Why the lens comes first
The accepted answer puts the argument in terms of what is recoverable. If the lens delivers a low-contrast, unsharp image, no sensor behind it can reconstruct detail that never arrived — and the same holds for the other optical characteristics it imposes. A better body improves what happens to the signal after it arrives. It cannot improve the signal.
The practical version of the advice
- Inexpensive bodies are usually good enough for what most people do, and the advanced features of expensive ones often go unused.
- A better lens, by contrast, produces a difference you can see in ordinary use.
- The best formulation in the thread was to identify what is actually limiting your pictures and spend there — which for some people is neither the lens nor the body.
The pushback
One answer took issue with the whole framing, including the popular version that says only the photographer matters. Its position was that an image is produced by an integrated system — lens, body, and the person deciding what to point it at — and no single element can claim the result. It is not a disagreement about which to buy so much as a warning against the slogan, and it is the most-voted answer in the thread.
Where a body does decide the outcome
- Autofocus capability, which determines whether you get the frame at all for anything moving.
- Frame rate, for the same reason.
- Low-light performance and dynamic range, which are properties of the sensor rather than the glass.
- None of these is contradicted by the lens argument. They are simply the cases where the limiting factor sits on the other side of the mount.