Small Sensor – Low Light
Shedding Light on Some Common Misconceptions
In low light situations, a bigger sensor has an advantage over a smaller sensor. But how significant is the difference in practice and does it really prevent you from getting the shot you want?
The Problem With Low Light
Low light situations are only challenging when you need fast shutter speeds. If the photographic situation allows you to use slow shutter speeds, you can virtually use the lowest ISO setting of your camera every time and still get the shot. Just use a tripod or rely on in-camera or in in-lens stabilization.
Of course, if the exposure times are very long, you might want to perform a dark frame subtraction either in camera if you have a model that is capable of doing that or in post production.
This means that we have to look at scenarios where freezing the motion is required to get the shot. Then have to overcome two challenges that we don’t have to deal with when photographing still subjects:
1) Our cameras have to focus on a moving subject.
2) High ISO settings are needed to get fast enough shutter speeds to prevent motion blur.
Autofocus in Low Light
Low light requires wide apertures, and this puts autofocus systems to the ultimate test.
Having more depth of field with a MicroFourThirds camera is actually beneficial. An MFT camera therefore has more wiggle room to work with. This is an advantage that can lead to higher hit rates.
Another slight advantage of a smaller sensor when it comes to focusing has to do with optics. Lens elements of a smaller system that have to be moved around by focusing motors are significantly lighter.
The difference can be quite obvious when shooting with medium format.
All in all, I am not suggesting that small sensor cameras have a major advantage when it comes to focusing, but it is safe to state that they are at least on par with their bigger counterparts.
High ISO - Image Noise
The problem with high ISO numbers is the resulting noise.
While luminance noise is usually acceptable, color noise rarely is.
Usually, when color noise takes over, converting the file to monochrome is the only solution to the problem.
In general, new cameras control color noise very well and using proprietary RAW converters can also really improve the noise performance, as those are tailor made by the camera manufacturer for their respective products.
It is also quite interesting examining where noise is most visible:
Dark areas are noisy areas - this problem can be somewhat mitigated by setting the black point.
Apart from that, noise is also more discernible in out of focus areas. The wider depth of field that you get from a smaller sensor camera is therefore actually a small bonus.
Low Light – Why and When Small Sensors Fail
If you over- or underexpose images under extreme lighting circumstances, this is usually when the problems begin.
When shooting with high ISO numbers, the overall dynamic range and the high fidelity dynamic range any digital camera can record will decrease at some point.
The relationship between ISO and dynamic range is not linear, at least not up to a certain point, but it exists.
When I was shooting with larger sensor cameras, the benefit of one or two stops more dynamic range just gave me more room for messing up and fixing it in post production.
This is the main reason why on average, large sensor cameras feel easier to work with in low light.
Lumix LX100
Conclusion
I am very confident to state that smaller sensor cameras are more than good enough to get the job done
What really ruins low light shots when working with small sensor cameras is not getting the exposure right, for example by being too conservative with the ISO setting.
Thanks to this revelation, I’ve developed a more attentive attitude towards exposure metering under all lighting circumstances regardless of which camera system I am working with.
