Olympus has at long last announced the replacement for the ageing E-5 DSLR, but it might not be what people were expecting. Richard Sibley tests the micro four thirds OM-D E-M1. Read the Olympus OM-D E-M1 review...
Olympus OM-D E-M1 review – Noise, resolution and sensitivity
Image: Shot at ISO 400, there is no shortage of detail in this image. However, there is more noise than I would expect in shadow areas
The OM-D E-M1 has no anti-aliasing filter in front of its sensor, which has the effect of increasing the amount of detail that the camera can resolve. In our test chart images, the E-M1 resolves about what you would expect from a 16-million-pixel sensor, reaching over 30 on our chart when shooting JPEG images at ISO 100-400. The resolution drops incrementally as the ISO increases, but JPEGs still look well defined at ISO 1600, and there is only a slight drop in resolution.
It is at about ISO 6400 that the resolution starts to drop noticeably. There appears to be heavier luminance noise reduction at this level, while at ISO 12,800 and ISO 25,600 images look mushy and reach only 20-22 on our resolution chart. Despite the obvious detrimental effect of luminance noise reduction, colour noise is only very slightly visible, even at these high sensitivities.
Looking at the raw files in Adobe Photoshop Lightroom gives a clearer idea of how much noise reduction is taking place in-camera. Colour noise is extremely well handled in JPEGs, and it was possible to remove virtually all colour noise from raw files at all sensitivities. Luminance noise is obviously far more visible in raw images, but with no luminance noise reduction applied, images are sharper and crisper.
I was a little disappointed with how soon luminance noise begins to appear in images. At ISO 400 and ISO 800, there is obvious luminance noise in raw files and JPEGs, although it won’t be a concern for most photographers. Without wanting to sound like a broken record, luminance noise kicks in about 1EV earlier than you would expect it to from the equivalent APS-C-sized sensor. However, it is important to reiterate that the images from the E-M1 are usable right up to ISO 6400. Colour noise can be completely removed from raw files and luminance noise can be softened slightly, without causing a huge loss of detail. However, the vast majority of photographers will take most of their images between ISO 100 and ISO 400, where luminance noise isn’t an issue.
These images show 72ppi (100% on a computer screen) sections of images of a resolution chart, captured using the Olympus M.Zuiko 75mm f/1.8 lens set to f/5.6 . 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.