Especially when shooting in misty, windy or salty environments, the sensor of your camera can become pretty much caked in dust or water droplets (that are often even worst than dust…), and pretty fast too.
This often happens even if you don’t change lenses. The old push-pull zooms are, in this regards, the worst offenders, sucking air in and out of the camera.
But don’t despair, there is a cheap and easy solution. For about 25€ you can separate your sensor from the outside world.
First though a disclaimer: for your sensor to be absolutely protected your adapter should be water sealed. Unfortunately, I don’t know of any manufacturer that offers such a product (and if you do, please, write me a comment!). Besides, legacy glass isn’t usually water sealed either.
Second disclaimer: you do this at your own risk. If you put this in use too early, when the silicone is still drying, and silicone vapors end up covering your sensor you’re on your own. Same thing if instead of silicone you decide to use Super Glue (cyanoacrylate vapors WILL coat your sensor). That being said, as long as you let the silicone dry at least a couple days this should be perfectly safe 🙂
Third (and I swear, last) disclaimer: don’t try to modify an adapter for rangefinder lenses. I think this solution will not work in this case, because rangefinder lenses are designed to extend deep into the camera
What you’ll need
- an adapter for the lenses you wish to mount; I used a K&F Chinese adapter because they are cheap but really well made, and they have an internal lip that happens to be the right fit to support a standard 49mm filter.
- an UV filter of the right size to fit in the back of your adapter (just the glass, not the mount as well); don’t cheap out on this, it would be stupid to spare a few bucks for a piece of glass that will let through the light for all your lenses and anyway the expensive ones are around 15€ (Rodenstock, Heliopan, B+W, etc.)
- a tiny screwdriver, to remove the metal strip that keeps the filter into its mount
- silicone sealant, to fix the filter glass inside the adapter and seal everything nicely
Assuming you’re reasonably handy this should be an easy modification. The most difficult part is to get the filter glass out of its mount without chipping or breaking the glass itself.
Once you’ve done this, the process of mounting the glass inside the adapter involves a thin coat of silicone sealant inside the flat part of the adapter (where the UV filter will rest), without smearing the silicone everywhere.
And please don’t do something stupid like I did, and let the silicone dry for at least a day or two before trying to clean up the filter from digital prints and dust (but, if silicone smears onto the filter, remove it pronto with denaturate alcohol or acetone). This tiny mistake costed me an half an hour and a good amount of Pec-Pads…
If you don’t think you have the dexterity, you can try your luck and buy a ready made adapter with a variable ND filter in it (but one of these will eat light).
Once you’re done, your sensor will be pretty much isolated from the outside harsh world, even when you’re changing lenses, and dust and stuff will only be able to enter the camera, if at all, from the un-sealed lens mount.
And if dust or water droplets should land onto the UV filter inside the adapter you will be able to clean it up even in the field, just with some lens cleaning tissues or a lens-pen. Much easier than trying to do the same thing with dirt sitting directly on your sensor!
By the way, yes I’ve tested my lenses with and without the UV filter in place (using a non-modified, hollow adapter, tripod, 2s shutter release, etc.) and I couldn’t see the slightest difference in terms of resolution or flare on the A7r, not even at the extreme borders.