Fast-aperture compacts

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A fast aperture is a big selling point for top-end compact cameras. Tim Coleman pushes seven of the best models to the limit to see which one comes out on top

Fast aperture compacts
Apart from manual-exposure control and raw capture, a feature that is often a selling point in high-end compact cameras is a ‘fast' (wide) maximum aperture and versatile lens, which all seven cameras in this group test offer. It is amazing that there are now compact cameras with apertures as wide as f/1.4, so what is so important about a fast lens, especially in a compact camera?

Compact-sized units, like most of the cameras in this test, usually use a ‘small' imaging sensor, so the amount of light collected by the sensor is more limited than it is in a larger DSLR. This, in turn, has a negative effect on low-light performance. Using a fast aperture increases the amount of light entering through the lens and makes the camera more versatile in low light. In turn, a lower ISO setting can be used for an exposure and/or a faster shutter speed, which makes handheld use and freezing movement without flash illumination possible in a wider variety of situations.

Another characteristic of a small sensor is the high focal-length magnification, so an extreme wideangle lens is needed to create a suitable ‘equivalent' focal length. In the Samsung EX2F, for example, with its 1/1.7in sensor (7.44x5.58mm) and a magnification factor of 4.55x, the lens is 5.2-17.2mm to create the 24-80mm focal range. Consequently, lens distortion, particularly
at wideangle settings, can be a downside.

A wide aperture enables a shallow depth of field. However, a small sensor limits control over depth of field, because the same focal magnification (crop factor) is applied to the effective depth of field. For example, the equivalent depth of field of a full-frame camera at f/9 is around f/2 (4.55x2) in a camera with the smaller 1/1.7in sensor. However, the Sony and Fujifilm cameras use a larger sensor than the other cameras in this group.

Each camera has a maximum aperture of f/2 or faster, while the zoom range and maximum aperture at the focal lengths of each camera varies. We know that using the fastest aperture on a lens does not produce the best image quality.

This test looks first at the key aspects of each camera's handling, and then compares the image quality when the camera is pushed to its ‘limits', such as its fastest aperture and when it is used in its ‘best' settings. Identical images have been taken with all cameras in a low-light scene, a high-contrast scene, and one where the focal length and depth of field make a difference. The quality will be analysed over the various apertures and across the frame for centre and edge detail.

Canon Powershot G15 Canon Powershot G15

Price: around £549
Tested: 10 November 2012

  • 6.1-30.5mm (28-140mm equivalent) Canon lens
  • f/1.8-2.8 maximum aperture
  • 1/1.7in CMOS sensor with 12.1 million effective pixels
  • ISO 80-12,800
  • 107 x 76 x 40mm
  • 352g inc battery

The Canon PowerShot G15 is the smallest and lightest version from the long line of popular PowerShot G-series compact cameras, but it is still the tallest and one of the heaviest in this group. Nonetheless, the camera fits comfortably in the hand and most of the key controls are at your fingertips. As with the Nikon P7700, a second dial is used for exposure compensation, up to ±3EV, making tweaks to exposure a speedy process. 

The main reason for the G15 being the smallest in its range is the fact that the 3in LCD is fixed rather than articulated, which is a little disappointing. However, the display is bright and has an improved 921,000-dot resolution over its predecessor. With Nikon removing the optical viewfinder in its P7700, the G15 is the only camera in this group with a built-in viewfinder.

It's an optical type that is linked to the zoom, but its usefulness is limited given that it does not feature a 100% field of view or any exposure information.

With a maximum aperture of f/1.8-2.8, the G15 is also the fastest in the G series, and is impressive considering the wide 28-140mm focal range. With a 4.55x focal magnification, the f/2.8 (f/13 equivalent) aperture at 140mm provides a shallow depth of field.  

Tested as: an Advanced compact

Rated: Very good

Score: 84%

Panasonic Lumix DMC-LX7 Panasonic Lumix DMC-LX7

Price: around £450
Tested: 15 September 2012

  • 4.7-17.7mm (24-90mm equivalent) Leica lens
  • f/1.4-2.3 maximum aperture
  • 1/1.7in CMOS sensor with 10.1 million effective pixels
  • ISO 80-6400 (extended to 12,800)
  • 111 x 67 x 46mm
  • 298g inc battery

With a wide f/1.4 lens that is reduced only to f/2.3 at its telephoto setting, the LX7 has the fastest lens in this group. Like all but the RX100 and XF1, there is an ND filter built in to reduce the level of light entering the lens, which in bright conditions is essential for achieving an accurate exposure when using the fast apertures available.

Another shared feature with the EX2F is a wide lens setting of 24mm, which is the widest in this group and a plus point when taking landscapes, although its more modest range extends only to 90mm. A new dedicated aperture ring on the lens barrel with aperture markings (which is unique in this group) gives an authentic feel to the handling. As before, aspect ratio and focus-mode controls remain on the barrel. The LX7 and the XF1 are the only models where the battery/ memory card door can open when the camera is attached to a tripod.

A resolution of 10.1 million pixels is the lowest in this group, although in our original test we found that the capacity to resolve detail, especially in low light, has been improved over its predecessor. It is perhaps in the low resolution (and therefore a lower volume of data to process) that Panasonic has been able to create a class-leading continuous high shooting rate of 11fps, while continuous AF tracking is possible in a 5fps burst.

Despite the high focal magnification, the fast f/2.3 (f/10 equivalent) aperture at the 90mm setting provides good depth of field.

Tested as: an Advanced compact
Rated: Very good
Score: 81%

Fujifilm XF1 Fujifilm XF1

Price: around £365
Due to be tested: 1 December 2012

  • 6.4-25.6mm (25-100mm equivalent) Fujinon lens
  • f/1.8-4.9 maximum aperture
  • 2/3in CMOS sensor with 12 million effective pixels
  • ISO 100-3200 (extendedto 12,800)
  • 108 x 62 x 33mm
  • 225g inc battery

Fujifilm adds the most compact model to its X-series range so far. The XF1's leather finish and silver top-plate give a classic feel and arguably the best looks of any camera on test here. This is one of the smallest cameras in the group, too, but with the same 2/3in (8.8x6.6mm) sensor as the Fuji X10, which is approximately 30% bigger than the 1/1.7in sensors used in most of the cameras here, and with a focal magnification of 3.93x.

A standout handling feature of the XF1 is its manually controlled zoom lens, which also turns the camera on and makes for a rapid start-up to ready-to-shoot time. It's a little more fiddly than the X10's, but precise adjustments are possible, and the lens has the key focal lengths of its 25-100mm range marked out on the barrel as an aid.

Handily, the lens folds into the body, so the camera packs away to a very compact size and is the ‘thinnest' in this group. Two function buttons allow a good level of customisation, with the E-Fn button used to assign a control to six of the buttons on the camera's rear. There is a modest built-in flash, but no hotshoe to attach further accessories.

The camera has a maximum f/1.8 aperture at its wide 25mm end, but by 70mm and beyond this is reduced to f/4.9, which is disappointing and effectively eliminates the advantage its larger sensor gives for depth of field. The X10 has a f/2-2.8 maximum aperture.

To be tested as:
an Advanced compact
Rated: Not yet rated

Nikon Coolpix P7700Nikon Coolpix P7700

Price: around £455
Due to be tested: 8 December 2012

  • 6-42.8mm (28-200mm equivalent) Nikkor lens
  • f/2-4 maximum aperture
  • 1/1.7in CMOS sensor with12.2 million effective pixels
  • ISO 80-3200 (extended to 6400)
  • 119 x 73 x 50mm
  • 392g inc battery

It seems Nikon has responded to feedback questioning the usefulness of the optical viewfinder in its P7100, because the P7700 does not have one built in. It may be smaller in height than its predecessor, but the P7700 is still the ‘chunkiest' and heaviest camera in the group at 392g. A big contribution to its bulk is its articulated 3in LCD screen, which has a 921,000-dot resolution. The EX2F is the only other camera with a fully articulated LCD screen.

Quick camera navigation and changes to exposure are possible through the front and rear dials, and with three top dials for shooting modes, exposure compensation and exposure modes, the camera has the highest number of controls on its exterior. This is the only camera in the group with the ability to add GPS data to images, via an optional unit. An optional external flash unit can
be attached via the hotshoe.

The P7700 offers the most extensive focal range at 28-200mm, making it the best model in this group to get in close to subjects. At its widest setting the maximum aperture is f/2, making this the ‘slowest' camera in the group. However, the aperture is only reduced to f/4 at the 200mm setting, which means that at the more telephoto settings it is very possible to achieve a shallow
depth of field.

Tested as: an Advanced compact
Rated: Not yet rated

Samsung EX2F Samsung EX2F

Price: around £380
Tested: 6 October 2012

  • 5.2-17.2mm (24-80mm equivalent) Schneider-Kreuznach lens
  • f/1.4-2.7 maximum aperture
  • 1/1.7in back-illuminated CMOS sensor with 12.4 million effective pixels
  • ISO 80-3200 (extended to 12,800)
  • 112 x 62 x 28mm
  • 294g inc battery

Like all the cameras in this group, Samsung's latest high-end compact has a CMOS sensor, while its predecessor, the EX1, uses a CCD type. The EX2F's 24-80mm range is the most limited in the group, but good for those who like to shoot wide. Its core specification is most similar to the LX7.
Where the EX2F stands out is that it is the only model here to feature built-in Wi-Fi. Combine this functionality with an extensive in-camera editing capability, and ‘complete' images can be shared without the need for a computer.

This is one of only two cameras to have an articulated LCD screen, which is a bright AMOLED type. The camera is constructed from magnesium alloy and feels solid in the hand, while the front dial speedily adjusts settings.

There are a couple of frustrating handling issues, though, the first being that the lens resets to its widest setting after playback, so the scene needs recomposing. Also, there is no orientation sensor, which means rotating every portrait-format image post-capture.

Its fast f/1.4 maximum aperture is reduced to f/2.7 by 80mm, which means that the EX2F cannot quite match the LX7 for depth of field control at the more telephoto settings. Like the LX7, there is a built-in ND filter to reduce the level of light entering the lens, which is handy for using the f/1.4 aperture in bright conditions or for long shutter speeds when blurring movement.

Tested as an: Advanced compact
Score: 82%

Sony cyber-shot DSC-X100Sony cyber-shot DSC-X100

Price: around £550
Tested: 14 July 2012

  • 10.4-37.1mm (28-100mm equivalent) Carl-Zeiss Vario-Sonnar T lens
  • f/1.8-4.9 maximum aperture
  • 1in (13.2 x 8.8mm) CMOS sensor with 20.2 million effective pixels
  • ISO 125-6400 (extended to 25,600)
  • 102 x 58 x 36mm
  • 240g inc battery

Not only does the RX100 feature the largest sensor in the group, a 1in (13.2x8.8mm) CMOS type, but it has almost twice the resolution at 20.2 million pixels and therefore can produce prints nearly twice the size. Perhaps what is most impressive, though, is that all this has been packed into what is the smallest and most lightweight body in this group.

The RX100 slips into a pocket, is made from magnesium alloy, and its design is simple and elegant. In-camera menus are vast and similar to those found in the Alpha range, which is testament to just how many shooting modes and functions are here. Its lens ring can be used for aperture, too, although rather than being ‘stepped' it rotates smoothly.

One downside of the large sensor is that the maximum aperture is reduced more dramatically at the telephoto setting, from f/1.8 to f/4.9. Also, the minimum focus distance is 5cm (compared to 1cm in most of the other cameras). The RX100 does not feature a hotshoe port, either, which means there is no option for external flash, although it does have a built-in flash.

With the largest sensor, the focal magnification is the least at 2.72x, which means the greatest control over depth of field. Its f/1.8 max aperture has an equivalent depth of field of f/5, while in most of the other cameras it is around f/9. However, at the telephoto end, things are evened up somewhat on account of the reduced maximum aperture.

Tested as: an Advanced compact
Rated: Very good
Score: 87%

Olympus stylus xZ-2 Olympus stylus xZ-2

Price: around £479
Tested: 17 November 2012

  • 6-24mm (28-112mm equivalent) Olympus i.Zuiko lens
  • f/1.8-2.5 maximum aperture
  • 1/1.7in CMOS sensor with 12 million effective pixels
  • ISO 100-12,800
  • 113 x 65 x 48mm
  • 346g inc battery

Like most cameras in this test, the XZ-2 uses a 1/1.7in sensor with 12-million-pixel resolution. By including a tilt mechanism in the LCD screen this time round, the XZ-2 is larger than its XZ-1 predecessor, very similar in size to the EX2F, and closer in size to the Nikon and Canon models. The screen is also brighter than before, has an anti-smudge surface and is the only one in this group with touch functionality.

Touch controls available are limited to shutter and AF, with the exposure controls displayed along the side of the screen changeable only via the buttons on the camera body.

The XZ-2 handles better than the XZ-1, with a more ‘stubborn' shooting-mode dial reducing the likelihood of the dial shifting when the camera is in a pocket.

The hand grip on the front is new, but can be removed, while a switch next to the lens changes the function of the lens ring between zooming or manual focusing and changing the exposure modes such as ISO and aperture. Also, within the switch is a second function button. Like the LX7, an accessory port under the hotshoe allows the use of an EVF.

There is only a minimal reduction in the maximum aperture through the focal range, with f/2.5 at 112mm, so it is very possible to achieve a shallow depth of field at any given focal length.

Tested as: an Advanced compact
Rated: Very good
Score: 84%



Image: The coverage at the widest and telephoto setting of each camera is indicated here

Image: These images are recorded at 50mm f/4. Five of the cameras use the smaller 1/1.7in sized sensor, while the RX100 uses the 1in sensor and XF1 the 2/3in size. The RX100 offers greater control over depth of field, with more obvious background blur here  

Resolution

We show the section of the resolution chart where the camera starts to fail to reproduce the lines separately. The higher the number visible in these images, the better the camera's detail resolution is at the specified sensitivity setting.

Resolution and detail

If the cameras are closed down a couple of stops to the optimum aperture for detail, centre sharpness and resolved detail actually vary quite a lot. Unsurprisingly, the RX100 is in another league, because with almost twice the resolution its images are approaching twice the size. Its high resolution gives greater scope for playing around with images, too, allowing heavy cropping.

More surprising is what must be the difference in lens quality between ‘similar' models. Considering its broad zoom range, the P7700 gives an excellent performance, while the EX2F has a slight edge over other models for sharp detail.

Working in low light

With the exception of the RX100 and XF1, all the cameras use the same sized sensor with a similar number of pixels. The low-light performance is relatively similar, then, with resolved detail dropping by a similar rate in the 1/1.7in sensors. The XF1 has a larger sensor and therefore larger photosites, and its ability to collect light is a little better than most of the other cameras, holding its performance better.

The RX100's sensor is almost twice the size of all but the XF1 unit, but it uses almost twice the number of pixels so its sensor is almost as densely populated with photosites. Its low-light performance is still at an advantage, then, because of its high resolution.