Introduction

These tests investigate the vibration sensitivity of long lenses on one or two tripods, the utility of IS on a tripod is also investigated although the common wisdom is that IS is of no help on a tripod and for older IS models can cause instability.

Tests were conducted over a range of shutter speeds one stop down from maximum aperture using the ISO to vary the required shutter speed.

Each setup is tested with three different sets of exposure, mirror lockup with a timer exposure, timed exposure but no mirror lockup and shutter button release in the normal way with the photographer looking through the viewfinder.

Three lens configurations are investigated as selectable from the above menu, 300mm + 2X TC (results limited my manual focus), 300mm + 1.4X TC (including IS off, IS Mode 1 and IS Mode 2) and 200mm + 2X TC.

Conclusions

Not using mirror lockup had a significant detrimental effect for shutter speeds of less than 1/125 for both 600mm and 400mm setups and on both heavy and light tripods although the impact was less for a heavy tripod. So it seems this threshold is due more to the mirror slap vibration duration than other issues. Methods to damp this vibration would prove beneficial is with very sturdy tripods.

Even with mirror lockup used the light weight tripod showed degradation below 1/60th.

Using IS on the tripod did not degrade sharpness as suggested by Canon, possibly because the light tripod used for this test was not study enough to cause IS control loop instability.

Direct release of the shutter by the shutter button generally caused more degradation over the mirror slap for shutter speeds below 1/60 although this trend was absent from the 200mm + 2X case, possibly due to the shorter distance between the TMA mount point and the end of the lens. Where IS was used this seemed to mitigate the degradation of direct shutter release to some extent.

The two stop advantage of IS showed that little advantage in sharpness was expected by using a tripod for shutter speeds of 1/100th and above for a 400mm focal length although for lenses without IS even the light tripod gave a significant advantage for shutter speeds below 1/250th, a monopod was about 1 stop better than this.

Last Updated 23/05/2008

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