RustyBug
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alundeb wrote:
How is the APO correction of the A 150 / 2.8 compared to the Sigma 150 2.8 APO macro OS?
How is the center MTF of the A 150 / 2.8 compared to the Sigma 150 2.8 APO macro OS, wide open aperture, at long distances?
These are very fair questions.
I don't have anything to offer in the form of A/B comparison shots or test data, but I can tell you that I rented the Sigma a few years ago and it was a fine enough lens, but I wasn't compelled to buy one as I already owned the Mamiya 150/2.8 A (which I paid a whopping $150 for). Of course, mine is not AF, which you can get @ B&H for $3,490, if you prefer. 
http://www.bhphotovideo.com/bnh/controller/home?O=&sku=567935&is=REG&A=details&Q=
The other very valid point here is that some lenses are "optimized" to different subject distances (macro, portrait, infinity), while others are designed to have a "broader" use range. In the case of the Mamiya 150/2.8 A, I recall doing some A/B testing with it against my Zeiss 80-200/4. Sure, not exactly apples to refrigerators testing, but it was the best 150 vs. 150 I had at the time, and the Zeiss is certainly no slouch.
What I learned was that at near mfd and infinity, the Zeiss slightly trumped the Mamiya (perceived sharpness to my untrained eye, not objective mtf data). But at middle distances, it reversed and the Mamiya showed what it was really made for. If you think about it, the 150/2.8 A would be a "portrait" lens on the larger format (the Zeiss more of a general purpose lens), so it being finely tuned / optimized to those distances seemed to make sense to me.
As such, I use my Mamiya 150/2.8 A for my middle distances in its "sweet spot" mostly, but even when I do use it @ mfd or infinity, it is no slouch. (refer to tractor vs. tractor gauge @ mfd/crop).
As most people know who are Zeiss fans, mtf data often times doesn't fully reflect what you get out of a lens when shooting it in real world because the testing is typically performed at a single subject distance, and in the real world we shoot at a variety of distances. There has been a plethora of times that we have had raging debates over Zeiss with advocates simply saying things like ... "Quit trying to refute it with test data. Just go shoot it and you'll see."
Well, that's the way I feel about MF on FF. I've offered up as best I can the information that I know from my few years of shooting a mixed bag of FF on FF and MF on FF. I've never stated that MF glass was better than FF. Nor have I stated that FF was better than MF. I asked early on for some definition @ better. For those of us who are regular mixed bag (Oly, Zeiss, Leica, Nikon, etc) alt shooters, we know that drawing style's can be different and not necessarily better/worse, as optics are always a series of compromises in properties (i.e. bokeh vs. resolution, mfd vs. infinity).
What I have simply stated is that if you like the look of MF, give some due to the fact that the "look" comes (in part) from the optical projection and I advocate using some of the excellent MF glass that is out there on FF. As Jim has also pointed out, and I indicated as well, each lens stands on its own merits and there is some excellent MF glass out there (i.e. be selective). We can argue till we're blue in the face at why MF on FF is / isn't better than FF on FF or MF on MF. The OP was looking for an alternative solution to his current quest for more of an MF look ... I simply offered up one for consideration ... one that I had found I enjoy following a similar research effort into "bargain entry" @ older MF cameras.
My goals here really aren't to debate better, but to simply share with fellow FM'ers that MF on FF can look really nice and the files produced from it have a different look to them than their FF counterparts even if not being shot on the larger MF format. For me, they render "MF-like" without obtaining an MF platform camera (because they are an MF projection) more than I'll ever get out of FF glass.
I'm not saying that shooting MF on MF is fully replaced by MF on FF ... that would be pretty silly. But, neither am I going to allow that silly "equivalency" thing deprive me of using some really nice glass. The MF on FF files produced, btw, seem to be even more pliable in post for fine tuning than FF on FF. I never get tired of seeing how nice the files "develop" in post ... it kinda reminds me of watching a print come to life in the darkroom.
Anyway, HTH. Even if you don't have an MF camera, you can mount some excellent MF glass on FF (or crop) and reap the benefit of the projected image (albeit cropped). Today is Independence Day in the U.S. ... think about it and consider the possibilities of breaking away from the "established".
After all, this is the "Alt" Forum ... enjoy.
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