SAL70400G adapted to E-Mount with SAL20TC 2x teleconverter?

[bh4017]

Evening all,

I have a SONY A7R III camera and a SAL70400G lens which I use via an LA-EA4 adaptor. This setup works absolutely fine; the camera recognises the lens, I can use the autofocus and adjust the aperture. All good.

I then became interested in a SAL20TC teleconverter to complement this setup. The SAL20TC is listed as being 'compatible' with the SAL70400G, although it is apparently manual focus only. That didn't concern me, so I purchased one.

Unfortunately I have experienced extremely limited success with the teleconverter. The camera can no longer recognise the SAL70400G lens when it is connected with the teleconverter, and as a result I can't adjust the aperture (in-body adjustment only unfortunately). The teleconverter does otherwise work of course - it's just magnification optics at the end of the day. But the problem with being unable to adjust the aperture is I'm stuck with the smallest aperture possible (as it is immediately from power on). So this is basically unacceptable and I view my purchase as a failure.

But here's my question: have I got a dud teleconverter, or is it just that my setup is over ambitious? I am basically going from an E-Mount camera to an A-Mount adapter to an A-Mount Teleconverter to an A-Mount lens. Have I gone too far?

If you have this same setup I would be very interested to read about your experience!

 

[AlwaysOnAuto]

If I'm reading this correctly, the converter isn't 'talking' electronically to the camera if it is manual focus only with the lens. So, that means it's essentially the same as a 'dumb' adapter. Hence no aperture control via the camera since the converter is in between it and the lens.

 

[michelb]

It is mentioned in the camera and LA-EA adapters instructions that this in NOT COMPATIBLE. Sony has made this impossible for who knows what reason.

Some other brands converters may work ( Tamron, Sigma, Kenco) but depending on their level of communication between body and lens, you may experience the same issue with some.

I have tried a few myself and some appear to work but then lose communication often ( no more aperture shown on camera which indicates it won't stop down the lens when you take a picture). Some twisting of the set-up that may affect the contacts between body/adapter/converter and lens.

Hey, we are taking about a 4 item set-up that is supposed to work all together, so that is a lot to ask


And by the way, any lens TC combo that provides a maximum aperture of F8 and slower is unlikely to AF on any body since the AF sensors in the adapter are just not getting enough light to operate properly. Same applied to AF bodies of before.
The bodies recognize that fact and default your body to MF when you use such a combo.

 

[bh4017]

It is mentioned in the camera and LA-EA adapters instructions that this in NOT COMPATIBLE. Sony has made this impossible for who knows what reason.

Thank you for your reply. Following this I consulted the instructions and I did find a reference to this:

   ---            

I will consider, based on this, whether there is any utility in keeping the teleconverter or if I am better off selling it on.

I buzzed out the connections on the converter and they are not a straight-through connection. I guess there must be some intelligence between the input side and output side so that SONY can detect the connection of the teleconverter.
I do wonder if it would be possible to modify the converter such that it literally becomes a pass-through dumb piece of glass. In this way the camera would think it is connected direct to the lens (via the LA-EA4 adapter) and it might work. Of course, implementing such a modification in practice could be very difficult.

 

[Ziggy99]

From memory the LA-EA4 has a PDAF module in it and to use it a body would have to turn off sensor PDAF.

And it's over f8 that the R III uses CDAF only. It works but is slow and with active subjects you lose shots.