Is this just a hypothetical question? Yes and no and no, in that order.
Yes, because at the moment I don't have a digital camera that produces enough megapixels to print at more than 720dpi at my normal print sizes. It might be an issue if I chose to print small enough. Nor do I intend to purchase a drum scanner for my medium format negs.
No, it's not hypothetical, in the sense that high megapixel cameras are starting to become available, and I could purchase one if there was a clear benefit. Your 30 April newsletter seemed to be an invitation to do so, in order to use all those extra megapixels. But given Roy's description of how QTR resamples, I just can't see how that makes any sense, beyond a certain (720dpi) point. Perhaps for mega-sized prints.
And no, because there is the general issue of workflow and resampling or not for QTR. This is the real reason for my question. For some time I resampled my images (up) to 720dpi for K7 printing with QTR. I don't recall why I did this, but I must have read somewhere that QTR expects 720dpi. Then somewhere along the line I read your comment to just give QTR whatever optical resolution you have, be it high or low, and let it deal with it. The implication to me was that QTR wasn't resampling. So I did this. It was a more convenient workflow, as it meant that I didn't have to save temporary images for printing, I could print the master copy.
But then came Roy's recent post indicating that my initial understanding was correct - QTR expects 720dpi, and either resamples the image itself to get it as an input resolution (on Windows), or relies on the OS printing pipeline to do it (MacOS). As I mentioned in my initial post, this is precisely the issue that has caused so much debate, esp on Lula, about how to print using the Epson driver. Do you resample or not, if so what to resample to and how best to do it, and if you don't is there any resampling occurring anyway, and if so what software is doing it and how is it doing it?
This statement of Roy's on Yahoo-QTR has caused a fair bit of off-forum consternation and argument about what the best K7 workflow is. In reading what you and Roy have said, there is the appearance of an inconsistency. True, Roy like you says to just throw whatever optical resolution that you have at QTR. But for different reasons. He thinks that any resampling effects are not likely to be seen. I am not a Mac user, but based on what I've read on Lula I'm really surprised that he says this, given the reports of noticeable resampling artefacts that the MacOS printing pipeline produces. At least on Windows any resampling is done by QTR and therefore was programmed by Roy and therefore hopefully is better quality. There are some, including those who occasionally post on this forum, who think you should never resample, and only print at the physical size that corresponds to the optical resolution at 720dpi. Personally I think that's one step too far.
You may well say, why not make comparative prints yourself and see? Because I'm more interested in making images rather than multiple test prints and staring at them. How would you ever know whether your tests cover all types of images? It ought to be possible to specify the optimal workflow and just stick it. So that's why I raised the question - not because I necessarily want to print 1000dpi images, but because I want to understand the optimal QTR K7 workflow.
Thank you for your responses.