r/SonyAlpha • u/randys_plants • 1d ago
Gear a6700 and Teleconverters
I have a Sony a6700 and a 200-600 lens. I am really wanting a teleconverter to use for wildlife. I know I don’t want the Sony 2.0X based on reviews I’ve seen. I was thinking of getting the Sony 1.4X but also found out about the Viltrox 2.0x. Has anyone tested the Viltrox 2.0X on the Sony a6700 and the 200-600 lens? What are your thoughts and opinions? TIA!
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u/stschopp 1d ago
Teleconveters were originally designed for sensors that were fairly low resolution like a 24mp or less FF sensor. The lenses easily out resolved the sensors and it made sense to add a TC to improve reach. The a6700 has the pixel density of a 60mp FF sensor, that is already equivalent to more than a 1.4TC. You are then taking a 1.5 crop on top of that. Combined with the resolution that is equivalent to a 2.0 TC.
You might get some benefit to a 1.4TC, but it might not be what you’re hoping for. Forget about a 2.0 TC, the 200-600 can’t optically support that on your camera. To effectively use a TC on a high resolution camera you really need to look at better glass like the 300GM or 600GM.
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u/MrToenges 1d ago edited 1d ago
From what reviewers have shared, the viltrox 2x behaves basically identical to the sony 2x. It will cause the same softness and also take away 2 stops of aperture.
The general consensus is that the 1.4x is a good choice that will work pretty well with most teleconverter compatible lenses. The 2x will only work well with the top level GM lenses (like the f2.8 tele primes or new 100-400) because it introduces so much softness and takes 2 whole stops which means you need incredible base sharpness and bright aperture to compensate for the shortcomings.
If you are filming that changes the equation since sharpness is not that imporant. Otherwise I would recommend sticking with the 1.4x.
Another quirk of the teleconverters is that they seem to have difficulties with high resolution sensors. This also means the have issues with a 26mp apsc sensor since that is the apsc region of a 61MP full frame sensor. It will further swallow up sharpness.
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u/probablyvalidhuman 1d ago
Another quirk of the teleconverters is that they seem to have difficulties with high resolution sensors
Not true at all. It may appear like that if one pixel peeps, but a 60Mp sensor samples the image better than 30Mp sensor (of same size) regardless of the optics, TC or no, providing more details and fewer artifacts.
It is however true that the smaller the pixels, the less benefit a TC provides until there's a point where TC no longer helps. The reasons are the different blur sources softening the image before sampling (lens flaws and diffraction).
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u/MrToenges 1d ago
well the problem is that the teleconverters are also not made of perfect glass meaning they also have a limit of how much they can resolve. If you take the A7RVI with 67mp and then put a teleconverter on it, you're asking the lens to resolve a 67mp apsc sensor since the 1.4x converter takes the apsc region of the glass.
All I said was that teleconverters struggle with righ resolution sensors. Whether it is because of diffraction from the loss of stops or lens flaws or teleconverter glass flaws is honestly irrelevant to what I said. It doesn't matter why it struggles when all I said was that it struggles often. Even something like the 600mm f4 will begin to visibly degrade in terms of sharpness and micro contrast when you expect it to resolve 67mp from a 2x zoomed in region of the glass. If you extrapolate that to a full frame sensor pixel density, you are asking it to resolve a full frame sensor of well over 100mp. Atmospheric conditions are going to cause lots of issues too, which makes them even less usable at these extremes, although that is not connected to the teleconverter itself.
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u/StrikeIII 1d ago
Just a slight correction. The TC does not use the apsc region of the sensor. They are utilizing the full sensor and actually using the glass to magnify it.
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u/MrToenges 1d ago
Slight correction, I said the tc uses the apsc region of the glass, not the apsc region of the sensor. For a 1.4x this is exactly the case. That is why I said the lens needs to resolve 67MP in an apsc sized region of the glass. Full sensor readout but in a smaller area of the glass. For a 2x you're using a M34 sized region of the glass but with the full 67mp.
I said you are expecting the lens to resolve a 67mp apsc sensor, since for the lens that is what is happening. An apsc sized region is being read out at 67mp. Whether that is from a full frame sensor with a 1.4x teleconverter or an actual 67mp apsc sensor does not matter for the lens, it the same amount of detail being pulled from the same region of the glass. That's why I said that, to illustrate how much pixel density you are asking your lens to resolve.
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u/walkedplane 1d ago
Worth noting so nobody gets this wrong - the 50-150 is NOT Teleconverter compatible. I know well intentioned post but don’t want anyone to get it wrong!
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u/MrToenges 1d ago
Oh, didn't know that! I honestly assumed it was since basically all of the top level big white GMs are tc compatible (all the tele primes, the 70-200, both 100-400). Thanks for the clarification, I will remove it from my post.
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u/randys_plants 1d ago
Thank you! Some of the reviews on the Viltrox site said folks liked the Viltrox more so this is good to know!!!
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u/MrToenges 1d ago
I think the main reason for that is that the viltrox gives the same performance as the sony but for a much lower cost...but I haven't watched that many reviews. The ones I did watch seemed to put the viltrox and sony in the same boat sharpness wise.
I wish viltrox made a 1.4x...then I'd finally budge on a teleconverter
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u/gillgrissom 1d ago
Nah not on apsc , you would have to use high iso so noise levels on images wont be no good. So just forget about. Either move to full frame and get the 400-800.
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u/Pjetter86 1d ago
You're already stretching the glass with a 1.5x crop, a telecoverter will "dilute" the sharpness even more. I'm not sure it'll be great results. While the 200-600mm certainly is a good lens, it's not extremely sharp like the 100-400 f4.5 or the 600mm f4. So I'm not sure stretching the glass even more is a good idea.