The rumour mill
Sir Howard Stringer, CEO of Sony, was being interviewed by a Wall Street Journal tech reporter when he made some comments about supplying Apple with sensor technology for their device cameras – which was noted as odd since nobody is aware of Sony technology being used in Apple devices currently.
Seth Weintraub from 9 to 5 Mac was there in person and noted that Stringer specifically mentioned that factories affected by the Japanese earthquake and tsunami would mean delays in providing components to companies like Apple.
This added fuel to rumours of a delay for the iPhone 5 and also led to speculation that the iPhone 5 would have an 8 megapixel camera – since rumours were already circulating that Apple intended to switch from the current OmniVision sensor to the Exmor R.
What does it mean for image quality?
As a fan of iPhoneography I was interested in this news, and curious as to what this news might actually mean for the picture quality. So I began researching the Apple and Sony cameras to see what we could expect…
Are more megapixels always a good thing?
The iPhone 4 has a 5 megapixel camera, so an 8 megapixel camera sounds like an improvement, however more megapixels does not automatically mean better pictures – you also need a larger image sensor to cater for the increase. When the iPhone 4 was released Steve Jobs explained that improvements in the camera were not made by squeezing more megapixels onto the same size sensor, but that it had a larger sensor as well.
A larger sensor allows for larger pixels, which allow for greater light sensitivity which makes for better pictures – especially in low light situations.
While there has been some disagreement over which Omnivision sensor the iPhone 4 uses, given that Steve Jobs referenced the 1.75 μm pixel size at the launch it would appear to be the OmniVision OV5650.
Comparing the sensors
So what does this tell us? Well, let’s compare the specs of the Omnivision sensor and the Sony sensor:
|OmniVision OV5650 (iPhone 4 sensor)||Sony IMX105PQ (Sony Ericsson Xperia arc sensor)|
|5 megapixels||8.13 megapixels|
|1/3.2 inch||1/3.2 inch|
|backlit sensor||backlit sensor|
The Sony sensor is the same size sensor, with more megapixels but smaller pixel size. This is the opposite of what Steve Jobs highlighted at the iPhone 4 launch – it is squeezing more pixels onto the same size sensor.
From what I have read this might give you finer detail in good light, but the image quality will suffer in low light, which is why at the time of the iPhone 4 an 8 megapixel spec would have resulted in poorer image quality – however Sony claim to have developed “a unique formation of photo diodes optimally designed” to perform better in low light.
OmniVision have their own, similar, technology, but there were reports that production delays meant that their sensors would not be ready in time for the iPhone 5.
A picture is worth a thousand words
The new Sony Ericsson Xperia Arc has an 8 megapixel camera, using Sony’s Exmor R sensor and luckily for us, someone has published some comparison photos on Flickr:
At first glance the above images seem impressive and appear to indicate that the Sony sensor is performing well in extreme low light – but if you examine the images closely (click to view full versions) there is a lot of colour noise in the low light image. There are also reports of the Arc images being overexposed under certain conditions (see image at top of post), so I wonder how much real improvement has been made and whether image processing in the Arc might be skewing the first impressions.
As an experiment I tweaked the levels on the iPhone4 low light image in Photoshop for comparison – the aim is to have clear low light images, not just more detail with more noise which can be achieved with image processing. When you compare these two images the Arc image does not have significantly less noise and the iPhone actually displays more detail – see the grain of wood in the desk or the M logo on the tie on the right hand toy (compare the images at full size).
The same can be seen in the following comparisons in less extreme conditions, there is more obvious noise in the iPhone4 image which gives it a grainy appearance, however in the Arc’s image you can see more unwanted colours are creeping in.
The Arc image is also slightly blurry which may be caused by diffraction due to the smaller pixel size. Despite it’s visible noise the iPhone image is actually picking up more detail – look at the fabric of the jeans for example, and it’s very obvious in the ivy image. All of the below images are actual full size sections of the original images.
While the Sony “leak” and the rumours of delays seem to point to a Sony sensor being used in next generation Apple products, other sources have said that Apple will stick with OmniVision sensors for the iPhone 5, but regardless of the provider the question is: have current 8 megapixel sensors yet developed to the point where Apple will be happy implementing them in the iPhone 5?
If the Arc is anything to go by it would seem that while they may have improved the low light situation with the same size sensor, there are definite noise and diffraction issues. When comparing the images that are available online, many of the iPhone images are better. The iPhone 4 images have less colour noise, are not overexposed and show more detail with less blur with any reasonable light source.
This leaves us with the obvious remaining advantage of an 8mp camera, a larger image size – 3264 x 2448 vs 2592 x 1936 – but if it’s at the cost of sharpness, detail and colour, I’m not interested.
Since the trend in Apple devices is to go smaller and lighter, a larger sensor again seems unlikely, but implementing an 8mp sensor that isn’t a clear and resounding improvement doesn’t seem like a move Apple would make either. After the improvements from the 3GS to the 4, this would seem like a step backwards.