<span style="font-size: 10pt; font-family: Arial; mso-ansi-language: EN-US;" lang="EN-US"]For me it's simple. If you are a pro go for the f2.8. If you are an amateur wanting to use it as walk around lens, take it on trips/vacation etc with you go for the f4. <span style="font-size: 10pt; font-family: Arial; mso-ansi-language: EN-US;" lang="EN-US"]It&rsquo;s too heavy the f2.8. You'll start having problems with your neck after a couple of hours!<o></o>