[parinya-ekparinya]

By saying better, I mean a lens is able to acquire focus accurately.

Listed in the lens catalogue, the DA 16-85mm and the DA 17-70mm may not provide accurate focus using CDAF with a teleconverter. If we omit the lenses that are applicable for both PDAF and CDAF, the thing is opposite for the rest; that is other lenses may not provide accurate focus using PDAF with a teleconverter.

Based on my understanding, CDAF is usually more accurate but slower than PDAF. However, I have no clue how equipping a teleconverter may cause some lenses to work with PDAF but not CDAF.

[othar]

However, I have no clue how equipping a teleconverter may cause some lenses to work with PDAF but not CDAF.

As I understand it only PDAF is influenced by AF fine adjustment. Therefore I suspect that, when a teleconverter is put between the camera/lens combination a new focus adjustment would be necessary for best focus results (which noone does for a handfull of shots before removing the teleconverter again) -> PDAF focus may get worse with the teleconverter applied.
The teleconverter also reduces the light by half a stop or a stop (I am not certain, I don't use teleconverters, just guessing here), depending on the maximum aperture of the lens this might has negative aspects for the accuracy of CDAF.

[vonBaloney]

With loss of light, PDAF can hunt but if it does lock on focus, that focus is usually just as accurate as usual (just can be harder or impossible to acquire). Whereas CDAF can be prone to getting a "false lock" with lowered light reaching the sensor. I would expect the newer model bodies to be better performing in both modes than the older ones (which I am still using). As far as certain lenses being worse than others, there seems to be problem with wide-angles in particular -- probably has to do with the fact that with the greater depth-of-field, everything is often *almost* in focus and the contrast detection just can't make those fine distinctions. Again, newer bodies may be better with this, but I know for instance with my K-01 (which only has CDAF) using something like the Sigma 8-16, trying to auto-focus on anything more than a foot away is totally unreliable (even without a TC, but you usually wouldn't be putting a TC on short/wide lenses anyway.)

[Ausable]

I tend to agree with Othar. Adding additional elements between a lens and a camera could conceivably change the micro focus adjustment required.

The 17-70 in-depth PF review pointed out that the tested lens had AF problems focusing in dim light. Add a TC behind that and you can anticipate more AF difficulty.

The loss of light with a 1.4x TC is one stop.

[kypfer]

I use tele-converters quite regularly, so I might be able to contribute to this discussion, but I'm really not sure how one can "choose" between CDAF and PDAF ... is it simply a case of a choice between LiveView and optical viewfinder, or spot or auto, or is there something else I'm unaware of?

[wooly11]

Hi I simply set up fine adjustment with my 55-300 plm on it own and then reset it with the TC the camera records the settings as if it is a different lens - Michael

[stevebrot]

The softer the lens, the harder it is for AF to function. Using a TC always comes at the price of decreased contrast/resolution, some lens/TC combinations being worse than others. I guess that summarizes it.


Steve

[othar]

I use tele-converters quite regularly, so I might be able to contribute to this discussion, but I'm really not sure how one can "choose" between CDAF and PDAF ... is it simply a case of a choice between LiveView and optical viewfinder, or spot or auto, or is there something else I'm unaware of?

Simply a case of a choice between LV (CDAF) and OVF (PDAF), yes

[kypfer]

Simply a case of a choice between LV (CDAF) and OVF (PDAF), yes

Thank you
As an almost exclusive user of the optical viewfinder, I'll now be able to consider if I've got anything useful to contribute!