Looking for the perfect smartphone camera.

During Black Friday sales in 2015, I acquired my first smartphone – a Lumix CM1.  Never heard of it?  Few have.  Fewer have one.  The likely reason is that it’s a stinker of a smartphone.  It has difficulty running multiple apps, often freezes and I have to reboot it, and is more than twice as thick as an iPhone.  Any iPhone.   I’ve had cellphones since they started becoming small enough to carry discreetly but rarely carried them because nobody ever calls me.  I resisted getting a smartphone because I’d rather browse the Internet and be able to do real work on a laptop.  And of course I don’t need another camera and certainly not one that comes as an afterthought on a phone.

But the Lumix CM1 was special, it was designed as a camera first, and then as a smartphone.  It had a one inch (diagonal) Sony Exmor R  20 megapixel CMOS BSI (back side illuminated) sensor, likely the IMX183.  Just like the sensor found in the well regarded Lumix ZS100 and ZS200 (also known as the Lumix TZ100 and TZ200) compact travel camera.

updated-sensor-sizes-medium-format-to-mobile-phone

Most smartphone cameras have tiny sensors (because of space limitations) of the size found in the smallest three in the figure above.  When you cram even more pixels onto that sensor to foist upon an unsophisticated purchaser, each photodiode sees very little light especially relative to the accompanying signal generated by heat and electronic noise.   This makes smartphone cameras only good at taking shots in the exterior with full sunlight.  Indoor shots or shots at dawn or dusk become noisy and unacceptable.  The advantages of the much larger 1 inch sensor (nearly 5x the area) becomes apparent.  BSI moves the circuitry from around the active photodiode sites to the back of the sensor so even more light falls on each pixel.   The CM1 also benefited from being designed with full manual control over all settings, a Leica DC Elmarit  f/2.8, 10.2mm aspherical lens, and hard switched controls that were not all embedded into its Android operating system touchscreen.

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Comet Catalina  Jan 08, 2016 with Lumix CM1
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Canada Day 2016 – Lumix CM1
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Shanghai’s Financial District from Victor Sassoon’s Cathay Hotel Terrace with Lumix CM1

And for more than two years I enjoyed carrying a real camera with me everyday, able to capture those unexpected moments of life.  I even quietly endured the taunts of friends with iPhones ridiculing the brick I was carrying.  But the inevitable did happen and I dropped the phone and badly cracked the Gorilla glass over the touchscreen.   Since the phone is so rare, nobody (I mean nobody) makes a protective carrying case for it.  I actually made a decent one and you can follow it’s fabrication on this Instructables link:

https://www.instructables.com/id/Semirugged-Cellphone-Case/

It was good at protecting the camera lens assembly and not so good for preventing trauma to the screen side.   I think maybe the time has come for a change.  Because the CM1 is really a lousy smartphone.

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Damaged Lumix CM1!

The Huawei Mate 9 Pro became available in January 2017 but it is already two generations old.  The Mate 10 and Mate 10 Pro was to be Huawei‘s big entry into the US but political pressure alleging that these Chinese made phones were a “security risk” caused AT&T to cancel their marketing agreement.  And just last week, the new P20 and P20 Pro were unveiled.  So this means I managed to snag an used unlocked phone for only $400 USD from eBay.  The original price was likely in the $800 range but what makes this an even better deal is that the Mate 9 Pro is exactly the same as Mate 9 Porsche Designed phone that sold only at Porsche dealerships in China for $1500.  It has a gorgeous curved AMOLED screen in quad HD resolution, 128GB of storage, 6GB RAM and a 64 bit 8 core processor.   It also comes with two Leica branded cameras with optical stabilization (OIS) on the back , a 12MP color and a 20 MP monochrome camera.

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Huawei Mate 9 Pro in “Pro” camera mode with full controls except aperture.

Before proceeding with a technical discussion, lets clear the air about Huawei‘s obsession with upscale branding.   We know that Leica did not make the camera modules because they have a similar arrangement with Panasonic/Lumix who have for a decade made Leica branded digital cameras and lenses.  Leica states that it is a collaborative relationship but likely what happens is that Leica approves the optical design and build ensuring that some degree of Leica standards is connoted.  Dissassembling the earlier Huawei P9 smartphone clearly reveals that Sunny Optical manufactures the paired camera module and after some research I can confirm the 12MP sensor is the Sony Exmor RS IMX286 (1/2.9″) with 1.25 um pixels and the 20 MP sensor is a special monochrome version of the Sony Exmor RS IMX350 (1/2.8″) with 1 um square pixels.   The IMX350 sensors feature electronic stabilization and phase detect focusing which is further complemented by Huawei’s laser ranging system to help focusing in dark situations.  The S in the new Exmor RS class of Sony sensors refers to a new stacked architecture where the sensor is built up in layers to allow the data readoff circuitry to reside behind each photodiode rather than on the periphery allowing faster transfer rates.  Perhaps adding value to the Porsche Designed Mate 9 Pro, the camera modules found inside surprisingly bear the Leica Camera AG mark!

Screen Shot 2018-03-30 at 10.22.48 AM

The idea of pairing a more populated megapixel monochrome sensor with a less populated color sensor is an idea borrowed from astronomical digital imaging.  The monochrome sensor can get away with smaller pixels yet be more sensitive to light because it has no intervening colored Bayer layer.  It also has higher resolution since every pixel records tonal detail undiminished by an antialiasing filter whereas a color sensor derives resolution data from only the green pixels (50% of all pixels in the sensor) blurred by an antialiasing filter.  The idea of the second color sensor is to provide color data which can be upsized to match the number of monochrome pixels and then overlaid with the monochrome data as a luminance layer to provide a very sharp color image.   Astronomers use this method because it saves a lot of time since astroimaging exposures are very long.    All astronomical cameras are monochrome, a monochrome image is obtained and then RGB color filters are introduced in a filter wheel while the resolution of the camera sensor is reduced by “binning” – 4 touching pixels are treated as one large pixel and its combined signal is output as the value of one pixel.  This make the sensor more sensitive despite the intervening color filter and reduces exposure time.  The RGB frames are combined to create a master color file which is upsized and combined with the monochrome file to create a full sized high resolution color image.

So despite having two much smaller camera sensors than the Lumix CM1, the Huawei has a combined 35% of the imaging sensor area.  But with the introduction of a monochrome sensor and the powerful laptop processing power of a current generation smartphone, it promises images that could rival the Lumix CM1.

 

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Lumix CM1 1/50s, f/2.8 10.2mm, ISO800                              Huawei 1/30s f/2.2, 4mm, ISO250

Don’t forget to click to access 100% scale and pixel peep.  These are cropped to compare the detail visible on the book spines taken about 10 feet away.  Both are very equivalent in sharpness and noise with perhaps better exposure on the right.  And the real world verdict is that the Huawei can be shot at longer exposures and lower ISOs with its OIS despite having a much smaller sensor.

Here’s a legitimate head to head image comparison of a brook in our neighborhood that I often go for nature hikes with my wife.

DonRiverBrook
Lumix CM1 f/6.3 10.2mm ISO200  30s
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Huawei Mate 9 Pro f/2.2 4mm ISO50  1/5 s

I couldn’t find the very strong neutral density filter that I used for the Lumix CM1 but that did require a tripod to shoot at a 30s exposure..  Since the aperture of the Huawei is fixed at f/2.2, the ND12 filter I had was actually a good match since it allowed me to handhold the shot at 1/5s showing the benefits of optical stabilization that is missing from the CM1.  The Huawei also has a maximum exposure of 30s.

And the often forgotten benefit of having a true monochrome sensor is the ability to shoot true monochrome images full of nuanced shadows and sharp detail that is often missing when one simply converts a color image to grayscale.

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The reluctant model (our 16 yr old dwarf rabbit who was happily napping in the sun until startled by a strange new looking camera!)

There are caveats of course.  The aperture is fixed at f/2.2 and you cannot adjust it, even to stop it down.  There is a control to adjust aperture but that is a fake software effect that varies the amount of background bokeh that appears.   You can only shoot RAW in color, not in monochrome and the RAW file is smaller than 20 MP whereas the JPG is full sized.  But the Huawei comes with a lot more effects than the Lumix such as time lapse, panoramic imaging, and HDR.  And the Huawei’s lens assembly remains flush whereas the Lumix CM1 lens has to deploy and stick out 5mm further when powered on.  This often happens accidently when the phone is lying screen up on my desk and I can hear the lens thunking against the table and delivering a camera error fault.

OLYMPUS DIGITAL CAMERA

And finally the Huawei has Android Version 8 and is such a powerful phone that I will likely never tax its limits!  But being a brick can be a good conversation starter.

If this is your first time here, click the HOME button on the upper right to see the complete list of topics in this blog.

Addendum #1:

In the past I’ve run MTF curves shot with ISO12233 charts to quantify lens and camera performance but with the weak focal length of these cameras, I had to place both mere centimeters away from the chart and at that distance I wonder how useful the MTF curves will be.  They turned out to be all very similar and all very excellent.  But you can check out the images if curious.

 

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From top to bottom:  CM1, Huawei Color, Huawei Color Raw, Huawei Mono

 

 

One thought on “Looking for the perfect smartphone camera.

  1. It will be good if Panasonic produced actioncam or tiny point-and-shoot camera with this lens Leica DC Elmarit 10.2mm f/2.8 and 1″ sensor. Dreams…

    Like

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