Why isn’t the PMW-200 as sensitive as an F3 or FS100?

This keeps cropping up here and there. The question being asked is why, as it is a new camera, isn’t the PMW-200 just as sensitive as cameras like the PMW-F3 or FS-100. Why didn’t Sony design new sensors for the PMW-200 with the same low noise as an F3?

Let’s take a look at this, first what would happen if you fitted the PMW-200 with the sensor from an F3 but only used the centre 1/2″ portion? Well the resolution would fall short of what is needed for SD, let alone HD, because the cropped area would not have enough pixels to produce an HD image, you need the whole F3 sensor area to get enough pixels. What does that tell us about the F3’s pixels? It tells us that the pixels are much bigger than those in the PMW-200.

Pixel size is the primary thing that determines the signal to noise ratio of the camera. Cameras like the FS100,F3, C300 and GH2 etc have big sensors with big pixels, that’s why they have low noise. That’s why 1/3″ cameras don’t do as well as half inch and half inch doesn’t do as well as 2/3″ and so on. It’s down to the laws of physics. Over the last few years any noise and sensitivity improvements in sensors have been tiny, what we have seen with the large sensor cameras is simply the result of bigger pixels on a bigger sensor. Modern sensors like the ones in the EX have QE’s (Quantum efficiency) approaching 70% where 70% of the photons of light falling on the sensor are converted to electrons. If you want a bigger output and thus a better ratio of signal to noise then you use bigger pixels so that you capture more photons and as a result get more electrons. To do that without sacrificing resolution you need a bigger surface area and thus a bigger sensor.

To expect a significant improvement in sensitivity and noise performance when the sensor size and layout is not changing is not realistic as there have not been any changes to the laws of physics or core sensor technologies in recent years. The PMW-200 is designed to be easy to use, have a good zoom range and be easy to focus. As many have already discovered using cameras with Super35mm sized sensors for run and gun, news and documentaries is often very hard. You can’t get fast compact high ratio zooms without spending a small fortune, the shallow depth of field makes focussing very tricky. There are many productions where a smaller sized sensor is more appropriate and that’s where the PMW-200 comes in.

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