I’m not saying don’t use PhoPhoto. Use it. Have a ball. I am saying that when your working space is far greater than your printer/paper space you are knowingly introducing an unnecessary unknown. Which adds mystery to the output but nothing else of value.
If some one can explain how a color outside the print space is of some value during editing, I’ll read it. But at the moment, it’s mere religion.
It's neither a religion nor an unknown-even if _YOU_ don't yet know how to do it.
Look, you have a capture space, a working space and a printer space. To take a capture space and by virtue of converting to a working space, clip or throw away color, you've forever limited the usability of such color and lessened the value of the image for the future.
Going from ProPhoto RGB, which contains not just "most" of the colors cameras can capture, but _ALL_ colors a camera can capture, to your output profile allows _YOU_ to decide how the color transforms will be handled.
It's _NOT_ religion that today's inkjet printers can use a meaningful amount of color outside of even Adobe RGB, and it ain't just Canary yellow but in the case of the new K3 inks a LOT of dark deep saturated colors that fall outside of Adobe RGB, but within ProPhoto RGB _AND_ the K3 ink gamut.
Color outside the print gamut itself can be useful in that YOU can control how those colors are remapped. How? Photoshop Soft Proofing-if you know how to use it. The Absolute Colormetric use of Soft Proofing (using ink black and paper white) can show you exactly how to adjust what are out of gamut color into the gamut of the output device. You can alter the relationships of the colors and actual produce results by virtue of those out of gamut colors. Yes, they won't "print" but they will absolutely impact how the final output looks. Yes, today's displays can't show you "everything" but using Soft Proofing correctly, you can be about 90% accurate in your visual predictions on-screen to print.
If you don't have the data, you can't do anything with the data...hense the reason for working with data outside of the color space of the output and if you know what you are doing, working with data outside the color space of your monitor.
Personally, with the recent rate of progress in cameras, output devices and displays, if you _DON'T_ work now with an eye to the future, you are being incredibly short sighted. Michael's review of the 4800 not withstanding, the total volume of color capable of being reproduced by the 4800 vs the 4000 is seriously larger-even if he didn't do the volume mapping to prove it to himself.
We'll have computer displays very shortly that will have at least if not larger color gamuts than Adobe RGB and luminance output that is bright enough to work in normal room light.
To be honest, even ProPhoto RGB is actually too small a color space to work in when limited by 16 bit. With the deployment of even limited HDR space in Photoshop CS2, we're looking well beyond the current limitation of 16 bit integer to 32 bit floating point and new color spaces that will extend even beyond what ProPhoto RGB can contain.
Will we see cameras that can capture or printers that can print it? Not for a while yet, but remember, image processing is also an advancing art and still limited to the current algorithms in use-which keep getting better. But even if you can't capture or print the colors, you CAN archive them in your files for a time in the future when you may be able to. Also, understand that image processing is just really elaborate math-and the more data you have, the more refined and accurate the results of your processing algorithms. Which translates to better results even in smaller gamut output.
There are a lot of people out there with a little bit of knowledge and often the "nearly blind" will end up leading the "blind". The "unknown" won't stay that way long, and there's little value in "religion" as you term it...but there is science, if you are inclined to learn it.