Hi Evgeny,
Before I switched to Sinar, I used the Aptus 65 on the Contax 645. In general, the Aptus 65 produces great images for outdoor and landscape, and Leaf does a good job with processing its images via their LC software. However, I always had problems with skin tones using that back. Too much of the time I found a slight magenta cast on both caucasian and oriental skin. Maybe things have changed now with upgraded firmware/software, but I switched to the Sinar backs by then (for other reasons too, like the interchangeable adapters, etc.).
To answer your other questions:
- back firmware instability (does this still the case?) .... yes, I experienced frequent "lock-up" of my Aptus 65, fixed by resetting power.
- wide angle photography problems, because of small 7.2-micron pixel (what about Contax 35mm lens?) .... no problems with Contax 35mm lens.
- long useful exposure is limited to 8 sec, after which image quality quickly degrades (how is it compared to my 54M?) .... I don't use long exposure.
- poor color accuracy, especially in tungsten light (how is it compared to my 54M?) ... yes, I had color issues.
- noise levels at high iso (how is it compared to my 54M?) ..... yes, it is very noisy at higher iso, another reason I switched to 75LV.
- slow capture rate (I think it's the same as 54M) .... not very fast, which is why Leaf introduces the S version later.
- higher power consumption (well, that huge screen..) .... I did not notice battery drain to be that much different form other backs.
If you shoot mostly in studio, and can shoot tethered, I would keep the 54M. To me, tethered shooting in a studio is a huge advantage as I can compose and focus more accurately on the computer screen. If you are experiencing moire with the 54M, then I would recommend the 75LV or even the 54H. The 54H has hardware to remove moire, and is perhaps the best overall studio back as it can produce moire-free images from 22MP to 88MP.
David
