Filter thread in front of sensor?

[Marc Berger]

What do you think about this: to tap a thread in front of the sensor to be able to screw a glass filter? Diameter approx. 49mm? It seems the space around the sensor is big enough. It would help to mount protection filters (easy to clean during field work), Nd filters, IR filters (like the one from Leica) and so on.
Just a thought.
Cheers
Marc

 

[Shawn Booth]

Uh... hmmm...

Well, you could just use a matte box with an optical flat to protect your lens which is PL mounted in front of the sensor.
Plus, I would think that putting anything between the sensor and the rear element would be "bad" and even cause distortion/reflection to your image.
But these are only "thoughts".

 

[sparkhope]

What do you think about this: to tap a thread in front of the sensor to be able to screw a glass filter? Diameter approx. 49mm? It seems the space around the sensor is big enough. It would help to mount protection filters (easy to clean during field work), Nd filters, IR filters (like the one from Leica) and so on.
Just a thought.
Cheers
Marc

that's pretty funny.

 

[Marc Berger]

Well, the only argument against it would really be distortion, reflections, but in case this would not pose a problem, an extra filter in front of the sensor would be a comfortable solution for changing the mount outdoor. Changing a filter is less difficult then cleaning the sensor surface.

 

[Bill Anderson]

A filter placed behind the lens is okay as far as the optical component goes; focused (columnated) light from the lens and reduced angles of light passing through the filter isn't a bad thing, but I'm not sure how practical it would be. Having enough room to insert a filter and removing the lens every time you wished to remove or change filters would be an issue worth considering; Increased dust in camera; dust particles on interior filter would have greater effect on sensor (size/distance ratio- secondary shadow) And I'm not so sure it's a great idea to add another piece of glass (IR Blocking) permanently to the optics if it benefits only a small percentage of your typical shooting scenarios.

 

[Marc Berger]

Hi Bill
I see it more like a solution to protect during harsh shootings. I would leave the filter the whole day on the sensor, and clean the filter with a lens cleaning paper if necessary. Much more simple then trying to get the glass on the sensor clean with a sensor swap and liquids. Little particle of dust and sand scratch it so easy. In another thread they talked about the same magenta problem like the Leica M8 have, and I don´t see any 6x6 filter like the one Leica developed to solve this problem.
Cheers!
Marc

 

[Bill Anderson]

Sounds good marc.

 

[jbeale]

Note, because any filter will have an optical index different from air (1.0) it will change your effective optical path length, meaning you have to reset the lens mount flange depth (it will have to move a bit inwards, towards the sensor). If the Red's adjustable flange gives you enough travel to fix it, then you're set; but otherwise you'd have to have a custom mount machined.

 

[chuck colburn]

If your filter is not absolutly plano (flat) and paralell this is not a good idea. Also as stated it will cause your flange focale depth to change appx. one third the thickness of the filter which would require you to reset the back focus of the lens mount to compensate for that error.