Every lens datasheet carries a performance chart. Very few people use it, because the axes look unfamiliar — but the idea behind it is simple, and it is worth ten minutes.
What the chart shows
The chart answers one question: how much fine detail does the lens preserve? Moving along the horizontal axis means finer and finer detail. The vertical axis shows how much contrast survives. Coarse detail comes through almost perfectly; as the detail gets finer, contrast falls, until eventually fine lines blur into uniform grey.
Matching the lens to the camera
Every camera has a limit to the finest detail its sensor can record. The useful question is how much contrast the lens still delivers at that limit. Too little, and edges become soft and inspection software loses precision. Our acceptance testing sets a floor comfortably above that point, so there is margin in every unit we ship.
Centre and edge are different
Always look at both curves. A lens can be excellent in the middle of the image and much weaker at the corners — and if your inspection uses the whole image, the corners are doing real work.
The mismatch to watch for
If the lens comfortably outperforms the camera, a higher-resolution camera would genuinely see more. If the lens is the weak link, a better camera buys nothing at all — it just records the same blur in more detail. Knowing which side of that line you are on saves real money.
Talk it through
If this note touches something you are specifying right now, our application desk will look at your part drawing and recommend an optic.
