In other articles I have compared focus accuracy and noise between the Sony A9 and Olympus EM1x cameras, This time I’ll look at Dynamic Range on Olympus vs Sony, specifically when photographing birds in flight (BIF).
Note: All Olympus lenses follow the micro four thirds (MFT) standard, which means that they have a full frame equivalent (FFE) focal length of 2x the MFT focal length, and a full frame equivalent aperture from a depth of field perspective of 2x the MFT aperture. However, from an exposure equivalent, there is no 2x factor. An MFT f4 lens exposes as an f4 lens. When I refer to an Olympus lens below, multiply its focal length by 2 to get the FFE focal length (e.g. 300mm MFT=600mm FFE).
Why is Dynamic Range important for BIF?
Dynamic range (DR) is defined by the ratio in stops between the highest and lowest gray luminance a sensor can capture. A high DR is important for photographers shooting landscape sunsets, although bracketing and HDR processing is so easy these days, that few would trust a difficult scene to a single exposure any more.
However, it is impossible to bracket a bird in flight, so we must rely on the inherent DR of the camera. Birds with white heads and dark bodies, such as the white-backed vulture, or the bald eagle pose a real challenge to expose correctly, particularly when the head is in sun and the body in shade. Good dynamic range is as important for BIF as it is for landscape – which is not often, but critical when needed.
The headline dynamic range figure that most people quote is the DR for landscape photography, which is measured at the base ISO of the camera (ISO 50 for Sony and ISO 200 for Olympus). There are many definitions of DR, but one commonly used test (DXO) gives the landscape DR of the Sony A7Riv as 14.8 stops and the E-M1x as 12.8. Two stops difference – is this the Achilles heel of the Olympus system?
This is a long and moderately complex post so I will give you the elevator summary now. It turns out that the Olympus EM1 ii, iii and x cameras with the Olympus pro telephoto lenses have the same or better dynamic range for BIF as any Sony camera used with the Sony 200-600 lens. Below I compare dynamic range on Olympus vs Sony cameras in detail for the E-M1x, and Sony’s flagship full frame systems.
The Olympus system and the Sony system
In this analysis I will compare the EM1x plus the 300mm f4 and the 40-150 f2.8 to the A9ii with the 200-600 f5.6-6.3 zoom. In a prior article I have discussed the reasons the 200-600 is the best all round Sony lens for BIF IMO (the other Sony telephoto options are too heavy, and expensive or too short, or both, and have severe depth of field limitations for large birds).
The 200-600 is an excellent lens, but it is slower than the two Olympus Pro telephotos. At 600mm and f6.3, it is 1.3 stops slower than the 300mm f4. At 200-300mm it is 2 stops slower than the 40-150 f2.8. At 420mm, it’s 1.3 stops slower again than the 40-150 plus TC. This makes a huge difference in DR performance as we will now see.
The effect of fast glass on ISO
Like many other bird photographers, I shoot with the lens wide open, at a fixed shutter speed, usually 1/2000, and use auto ISO and exposure compensation to manage exposure. At a fixed exposure compensation, the only variable here is ISO, and using a slower lens results in a higher ISO.
Shooting with the lens wide open with the Olympus system results in ISOs between 1.3 and 2.3 stops lower than when using any Sony camera with the 200-600 zoom wide open, because of the lens speed difference noted above. This has a big effect on noise and dynamic range . Let’s look at noise first.
Measured Dynamic Range on Olympus vs Sony cameras
As noted above, most people quote the headline ‘landscape’ dynamic range value. Not everyone knows that dynamic range is hugely influenced by ISO, and DR values drop precipitously as ISO increases. The most comprehensive source of independent sensor performance comparisons is DXO labs’ sensor database. The key measurement graph from DXO for this area is the dynamic range plotted against ISO. It is shown below for the two top full frame cameras from Sony and for the Olympus E-M1ii, the last OMD camera DXO tested.
The E-M1ii has the same base sensor as in the E-M1iii and E-M1x, but sensor performance has probably improved since then, so this may be a conservative view. See here for the original DXO data, and here for an explanation of the DXO charts. The upper lines are the A9ii and the A7Riv and the lower one is the E-M1 ii . The horizontal scale is ISO, (which increases by a factor of 2 for each stop), and the vertical scale is dynamic range in stops (higher is better).
There are several interesting features of the chart above. Firstly, note the steep decline in DR as ISO increases. The headline DR of nearly 15 stops of the A7Riv (top/red line) declines to 10 stops at a measured 6400 ISO, and a similar slope is seen for all three cameras. Secondly, you can see how the A9ii DR is optimized to be best between ISO 800 to ISO 25600, specifically for wildlife and sports photographers. Very smart.
You can also see that at the same ISOs, the E-M1x has lower DR than the two Sony cameras, around 1.3 stops of DR worse than the A9ii for example between ISO 3200 and ISO 6400. But wait! The fabulous Olympus Pro telephotos ride in to the rescue!
The effect of fast glass on Dynamic range
Remember from above, that shooting wide open with any Sony camera and the 200-600 zoom results in ISOs between 1.3 and 2.3 stops higher than with the Olympus system in the same conditions, because of the lens speed difference.
As a result, at 1.3 stops higher ISO the DR difference disappears between the EM1x and the A7Riv, and is only around 0.3-0.4 stops better on the A9ii. At 2-2.3 stops higher ISO, the dynamic range of the E-M1x is better than either of the Sonys. You can check these values by looking at on the chart above for the DR at 3200 for the EM1x, and the DR at ISO 8500 (1.3 stops) or ISO 12800 (2 stops) for the other two cameras.
Let me just say that again, so it is clear. In the same lighting conditions, the Olympus system has essentially the same dynamic range as the Sony system, because the Olympus lenses are faster. There is no DR sacrifice when using the Olympus system. This is also borne out by my own experience shooting Sony cameras and the Olympus system under the same conditions. I have seen no difference in the ability to recover shadows or highlights.
Measured Dynamic Range vs manufacturer ISO reading
As with the noise comparison post, there is again an interesting wrinkle in the DXO data. DXO uses absolute ISO values when they measure the camera DR. In the chart above, it is the absolute (true) ISO values which are plotted and shown on the horizontal scale. However, on the live DXO chart, you get a pop up showing the manufacturer’s ISO values for each data point. The latter are what you actually see when shooting, so it’s instructive to see how the real DR is related to manufacturer’s ISO values. This is shown on the annotated chart below.
This is particularly interesting. When the EM1x shows an ISO of 3200, it has a DR of 10.4 stops. When the A7Riv shows ISO 3200 it has a DR of only 10.7, essentially the same as the EM1x. The A9 at 3200 has a DR of 11.3, only 0.7 stops better than the E-M1x. So even without it’s fantastic lenses, the EM1x has essentially the same DR as the Sony cameras.
But we know that in the same light, the Olympus system runs at an camera indicated ISO that is 1.3 to 2.3 stops lower than the Sony, because the pro telephoto lenses are that much faster than the Sony 200-600. I show that this is actually the case with some real photo examples in this post. At ISO 6400 (1 stop slower) the A9ii DR is 0.1 lower than the EM1x, and the AR7iv is 0.7 stops lower. The Sony DR is even lower than the E-M1x as you get to ISO 8000-12800 (1.3-2 stops slower).
Does this apply to all ISOs?
The benefit of the fast Olympus lenses is mostly at medium to high ISOs. The base ISO of the Olympus is 200, so in very good light, the fast lens benefit is reduced if the Sony ISO is below 600 (1.3 stops above ISO 200), and eliminated at ISO 200 on both cameras. At 1/2000 shutter speed and f6.3, it’s rare to require an ISO as low as 200 in most BIF situations. I did all my testing on the Sony cameras between 11am and 3pm in August, so it was as bright as it’s likely to get in the UK, and I never got to an ISO below 1000. On one very bright day with the A6400 I did get to ISO 200, for a small number of shots, but never below that. Lets look at how the cameras behave at this ISO level.
As far as dynamic range is concerned, the intrinsic differences between the Sony and Olympus camera sensors at ISO 200 are very small. At an indicated ISO 64/200 on the EM1x, the DR is 12.83 stops. On the A9ii at ISO 200, it is 13.1, an undetectable difference. So once again, the Olympus gives nothing away. None of this is to criticize the Sony A9 – its a great camera. It’s just that the Olympus system is equally great across all key areas including dynamic range.
Enough already with the dynamic range on Olympus vs Sony
OK, that’s it. Just wanted to make clear that once more, you give nothing away when you use the E-M1x plus the Olympus pro telephoto lenses for birds in flight. The fast lenses make up for the limitations in the sensor. Against the Sony A9 with the Sony 200-600, you do not sacrifice focus hit rate, image noise, or dynamic range. In fact you edge out the A9 in all these areas.