I have done a search of the forums and opinions differ somewhat. Some say that it is as good as impossible to see through a R72 filter, although at least one member says that looking through a R72 for about 30 secs reveals the scene enough to focus. However this was the intense sun of Australia and not the much weaker sun of the U.K.
At least one other has mentioned that his autofocus camera will work with a R72.
So does the AF system effectively "see" sufficiently well to focus even if the eye fails to do this and is it possible for the eyes to acclimatise to the R72 filter sufficiently well to allow for manual focusing after waiting about half a minute.
I am aware that both autofocus and manual focus are perfectly possible with a red 25A but if the "wood effect is desired then the 25A really won't "cut it"