I see... I somehow hate not being able to see data that "must be there" :-) Here I have at least two problems:
1. Have no idea how to find out where this tag/value might be (as I can't force exiftool to show tag by it's tag number),
2. Perl is something like chinese for me.

So, I've cheated a bit (hoping Canon doesn't make big changes). Inside "Canon.pm" file, I've found a part responsible for decoding (among other things) those two tags for 40D (as far I understood this stuff). So, I've duplicated and added following:

-to force exiftool decoding 450D as being 40D (you know better than I am).
And yes, the same two tags (as for 40D) have expected values. I tried several shots, and values seems to be right (as nobody can't know for sure, what EXACT values are to be expected) -I believe, those values show Deepth of Field (which doesn't have exact predictable value).

I've also downloaded some other files of XSi/450D, XTi/400D and XS/1000D and changed above lines according to those cameras. My findings are:
XTi/400D: doesn't contain 0x0043 and 0x0045 tag values -exiftool decodes ok.
XSi/450D: does contain and populate 0x0043 and 0x0045 tags -same as 40D,
XS/1000D: does contain and populate 0x0043 and 0x0045 tags -same as 40D.

Somehow I have feeling, that tags 0x0013 and 0x0014 are becoming obsolete, last time used in: 400D/XTi, 30D and older 1D's (and, as far I could findout, in 5D) -all their successor don't populate those tags.

Of course, I can give no "proof"... but I am quite sure of above. It that enough for exiftool update? :-)

Greetings,
Bogdan