<p>Curt, Hosteen and Patrick,<br>
Thanks for the response, guys. My principal interest is bird photography, which often can benefit from fill flash. Fluffing around with manual ISO settings to achieve a balance between shutter speed and overall exposure (as I have been doing) is not always productive - the bird usually disappears! <br>
I feel Curt has confirmed my suspicions. As an example, the D7100 with Auto ISO and fill flash (with a SB 800) works perfectly in the field, with some clever exposure adjustments for background and subject.<br>
Looks like it might be time for an upgrade.</p>