When I first purchased the 70-200 IS 2.8 a little over two years ago I was concerned that I had received a soft copy and returned for exchange. The replacement was slightly better wide open @ 200mm, but still not up to what I expected after reading many excellent reviews. I sent the second copy to canon and it was corrected for back focus. I received it back from Canon and just assumed that this was as good as it could perform. When I purchased a full frame body this lens really began to shine. Is it just me, or does this lens perform better (sharper) with a full frame vs APS-C sensor? I didn't notice as big a difference with my other lenses, but the 70-200 was like night and day @ 200mm wide open.
Buster H wrote:
When I first purchased the 70-200 IS 2.8 a little over two years ago I was concerned that I had received a soft copy and returned for exchange. The replacement was slightly better wide open @ 200mm, but still not up to what I expected after reading many excellent reviews. I sent the second copy to canon and it was corrected for back focus. I received it back from Canon and just assumed that this was as good as it could perform. When I purchased a full frame body this lens really began to shine. Is it just me, or does this lens perform better (sharper) with a full frame vs APS-C sensor? I didn't notice as big a difference with my other lenses, but the 70-200 was like night and day @ 200mm wide open....Show more →
This experience isn't that uncommon. I've noticed similar discrepancies in the experiences of others with the 50 1.4, for example: on a high density APS-C sensor it can seem soft at 1.4, but on full frame it can be very good wide open.
The thing to keep in mind is that an APS-C sensor is "sub-sampling" about 38% of the lens' image circle compared to a full-frame camera, and so emphasizes optical deficiencies.
