<p style="margin: 0cm 0cm 0pt;" class="MsoNormal"]<span style="font-size: small;"]<span style="font-family: Calibri;"]I have the 5D+5D MKII, Sigma 17-35, Canon 24-105L, Canon 70-210L F2.8 IS, Canon 100-400L <o></o>
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<p style="margin: 0cm 0cm 0pt;" class="MsoNormal"]<span style="font-size: small;"]<span style="font-family: Calibri;"]I read that you are afraid to duplicate the focal range of the 70-210 and 100-400, in reality they are 2 very different lenses.<o></o>
<p style="margin: 0cm 0cm 0pt;" class="MsoNormal"]<span style="font-size: small;"]<span style="font-family: Calibri;"]Personally I use the 70-210 for portraits, indoor or low light sport or events, while I use the 100-400L every time I need the extra reach, and mainly outdoor, nature pictures outdoor sport etc.. For me they do not compete too much.<o></o>
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<p style="margin: 0cm 0cm 0pt;" class="MsoNormal"]<span style="font-size: small;"]<span style="font-family: Calibri;"]I also considered to sell the 100-400 to buy the 300 f2.8 + 1.4x and 2x. The 300 f2.8 is still light and small enough to be used without a tripod, and it is really nice also with 1.4x or 2x. I tested it 2 times, and I have to say that although is by far superior in image quality, I prefer to walk in the forest with the smaller 100-400, plus the possibility to zoom in and out is a big plus for me, especially if your fix lens is a 300+.<o></o>
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<span style="font-size: 11pt; font-family: 'Calibri','sans-serif'; mso-ascii-theme-font: minor-latin; mso-fareast-font-family: Calibri; mso-fareast-theme-font: minor-latin; mso-hansi-theme-font: minor-latin; mso-bidi-font-family: 'Times New Roman'; mso-bidi-theme-font: minor-bidi; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA;"]As far as the 500f4 prepare to use it almost exclusively with a strong tripod and the right support, so budget for 1.000 $ extra and the extra weight, as hand holding a lens like this is not really easy.