Originally posted by falconeye Of course, it doesn't make sense to compare MF to FF.
But it isn't as unreasonable as it seems.
Many tests compare APSC to FF, an invalid test too. But if you do, you'll notice that resolution and DR go up while speed and features don't go down. With MF vs. FF, resolution goes up, DR goes up just a bit and speed and features typically go down. It isn't unreasonable to mention this to readers unaware of it (but who would be? ...).
The mistake many reviewers do is to mix up test and trivialities. An introductory article about the pro and cons of MF and a test of the 645D against its peers would have been more interesting even to unaware readers.
And then to rate the 645D down on features or performance is ridiculous when it may be best in its class for both.
To me, it makes sense to compare the D3X to the 645D for specific practices like landscape, budgets for the systems are comparable, so one may consider one or the other systems.
IMO, that makes sense to compare completely different approaches in the light of a domain of photography. What is the best camera for studio? For weddings? For landscapes? For street photography? Photozone does this, and I think it's the best approach.
For the later for example, I wouldn't call it an heresy to compare a mirrorless camera, to a Leica X1, to a Pentax K5 + prime. Ultimately what is better is a personal answer but a comparison of the systems in a magazine makes sense to me.