Hi Rich,


I thought you were shooting the 1D Mk IV, which is APS-H, correct?And that is 1.3x FF and with a TC it is 1.3 x 1.4 x FF? If I am off on how this works, everyone, please just ignore this post..........


You may be able to answer this from experience already, but have you considered taking your gear out for a few tests this weekend?It seems to me that you have the ability to simulate most of these focal lengths that you are considering using a combination of your 1DIV, 7D and TCs (judging from your profile). If so, below is a table with the FF equivalent focal lengths of the lenses in consideration. So, for example, if you want to see what the 500 mm f/4 would give you in terms of angle of view on the 1DIV, you could try the 7D + 300 mm + 1.4 TC.
<table cellpadding="0" cellspacing="0" border="0" style="width: 514px; border-collapse: collapse;"]
<colgroup><col width="64" style="width: 48pt;"]</col><col width="75" span="6" style="width: 56pt; mso-width-source: userset; mso-width-alt: 2742;"]</col></colgroup>
<tbody>
<tr height="20" style="height: 15pt;"]
<td width="64" rowspan="2" height="60" class="xl69" style="border-bottom: black 0.5pt solid; text-align: center; border-left: #f0f0f0; background-color: transparent; width: 48pt; height: 45pt; border-top: #f0f0f0; border-right: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]Actual Focal Length</td>
<td colspan="6" width="450" class="xl66" style="border-bottom: windowtext 0.5pt solid; text-align: center; border-left: #f0f0f0; background-color: transparent; width: 336pt; border-top: #f0f0f0; border-right: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]FF Equivalent Focal Lengths (mm)</td>
</tr>
<tr height="40" style="height: 30pt;"]
<td width="75" height="40" class="xl65" style="border-bottom: windowtext 0.5pt solid; text-align: center; border-left: #f0f0f0; background-color: transparent; width: 56pt; height: 30pt; border-top: #f0f0f0; border-right: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]APS-H</td>
<td width="75" class="xl65" style="border-bottom: windowtext 0.5pt solid; text-align: center; border-left: #f0f0f0; background-color: transparent; width: 56pt; border-top: #f0f0f0; border-right: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]APS-H x 1.4x</td>
<td width="75" class="xl65" style="border-bottom: windowtext 0.5pt solid; text-align: center; border-left: #f0f0f0; background-color: transparent; width: 56pt; border-top: #f0f0f0; border-right: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]APS-H x 2x</td>
<td width="75" class="xl65" style="border-bottom: windowtext 0.5pt solid; text-align: center; border-left: #f0f0f0; background-color: transparent; width: 56pt; border-top: #f0f0f0; border-right: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]APS-C</td>
<td width="75" class="xl65" style="border-bottom: windowtext 0.5pt solid; text-align: center; border-left: #f0f0f0; background-color: transparent; width: 56pt; border-top: #f0f0f0; border-right: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]APS-C x 1.4x</td>
<td width="75" class="xl65" style="border-bottom: windowtext 0.5pt solid; text-align: center; border-left: #f0f0f0; background-color: transparent; width: 56pt; border-top: #f0f0f0; border-right: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]APS-C x 2x</td>
</tr>
<tr height="20" style="height: 15pt;"]
<td height="20" class="xl67" style="text-align: center; background-color: transparent; height: 15pt; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]300</td>
<td class="xl70" style="text-align: center; background-color: #ffff99; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]390</td>
<td class="xl68" style="text-align: center; background-color: #d7e4bc; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]546</td>
<td class="xl71" style="text-align: center; background-color: #b8cce4; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]780</td>
<td class="xl70" style="text-align: center; background-color: #ffff99; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]480</td>
<td class="xl68" style="text-align: center; background-color: #d7e4bc; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]672</td>
<td class="xl71" style="text-align: center; background-color: #b8cce4; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]960</td>
</tr>
<tr height="20" style="height: 15pt;"]
<td height="20" class="xl67" style="text-align: center; background-color: transparent; height: 15pt; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]400</td>
<td class="xl70" style="text-align: center; background-color: #ffff99; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]520</td>
<td class="xl68" style="text-align: center; background-color: #d7e4bc; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]728</td>
<td class="xl71" style="text-align: center; background-color: #b8cce4; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]1,040</td>
<td class="xl70" style="text-align: center; background-color: #ffff99; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]640</td>
<td class="xl68" style="text-align: center; background-color: #d7e4bc; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]896</td>
<td class="xl71" style="text-align: center; background-color: #b8cce4; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]1,280</td>
</tr>
<tr height="20" style="height: 15pt;"]
<td height="20" class="xl67" style="text-align: center; background-color: transparent; height: 15pt; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]500</td>
<td class="xl68" style="text-align: center; background-color: #d7e4bc; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]650</td>
<td class="xl71" style="text-align: center; background-color: #b8cce4; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]910</td>
<td class="xl75" style="text-align: center; background-color: #b2a1c7; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]1,300</td>
<td class="xl68" style="text-align: center; background-color: #d7e4bc; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]800</td>
<td class="xl71" style="text-align: center; background-color: #b8cce4; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]1,120</td>
<td class="xl75" style="text-align: center; background-color: #b2a1c7; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]1,600</td>
</tr>
<tr height="20" style="height: 15pt;"]
<td height="20" class="xl67" style="text-align: center; background-color: transparent; height: 15pt; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]600</td>
<td class="xl68" style="text-align: center; background-color: #d7e4bc; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]780</td>
<td class="xl71" style="text-align: center; background-color: #b8cce4; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]1,092</td>
<td class="xl75" style="text-align: center; background-color: #b2a1c7; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]1,560</td>
<td class="xl68" style="text-align: center; background-color: #d7e4bc; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]960</td>
<td class="xl71" style="text-align: center; background-color: #b8cce4; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]1,344</td>
<td class="xl75" style="text-align: center; background-color: #b2a1c7; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]1,920</td>
</tr>
<tr height="20" style="height: 15pt;"]
<td height="20" style="background-color: transparent; height: 15pt; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]</td>
<td style="background-color: transparent; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]</td>
<td style="background-color: transparent; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]</td>
<td style="background-color: transparent; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]</td>
<td style="background-color: transparent; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]</td>
<td style="background-color: transparent; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]</td>
<td style="background-color: transparent; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]</td>
</tr>
<tr height="20" style="height: 15pt;"]
<td height="20" style="background-color: transparent; height: 15pt; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]</td>
<td class="xl72" style="text-align: center; background-color: #ffff99; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]f/2.8</td>
<td class="xl73" style="text-align: center; background-color: #d7e4bc; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]f/4</td>
<td class="xl74" style="text-align: center; background-color: #b8cce4; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]f/5.6</td>
<td class="xl76" style="text-align: center; background-color: #b2a1c7; border: #f0f0f0;"]<span style="font-family: Calibri; font-size: small;"]f/8</td>
<td style="background-color: transparent; border: #f0f0f0;"]</td>
<td style="text-align: center; background-color: transparent; border: #f0f0f0;"]</td>
</tr>
</tbody>
</table>


EDIT-added colors to show maximum aperture for the lens combinationsin consideration.


The other thing I am wondering, and I apologize if you already mentioned it, but are only going to exclusively shootFF/APS-H or are you willing to use your 7D? If so, that opens up even more options to consider [:|].


So, my thoughts, assuming my table is correct and you are shooting a APS-H,it seems that the 400 mm f/2.8 with the two teleconverters is a great option (so no, it makes complete sense to me....I detect no craziness). It would natively give you a similar focal length to what you've been using (520 mm vs 546 mm) and the ability to reach out much further. And, honestly, 1,040 mm FF equivalent at f/5.6 soundsamazing. Given that the 500 f/4 is only ~100 mm "longer" at f/4 in comparison to the 300 mm + 1.4x, I am not sure it is worth it. I could see keeping the 300 mm and the 600 mm, that would be an amazing range to have covered, but the 400 f/2.8 seems to get most of the functional range with one lens.


Brant