Hi,
Don't flame me if this topic has already been beaten to death.....
I was going through the EXIF data of my photographs and exported to focal lengths used to a spreadsheet. In 35mm terms I found (stumped by that) that the distribution of photographs is far from uniform: I basically found a peak around 24mm, one around 50mm and a peak, but lower, around 90mm. The three peaks pretty much summed up to 80% of all shots taken.
Do you have similar experience?
That's it man, I'm warming up the blow torch now, gonna let you have it....
Okay, just kidding.
Primes vs Zooms of course is one of those classic "arguments" or discussions with strong proponents on both sides of the house. I tend to be a centrist on the matter and look at it more practically so I have both and love both. I'm actually in a somewhat similar situation as you are: I'm currently a low ISO DX body shooter (Nikon D2X, D300) who shoots studio and landscape, with intentions to go FF once a more affordable higher resolution Nikon option becomes available as I don't shoot much for $$$ these days and thus can't really justify a D3X at the moment. I have a deep investment in Nikon glass and prefer Nikon glass over both Canon and Sony so I'm not switching just because somebody has a body I might like this year and Nikon doesn't.
Like you, I also have a chemical darkroom background as well as a large format/medium format background although I always gravitated to the 35mm format for portability and for ease of use in fast moving situations. Since I shoot people, often moving, in a studio space, the DSLR "form factor" fits my personality the best even though it's obvious that a 40 grand Phase camera/back would give more "ultimate" image quality. I also print mostly 16x20" - that's actually my most common size. Where we differ is since I do studio shooting where AF is required given my personal style and preference for fast moving sessions, I don't really see, at this point in my own personal plan, that a large investment in manual focus lenses make sense. Perhaps over time as I likely gravitate towards a higher percentage of my work being landscape that might be the case, but at this point in time, my approach has been to focus on slowly building a lens collection that offers as good as I can get in the focal length ranges I use, that are AF. This of course eliminates the Zeiss lenses since they are MF, which are quite nice, but really only the 100/2 Makro Planar interests me and it still may be the one Zeiss that I get even though it's MF, since it is so bloody good an optic.
I made this choice of concentrating on the lenses first because it became evident that the camera bodies would come and go across the years while excellent glass would (or perhaps better stated, could) remain a constant. In the Nikon line, through various tests, I've discovered that a lot of times the best image quality option happens to be a zoom, and sometimes it happens to be a prime - so instead of getting into a holy war and picking one side, I have chosen what I feel, after my own careful, extensive, and exhaustive evaluation, the lenses that work the best for me, and I've always got my eye out for the new ones being released that may replace my "weakest" links in the current collection. So given I have fairly high standards for the image quality of the lens along with the requirement of it being AF, and frankly, a secondary "like" for a zoom since it allows for quick framing changes when shooting in the studio, I've ended up with a mixed kit of the 14-24/2.8, 24-70/2.8, 60/2.8G AFS, 70-200/2.8G AFS VR2, and 200/2G AFS lenses as my core kit - these are all lenses that to me represent the best I can get in AF lenses in most any mount and in the two zooms at the "edges" (the 14-24 and the new VR2 70-200), they actually have tested better than the primes I've had that they've now replaced. I've also got the 85/1.4 AF-D and 105/2 DC (and a couple of 50's) and the two portrait lenses are quite nice for work with people, but there are potentially better options for landscape work, including the new 70-200 VR2 which shocked me in recent tests I've done by actually being sharper with better contrast in many cases than either the 85 or 105 I own. So much for the zooms aren't as good as primes argument - at least in Nikons current lineup, they've put more emphasis on extremely high performing zooms that easily meet and often exceed a lot of Nikons "classic" primes from 10 years ago. This isn't saying that zooms are better, it's obviously more of an indication that lens design and lens design capabilities have grown tremendously over the past years and thus a newly designed pro zoom, at least on the Nikon side of the house, is extremely competitive with most any current prime. Of course once Nikon starts updating their prime lineup this may change, but even then, I'm seeing that the new zooms are tremendously sharp, particularly at the apertures a studio or landscape shooter often use.
As far as how much you'll see the differences in lenses, this is all of course determined by the quality of your support system (I own the heavy 5530S Gitzo for a reason), the quality of your shot discipline, and the quality of your raw conversion and post processing as well as your own personal level of discernment and what you (not me, or another forum member) feel is most important when you look at image quality. In the latter case, since my own personal reference is the smooth tonality and natural (not forced, but natural) resolution and sharpness of a large format chrome on a lightbox or a very well done print from an 8x10, I happen to value resolution, contrast, and the overall rendering of the lens instead of just concentrating on how sharp the lens is. Some folks are most sharpness obsessed, some folks are really into the bokeh characteristics and on it goes - I'm not sure anyone here can make that decision for you. But getting back on topic, if you've got well trained eyes, know what to look for, have mastery in your technique and shoot with good discipline on a solid support, yes, you'll see the differences at 16x20", easy. Will these differences turn a shot with poor artistry into something great - of course not, but it can make the difference between what I call "gallery quality" and just a good medium size print. My goal always has been to produce a 16x20 print that looks like it came from one size larger a format than what it was shot on, and if I'm good and the gear is good, I can often get there. You may have other ideas.
That being said, if you are good with manual focus, value sharpness and resolution as extremely important aspects, you might do very well with a simple three prime outfit of a 24, 50, 100 or whatever, maybe all or parts of it from Zeiss. If I were going all prime on Nikon myself, I'd likely get the new 24/1.4 that was announced, a 35/2 Zeiss, the 60/2.8G Nikkor, the 100/2 Zeiss, and the 200/2 Nikkor and I could cover most of what I would do - I just happen to like zoom flexibility in the studio and hence I went with my current kit. At the end of the day though, everybodies preference is different and it may very well be different on the Canon side of the house where the pro zooms at this point in time aren't anywhere as good as Nikons, but whose L-II lens primes are extremely nice. If I was a Canon shooter, I'd be tempted by their 17 T/S, their 24/1.4, their 100 Macro and 200/2 exotic, with perhaps the Zeiss 50/2 Makro Planar filling in the middle.
-m
PS: This post is already terribly long winded, but as I gaze into my crystal ball, I see the quality of every manufacturers lens lines converging: the point being that the higher megapixel FF options require a lot of sharp glass, and thus I see sharpness as being a design point. We have seen this so far in the new Nikon zooms - all are very, very sharp, to the point where one really can't go THAT much sharper. We're seeing it from Canon in their L-II primes and the 17 TS - really nice lenses. Sony/Zeiss has some really nice lenses. I'm almost worried that as everyone "chases" sharpness in order to appease the pixel peeping culture these days that some of the character and rendering styles that used to define some lenses gets lost in translation. At least on Nikons side I have heard that the new 24/1.4 was designed with bokeh and imaging qualities wide open as being a very important parameter, which may mean that on a test chart it may not be edge to edge sharp at 1.4 but perhaps instead have a very beautiful rendering when shot wide open due to the more artistic (versus purely engineering based) thought as to the trade offs that occur in all lens designs. We shall see.
