's not as bright...

Thanks guys.

I don't see what "mode" you were shooting in. If you were in M mode, then you simply didn't watch your meter and/or get your shutter/ap. settings correctly. Now, if you were in Av mode..... or Tv mode.... and you got an overexposed image, then possibly when the camera 'grabbed' the other half of the exposure (av or ap), then it could have been maxed out and blinking at you, telling you there was a problem......but was un-noticed.