Fuzzy Dark Objects Against Bright Red Background

Question

For as long as there have been digital cameras (Canon ones, at least, which are the ones I've looked at more images from), there's been a tendency to blur bright red objects - sometimes severely.  Ever take an image of a car and notice missing detail in the taillights?
Let me say at this point that Camera Raw seems to do this less than most. Thank you for that, Adobe!
I understand how de-Bayering works, and that with a Bayer pattern camera there's really only half as much information directly measured for the red and blue colors as for green, but what I'm talking about seems if anything only indirectly related to that...  Note that you don't really see the same issues with Blue objects.  It seems to be more related to the transitions between colors.
Here's a sample image converted in Photoshop...  Felt letters on a cloth background.  Note that the dark letters look significantly fuzzier against the bright red background than do most of the lighter letters.  You might have to blow the image up by clicking on it to see this clearly.
All noise reduction, sharpening, and lens distortion correction were turned off for this conversion.
I thought of the possibility that the dark letters might be just merging more with their shadows more than the lighter ones...  But I don't think this is the entire issue here.  There are really no shadows visible behind most of the letters near the top, yet the dark ones are still fuzzier than the others at the top as well.  Visually things just don't look quite right, and this is an extreme example.
From what I have been able to see, the 2003 process blurs the dark letters very slightly less than the 2010 process does.
I'm not really complaining about ACR's performance in this area - in fact I find I can recover more detail in red objects than with other converters.  I'm just curious.
Your thoughts?
Here's the raw file, by the way:  http://Noel.ProDigitalSoftware.com/temp/IMG_3468.zip
-Noel

Answer 1

Yes, you've made the point well about the need for the green channel to show fine luminance detail, and to be fair the violet letter on red background in the image above is pretty fuzzy (red and blue data, but little green data).
I've always also suspected, however (and you touched on it with your comment about selective sharpening), is that the red channel may be more noisy and subject to more noise reduction - in Canon cameras at least - because the light levels reaching the red-filtered photosites are somewhat suppressed by the Antialiasing/IR suppression filter (which is blue-green colored), and thus the measurements must already be boosted to compensate.
-Noel