Noise, resolution and sensitivity
Image: The Sony NEX-5 does a good job of controlling colour noise even at high sensitivities. However, there is a slight loss of image detail caused by noise reduction
With a maximum ISO sensitivity of 12,800, the Sony NEX-5 has the highest sensitivity of any MSC that is currently available. At the camera’s lowest sensitivity of ISO 200 there is no noticeable colour or luminance noise, although the raw files do display slight signs of coloured moiré patterning. This colour patterning is only noticeable in very fine areas and can be easily removed by applying a colour noise filter to the image.
In terms of resolution the NEX-5 performs as well as most DSLR cameras, reaching 24 on our resolution chart. However, I would have expected it to be a little higher given its 14.3-million-pixel sensor. Where the 14.3 million pixels seem to come in to their own is at higher ISO sensitivities. Even at ISO 3200, the NEX-5 still reaches 20 on our test chart. At this sensitivity JPEG files show minimal colour noise, although there is a slight speckled effect from luminance noise.
At the maximum ISO 12,800 sensitivity, images look surprisingly good. Viewed at 100% they have a slightly smudged appearance and detail is lost, but the noise reduction has done a good job of keeping colour noise to a minimum. As most people won’t use the extreme ISO settings and will rarely be printing images larger than A4 in size, the NEX-5 produces good photographs.
Unfortunately, the small flange back and wideangle focal length of the 18-55mm lens has introduced distortion and a slight softening of detail towards the edges of images. Chromatic aberrations are also sometimes noticeable. However, the biggest worry is the distortion, which gives the impression that objects are being slightly pulled towards the corners.
Left: These images show 72ppi (100% on a computer screen) sections of images of a resolution chart, captured using matching 105mm macro lenses. 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. Right: This graph shows the brightness values recorded by the test camera when it is used to photograph a stepped graduation wedge. The wedge has transmission values in 1⁄2EV steps ranging from 0 to 12EV. The camera’s exposure is set so the 12EV section in the wedge has a brightness value of 255. Software analysis of the image then determines the recorded brightness values of all the other steps and calculates the camera’s dynamic range.
