Does Dodge & Burn Avoid Extremes?

I have a scan of a 50-year-old photo of someone's face. The subject was wearing dark blue, and the color has seeped into the chin and jaw area. Above it there is u-shaped blown-out highlights area. I'm trying to use dodge & burn to even out the area. The dodge tool works everywhere except where it's the darkest and the burn tool works everywhere that isn't the lightest. It's like the tools just skip over those areas. Does Photoshop protect these extreme areas for some reason?  I thought that might be the case and screengrabbed my monitor into a new file. It couldn't have any hidden layer information that way, right? 

The attached photo shows the original, after dodging and after burning. I cleared away distracting portions of the image. in the middle "dodge" illustration you can see PS didn't touch the darkest areas. In the rightmost "burn" image, you can see it didn't touch the brightest pixels.

Any idea why this is happening? 

Scott