Our current video cameras are operating at the limits of current sensor technology. As a result there isn’t much a camera manufacturer can do to improve sensitivity without compromising other aspects of the image quality.
Every sensor is made out of silicon and silicon is around 70% efficient at converting photons of light into electrons of electricity. So the only things you can do to alter the sensitivity is change the pixel size, reduce losses in the colour and low pass filters, use better micro lenses and use various methods to prevent the wires and other electronics on the face of the sensor from obstructing the light. But all of these will only ever make very small changes to the sensor performance as the key limiting factor is the silicon used to make the sensor.
This is why even though we have many different sensor manufacturers, if you take a similar sized sensor with a similar pixel count from different manufacturers the performance difference will only ever be small.
Better image processing with more advanced noise reduction can help reduce noise which can be used to mimic greater sensitivity. But NR rarely comes without introducing other artefacts such as smear, banding or a loss of subtle details. So there are limits as to how much noise reduction you want to apply.
So, unless there is a new sensor technology breakthrough we are unlikely to see any new camera come out with a large, actual improvement in sensitivity. Also we are unlikely to see a sudden jump in resolution without a sensitivity or dynamic range penalty with a like for like sensor size. This is why Sony’s Venice and the Red cameras are moving to larger sensors as this is the only realistic way to increase resolution without compromising other aspects of the image. It’s why all the current crop of S35mm 4K cameras are all of very similar sensitivity, have similar dynamic range and similar noise levels.
A great example of this is the Sony A7s. It is more sensitive than most 4K S35 video cameras simply because it has a larger full frame sensor, so the pixels can be bigger, so each pixel can capture more light. It’s also why cameras with smaller 4K sensors will tend to be less sensitive and in addition have lower dynamic range (because the pixel size determines how many electrons it can store before it overloads).
8 thoughts on “Why hasn’t anyone brought out a super sensitive 4K camera?”
So why the sony a6300 appears to be more “sensitive” than a sony fs5 ? Better electronics than fs5 ?
But the FS5 is more sensitive than the A6300. Remember, on an electronic camera ISO is not a sensitivity rating, it is an exposure rating. At a like for like exposure the A6300 is a lot noisier.
Thanks for your answer Alister, but what about that video around 5’10 (ok , I know it’s a youtube compression, but still…) :
That’s gain and amplification, that’s why it gets grainy and noisy. The picture does get brighter but you are not actually seeing any additional picture information in the shadows because it’s masked by the noise. A common mistake is to confuse a change of amplification with a real change in sensitivity. If you actually increase the sensitivity then more and more textures and fine details should come up out of the shadows and the noise should not significantly increase.
Thanks again, but if I look at the tree, it seems that is what happen with a6300 (more texture and detail) and not with the fs5…
Could you explain why some of the ENG cameras with much smaller sensors, like the PMW-300, perform surprisingly well. Obviously not having the sensitivty of a A7s, but still performing well. Is it some kind of electronic fix with the lens and the cmos sensor?
They are HD sensors, not 4K, so a lot fewer pixels, so the pixels can be reasonably large, even though the sensors are small. They are normally around the equivalent of 300-350 ISO but usually have fast f1.8 lenses.
Some standard definition cameras are even more sensitive, again fewer, bigger pixels.
As you go up in resolution you need more pixels, so unless you make the sensor bigger, the pixels have to be smaller and the sensitivity reduces.
The laws of physics play a large part in all of this.
We start off with the light in our scene which passes through a lens.
If we take a zoom lens of a certain physical size, with a fixed size front element and as a result fixed light gathering ability, for example a typical 2/3″ ENG zoom. You have a certain amount of light coming in to the lens.
When the size of the image projected by the rear of the lens is small, you get an effective large aperture. Increase the size of the sensor and you have to increase the size of the projected image. This spreads what light you have “thinner” and as a result the projected image is dimmer, so the effective aperture is smaller and the DoF narrower. But, a bigger sensor can have bigger pixels and this makes up for dimmer image coming from the lens. So where a small sensor camera (1/2″, 2/3″) will typically have a f1.8 zoom lens when you scale up to a s35mm sensor the lens becomes the equivalent of f4 to f5.6. But because for like for like resolution the pixels size is much bigger the large sensor will be 2 to 3 stops more sensitive, so the low light performance is almost exactly the same and the DoF remains the same. Basically it’s all governed by how much light the lens can capture.
This is why using prime lenses that are much more efficient at capturing light has revolutionised low light shooting as the simplicity of a prime compared to a zoom makes fast lenses for large sensors affordable. Going the other way. If you were to take one of todays fast primes like a 50mm f1.4 and build an optical adapter of the “speedbooster” type so you could use it on a 1/2″ sensor you would have a lens the equivalent of a f0.5 6.5mm lens that would turn that 1/2″ camera into a great low light system with performance similar to an A7s with a 50mm f1.4.