Many of the photos I've taken in low light situations seems to have what looks like red or green dots on them in random locations.  I thought these were "hot pixels" resulting from the longer exposure required for a low light picture.   I also thought this was a sign that my camera's sensor was becoming defective.

After doing a little research, apparently these "hot pixels" are actually "stuck pixels" as found on a Flickr discussion regarding this topic:

Stay away from Pixel Mapping unless you have DEAD or STUCK pixels...

Pixel Mapping is NOT for hot pixels...

DEAD pixels are ones that no longer work, and would result in a black dot at the same spot on ALL images.

STUCK pixels are ones that are stuck on and would result in a colored dot (usually always the same color) in the same spot on ALL images.

Those are the ONLY pixel issues that Pixel Mapping will resolve.

I think I read that Olympus recommended that you DO NOT run pixel mapping to often as it could result in good pixels being mapped as bad, and once a pixel is mapped as bad it is turned off and can not be turned back on (at least not by the user).

I addition to being able to remove "stuck pixels" through pixel mapping, a feature I never used on my camera was the noise reduction.  A F.A.Q. section on the Olympus web site explains how noise reduction works on the E-500 and how to turn it on:

How does the EVOLT E-500 combat noise commonly found at high ISOs?

My online search seems to show that hot pixels and/or stuck pixels are just part of the dSLR world and having a few spots on one's image isn't justification for throwing-out one's camera.  Between using the camera's pixel mapping and noise reduction, or through manual photo processing, the hot pixel issue is one that I have to learn to live with but can fix.

Another cool tip found on the Flickr discussion group was how to get use data out of my camera, such as how my pictures I've taken with it:

Hot pixels is normal on almost every SLR camera and can be removed quite easily.

I would be more concerned with shutter activations because that is a major mechanical part in the camera that can go wrong.

Apparently, Olympus guarantees the E500 for 50,000 shots. I’ve taken 61,565 shots and there is no sign of failure but I’m ready to accept a problem!

If you want to check the usage stats on a E500 follow this procedure…

1. turn the camera on
2. open the memory card door
3. press “play” and “OK” at the same time
4. press the following buttons in the following order - "up" "down" "left" right"
5. fully press the shutter release button
6. press the “up” button
7. press the “right” button – takes you to page 2

On page two you will see…

R: wwwwww – how many times the shutter has fired
S: xxxxxx – how many times the flash has fired (includes hot shoe flash)
M: yyyyyy – number of times mirror lockup has been activated
U: zzzzzz – SSWF count - number of times sensor cleaner has been activated

My E500 says:

R: 061565
S: 014403
M: 000088
U: 008833

If you shoot RAW then isolated pixels aka hot pixels is an easy situation to deal with. Lightroom and Photoshop ACR will automatically remove them for you and other RAW processors will give you an option to remove them.

Although I like my Olympus E-500 for taking photos in daylight, I've been very frustrated with it when taking photos in low light situations.   Since it's winter here in Wisconsin, I find myself almost always in low light situations these days and I started leaving my camera at home because I knew that I wouldn't be able to get good shots with the built-in flash.

As with most cameras, the built-in flash usually resulted in a lot of "red eye", unnatural shadows, and over-exposed subjects with dark backgrounds.   If I turned the flash off, I just ended-up with a blurry mess (even at high ISO settings) since I rarely wanted to shoot subjects that were not moving.  

One thing I really don't like about the E-500 is that is strobes the built-in flash in order to get a focus lock.   Not only is this very distracting, especially if the subject of your photo is a person or an animal, but it doesn't seem to work very well since the camera doesn't get a focus lock very quickly.

After attending a wedding a few weeks back where the photographer was taking one great shot after another in low light, I asked the photographer what his 'secret' was.  He said that he was just using a 'fast' lens along with the external flash and had his camera set on auto focus.  Obviously, there there wasn't anything magic about what this photographer was doing to get good shots, but he did have a good external flash that I did not have.   So, thanks to a decent sale on Amazon.com, I purchased the Olympus FL-50 external flash.

Although Olympus offered cheaper models than the FL-50, I decided to get their flagship model because it is the brightest flash offered.  As someone stated on the DPReview.com forums, "You can always tone-down a bright flash to make it dimmer, but you can't make a dim flash brighter."

This is the first external flash I've ever owned, so I wasn't expecting to be able to take decent photos for quite a while until I learned how to use it.   However, I was pretty pleasantly surprised with how quickly I was able to start taking very nice indoor shots while just leaving the flash in it's auto mode.

Because the FL-50 blocks the built-in flash on the E-500 from popping-up, the flash uses it's own red light to assist the camera with focusing in low light situations rather than strobing the built-in flash.  To me, this is a HUGE reason for buying this flash.   No more annoying disco-tech strobing and the camera does get a focus lock much more quickly with the IR light.

The other feature I really like about the FL-50 is it's pivoting head.   It can be pivoted vertically and horizontally so you can make that the light is bouncing off the correct object regardless of if the camera is vertical or horizontal.

The only thing I don't like about have a flash on the camera is that the camera feels very awkward now because it's so top-heavy.  If I'm not holding onto the camera and just have it hanging around my neck by the strap, the heavy and tall flash has a tendency to cause the whole camera to fall over.   I suspect this would be an issue with any flash, but is still a bit annoying.

So far, I'm very happy with my purchase.  I've got a lot to learn about how to use an external flash, but even in the few times I've used it so far, I've greatly increased the number of successful photos taken as compared to when I was just using the built-in flash.