Hi,
I have been using Canon gear (30D + 50f1.4 + 70-200f4IS) alongside my Pentax K10 lately, especially for action shots (mainly my son sporting events) and, because I am a gearhead, I rented a 5D at my local club with the 17-40f4 for the week, you know, just to appreciate the special FF quality...
Yesterday, I tested side by side my K10+12-24f4 with the 5D + 17-40f4 using the same framing of mainly landscapes (forrest).
When I oppened the raws in PS, I was amazed at the level of details and fantastic IQ I got from the 5D!
But then I also developped the K10 pics, did a side by side comparison and... couldn't really find any difference between them, even at 100%, except for the meager pixel count difference.
I did not find more detail in the (excellent) 5D files in these conditions (ISO 100, lenses stopped down between f8 and f11), only when I upped the ISO past ISO 800 would I see the 5D jump ahead significantly.
It was confirmed later on when I looked at my first portrait with the 5D indoor at ISO 1600: excellent sharpness and low noise, the K10 is not able to match this and is a winner in low light.
But frankly, I was prepared to be amazed by the low ISO quality, level of details and high dynamic range of the FF 5D but I couldn't really find one good example of this in the 20 or so shots I took yesterday.
I will test this also with the 70-200f4IS against 50-135SDM and probably also make some comparisons with the 50s f1.4 for portraits and in various light conditions but is it me or are modern APS-C able to match (at least yesterday's) FF quality for landscape shots?
I also thought that if the K20 exceeds high ISO performances of the K10 by at least a stop, I would be interested in seeing a comparison of 5D output to K20 output and would be very surprised if the K20 could not match or exceed it in just about any conditions.
On a side note, it remains true that, generally speaking, the AF and metering (pattern) of the Canons is more reliable than the Pentax's one: some work is still needed on the Pentax side on this.
But I also found Pentax colors to be more accurate (especially reds and blue) and Canon's balance to be a bit too warm (magenta/yellowish) for my tastes but this is largely irrelevant when shooting RAW.
Well, sorry for the rambling but I would really like to know if other people have experienced the same "lack of amazement" as far as landscape pictures abilities of a FF camera: maybe I was expecting too much from my internet readings... or maybe the pixel count is really what matters for this kind of shots after all ...