Sony’s Cyber-shot DSC-RX1 was one of the most talked about cameras of 2012, but now the RX1R has had the anti-aliasing filter removed from its 24.3-million-pixel, full-frame sensor. We find out just how much difference this makes to image quality. Read the Sony Cyber-shot DSC-RX1R review...
Sony Cyber-shot DSC-RX1R review – Moiré patterning
The fine houndstooth chequered pattern of this dress proves difficult for both cameras. However, the anti-aliasing filter of the RX1 reduces the issue, resulting in softer moiré patterning. The RX1R moiré is very severe, but the bottom pull-up shows that it can be removed fairly easily, or at least reduced in Adobe Camera Raw
One of the main purposes of the anti-aliasing filter (or low-pass filter, as it is also known) is to reduce moiré patterning in images. This patterning occurs when two linear grids are overlapped out of alignment with each other. One common example of this phenomenon is when photographing net curtains. Where the grid mesh of the curtains overlaps, a new concentric pattern appears to be created.
The same thing occurs when the grid array of a digital camera sensor is exposed to a similar linear pattern, such as tightly woven fabric or intricate brickwork on a building. The anti-aliasing filter is designed to blur the image slightly, and the stronger the filter, the more the image is blurred, with different manufacturers using different strengths of filter depending on the sensor used. The slight blurring is usually enough to remove moiré patterning completely, although it does of course impact on image sharpness. The anti-aliasing filter is one the reasons why digital images require sharpening.
With no anti-aliasing filter, moiré patterning is something that has to be considered when judging the image quality of the RX1R. I did find that I was able to see the effects of moiré patterning in my images when shooting a scene that included the edge of a closed book showing the stacked pages. When shooting JPEG files on the RX1, the image shows some of the fine lines of the pages in the book. The RX1R image is a little sharper, but the fine line of the book’s pages have a strange cross-hatched pattern running through them.
A dress with a fine houndstooth check pattern caused even more of an issue, with swirled coloured moiré patterning on the image taken with the RX1R. The same image taken with the RX1 also displays moiré patterning, but the effect is softer, as is the amount of detail displayed in the image. Of course, the strength of the patterning, and even whether it occurs at all, is also affected by the distance from the subject. When taking a portrait, it may be possible to reduce moiré patterning on a dress by simply moving slightly closer to the subject. However, it obviously isn’t ideal to have technical issues dictating the composition of an image.
Using Adobe Photoshop Lightroom 5’s localised moiré reduction tool, I was able to remove almost all the moiré patterning in the dress in the image taken with the RX1R. This removed the false colour patterning quite easily. If you weren’t previously aware of the moiré patterning you would struggle to find it, but if you know where to look then it is still visible, just reduced in strength.
Sony’s product manager was quite open about moiré patterning at the launch of this camera, saying this would be an issue for some photographers. He also stated that whether or not it would be a problem depends on the type of photography the camera is used for. If you only ever shoot landscapes, you may never see any moiré pattering in images from the RX1R. However, portrait, fashion and even some architectural photographers may find themselves at the mercy of moiré. Thankfully, the latest software seems to be very efficient at removing the patterning, although it may be time consuming if you have to remove it from a number of images.