Well, I have learned something today. After reading this thread earlier today I started wondering if I would see much difference due to pixel size when using the 100-400 on a 5Dii and comparing shots to the 70-200 IS ii on a 7D which has slightly smaller pixels than the D800. Everything was tripod mounted for this testing. I maxed out the zoom on the 70-200 and set the 100-400 to closely match the framing. On shorter distance to subject shots the 7D combo had nice clean images. Once I went out to long shots, over a 100 yards, I started to notice a decline in the shots from the 7D when looking at the images with 100% view. There was an increase in noise. The 5D combo just kept going. I can only assume that I hit the limit of what the 200 mm focal length was able to deliver to a smaller pixel in comparison to what the 320 mm focal length delivered to the larger pixel on the 5D. I realize that using two different focal lengths introduced another variable into the comparison, but I must admit that one reason I use the 7D is for the ability to have a high pixel density on a cropped sensor to allow more pixels on a small target for cropping in post processing. The other is for action shots at distances less than where it started to have issues. I also put the 70-200 on the 5D afterwards as a reality check and did not have the same issue. In real world shooting it isn't a problem for me given the required subject distance to encounter this issue.


Just thought I'd pass on the info.