ND filter instead reflex mirror

[domasa]

Camera EOS C300 has three internal ND filters:

ND 0.6 – 2-stop reduction
ND 1.2 – 4-stop reduction
ND 1.8 – 6-stop reduction

This is better than screw and unscrew ND Variable filter on lens after each change of luminance (filming in the dark church/sunny garden before church).

I use my 5D Mark III mainly on video. Why not use dark ND filter instead reflex mirror? 


Would be possible control reflex mirror in video mode? (flip-up/flip-down)

If yes - some company could be create ND filter (like "Mosaic Opto-Electronics, Inc." creates VAF filters) 

Reflex mirror replacement should be relatively easy:
https://shimworld.wordpress.com/2009/08/24/cleaning-the-5d-mk-ii-viewfinder/

[ilia3101]

The mirror is stuck on to an opaque piece of plastic, with only a hole in the middle, so could work for 3x crop maybe - if you remove the second autofocus mirror thats behind it behind it aswell. You see I have experience with how it works; my mirror fell off a few weeks ago some superglue fixed it.
You could cut a bigger hole out of the mirror holder, but tbh it probably isn't a good idea.

[domasa]

The mirror is stuck on to an opaque piece of plastic, with only a hole in the middle, so could work for 3x crop maybe

This is bad news.

In my link replaced only focus screen. Not reflex mirror. Sorry for mystification.
Replace mirror probably require disassemble all camera

[dfort]

Most professional video cameras have built in neutral density filters. That's one of the features that is hard to copy in a DSLR. There are a few Canon lenses that have a behind the lens gel filter holder.



Here's a link if you want to learn more about this feature. It isn't as convenient as the built in filters of a C100 or C300 but it is pretty easy to slip in a filter in the field compared to installing a VAF filter.

When I was a still photographer using 4x5 and 8x10 view cameras it was quite common to put gel filters behind the lens but this practices seems to have been largely forgotten. There are some huge filters designed to be used for wide angle lenses.



There is an interesting lens adapter called the ND Throttle that has a built in variable neutral density filter but unfortunately it only works on mirrorless bodies. As far as the Magic Lantern enabled cameras not even the EOSM is supported.

Switching out the mirror for an ND filter is an interesting idea but it isn't a trivial hardware hack. The camera will not record with the mirror down.

[garry23]

I use this with my 5D3: https://fotodioxpro.com/products/p645-eos-pro-ndthrtl

[dfort]

Hi @garry23 -- Oh yeah, now I remember you mentioned a while back that you're using medium format lenses with that ND Throttle.

I take it that this means no automation on the lens which I suppose if fine for landscapes but it looks like the OP is for weddings. Tough to follow a moving subject without auto focus.

[garry23]

@dfort

You know me: don't do that videography stuff 

Things work well on a tripod and allow you to work at a leasurly pace.