Dan, I understand why you would take what I said as not being well informed.
My statement is based upon my verbal discussions with someone who has done extensive tesing of HD cameras with both halogens and HID lights. I would not make a presumption based upon speculation. The source who I will not mention outright has sent a full test report to me for review and all I can say is that this individual has been around quite awhile and done his fair share of work underwater.
I'm not going to debate the issue of shooting SD -vs- HD. Those who shoot it have their reasons to shoot it. I am sure that down converted SD from HD looks very good - since I do not have an HD camera yet, I can only takes others word for it. But this is just a piece of technology - just as SD is. I've seen world class images taken with little more than a simple camera - and I believe the same can be said for video. Use what you have and eek out all you can from it. Is HD the future - that's a given.
There is a sense of elitism that is apparent here in this part of the forums. Some of us don't have thousands of dollars to spend on HD gear and the associated added costs to work with it (computer upgrades, monitors, etc). Just because one still shoots SD does not make them any less professional than someone who shoots HD.
To make a statement that one is limiting themselves is a subjective one - I have spoken with other VERY talented underwater shooters who are still shooting SD for their day in and day out work and will hire out HD if the project warrents it or the client will allow it to be worked in to the budget.
I may not be the most informed on the topic of HD, but what I have learned so far, HD is still evolving and will continue to. But until I can afford HD, I will be quite content with the SD gear I will soon have and be secure in what I learn - and make money in the process.