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We put the HTC One's ultrapixels to the test

172

Shortly after the launch of its latest flagship smartphone, the One, HTC published a white paper explaining the thinking behind the 4MP 'ultrapixel' camera in its latest device. This covers some key factors affecting image quality, including the lens, sensor and processor, in a fairly non-technical way. The document is light on numbers though, and worryingly high in quotes from journalists so scientists and engineers may find it unsatisfying.

The core of HTC's argument is based around the idea that using fewer, larger pixels on a sensor that's the same size as the 13MP unit found in competitors such as the Sony Xperia Z should offer better image quality. This of course runs counter to conventional marketing, which has always contended precisely the opposite, i.e. that more pixels are better. We're a little dubious about these claims - there’s a pretty strong argument that what really determines image quality when looking at the image as a whole is the total amount of light captured by the sensor, not by each individual pixel.

However, the HTC One's advantages are not all about pixels - HTC is also talking about the (pretty unarguable) low-light advantages offered by the optically-stabilised F2.0 lens, along with the improvements to video footage that image stabilisation brings. The fast sensor read-out means its electronic shutter completes the exposure more quickly than previous sensors - 1/48sec vs 1/30sec - which should reduce the 'rolling shutter' effect in movie recording.

And there is an argument for using fewer pixels on a smartphone, since most images are shared at much lower resolution than 4MP, it's difficult to imagine the main advantage of high resolution sensors, i.e. higher image detail, being especially important to smartphone users. We have now finally had a chance to test HTC's ultrapixel-claims first hand. Andy Westlake at our London outpost got hold of a HTC One review sample and has shot a range of comparison scenes in different light situations with his the new HTC flagship and his iPhone 4s.

The current weather in the UK (only very brief moments of sunshine) meant we could not take as many shots as we would have liked to but the images below should give you a good idea of what to expect from the HTC One. We will follow up with a more detailed test under controlled lighting once we receive a test unit here at headquarters in Seattle.

Daylight, low ISO

The 4MP backside-illuminated CMOS sensor in the HTC One is made by ST Microelectronics and also being used in a number of video devices. This explains the, for a still camera, unusual aspect ratio of 16:9. Switching to 3:2 or 4:3 aspect ratios crops the image sideways. The latter for example reduces the overall pixel count to 3MP.

In the well-illuminated scene below the Apple sticks to its base ISO setting of 50 while the HTC reports a slightly unusual sensitivity of ISO 112. The HTC is doing a decent job in these conditions albeit with a much warmer color response than the iPhone, but the latter is clearly better. In good light more pixels simply means more detail and this is clearly visible in the samples below. Whether this persists in typical social media use is a totally different question though.

 HTC One, ISO 116, ISO 112
 100% crop
 Apple iPhone 4s, ISO 50
 100% crop

Here we've got another shot in good light but more overcast conditions. Both phones struggle rendering the distant low-contrast areas but again the Apple's 8MP sensor captures more detail overall. On the flip-side the HTC produces a cleaner image with visible less shadow noise.

 HTC One, ISO 102
 100% crop
 Apple iPhone 4s, ISO 50
 100% crop

Digital Zoom

Digital zoom is generally awful on smartphones apart from the Nokia 808 with its PureView technology and both the HTC One and iPhone 4s are no exception. That said, with its comparatively low 4MP pixel count the HTC's image quality is deteriorating faster than the digital zoom of higher resolution smartphone cameras as you can see in the samples below.

 HTC One - 4x digital zoom, ISO 116
 100% crop
 Apple iPhone 4s - zoom, ISO 50
 100% crop

Low light, high ISO

In low light the HTC One is clearly better than the iPhone, producing a much cleaner, more noise-free image and giving brighter, more colourful images. It's difficult to isolate the effect the effect of the ultrapixels in this context as both the IS and the fast F2 lens playe a role too but in a way that’s academic, it's the end result that counts.

These images have been shot in Auto ISO mode but the HTC allows you to select ISO manually. However, a lack of information about shutter speed renders this feature pretty much useless.

HTC One, ISO 395, 1/15 sec
 100% crop
Apple iPhone 4s, ISO 800, 1/15 sec
 100% crop

When taking into account that many editing and sharing apps for smartphones reduce the size of images it also makes sense to compare the low-light samples above at roughly the same size. For this purpose we have reduced the iPhone 4s image to the same width as the HTC image (1520 pixels). Due to the Apple's 4:3 aspect ratio you end up with an image just over 3MP but the size of objects in the image is approximately identical in both photos.

As you can see in the 100% crops below the low-light advantage of the HTC is somewhat reduced when looking at images of the same size but the HTC One's image is still visibly cleaner with less luminance and chroma noise. So, when shooting in low light the HTC offers a real advantage over higher resolution sensors, even when the image size is reduced for sharing, social media or editing.

 HTC One, ISO 395, 100% crop
 Apple iPhone 4s, ISO 800, reduced image size

Soft image areas

In quite a few, but not all of our HTC One sample shots we noticed extreme softness on the right side of the frame. We haven't been able to determine the exact reasons for this but we are suspecting the effect could be caused by the image stabilization system decentering one of the lens elements. Once we get a review unit here in Seattle we will check if this is only a problem with the particular copy of the phone that Andy had in London and invesitage further. The problem is very visible in the samples which were taken within a few images. Exposure data for the two images is identical but if you click through to the full version of the image on the left you can see that are large area on the right side of the frame is extremely soft, making the image pretty much unusable.

 This picture shows extreme softness on the right side of the frame.
 This one, taken only minutes later at the same settings, does not exhibit any signs of softness.

First image quality impressions

Overall, from what we can see from these first sample shots, the HTC One with its 4 "ultrapixels" CMOS sensor performs pretty much as we would have expected. In low light and at higher sensitivities the HTC delivers cleaner images than the higher-resolution iPhone 4s. However, this is as much due to the optical image stabilization and fast F2 lens as the sensor. The HTC's advantage decreases if you compare images at the same size but is still clearly visible.

It doesn't come as a surprise that in good light the HTC trails noticeably behind its higher resolution peers in terms of detail capture. In good light more pixels simply mean more detail. The question is by how many users this will be viewed as a disadvantage, given a large proportion of smartphone images is being edited and shared at lower resolutions anyway.

We should also mention the HTC's strong tendency to produce purple flare with light sources that are located just outside the frame, a very similar effect to the one found on the iPhone 5. This is very obvious in the first image of our sample gallery below.

We will analyze the purple flare effect and image quality of the phone in general in much more detail once we receive a reviewable unit at our studio in Seattle. In the meantime we have included a few additional sample images in the preview gallery below for you to examine.

Sample Gallery

There are 12 images including a couple of panoramas in our HTC One preview samples gallery. Please do not reproduce any of these images on a website or any newsletter / magazine without prior permission (see our copyright page). We make the originals available for private users to download to their own machines for personal examination or printing (in conjunction with this review), we do so in good faith, please don't abuse it.

Unless otherwise noted images taken with no particular settings at full resolution. 

HTC One Preview Samples
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Comments

Total comments: 172
12
dpLarry
By dpLarry (Mar 30, 2013)

if you look at the prices of say sensors from the suppliers for example Sony (one of the main suppliers of sensors), the number of pixels on a chip is irrelevent to price. That mean a 1/3" sensor has the same price regardless whether it is 4mp, 8mp or 13mp.

0 upvotes
nightryder21
By nightryder21 (Mar 29, 2013)

When the One review, please make sure to compare it to the 808 and 920 as well please.

4 upvotes
CyberAngel
By CyberAngel (Mar 30, 2013)

This exactly what I was thinking of...
HTC One vs Lumia 920 vs Nokia 808

0 upvotes
Lan
By Lan (Mar 29, 2013)

There's an outside chance that the softness *may* be camera shake related - is the shutter release control on the right hand side, and the camera module on the left?

The soft side appears to streak slightly in the direction I'd expect for rotational shake.

Does the IS include rotational correction, or is it just linear?

Comment edited 56 seconds after posting
0 upvotes
CyberAngel
By CyberAngel (Apr 3, 2013)

I think linear in both HTC One & Lumia 920

This CAMERA has also rotational:
http://www.dpreview.com/reviews/olympusem5/

0 upvotes
tompabes2
By tompabes2 (Mar 29, 2013)

HTC released a software update and the images are much better now. Pictures are both sharper and with less noise, and also the corner softness issue has been fixed. So I think that Connect will have to repeat the test... :-)
But it's in low light that the HTC really shines, even if I suspect that the optical stabilizer is more useful than the "ultrapixel".
This camera will turn out to be good: almost on par with the others in daylight and much better in low light, so a good overall compromise.

5 upvotes
bobbarber
By bobbarber (Mar 29, 2013)

Nice. I don't see any reason why they couldn't be printed at 8x10. I got nice prints that size out of my first 2 Mp Kodak digital camera.

1 upvote
Pixel Judge
By Pixel Judge (Mar 29, 2013)

All these sample images look fine on my 24" HD screen.
That been said, I won't print my photos to that size using any camera phone, regardless it's 4mp, 13mp, or 40mp.

0 upvotes
warmonger87
By warmonger87 (Mar 29, 2013)

Can you include file size comparison between the HTC and the iPhone? One of the advantages to the small pixel count approach is lower storage (and thus, bandwidth) usage.

I'm not terribly impressed by the HTC One images, but if they're small and quick to work with, the compromise might be worth it for typical smartphone users, i.e. non-photographers.

1 upvote
Lars Rehm
By Lars Rehm (Mar 29, 2013)

Just click on the thumbnails and download the original images, you'll then see how large the files are.

2 upvotes
Kendall Helmstetter Gelner
By Kendall Helmstetter Gelner (Mar 29, 2013)

Two observations:

1) In the cloudy day image, the HTC image looks like heavy noise reduction has been applied (lots of smoothed over detail).

2) In the darker shots the iPhone 5 would probably have done even better than the HTC, that was the largest aspect of improvement over the 4s. It's really unfortunate you could not find the latest generation iPhone to compare against.

0 upvotes
Lars Rehm
By Lars Rehm (Mar 29, 2013)

you'll get all sorts of comparisons in our full review, the focus here is really on the HTC. But also, up to ISO 1000 we did not find too much difference between the 4s and 5: http://connect.dpreview.com/post/1343713337/apple-iphone-5-review?page=3

1 upvote
dpfan32
By dpfan32 (Mar 29, 2013)

the One photos are maybe 100 pixels!!! Please provide the full size photos!!!!

0 upvotes
Lars Rehm
By Lars Rehm (Mar 29, 2013)

Seems some of the links have been messed up, corrected now.

Comment edited 8 minutes after posting
1 upvote
tazmac
By tazmac (Mar 29, 2013)

You guys can't afford an iphone 5 to make it fair? Otherwise I am looking to get the One myself!

0 upvotes
Lars Rehm
By Lars Rehm (Mar 29, 2013)

Unfortunately our guy in the UK only had a 4s available but the image quality is very similar. This is all about the HTC though, don't focus too much on the comparison phone.

Comment edited 9 minutes after posting
0 upvotes
JadedGamer
By JadedGamer (Mar 30, 2013)

The main difference between the 4S and 5 is the lens not the sensor, though.

1 upvote
TheProv
By TheProv (Mar 29, 2013)

About softness, maybe you have the same pre-production One that hardwarezone had. They also reported softness, and HTC send them another One , that hadn't issues, in fact it gives visibly sharper images than the old One they had.

Look at here: http://www.hardwarezone.com.sg/review-htc-ones-camera-tested-updated

0 upvotes
Lars Rehm
By Lars Rehm (Mar 29, 2013)

Generally the sharpness of the camera is perfectly ok, but you only SOMETIMES get the softness which suggests that something is decentering the lens elements. So I suspect its not the same issue but we will definitely check when we get another unit next week.

3 upvotes
zos xavius
By zos xavius (Mar 29, 2013)

@lars does the lens move in a form of optical stabilization? If that's the case the softness could be due to the lens not moving perfectly with your own shake when taking the picture. It could also be possible that the camera reads the frame from left to right and you move your hand more during the second half of the exposure. i have to admit, I'm not really all that wowed with these images at the pixel level. Looks like there is a lot of noise reduction going on. Maybe the ultrapixels are hype? :)

1 upvote
Andy Westlake
By Andy Westlake (Mar 29, 2013)

Just to absolutely clear, the phone we're using isn't pre-production and came fresh out of standard retail packaging.

3 upvotes
Total comments: 172
12
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