Here are some more results examining the effect that image stabilisation technology has on lens resolution.
Image stabilisation technology is great for providing a steadier viewfinder image but the jury is out on whether or not it actually produces sharper pictures. One way to investigate this is by switching-on image stabilisation and repeating MTF testing to compare the results with those obtained previously. This type of investigation has been covered a couple of time previously and the latest results, reported here, simply add to the body of data that is available.
First a health warning: lens manufacturers tend to advise that image stabilisation should not be used when the camera is mounted on a tripod yet that is exactly the situation that applies during MTF testing. With this in mind it would be perfectly reasonable for lens manufacturers to point out that these results may not apply to real-world photography.
To counter this, at some stage I will do hand-held MTF testing, with and without image stabilisation, but that will be a rather difficult test given that the test chart and sensor plane have to be carefully aligned.
The test reported here was undertaken using Nikon’s 24-120mm f/3.5-6.6 ED-IF G-series lens. The results show that image stabilisation (or vibration reduction, to use Nikon’s terminology) is likely to degrade image quality under most conditions. There may be a slight improvement beyond f/22, when the exposure time extended beyond 1/13s, but the overall image quality is degraded by diffraction effects in this region so any gain is likely to be fairly marginal.
As has generally turned out to be the case previously, image stabilisation appears to be most useful in terms of making a lens more useable thanks to a clearer viewfinder image. Ironically, the firmer that you are able to hold the camera, the more likely image stabilisation is to degrade the image quality. The most extreme case of a firm (stable) grip is provided by a sturdy tripod and in this case it is clear that the tripod’s pictures are not generally improved by switching-on image stabilisation.