« on: February 13, 2014, 06:13:36 PM »
Have you the Tammy? Can you contribute for anything here at all?
You said it. You don't own it, and you've rejected the postings that are contrary to your opinions from owners of the lens.
In the case of the 1D X, you have 6.95µm pixels, or an area of 6.95^2µm: 48.3µm^2. The 7D has 4.3µm pixels, or an area of 4.3^2µm: 18.49µm^2. Again, because were working in two dimensions here, it's not a linear scale, you can fit 48.3/18.5 7D pixels into one 1D X pixel. That comes out to 2.61x 7D pixels per 1D X pixel. You would need a 2.6x TC in in order to completely normalize the crop difference between the 7D and 1D X, all else being equal.
Wouldn't that be a sqrt(2.6)x teleconverter? Every teleconverter I've seen lists their focal length multiplier, meaning a 2x teleconverter puts 4x the pixels on a target.
Back to the topic, I'm interested in AI Servo performance of the Tamron. I really want to try to get a hold of this lens for a trip in March, but I'm a bit concerned by the varying stories I've read regarding AF in servo mode. I have a 6d so for it center point is really all that matters. I would like to purchase a 5d3 eventually though, so if the lens is not going to behave well for other AF points (I've read it's fine and I've read it's useless except for the center point) that's a bit of useful data to consider.