Ive been shooting on Canon for like 5 or 6 years now and I usually stick to street photography or some light landscape stuff so my 24-70 f/4 has basically been glued to my sensor for the longest time. But I ran into a bit of a wall this weekend because my sister basically voluntold me to be the official photographer for my nephews soccer tournament next month. I went out to one of their practices just to test things out and man I felt so out of my league. Trying to get action shots from the sidelines with a 70mm focal length is a joke. I ended up having to crop in so much that the images looked like they were taken on a flip phone from 2005 and the noise was just gross.

So now Im frantically looking for a telephoto that wont break the bank because I really didnt plan on spending two grand on a lens this year. Im using an EOS R7 right now which is great for the burst speed but I need something with actual reach for field sports. Ive got about 500 maybe 600 dollars if I stretch it to work with and I'm stuck between a couple options. I've heard the RF 100-400mm f/5.6-8 is surprisingly sharp for the price but that f/8 at the long end scares me a bit since Im up in Seattle and the weather is usually gloomy as heck. Im worried about having to crank my ISO to 6400 just to keep a decent shutter speed for the kids running around.

The other thought was maybe finding a used EF 70-300mm f/4-5.6 IS II USM and just using my adapter. I know its older tech but that extra stop of light might be a lifesaver. Has anyone actually compared these two on a high-res crop sensor like the R7? Is the newer RF glass actually better even with the slower aperture or should I stick to the older EF stuff for the better light gathering?