Hi Charles,
I'm pretty sure you have the same red spot issue that has bitten many others. I was in a discussion about this very issue a few months ago:
http://luminous-landscape.com/forum/index....c=40262&hl=I didn't know that the 70-210 had this problem, particularly, but I think strong back light such as yours can bring it out in many otherwise fine lenses. If you read my post you'll see that I've owned a couple of lenses that were simply unusable, even in conditions less extreme than what you describe.
For what it's worth, here are some suggestions.
1.- Buy the new VR-II lens. Likely it's coating and design will prevent the problem in the future. Of course, I don't KNOW this, but, hey, it's not my money! What's a couple of thousand dollars more of less?
2.- Unless you have creative reasons for your set up, I'd turn down the background light a bit, so it registers more in the 250-250-250 range. Reasons?
[blockquote]
a.-The edges of your subject will be cleaner, especially hair. Even though 255 isn't off the tonal scale, it still creates a lot more flair and edge fuzziness. Unfair but true.
b.-The difference between 255 and 250 in terms of f-stops can be surprisingly large. Could be a full stop. Imagine how much better behaved the red spot will be if it's a stop darker. Might disappear altogether.
c.-Granted, this will create work for you in post-production if you want to clean up or erase the white background. As a worst case, though, you can apply a constant adjustment curve that will bring your results back to where you would have been with the brighter background. Then do a rough bit of black painting in the layer mask so your skin highlights don't turn white.[/blockquote]
3.-To repair the pictures you've already shot, you could make a couple of Adjustment Layers. One would be Hue/Saturation, in which you select the reds and turn their saturation down. The other Adjustment Layer would be a Curve. Make a dark curve and use the "Blend If" settings so the curve only applies to the tones of the spot. Then, for both adjustment layers, paint a soft white dot into their black Layers Masks which correspond to the position of the red spot.
4.-If you shot raw, the new Adjustment Brush might be a great help. I used Auto Mask to help define my spot, then fiddled with Brightness, Contrast, Saturation and a bit of Color to get the spot to match the surrounding area. The Adjustment Brush can also be copied from one file to the next if you synchronize "Local Adjustments". Come to think of it, this method can also work for existing Tiff files, provided you tell ACR to open Tiff files, and you haven't made any other adjustments in those Tiff files yet. MB