I just got my R7 and I am so hyped to take it out for some real wildlife shots but I am honestly spinning in circles trying to pick a lens. I'm heading out to Yellowstone in about six weeks so the pressure is on to buy something soon. I've been looking at the RF 100-400mm f/5.6-8 because it's so cheap and light and the reviews say the autofocus is snappy but then I worry about that f/8 aperture. Like if I'm trying to catch a bear in the brush at dawn is it just gonna be a grainy mess? My logic was that the R7 crop factor makes that 400mm behave like a 640mm which is awesome for reach but some people on the forums keep saying the RF 100-500mm L is the only real choice for this body. The problem is that lens costs like three times my $1600 budget and I really don't want to carry a brick around all day. I also saw some people using the old EF 100-400mm II with an adapter and they say it's sharper but then I'm adding bulk and a used one is still pricey. I just want something that wont hunt for focus when a bird moves. Is the budget RF 100-400 actually good enough for the R7 sensor or am I gonna regret not saving up for the big white lens...