– Internal ND filters are smaller and lighter.
– They can avoid reflections you can get with multiple filters in the mattebox.
– Internal ND filters can reduce flares and narcissism (double image from reflections between the rear element of the lens and the sensor)
. An ND filter between the rear element and the sensor can reduce these reflections.
• An internal ND (or clear filter) protects the sensor from dirt contamination during lens changes.
The new ARRI ALEXA INTERNAL FILTER MODULE IFM -1, are not the same as current external ND filters.
– An anti-reflective multi-coating, which is absent in most external filters, maintains high image contrast.
– Water white optical glass is precision polished.
– A broadband absorptive coating ensures an even attenuation of the light over the full spectrum, which is why they are called Full Spectrum Neutral Density (FSND) filters. There is no color shift at any density.