Thoughts on a6700 + 70-350mm F4.5-6.3 G OSS + teleconverter

[JTPR]

I have the a6770 which I like very much, but I also bought the FE 200-600mm f/5.6-6.3 G OSS, which has great IQ and reach, but is just much too heavy handheld for me now at my age.  I definitely need a much lighter outfit.  

So I'm thinking of the 70-350mm lens.  Together with a 2x TC, how many stops will I lose?  Also, will the IQ be just too soft at the far end of the zoom?  Thoughts appreciated.

[Phormula]

The fact: 2xTC will make you lose two stops, so your lens will become roughly a f/9-13 lens.

The answer: it depends.

Teleconverters are a quick fix to extend the focal length of a lens. They were popular in the old days of prime lenses because zooms were expensive and primes were fast, light and with good optical quality. Plus, film was more forgiving than digital on image quality. 

That said, the answer is yes if you will use your 70-350 mostly without, and you add the TC in some specific cases, but if you plan to keep it 100% of the times, either you are going to accept compromises in image quality and handling, or you'd better stick with what you have. Keep in mind that the 70-350 wide open is already soft at the long end, the TC will add extra softness and you will be forced to use it wide open and ramp the ISO up to be able to manage the outfit without a tripod.

If the issue is handholding your current outfit, what I can recommend and what I use when I need to hold the camera for a long time, e.g. when following an airshow or sports from the side, is a monopod. It removes a lot of the strain, does not impact on image quality, actually it improves because of less fatigue, and I often use it as a walking stick. Plus, it comes at a fraction of the cost.

[Pieter]

Another fact and the actual answer: the 70-350 doesn't take teleconverters so whatever you're considering is not a real option.

[FunWithCameras]

Sony only supports teleconverters (both the 1.4x and 2x) on a select group of lenses - all of them white, and not even all of the white ones (for example, the 70-200 f/4 mark 1 does not support a teleconverter). 

One possible reason is that the lens has to be designed with room at the body end to receive the part of the teleconverter that sticks out.

There are "conspiracy" theories that suggest Sony wants you to buy expensive lenses to use teleconverters. I don't believe that, but hey, there are plenty of posts online making those claims.

Anyway, you can find lists of supported lenses on Sony's website under both the teleconverter pages.

From memory (so I might miss one or two):

• 70-200mm f/2.8 GM both mark 1 and mark 2
• 70-200mm f/4 G II (only)
• 100-400mm GM
• 200-600mm G
• 300mm GM
• 400mm GM
• 600mm GM

I think that's all the lenses that can be used with teleconverters.

I have seen a few reports that there is at least one Sigma lens which can be used with a Sony teleconverter, but I don't remember which lens (or lenses).

And before you ask, there are no third party teleconverters for the E mount (unlike, for example, Canon's EF mount, where there are multiple third party teleconverters). Apparently the reason that there are no third party teleconverter has to do with Sony licensing - they license out the lens side of the mount, but not the camera side of the mount - I speculate that maybe Sony want to keep the option to innovate on the camera side? 

[FunWithCameras]

I double-checked on the Sony website, and it lists the lenses I did, although it does omit the 300 GM (how dare they omit a lens that hasn't shipped yet?)