The math hasn't changed. However, people weren't nearly so focused on sharpness back then, and seemingly more aware of DOF.

Before I moved into digital photography, I had a pro scan some of my old 35mm Kodachrome 25 slides; after setting up my computer and a projector/screen so I could compare images to slides, I discovered that every detail visible on the slides were also visible on the (6mp) images. At one time, I wondered if that was an artifact of my lenses. However, recently I mounted my 1984 50mm lens (the one I used in taking some of the Kodachrome 25 pictures in the comparison) on my 16mp Pentax K-30, and I discovered that it was at least as sharp as the lenses I use now, so I'm becoming convinced that the comparison was valid, that the digital age has simply caused us to become addicted to more sharpness ( which is why I tend to use the term "needle sharp" instead of "razor sharp" ).

As usual, there are tradeoffs. A smaller aperture, to get more DOF, will always require slower shutter speed and/or higher ISO setting; beyond some point, getting that greater DOF will cause some detectable diffraction. Fortunately, with digital photography, experimenting costs nothing monetarily (but will of course cost time), and feedback is very fast, so the best course is probably to experiment with the photo equipment you have and then decide for yourself which combination of settings is most pleasing to you, taking your style of photography and your way of looking at pictures into account.

Off on a tangent.... Portra has a nice range to 800. yes. Speed not as limited as commonly imagined, and the resurgence of film has some new emulsions introduced, along with some old emulsions revived. Keep eye open on this. You may want to look at the APUG web site which is large format, or www.rangefinderforum.com....

Lot's of MF activity there.

What I want to mention here is that you mention landscapes and I like panoramic landscapes.

I was on the verge of pulling the trigger on about $2500 of 6X17 equipment, but I gotta say, I'm a real cheapskate.

So, I started shooting two and three frames overlapped with my Fujica G690 6X9. Then I send the film to ProPhoto Supply in Portland, for processing and Hi rez scanning (I usually just get the overlapped frames scanned by specifying frame numbers)

Then when I get the negs and scans back, I load the scans into my computer. Then I stitch the frames with Pano software, although Elements and Windows Live Photo Gallery have good stitch features.

It's been working well and I can get close to 6X17 with two properly overlapped 6X9's, and close to 6X24 with three.

And, I'm doing this with a less than $500 camera.