Whatever the weather
An interview with the ZEISS Milvus product manager that reveals the lengths ZEISS go to protect Milvus lenses from dust and water. Photographers can concentrate on getting the shot knowing they can rely on the performance of their kit even in rain or a sand storm.
Whatever the weather
Christophe Casenave is the product manager for the ZEISS Milvus family and ZEISS’s expert on weather sealing. In this interview, Christophe talks about why photographers have no need to worry about their ZEISS Milvus lens if they ever get into a rain or sand storm.
Why does ZEISS offer some of its lenses with special protection against moisture and dust?
Put simply, because our customers ask for it. Professional photographers know that blue skies rarely make the best photos. Bad weather is when you create great photographs, for example a storm with dramatic cloud formations. To ensure that photographers don’t have to worry about their expensive equipment, we offer some lenses with weather sealing. An example is the ZEISS Milvus family. The weather sealing draws on our experience with cine lenses: filmmakers shoot in the desert or in the rain forest where weather-proof lenses are an absolute must.
Where can dust or water penetrate a lens?
Dust and water can enter the lens wherever there are gaps between the inside of the lens and the external environment. In practice, there are two places where this can happen: where the lens is screwed to the camera and between the elements that move against each other, for example the movable lens barrel or the rings to set the focus or aperture. When focusing a Milvus lens, the lens barrel moves forward or backwards. A Milvus lens has up to ten such interfaces where dust or water drops could get inside without the special weather protection measures.
What sort of protection measures?
A relatively simple one is the mount to the camera. We build an elastomer ring into the mount in the distinctive ZEISS blue colour. The elastomer must have the right softness; only then will the sealing work effectively. It’s a bit more complicated for the moving elements. For these we fix felt rings, or seals made of felt and foil, at every interface. This provides a thorough level of dust and water protection.
The four sets of weather protective rings in a typical Milvus lens
And what if a drop of water manages to penetrate the felt ring after all?
The next felt ring stops it. A drop has to get through five felt rings to reach the first lens element this system is highly effective as our tests show.
What sort of tests? How are they conducted?
We follow the test criteria of the internationally recognized standard DIN EN 60529. We test the dust protection in a chamber with two kilos of talcum powder per cubic metre of air swirling around and above the lens. This test lasts eight hours, during which time the focus ring and aperture ring are turned several times. To pass the test, none of the functions can be impaired and only small amounts of the powder may be found inside the barrel.
Another test is the so-called dripping water test. In this test, drops fall for 10 minutes at a slightly slanted angle onto the lens, which is turned every two and a half minutes by a quarter around the optical axis.
Apart from these weather-specific tests, we subject all lenses to stress tests when they are dropped and bumped. The lenses are also exposed to extreme temperatures in our special environmental laboratory, which simulates different environmental influences.
What results have you achieved? And what do they mean for photographers?
We have not found any moisture, humidity or dust in the lens. The ZEISS Milvus lenses always functions perfectly and can be guaranteed to work in these challenging situations. Milvus lenses resist very fine dust, and would even be tight in a sand storm. Furthermore, they keep out light drizzle. We cannot guarantee complete protection against very heavy rain; from a construction point of view, that’s very hard to achieve. However, what really counts is that photographers can be sure the imaging performance is not jeopardized and that the lens will not be damaged by dust and water.
Does water protection make a difference to handling the lens?
Besides the advantage of not having to worry about environmental influences, there is no difference in handling. There is no increase in weight and turning the rings is only minimally harder, barely noticeable. If you hold the lens to your ear, you may hear a tiny noise — the felt gliding over the metal, but you have to listen very closely.
Do the seals need any special care?
The additional weather protection does not need any special care or maintenance and guarantees a long lens life.
Thank you for the interview, Christophe.