The Camera Phone Challenge: Competing in a Digital Still Camera World

By Feisal Mosleh, October 2006

The camera phone has given many people the chance to capture those special moments when all they have at hand is their cell phone. However, they are often disappointed by the quality of the image, especially in low light conditions as consumers' taste in digital pictures is based on their experience with mid-range point and shoot Digital Still Cameras (DSC). Many of these are CCD based devices of 3, 4 and 5MP resolutions. Most offer autofocus, optical zoom, a strong flash, and exposure control.

It's reasonable to assume that mobile cameras will have “arrived” once they produce pictures of comparable quality to this perceived norm.

It's not just about higher Megapixels!

Though increased resolution offers the chance for a smoother, less pixelated picture, the overall image quality is determined by several factors including low apparent levels of noise, which goes hand in hand with a good low light performance, well adjusted white balance that results in more appealing, vivid colors. It's not just about gradually increasing resolutions alone.

For example, a higher resolution camera may produce a poorer perceived picture quality because it has a worse dynamic range producing poorer contrast. A lower resolution camera may produce brighter, more pleasing and better contrast photos. Several features will play their part in improving perceived camera phone image quality over the next few years: auto focusing, optical zoom, improved lens quality, better color management, stronger flashes, more sophisticated image processing and of course higher resolutions.

Special Constraints for Phone Cameras vs. DSCs

In many ways the phone camera is advancing along a path similar to that of digital still cameras (DSCs). Yet, in some ways it isn’t. Here are some constraints that mobile camera system makers must heed carefully to ensure their success and which makes the mobile camera’s market path a bit different from DSCs, both in pace and direction.

Size

Cell phones are small, and getting smaller, some as thin as 8mm, and thus the camera module must fit in a very small space. Typically, a camera module may be only 8mm x 8mm for a 1.3 MP camera. This means the sensor die must be very tiny. This trend continues reducing sensor and module dimensions. For example, Avago's latest 1.3MP can fit into a 6mm x 6mm module. CMOS sensors are much smaller than CCD ones and are therefore the preferred choice. DSCs use CCD and CMOS based sensors.

Power Consumption

As with most other features on a cell phone, the camera system must consume minimal power to conserve battery life. This power consumption has to be low in both standby and active camera modes. A typical consumption in active mode may be as low as 120 mW. If the unit has a flash, it must not drain too much power. This is why most cell phones have LED based flashes which consume less power than xenon flashes, typically only illuminate about a 2-3 meter distance. This is not generally strong enough for a bright picture in say a shot of friends in a dimly lit restaurant.

The need for low power consumption is also why cameras in camera phones are CMOS based and not CCD based. How many times have you replaced your DSC alkaline battery cells or even replaced them with higher performance rechargeable Lithium ion cells?

Produce good results in low light conditions

Many people would like to take camera phone pictures in low light at home, in the office and in the evening. This places a requirement of being able to produce good, low noise images in low light conditions – which CCD sensors are better at doing, than CMOS sensors but CMOS sensors use far less power and are much smaller in size. Most DSCs have the same or more stringent low light performance requirements but because they have less constraining power consumption specifications they can use CCD sensors and xenon flashes which need a large capacitor (opposes camera phone size constraints) and use more power.

Mechanical robustness

Cell phones must survive a stringent mechanical drop test so the camera module and its sensor must be capable of withstanding strong mechanical shocks. They must pass the famed cell phone drop test that tests in positive and negative directions in the x, y and z dimensions from a height of no less than six feet. When was the last time you dropped your DSC from your shoulder? Did it survive the crash? My cell phone survives several falls a week and the camera still works!

Consumer market supply chain and volume production

Cell phones are amongst the highest volume consumer electronics devices in the industry. Mobile phone cameras must possess a highly resilient supply chain that withstands sudden consumer demand surges for cell phones. A high performance, proven supply chain is critical. An example is that all camera components have a dual supply source for exceptional reliability and can ramp from say a million units a month to say 3 million units per month in as little as three months while maintaining excellent manufacturing consistency and high yields.

The manufacturing consistency and quality also has to be very high in volumes of millions if units per months, much higher than even the highest volume DSCs.

Price/Performance

In addition to these requirements, successful camera systems must meet a minimum level of image quality to be considered and their price is a critical factor due to the strong consumer characteristics of value for money. In fact the average selling price of a camera module may erode from 20% to 15% per year over its lifetime. Price/performance of a mobile camera is a strong selection factor.

A Factor of Ten

Comparing a DSC to a mobile phone camera is somewhat like comparing an SUV to a super-mini (econo compact) car. Sure they both take you from A to B, and reliability is valued by owners of both, but one does it with more thirst, bulk, and a higher sticker while the other is praised for value, fuel savings, and a lower price tag, albeit a ride with much less pomp and grandeur. Both face somewhat different market constraints.

Today a 2MP camera phone with autofocus can produce nice pictures, but not nearly as good as a mid-range (4MP or 5MP) point and shoot DSC. This is not surprising since the DSC is using a ton of post processing, larger pixels, more expensive lens and in many cases, sophisticated autofocus and optical zoom mechanisms that don’t need to be miniaturized to the nth degree. The DSC also has fewer constraints on power consumption and the size and quality of its flash and lens arrangement. Its overall size can also be somewhat bigger than a sugar cube!

But what about some of the recent 3.2MP autofocus offerings from Nokia (N73) and Sony-Ericsson (K790i, K800i) whose photos do rival some 3MP DSCs? In fact, in good light, the N73 beats my old 3MP dedicated camera! And then there is the new 5MP Nokia N95 but since that's not out yet, it's harder to judge.

True, there are some high end camera phones already arriving and some probably will take pictures that rival the older, lower end DSCs but the point and shoot DSC category is continually advancing in image quality and features.

Additionally, the issue is that many of the pictures shot casually are shot in lower light conditions and camera phones have a much tougher time producing picture quality comparable to today’s mid range point and shoot DSCs in those conditions.

It is a problem that is exacerbated by camera phones typically having less powerful LED flashes (although the Sony Ericsson K800i has a Xenon flash) so they cannot produce the same quality of picture even with a flash. Also, cost is a factor. For camera phones to have 3MP DSC quality in the mainstream - By “mainstream” I mean some significant percentage of worldwide volume, perhaps 35% or more of camera phones produced
at a reasonable price (say sub $200 camera phones, today, N95 and others are in the $600-800 or more range…) - will take a while.

The mobile camera is a factor of ten different from DSCs. Ten times smaller. Ten times lower power consumption. Ten times less expensive.

Little wonder then that it may follow a similar but different trajectory to DSCs. And facing the constraints it does, it will take just a bit more time before mainstream camera phones will produce pictures of comparable quality to mid-range point and shoot DSCs.

Feisal Mosleh is head of worldwide marketing, business development and systems engineering for Avago technologies’ mobile imaging business in San Jose, CA. He can be reached at Feisal.Mosleh@avagotech.com.