The A7 and A9 series consists of four separate models with a similar design, but different sensors and autofocus capabilities to fit different needs and market segments.

For the first time since the launch of the original A7, Sony has introduced a fifth model name and this time, it’s not about what is inside, but the how it looks on the outside. I wish I could tell you that the A7C has a completely new look, but instead Sony has taken the design of its APS-C cameras and fit a full frame sensor inside.
…
Continue here:
https://mirrorlesscomparison.com/sony-vs-sony/a7c-vs-a7-iii/