Controlling expectations - What the Lumia 920 cannot do well

The first entry for this blog set up my expectations for the Lumia 920. I expected it to perform better than a mobile phone to a point where it can challenge point and shoot cameras. The plus for me is the fact that you can take decent photos on a whim. I mean who doesn't carry their mobile phones around these days. It is perfect for the happy snapper, the impromptu moment or when you don't want to carry a digital SLR around.

Hints of this product targeting the casual shooter is apparent in Nokia's selection of features for the phone. The Lumia 920 features a 8.7 MP 1/3 inch sensor with a 26 mm (equivalent) F2.0 Carl Zeiss lens with optical stabilisation. This means for the normal person:

• Wide angle lens
• Fast lens for good low light performance
• Decent MP for printing photos. More than enough for facebook or sharing across the internet.

For a photographer is means:

• Fixed aperture (F2.0) will make controlling depth of field difficult. This would be very apparent for landscapes with an estimated hyperfocal length of 83 m! In other words, it would be difficult to take a landscape shot with all of the frame in focus
• Small sensor size, means more noise and artefact as we push longer exposure in low light
• Small MP and hence don't print any photos in large format.

Today I decided to see where the differences really lie between my digital SLR and the Lumia 920 in terms of landscape photography. More specifically, I wanted to see the how well each device performed for high dynamic range (HDR) landscape photography. Each device was allowed 3 shots of +/- 1 EV from regular exposure. Roughly the same landscape was framed the camera was secured on a tripod and a camera phone holder for the Lumia 920.

Photomatrix was used for the HDR produced by the digital SLR, while the HDR camera and Thumba was used to create the HDR effect for the Lumia. I should point out that the desktop tools for HDR photography is much more mature than the mobile equivalent. HDR camera at the time of publication is a very basic tool with no means to adjust the final merged image.

Comparing the sensor size. My trusty digital SLR has a huge advantage. The Lumia's sensor is a dwarf in comparison.

The first challenge for the Lumia was focus. With a fixed aperture of F2.0 where would you ask the camera phone to focus for all the frame to be 100% sharp? As mentioned above the hyperfocal length is 83 m, but this point may be some ripples on the horizon or tree branches swaying in the wind. It literally became a 'guessimate' for the 83 m on a feature that has enough contrast for the autofocus system to focus.

After 3 attempts, we were able to get this 'in focus' HDR.

Lumia 920 HDR at West Point. 3 exposures were used for the shot.

What you can see is good definition on the clouds and the capture is not too bad for a camera phone. There are some 'ghosting' since the HDR camera program did not compensate for foliage movement. The trees as a result have this artefact and lacked detail as the different exposures are used to create the HDR.

This image compares very poorly against my digital SLR and its HDR program photomatrix.

D200 HDR at West Point. 3 exposures were used for this shot.

Immediately you can see just how superior the digital SLR HDR is compared to the Lumia 920 HDR. There is more detail, less noise and things just pop out at you. This is due to a combination of things namely better HDR software, larger sensor and much better optics. Focus isn't an issue for a digital SLR since stopping down the aperture to F13 gave a hyperfocal length of only 2.4 m. This makes focusing to infinity much easier and contributed greatly to obtain the perfect shots first time and with minimum repeated attempts.

The astonishing difference can be seen in the detail captured between devices.

Side by side comparison of a digital SLR and Lumia 920 HDR.

It isn't surprising that the Lumia for landscapes lacks details in the capture. The sensor is only 5% of the size of a digital SLR sensor. Its resolving power would be considerably weaker. You can also see from this composite the noise is more apparent for the Lumia 920 picture. Again this is due to its small sensor.

Looking at purely resolving power now.

Night and day difference in terms of resolving power of the devices.

The 100% crops shows how much detail the digital SLR captured. You can clearly see the rocks and their definition. On the Lumia, these structures are just blobs. On reflection these results are not surprising at all. The digital SLR has a professional grade lens which is worth about 3-4X a Lumia 920s. The digital SLR camera isn't the latest and greatest, but does an amazing job on landscapes

So what does this all mean? Well in a few words, 'enjoy moments with the Lumia' but for serious photography nothing beats a digital SLR. This can be said for any camera phone, great for your snaps but there are limits. HDR landscape photography is one such limit.

The question begging to be asked is 'will revisions to the mobile HDR software improve the final output?' Most definitely it will, but only in terms of contrast and image saturation of colours. The lack of detail is purely the limitation of the phone's camera system and feature set.

I hope this entry will help readers get the most out of their camera phone. Knowing the strengths and weakness of a platform will improve the images capture on the device.