Hello everyone. I'm looking at making a purchase of a quality telephoto EF lens and I have some concerns. I own a Canon 80D and I know that there is a 1.6X crop factor with EF or EF-S lenses. My concern though is the amount of usable light available when you use an EF lens on a crop sensor camera as opposed to the full frame sensor. One of my main interests is wildlife photography and I am looking at potentially purchasing the Canon 100-400mm EF lens which has an aperture range of f4.5-5.6. My question is this: is there a significant amount of light loss in this situation and is it significant enough that I will not be able to produce sharp images when shooting wildlife in the field? Should I be looking at a 70-200 f2.8 instead, in order to help compensate for this light loss and deal with the loss of range?