Micro Four Thirds sensors

The imaging sensor is the heart of the digital camera, and, hence, it is not hard to understand that there is a lot of interest and mystique surrounding the issue of sensors. In this article, I am trying to make a bit of sense of the various generations of sensors used in the Micro Four Thirds cameras so far.

Some of the information here is based on a bit of guesswork. If you think some of this is wrong, then please feel free to comment it.

First generation, 12MP

In the beginning, it was simple. All cameras used the same sensor. And it was made by Panasonic. Period.

Sensor resolution	4032x3024 (12MP)
Sensor type	CMOS
Base sensitivity	ISO 100

This sensor was used in the cameras Panasonic G1 (September 2008), Olympus E-P1 (July 2009), Panasonic GF1 (September 2009), Olympus E-P2 (November 2009), Olympus E-PL1 (February 2010), Panasonic G2 and G10 (March 2010), GF2 (November 2010), Olympus E-PL2 (January 2011), Olympus E-P3, E-PL3 and E-PM1 (June 2011).

In March 2009, Akira Watanabe from Olympus declared that 12 megapixels was enough, and that they would not compete in the megapixel race. We know now that they have since released several cameras with more than 12 megapixels, so this turned out false. On the other hand, we can remember that the statement was given in relation to the Olympus E-system, their Four Thirds DSLR line. And those cameras have so far not exceeded 12 megapixels.

GH1 sensor

The Panasonic GH1 sensor was the first oversized sensor, with the multi aspect ratio feature. This feature is very clever, as it allows for using the full image circle also in 16:9 aspect mode, e.g., when recording video movies. Only the Panasonic GH1 and GH2 had this feature.

Sensor resolution	4000x3000 (12MP) in 4/3 mode, 14MP total
Sensor type	CMOS
Base sensitivity	ISO 100

This sensor was used in the Panasonic GH1 (March 2009), obviously, however, I think Canon probably also used it in their large sensor, non-interchangeable lens camera, Canon G1 X (January 2012). The Canon G1 X sensor has a size, resolution and other properties which are very similar to that of the GH1. I'm guessing that Canon bought this sensor from Panasonic, since I think it is very unlikely that they happened to make a sensor with exactly the same properties.

GH2 sensor

The Panasonic GH2 was the second, and, to this date, the last, camera to have the multi aspect ratio feature.

Sensor resolution	4608x3456 (16MP) in 4/3 mode, 18MP total
Sensor type	CMOS
Base sensitivity	ISO 160

Some tests have indicated that this sensor only has three native ISO modes: 160, 320 and 640. The rest of the ISO range is done using image processing.

Beyond the Panasonic GH2 (September 2010), a sensor derived from it was also used in the Panasonic G5 (July 2012) and Panasonic G6 (April 2013). One may be shocked to see that a brand new camera is launched with a three year old sensor. And in fact, this did cause a lot of anger online. People were generally expecting the G6 to have the same sensor as the Panasonic GH3.

However, I think it is important to realize that the sensor itself is just one part of the imaging pipeline. There are also the filters outside the sensor, the infrastructure for reading out the sensor values, and the image processing. And these parts are also important in creating the image, and have most certainly been updated for the newer cameras.

Even if the Panasonic G5 and Panasonic G6 cameras are said to have sensors based on that from the Panasonic GH2, they still do not have the multi aspect sensor feature.

Second generation, 12MP

It appears that this updated sensor was only used in Panasonic cameras. This may have been the same as the first generation sensor. However, with the changed base sensitivity, I am guessing we are looking at a new sensor design here.

Sensor resolution	4000x3000 (12MP)
Sensor type	CMOS
Base sensitivity	ISO 160

Used in the Panasonic GF3 (June 2011), Panasonic GF5 (April 2012).

Third generation, 16MP

Again, this sensor appears to have been used only in three Panasonic cameras.

Sensor resolution	4592x3448 (16MP)
Sensor type	CMOS
Base sensitivity	ISO 160

Used in the Panasonic G3 (May 2011), Panasonic GX1 and Panasonic GF6 (April 2013).

E-M5 and GH3 sensor (First generation Sony sensor)

This was the first Micro Four Thirds sensor to stir up significant controversy as to who actually produced it. At this point, people tend to mostly agree that this sensor was Sony sourced, which, if it is indeed true, is a strange move from Panasonic's side. How could they put a sensor from their main competitor into their top camera model, the Panasonic GH3? Either way, the sensor does perform well, and has been praised as the best sensor for Micro Four Thirds so far.

Sensor resolution	4608x3456 (16MP)
Sensor type	CMOS
Base sensitivity	ISO 200

Used in the Olympus OM-D E-M5 (February 2012), Olympus E-PM2 and E-PL5 (September 2012), Panasonic GH3 (September 2012) and Olympus E-P5 (May 2013).

Some of these cameras feature lower ISO than 200, the base ISO. However, it is believed that the sensor base sensitivity is still ISO 200, and that the cameras achieve a lower ISO through image processing, i.e., applying a different tone curve. For example, the Panasonic GH3 can use an ISO value down to 125, and the Olympus E-P5 goes down to ISO 100.

Even if there cameras (probably) share the sensor, this doesn't mean that they give you the same image. For example, we know that the Panasonic GH3 is very insensitive to infra red (IR) light, while the Olympus E-M5 is sensitive to IR. This indicates that they have very different filters in front of the sensor, which is important as to how they see the light. The E-M5 probably has a weaker anti-aliasing (AA) filter.

GH3 losing the multi aspect sensor

Compared with the predecessors GH1 and GH2, the GH3 lost the multi aspect sensor feature. And this was a setback. However, the consequences are not that severe. You lose the very widest field of view in video mode. If you prefer using longer focal lengths, this might actually be an advantage.

It's good to keep in mind that the lack of a multi aspect sensor in the GH3 is nothing extraordinary. In fact, out of all video enabled consumer system cameras, the GH1 and GH2 were the only to feature the oversized multi aspect sensors. All other do not have this feature.

On the other hand, most other video enabled system cameras have an APS-C sized 3:2 aspect sensor. When cropping such a sensor to 16:9 for video, this wastes a relatively smaller part of the sensor than when cropping a 4:3 sensor. Hence, the oversized sensor doesn't make that much sense with APS-C sensor. The illustration below shows this:



The Four Thirds sensor wastes 25% of the sensor area when cropping to video mode, and 7.4% of the image circle (diagonally). The APS-C, on the other hand, wastes only 16% of the sensor size, and 4.5% of the image circle. So the oversized sensor feature does not make as much sense with the more common APS-C sensor format.

Producing two sensor sizes was probably too costly for Panasonic. So I can understand their desire to standardize the sensor size from an economic point of view.

In fact, Panasonic has done the same also in the compact camera market. Their LX3 and LX5 premium compact cameras featured a 1/1.63'' (8.07 x 5.56 mm) multi aspect sensor, larger than the typical 1/1.7'' sensor mostly found in these cameras. The newest Panasonic LX7 has a standard 1/1.7'' (7.44 x 5.58 mm) sensor, from Sony, incidentally. It still achieves the multi aspect feature by having a slightly smaller image circle. This also allows for the very impressive aperture rating of this camera, f/1.4-2.3. The Panasonic LX7 has very impressive features for a small compact camera.

Panasonic MN34230 (E-M1, GH4, GX7, GM1)

In September 2013, the Olympus OM-D E-M1 was announced. One of the headline features is on-sensor PDAF, being the first Micro Four Thirds camera to offer this. Even if Sony has already supplied this feature on some of their higher end cameras, this camera uses a sensor from Panasonic.

Sensor resolution	4608x3456 (16MP)
Sensor type	CMOS
Base sensitivity	ISO 200?

PDAF promises faster and more accurate focusing of moving objects when using the AF-C mode. Autofocus with still images of non-moving objects should be the approximately as fast as before.

Due to the on-sensor PDAF feature, the Olympus E-M1 should be the first Micro Four Thirds camera to autofocus quickly using Four Thirds lenses when using an adaptor. The AF speed with the Four Thirds lenses is as quick as the premium Olympus E-5 Four Thirds DSLR camera, a very impressive feat.

Unfortunately, though, the E-M1 cannot use the PDAF feature during video recording.

Beyond the PDAF feature, the sensor is pretty much the same as the one used on Olympus OM-D E-M5 and other cameras from the same generation. You should not expect any significant changes to image quality. The Olympus OM-D E-M1 has even better JPEG processing, though, so JPEG users could experience some improvement to the image quality.

Summary

Camera	Announced	Sensor
Panasonic G1	2008-09	First generation 12MP
Panasonic G2	2010-03	First generation 12MP
Panasonic G10	2010-03	First generation 12MP
Panasonic G3	2011-05	Third generation 16MP
Panasonic G5	2012-07	GH2 16MP
Panasonic G6	2013-04	GH2 16MP
Panasonic GF1	2009-09	First generation 12MP
Panasonic GF2	2010-11	First generation 12MP
Panasonic GF3	2011-06	Second generation 12MP
Panasonic GF5	2012-04	Second generation 12MP
Panasonic GF6	2013-04	Third generation 16MP
Panasonic GX1	2011-11	Third generation 16MP
Panasonic GX7	2013-08	Panasonic MN34230
Panasonic GH1	2009-03	GH1 12MP
Panasonic GH2	2010-09	GH2 16MP
Panasonic GH3	2012-09	First generation Sony sensor 16MP
Olympus E-P1	2009-07	First generation 12MP
Olympus E-P2	2009-11	First generation 12MP
Olympus E-P3	2011-06	First generation 12MP
Olympus E-P5	2013-05	First generation Sony sensor 16MP
Olympus E-PL1	2010-02	First generation 12MP
Olympus E-PL2	2011-01	First generation 12MP
Olympus E-PL3	2011-06	First generation 12MP
Olympus E-PL5	2012-09	First generation Sony sensor 16MP
Olympus E-PM1	2011-06	First generation 12MP
Olympus E-PM2	2012-09	First generation Sony sensor 16MP
Olympus E-M1	2013-09	Panasonic MN34230
Olympus E-M5	2012-02	First generation Sony sensor 16MP
Kodak S1	2013-01?	?

Conclusion

It has angered quite some people that the newest Panasonic cameras GF6 and G6 "only" got older sensor designs, and not the sensor from the Panasonic GH3. This is in contrast to Olympus, which has put the same sensor in the top model Olympus E-M5 and more basic models alike.

However, if it is indeed true that the GH3 uses a Sony sensor, then this makes some sense. If Panasonic is sourcing the sensor from Sony, then that will cost them more per unit, compared with making their own sensor. And that is economically viable for their premium camera model, made for those willing to pay what it costs for the best image quality. The GH3 already carries a premium price tag.

In the more basic models, though, Panasonic must keep the costs down. Sourcing a sensor from Sony probably gives them some extra licencing costs, and there is also the alternative cost of having their own sensor manufactoring plant not making the sensors for their volume camera lines. So I would guess that Panasonic is going to be using their own sensor designs in most volume camera models also in the future, unless the shut down their sensor plants completely.

It's also important to note that while the sensor itself is key for the image quality, it is not everything. The rest of the image pipeline is also important, for example the image processing, i.e., the interpretation of the sensor readings. It has been said that the improvements to high ISO image quality the last years it mostly due to advances in image processing, and not primarily due to sensor hardware refinement.

Olympus and Sony have announced that they will continue to co-develop sensors for the Olympus Micro Four Thirds cameras.