Last summer, Aurora Aperture ran a kickstart campaign for small ND/LPR filters that are housed in mount adapters, i.e. behind the lens. Currently there is something similar from Aurora again, namely a "Rear mount filter system" for extreme wide angle focal lengths with a strongly curved front lens without filter thread, but in some cases you have to use a small screwdriver to install the mount. The project is already fully financed.
Originally, this was only available for a few selected Canon lenses that already had a mount for gel filters at the back; this was replaced by a mount for glass filters. With this new generation, the filter system will be extended and should also support some extreme wide angle lenses from Sigma, NIkon and Sony.
The new rear-mount filters consist of a slightly magnetic holder that is attached to the lens and into which the actual filter is then plugged in a metal frame. According to Aurora, the magnetic field should not interfere with camera functions such as IBIS etc. How the mount is attached differs from lens to lens -- with the already mentioned Canon, the gel mount is replaced, with two Sigma lenses, one shim ring is replaced, with others nothing has to be removed, the mount can simply be inserted.
The same range of filters is available as for the adapter filters: normal ND filters with 2, 4, 6, 8 or 12 stops, three ND filters with gradient (1.5 / 2.5 / 3.5 stops) and Light Pollution Reduction Filter (LPR). Except for the latter, Schott D 263® T eco glass is used as the basis.
The filters become cheaper the more you order - a single one costs on kickstarters, nine of them . For each filter order, you get one bracket in addition. The filters only fit one lens (type) each. The following lenses are supported:
EF 8-15mm f/4L Fisheye USM
EF 11-24mm F4L USM
EF 14mm f/2.8L USM & EF 14mm f/2.8L USM II
EF 15mm f/2.8 Fisheye
EF 16-35mm f/2.8L USM (EF 16-35mm f/2.8L II USM not supported)
EF 17-35mm f/2.8L USM
EF 17-40mm f/4L USM
Nikon AF-S 14-24mm f/2.8G ED
EF 14-24mm F2.8 DG HSM Art
EF 14mm F1.8 DG HSM Art
Sony E mount / L mount: 14-24mm F2.8 DG DN Art
Sony FE 12-24mm F4 G
Bilder zur Newsmeldung: