Megapixels not the be all and end all
Published by Steve Litchfield at 19:49 UTC, July 5th 2006
Steve Litchfield points out that megapixel numbers aren't the only things to bear in mind when comparing the digital cameras in smartphones.
It's easy to get swayed by figures, especially when talking about cameras, or in this case, cameras within smartphones. The megapixel number, i.e. the number of resolved pixels in each image at maximum resolution (e.g. 1600 by 1200 = roughly 2000000 pixels, or two megapixels), is perhaps that quoted most often, but it's only a very rough guarantee that the camera is any good.
Behind the CMOS sensor itself are custom electronics, sometimes built-into the camera module, sometimes elsewhere in the device, to convert the mass of generated electrons into raw image data and then to compress it into JPEG format for storing on your smartphone's internal or expansion disk.
And don't forget the quality of the optics as well. Whether the camera has auto-focus or not, whether it's plastic or glass, whether it's set up properly, all play a major part in the quality of the final images.
To test the real world performance of a good cross-section of current smartphone cameras, I took a sunny scene, with flowers around six feet away (to reflect a typical photo - though it had to be flowers since I couldn't find anyone else to stand still for me!) and snapped it with, in turn, the Nokia N70, N80, N90 and (to take in a typical/comparable camera from the Windows Mobile world) the i-Mate K-JAM. Before launching into the results, here are the specs:
| Device | Photo resolution | Notes |
| Nokia N70 | 2mp | |
| Nokia N80 | 3mp | In 'landscape' mode, of course |
| Nokia N90 | 2mp | With auto-focus and Carl Zeiss optics |
| i-Mate K-JAM | 2mp | In its 'software interpolated' mode |
Having snapped each shot, I then cropped the same area of detail so that you can compare them right here in this article:
Nokia N70
Nokia N80
Nokia N90
i-Mate K-JAM
Conclusions
To help you compare all four at the same time, I've also resampled each cropped portion and appended them to each other:
From left to right: Nokia N70, N80, N90 and i-Mate K-JAM
Looking at raw megapixels, the N80 might fancy its chances of being the best camera, but you can see here the benefit of higher quality components - it's not all about how many million data points you sample. In this case, the N80's photos are washed out slightly and it's evident that the smartphone can't handle the contrasts between light and dark as well as its two predecessors. The N90's image was by far the clearest, due to its proper focussing and higher quality lens, but curiously the colours themselves were a bit subdued. The N70's photo is my favourite as it's handled the contrast well and yet retained the actual (pinkish) colour of the flowers.
(I won't even comment on the quality of the K-JAM's image, but suffice it to say that it's fairly typical of the camera modules I've tried from the HTC-made Windows Mobile world. This isn't a dig at the OS, far from it, merely an observation that HTC use ultra-cheap camera components while Nokia do their research properly and invest more money in this side of things.)
So, are megapixels the be all and end all when thinking about your next smartphone? Absolutely not. As usual with such expensive purchases, go with review comments and feedback from other satisfied (or dissatisfied) users!
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Categories: Comment, Hardware
Platforms: General, S60 3rd Edition
Feature Discussion
marcb
Steve,
It was interesting to see how the various cameras compared. I wonder when photography sites will begin reviewing camera phones like digital cameras. Keywords like 2MP, 3MP and Carl Zeiss optics could have come straight out of a digital camera review just a few years ago.
Despite the overall washed out look I actually thought the N80 captured the most detail of the flower. (Is that an advantage of the 3MP?)
I'm a little surprised that overall I like the photo taken with the N70 better than that of the N90. Somehow the N90's photo seems a little ... um... smudgy? I would have expected the Carl Zeiss optics of the N90 to win. (I don't know which one is more true to the colors in the scene though.)
Marc
elp
The problem with the N80 seems to be the exposure. Is there an exposure compensation feature on the N80 or is it possible to override the automatic settings and choose the aperture and shutter speed manually? If that's possible, you should be able to get much better results by settings the exposure compensation to -2 or -3 IL or using the manual mode.
As for the N90, i can't seem to find the focus point which is why the picture looks blurry. Since you've extracted a part of the original picture, it is possible that the focus point is actually outside the part that you've shown us which would explain the disapointing results. What could have happened too is that you might have taken the picture before the N90 had had time to focus (i've never used this phone so i don't know how long it takes for it to focus and whether or not it allows a picture to be taken before focus has be acquired).
slitchfield
Yes, I gave the N90 time to focus 8-)
And yes, the N80's camera app does have a manual exposure tweaker, but a) it's limited to two 'stops' and b) it's not a setting that's saved and the user would have to remember to dive into the setup menus every single time they booted up the camera. 99.999999% of N80 camera use will be with automatic settings, which is what I tested.
As an experiment, I've put my N70 aside for a couple of weeks and am living with the N90 as my main smartphone. A high-res screen (though still on S60 2nd Edition) and proper focussing camera, at the expense of a more bulky and arguably awkward form factor.... should be an interesting fortnight!
Steve Litchfield
fig7
So the N80 is a bit rubbish as far as the camera is concerned. I'd like to see how the P990 and N93 do as these are the two camera phones I would consider buying. I think I'll wait for the N93 to arrive, but perhaps the P990 might still be worth the wait.
phil-t
Doing a comparison of a single scene accross camera's is just not scientific, or representative of a camera's all round performance.
Surely, a range of indoor/outdoor and possible standard ISO chart shots would give some more tangible results.
The N80 has captured much more detail then the others, but it has incorrectly exposed the scene, but that is a complex scene to meter, if it doesn't pick up on the bright sky portions, it will overexpose, this could be a software thing or just a matter of 'framing' the shot.
You are right in saying that it's not just about megapixels, the lens quality, auto-focus, and exposure, etc are all key elements, and need a more thorough investigation before coming to any conclusion..
slitchfield
Oh, sure. I did take half a dozen shots though, different scenes, and the N80 was the worst in all of them. The one included in the article showed the problem best though. It can't handle the same range of light and dark as the N70 and N90, which have different camera electronics.
I guess I should also do a comparison on indoor shots at some point as well, just for interest.
It wasn't a scientific comparison, just my own observations. I had planned to twist Nokia's arm to keep the N80 as my main device for a while, but I simply didn't want it - I preferred the N70 (and current toy, N90) 8-)
Steve
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