Nokia, its new device trio and EDoF

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You'll remember that I wrote a piece six months ago looking at the (then) new camera technology EDoF (Extended Depth of Field), used in Nokia's super-lightweight smartphones, the E52 and E55? It's entirely possible that some people either missed this or didn't 'get' how EDoF works, even after my piece, because there still seems to be some confusion over whether Nokia's decision to put EDoF cameras in their new C6-01, C7 and E7 is a good one or bad one. I'm definitely in the former camp, but agree that E7 users might be disappointed. Read on for some genuine C7 EDoF photo samples and commentary.

First of all, here's an example EDoF photo taken on the new Nokia C7, click through to download the original 8 megapixel version:

Click to download original or enlarge further

Looks pretty good, doesn't it? And, in my experience, EDoF is almost foolproof - almost zero camera knowledge is required to get a good shot. Given how many times I've asked a friend or family member to take a shot of me with one of my 'fancy' auto-focus smartphones and how often (about 80% of the time) they've completely messed it up, by not focussing properly or snatching the shot, I'm utterly open to EDoF being the way forward for many, many people.

The technology

Quoting extensively from my original article, EDoF stands for Extended Depth of Field and is a new idea, borne of the digital age. Rather than having a bulky and expensive auto-focus mechanism, the idea is that a cheaper fixed focus camera can be dramatically improved by using a custom lens which has been designed to focus the different colour components of light differently.

Simplifying things slightly, a digital camera's sensor is typically composed of clusters of RGB (Red-Green-Blue) pixels - essentially electronic 'buckets' into which photons of light fall and are counted. In the case of an EDoF lens, Red, Green and Blue regions of the visible spectrum are each focussed differently - the exact details are probably a commercial secret. When an image is captured (effectively three 'photos', in this case, one for each of the RGB components), every part of the photo's viewing area is analysed, in turn, with the sharpest of the RGB images for each individual part determining the detail used (for that part), with the other images supplying appropriate coloration. Then it's onto the next part, in turn. The exact size of each 'part' is also a commercial secret but is likely to be in the order of 10 by 10 pixel squares.

Here's a classic example of the output (taken on the 3 megapixel Nokia E55):

EDoF at work

Download the full, original image

EDoF at work - note that the grass in the foreground and trees and buildings in 
the background and everything in between ALL seem to be in focus - magical, isn't it?

This all sounds like a huge computational headache, but this is the sort of repetitive task that can be handled in custom electronics in the camera unit very quickly indeed - the EDoF calculations actually happen in a fraction of a second after taking the shot. In this way, the normal depth of field for a cheap, fixed focus camera is effectively extended and objects a metre or so away can be captured fairly sharply, something which wouldn't be possible with a vanilla 'fixed focus' camera, for which everything closer than two or three metres is blurred to some degree. There are advantages too, for users of casual ability, on phones with smarter, auto-focus cameras, i.e. there's less chance of messing up!

C7 examples

Here's another C7 EDoF example photo. Again, click through to enlarge or download the 8 megapixel original:

Click to download original or enlarge further

And another:

Click to download original or enlarge further

Now, these sample photos don't really push the boundaries of EDoF's limits - after all, Nokia's C7 team wanted to show how good the camera was. But if EDoF is a trick, then it's a really good one. The depth of field for Nokia's 8 megapixel EDoF cameras is quoted as from "50cm to infinity", which I estimate is a slightly greater range than for the EDoF units in the E52 and E55, for which subjects started to become blurred when closer than around a metre.


  1. The extra image processing can't work miracles. Once the light levels go down (say, in the evening, or indoors - and you'll note that the stellar examples above were all taken in blazing sunshine), you get a reduction in depth of field, plus the same sensor noise and the same blurred subjects as with any other small-lensed fixed focus camera. 
  2. Because the lens is fixed focus, there also can't (by definition) be a 'Close up' (or 'macro') mode, so anything closer to the EDoF camera than about half a metre is destined to stay blurry and out of focus. This has implications for both people who like to take 'arty' shots of flowers (and phones) and also for business-critical tasks like capturing business cards and A4 documents. The latter tasks may still be possible using tweaked software and by shooting at the aforementioned half a metre, but it's always going to be something of a kludge compared to a properly focussed capture.
  3. There can be no depth of field effect in photos. A common technique with a focussing camera is to shoot something fairly close - say, a pet at a range of a metre - and rely on the fact that the background isn't going to be in focus and will be slightly blurred, emphasising the subjects clarity. The very definition of EDoF means that you can't take this sort of shot on the C6-01, C7 and E7.

In summary

Adapted from my original table, here's a summary of the differences between the different sorts of Nokia phone camera:

Possible subjects (all assumed in good light) Fixed focus camera (e.g. on Nokia 5230, E63) EDoF 'full focus' camera (e.g. on Nokia C7) Auto-focus camera (e.g. on N95, E72, N97, etc)
Subject 30cm away (arty shot, phone reviewer(!) etc) Very blurry Blurry  Crisp (focussed, needs quite a bit of skill) 
Subject 1 metre away (flower, friend) Blurry  Crisp  Crisp (focussed, needs a little skill)  
Subject 4 metres away (group shot, weddings, etc.) Crisp  Crisp  Crisp (focussed)  
Subject far away (landscape, scene) Slightly blurry  Crisp-ish Crisp (focussed)

In summary, I think Nokia's use of EDoF cameras on the C6-01 and C7 is a very smart move and will let more people take better photos more of the time. EDoF on the E7 is trickier. I'd argue that anyone with enough 'drive' to lust after and purchase the E7 is going to be tech-savvy enough to expect a proper focussing camera. Not just to capture business documents, but because he or she is going to want the very top end functions and EDoF, excellent though it is, is definitely aimed at the mid-tier and people who aren't technical enough to cope with focussing under real world pressures and conditions.

As a postscript to this piece, it should be noted that EDoF cameras will likely take better video as well, for almost everybody. Many of Nokia's recent 5 megapixel cameras have been left focussed on infinity in 'video' mode, meaning that any subject within a couple of metres (people, pets) are always a little blurry - very disappointing. Because, by definition, EDoF units are focussed on a point in the middle foreground (the RGB differences being ignored in video mode), video from the C6-01, C7 and E7 should be surprisingly clear and a welcome surprise to anyone upgrading from a 5800, X6 or N97 (for example).

Watch this space for full reviews of each of these three new devices in due course. Rest assured that I'll put their cameras through their paces in my usual thorough fashion!

Steve Litchfield, All About Symbian, 23rd September 2010

PS. A final example C7 EDoF shot, for your enjoyment, again, click through etc.

Click to download original or enlarge further


Rafe's viewpoint of the C7/E7 camera design choice

The choice to include an EDoF camera module in the C7 and E7, rather than an auto-focus one has stirred some spirited debate. The E7, in particular, has attracted criticism for the camera specification. Shouldn't a €500+ device have a auto focus camera? 

First of all its worth pointing out that many people who buy these devices won't even notice - they just want a camera that takes decent shots - something that shouldn't be an issue here, as the examples above demonstrate. Moreover the 'grab and go' nature of EDoF is often more suited to the typical cameraphone use cases. It is worth noting that the camera module in the C7 and E7 is significantly ahead of anything else on the market, but we'll have to wait for some real world testing before a full assessment can be made. With that said it is clear that keen amateurs and professional photographers will notice the extra processing (e.g. sharpening) that gives EDoF's characteristic 'artificial' feel in some pictures.

Second the camera module choice in these devices is a design compromise, a trade off between two competing aspect of the the device design and functionality. In this case its all about the size of the device. Auto-focus camera modules require significantly more room. In the case of the E7 it is clear space is going to be at a premium. Remember, because of the hinge mechanics and form factor, the E7 effectively has only half the device thickness to play with. The E7 is already 3mm thicker than the N8, how much more would have been acceptable? Clearly that is a matter of opinion. It is never possible to make everyone happy. In this cases Nokia has to find the middle ground, or put another way, has to find the maximum happiness point on the design compromise curve.