Image Quality

A lot of the HTC One's early marketing efforts were focused on the camera's 4MP sensor. The sensor is the same size as on other current smartphones but fewer pixels means that the individual photosites are larger — approximately the same size as in an enthusiast compact cameras such as the Panasonic Lumix LX7. Of course fewer pixels in a camera runs counter to conventional marketing, which has always contended precisely the opposite, i.e. more pixels are better. This is presumably what has HTC prompted to come up with the term "ultrapixels." We're still talking megapixels here, but it definitely sounds more exciting.

The imaging sensor in the HTC One's camera module is the same size as most other current smartphones but comes with a lower 4MP pixel count and therefore larger individual photosites.

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 Samsung Galaxy S4 or Sony Xperia Z should offer better image quality. We would argue this is not always necessarily true. 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. The phone also comes with a fast F2.0 lens and optical image stabilization which offer unarguable advantages in low-light. The stabilization also helps to keep video footage steady. There is a good argument for using fewer pixels on a smartphone anyway. Images are typically shared online or edited at much lower resolution than 4MP and most users don't even come close to making use of their smartphone camera's full resolution.

Theory is one thing though, practical use is another. The actual image quality is determined by many more factors than just sensor and lens. Read on and have a look at our sample images below to see how the HTC One performed in our real life tests.

If you would like to see the HTC One in a side-by-side image quality comparison with the Samsung Galaxy S4, Apple iPhone 5 and Nokia Lumia 920 please also have a look at our comprehensive Smartphone Super Shootout and our comparison with the Apple iPhone 4S.

Daylight, Low ISO

In the well-illuminated scenes below the HTC is doing a decent job and produces good exposures and vivid colors. Close-up the images look a little over sharpened with some processing artifacts but the pixel-level detail is decent. That said, while these images are perfectly good for social sharing and onscreen viewing, most of the competition's higher megapixel-count sensor will simply capture more detail in this type of conditions. This is only relevant if you ever plan to print your images at larger sizes but worth keeping in mind.

ISO 114, 1/7860 sec
In good light the HTC One captures well-exposed images with good detail ...
ISO 113, 1/5486 sec
... but when examined close-up the images look slightly over-sharpened and generally overprocessed. There is also some luminance noise in areas of plain color.
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While the HTC One's 16:9 aspect ratio is great for landscape shots, video capture and viewing on a 16:9 screen, it's not ideal for traditional portrait shots, or shooting any subjects in portrait orientation for that matter. Most subjects look more attractive in portrait orientation shots when captured in a 3:2 or 4:3 format. The latter is available on the HTC One, albeit at a reduced resolution of 3MP.

Skin tones on the HTC can look a tad too saturated but switching to the portrait shooting mode or toning saturation down a little in the menu helps.

ISO 100, 1.738 sec
In portrait shots skin tones can have a slightly cool touch but the images show decent detail.
ISO 102, 1/1038 sec
This shot is a tad underexposed and shows some sharpening artifacts up-close but again, detail is good for a 4MP image.
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Like on most smartphone cameras things become more difficult when the shooting conditions are not ideal, as you can see in the samples below. Despite the larger photosites the HTC One struggles with high contrast scenes and you inevitably end up with clipped highlights when a high-contrast scene is exposed for the shadow areas.

We've also noticed significant softness at the edge of the frame in some of the HTC One's images. However, this is not visible on all images and usually only on one side of the frame, which leads us to believe that it is caused by the optical stabilization system tilting the lens. The effect was much more pronounced on an earlier unit we first tested at our London office, but it is still visible on the U.S. version we have here in Seattle.

ISO 101, 1/180 sec
Like on almost all smartphones, highlight clipping is an issue on the HTC One.
ISO 104, 1/2560 sec
Some, but not all, shots show distinct corner softness on one side.
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We also found two color related issues on some of our HTC One sample shots. On the left image below you can see that the One has, just like the iPhone 5, a tendency to produce a purple flare if a strong light source is located just outside the frame. In our case this light source was the afternoon sun. The same picture is ideal to demonstrate another one of the One's flaws: purple fringing. If you look closely at the reflection of the sun on the water you can see very strong fringing which almost adds a purple tint to the lake surface.

In some shots we also found a strong magenta color shading at the center of the frame. It's most visible in shots with an area of plain color at the center of the frame like the blanket in the photo on the right but if you look closely you can also see it in the indoor still life and the second portrait in the low-light section below. This is a common problem caused by the edges and corners of the frame receiving light from the lens at a very oblique angle. This means it’s most problematic when you have wide angle lenses whose exit pupils are close to the sensor. Like purple fringing normally this is corrected for by the software, so you don't see it. It's therefore surprising to see how badly the HTC is dealing with it.

ISO 175, 1/38399 sec
In this shot you can clearly see the purple cast caused by the sun just outside the frame and the heavy purple fringing on the surface of the lake.
ISO 230, 1/20 sec
This shot shows significant color shading in the center of the frame. In reality the entire blanket has the same gray color.
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Low Light, High ISO

In low light the HTC One is capable of producing a cleaner, more noise-free image and giving brighter, more colorful images than most higher-resolution competitors. It's difficult to isolate the effect of the ultrapixels in this context as both the ISO and the fast F2 lens play a role, but in a way that’s academic, it's the end result that counts. The difference becomes less obvious when images are scaled down to the same size as the HTC One output but is still visible as we demonstrated in this article.

Thanks to its fast lens and optical stabilization the HTC can keep the sensitivity low, even in very dark scenes like the cityscape on the left. The scene on the right was shot indoors and the phone only pushes ISO up to 188 which means you still get an image with good detail and textures, despite the lower light. However, this approach to Auto ISO will get you the occasional blurry image, so it's always good to take not one but several shots of a low-light scene. This way you make sure you've got at least one good one.

ISO 564, 1/15 sec
This night shoot is well exposed and pretty clean, despite the high ISO.
ISO 188, 1/24 sec
For this indoor shot the HTC keeps ISO very low, resulting in good detail and a fairly clean image.
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The HTC One does a better job at shooting portraits in low light than most of its competitors but the very slow shutter speeds mean that subject movement can be an issue and in mixed-ligh situations, like the image on the left, skin tones can be a little off.

ISO 736, 1/15
This low-light portrait is a touch soft due to subject movement but noise is well under control.
ISO 522, 1/17 sec
There is a lot of noise and artifacts in this image but, despite the slow shutter speed, it is sharp and still shows some detail at a 100% view.
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As explained above, the fast lens in combination with the optical image stabilization allows the HTC to keep the ISO down even in low-ligh situations. However, we would occasionally be happy to accept a touch more more noise in return for a sharper image. When shooting in low light the HTC's shutter speeds are often so slow that you really want to take more than one image of a scene if you want to be certain to get a sharp capture. Moving subjects will inevitably show some motion blur.

ISO 102, 1/30 sec
These images were taken in low light indoors, yet the HTC almost sticks with its base ISO ...
ISO 188, 1/24 sec
... resulting in very low noise levels but some camera shake. When in doubt, it's worth pressing the trigger more than once to make sure you've got at least one sharp image.
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We were impressed by the HTC One's flash performance. The options are the same as on most other current phones — Auto, On or Off — but the unit appears to be more powerful than most, allowing the One to keep the ISO at a lower levels than the competition for flash photography. Flash exposure tends to be on the conservative side but that keeps skintones from clipping and avoids the "deer-in-the-headlights" look of some other flashes. The red-eye effect is very much under control too.

ISO 101, 1/138 sec
This shot is perfectly exposed and there's enough ambient light to get some detail in the background as well, giving the image a "slow-flash mode appearance".
ISO 118, 1/120 sec
This flash shot is again very well exposed, but in very dark environments the One's AF can slightly struggle. We took various shots of this subject and in all of them the focus is slightly off.
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