FX Sensor Questions and Help

Started May 1, 2013 | Questions thread
PHXAZCRAIG Forum Pro • Posts: 13,955
Re: FX Sensor Questions and Help

24mp on DX and 24mp on FX is the same resolution and will give (all things equal) the same detail in prints.

However, all things aren't equal.   24mp on DX concentrates those pixel in a smaller area and thus demands more quality from a lens in the center area of the lens in order to make maximum use of those pixels.  24mp on FX spreads those pixels out over a wider area, and thus while not requiring quite as good lens resolution in center, it requires better lens performance at the edges and corners.   Corners on all lenses are not as 'good' as the center, particularly wide open, with less resolution there and potential vignetting issues.

All in all, it costs less to have an extremely good performing lens for DX than it does for FX.

Since FX lenses also have to cover a wider sensor area, they have to be physically larger, though this really only applies to any significance at focal lengths below 40mm or so.   Thus you see a lot of wide angle DX zooms, as they can be made significantly smaller and cheaper than wide FX zooms (or primes).

This adds up to a cost, size and weight advantage for DX compared to FX, though the difference primarily may exist only in a single (wide zoom) lens in your bag.

The main advantage between a 24mp DX and a 24mp FX camera (assuming mostly the same body and feature set, like the D7100 and D600, or a D300 and a D700) is that the larger sensor gathers more light, thus should have an advantage in dim lighting.   That advantage seems to be right around 1 stop, judging from the cameras I've seen since the D300 and D700 came out.

Dynamic range depends more on the sensor generation than anything else, though I suppose theoretically there may be an advantage to FX.

There's no doubt an FX system is more expensive and heavier than a DX system.   As FX is more expensive, those cameras have tended to have more features and better build than DX systems, which may make FX in general look like a natural upgrade from DX.  It's not.   Cameras that are very similar other than the sensors (like D300/D700 and D7100/D600) show little advantage in the resulting images aside from high-ISO performance.    For landscape work, the D7100 may well have an advantage over the D600 due to not have the corner performance issues of FX, and a bit more depth of field at equivalent f-stops, though stopping down is going to mitigate a lot of corner issues.   A d600 on the other hand may extend your no-flash shooting opportunities into situations you can't cover with a d7100.

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