H.264 is not an editing codec, you need to convert it to something else. I convert to ProRes and my laptop will then happily edit my 5DMkII footage.
Hope this helps.
Thanks, I’ve been using Standard, so I guess I can mess around with some of the other ones. I use ACR on my RAW files anyway but my interval sequences are 500 frames or more so using say the Landscape preset may be helpful with clouds and such.