EXTENDER 2X-II OR 2X-III?

[digiquisitive]

Anyone have educated and/or experiential information relative to how much better the MarkIII EF 2X extender is than the MarkII?  Why did Canon redesign it (if they did)?  Will be coupled with EF 300mm f/4 L IS and a 7D Mark II -- maybe sometimes with an EF 70-200 f/4L IS and same body. Thanks

[RobertTheFat]

A 2X extender turns an f/4 lens into an f/8 lens, and that's an iffy proposition, even on a 7D2. I know it's not an answer to your question, but I'd get a 1.4X III extender instead. That would cost you only one stop, making your lenses a much more manageable f/5.6.

[digiquisitive]

Thanks. I've been shooting those two lenses with a 1.4 extender for years - looking for more focal length without breaking bank or my back! Thanks again for the speedy response. I should have made that clear in my first discussion.

[Waddizzle · Accepted solution]

---

@digiquisitive wrote:

Anyone have educated and/or experiential information relative to how much better the MarkIII EF 2X extender is than the MarkII?  Why did Canon redesign it (if they did)?  Will be coupled with EF 300mm f/4 L IS and a 7D Mark II -- maybe sometimes with an EF 70-200 f/4L IS and same body. Thanks

---

The extenders do not have provisions to update their firmware to accommodate new lenses, AFAIK.  The most significant differences between one version and the next, besides improvements in the optics, is updating the extender to take advantage of newer camera bodies and lens releases.  And, that’s pretty much it.

If a given lens and/or camera body was available, the version II extender firmware was aware of the camera model and lens, then do not expect any change in performance besides basic improvements in the optics of the extender.

Extenders come in two basic types, 1.4x and 2.0x, which each having a 1-stop and 2-stop impact on the effective aperture.  In addition to having an impact on effective aperture, extenders can also impact the number of available AF points.  

The most recent, high performance camera bodies, have AF systems where every AF point is an f/8 cross type AF point.  This was not always the case.  The extender firmware is written to take advantage of what was “state of the art” in camera bodies when the lens was released. 

In order to maintain backward firmware compatibility, a performance ceiling must be established.  Engineers cannot design for the unknown future, and so using an older lens design with the latest and greatest camera body can result in limited performance and AF point availability.

The 7D2 has only one f/8 AF point, the center AF point.  At best, using a 2.0x extender with older lens designs will result in having only one available AF point.  Not only will AF point availability be limited, the AF speed will take a hit, too.  These are the prices you pay for using an extender.  You always have to give something to gain something.