EOS 70D Limitations

[tonybrown]

<p>I'm wondering if anyone has any insight on the following limitations of the EOS 70D. The autofocus is superb, but when used with an EF 500mm and 2X multiplier the camera reverts to Manual Focus for normal still photography. However with this lens combination, autofocus is achieved in Live View and in Movie mode, and it is very good. Another limitation is when using wifi with an iPad for remote control. This works great in Live View, but is not available in Movie mode. And finally, continuous recording is limited to 30 minutes, and requires restarting to continue. I am not aware of any physical limitation to the length of recording.</p>

[avinash_balakrishnan]

I assume you are referring to the 500 f/4 L. In that case the 70D wouldn't autofocus when you put your 2x converter as it become an f/8 lens. Canon made the 70D to AF with f/5.6 lens for the regular use, but its live view will AF at f/8 as Canon has made it so, but otherwise no. I've heard it autofocus with the f/6.3 telephoto zoom lenses from sigma and tamron (but I haven't tested it on the 70D as the tamron 150-600 is having trouble reaching me). I don't think any camera other than the 5D MK III or 1D series will AF at f/8. So its not an issue, its how canon designed the 70D I suppose.

[PuppyDigs]

<blockquote>

<p>I am not aware of any physical limitation to the length of recording.</p>

</blockquote>

<p>The limit mainly has to do with FAT format specifications being limited to 4GB. However, the 70D automatically and seamlessly splits files greater than 4GB for extended recording without interruption. You'll have to manually drop the two clips into your editor side by side to joint them.<br>

<br>

As for the LV video, you can connect a separate monitor to the 70D HDMI output if you need a larger screen. HD video burns batteries like water and I'm guessing an active Wi-Fi connection would overtax the battery and drain it in a few minutes.</p>

[tonybrown]

<p>Avinash,<br>

Thank you for your response. What you say about the design limits of autofocus on the EOS 70D makes sense. However according to the specification listed on the DPREVIEW website, the autofocus is designed to work with lenses down to F11: here is the quote:<br>

According the Canon the EOS 70D's Dual Pixel CMOS AF system has the following key characteristics:</p>

<ul>

<li>Usable phase detection AF area covers 80% of the frame horizontally and vertically</li>

<li>AF works at apertures down to F11</li>

<li>AF works in light levels as low as 0 EV</li>

<li>Can work with face detection to keep moving subjects in focus</li>

</ul>

<p>See: <a href="http://www.dpreview.com/reviews/canon-eos-70d/3">http://www.dpreview.com/reviews/canon-eos-70d/3</a><br>

In the light of my experience I'm inclined to believe you are correct and DPREVIEW got it wrong. Also, I have found the autofocus works with the EF 500mm F4 L and the 1.4X multiplier, that is equivalent to F5.6.<br>

Thanks again.<br>

Tony</p>

[tonybrown]

<p>One more comment on the difference between autofocus on the Live View and on the regular view. On one occasion I did find it autofocus on the regular view with the 500mm F4 and 2X multiplier. I suspect the real difference may be related to the difficulty of actuating the shutter at 1000mm equivalent without shaking the camera, since the Live View has less camera shake. In anycase I think the firmware has been programmed to exclude the 10oomm equivalent from regular autofocus and automatically displays the message M Focus when it detects the lens. This way Canon have avoided customer complaints?</p>

[ljwest]

<blockquote>

<p>In anycase I think the firmware has been programmed to exclude the 10oomm equivalent from regular autofocus and automatically displays the message M Focus when it detects the lens. This way Canon have avoided customer complaints?</p>

</blockquote>

<p>A very large portion of Canon's customers will never encounter this issue, because almost all (if not all...) of Canon's own lenses have a minimum aperture of f/5.6 or greater, and these customers will never try to use an extender.</p>

<p>Yes, this rule is built into the camera. The lens sends its specification to the camera, and if there is an extender, that is added on as well. The camera knows the capabilities of the autofocus system, and will force manual focus when appropriate.</p>

<p>If you have the Canon 500mm lens (or any other extender-capable lens from Canon), the caveat about extenders (Canon extenders, specifically) is in the manual section "Extenders" for that lens. Such as:<br>

<br />"With Extender EF2x II/III attached to the lens, only manual focus is possible."</p>

<p>(it then lists the exceptions to that rule, but the 70D will never be on that list)</p>

<p>3rd party lenses and extenders are hit-and-miss with this rule, however. The Tamron 150-600 which has a minimum aperture of f/6.3 will autofocus through the VF, for example.</p>

<p>Live View focusing is a whole other kettle of fish, and the restrictions above don't apply at all. I have a 100-400 f/4.5-5.6L, and I often use it with a Canon EF1.4x III extender. Through the viewfinder, my 7D will not autofocus, but with Live View, it will. The 70D should be even better in the Live View arena due to the dual-pixel technology, which is not present on my 7D.</p>

[avinash_balakrishnan]

Hi Tony, I don't think DP review got it wrong there. I think they are referring to the ability of the revolutionary dual pixel sensor that make the camera to AF in live view. And I don't have any experience with tele converters as I'm afraid to do that. So no comments in that regard. But I've read in many forums that the 5D MK III & 1D series are the only EOS cameras to AF at f/8. I've once used a friend's 5D MK III with a 70-200 f/2.8L (non IS) and not with anything at f/8.