Broken vari nd filter quick question

[manueldomes]

I just cracked thr front element of my vari nd filter. I'm in a shoot and would ideally want to retain some nd capacity. Can I rip off the broken front element and continue using the back filter? I know it's technically supposed to be a circular polarizer (which I haven't ever used so far).

Thanks!

[manueldomes]

Chipped off the front element of the tiffen with a screwdriver (took me 15 minutes - I guess I'll buy that brand again) and the back element does seem to take off about half a stop of exposure. 

Second question: I suppose I could just buy a polarizer filter that fits the front element and have a DIY spare vari ND?

[hijodeibn]

Don`t do that, certainly the back part of the vary ND could reduce a little bit the light, but trying to do a DIY vari ND most probably could generate some artifacts that later you will discover in your footage, just don`t waste time and get a new Tiffen vari ND and continue shooting safely….

[manueldomes]

No worries, the diy one would only be a spare filter, will definitely get a new one too. For now I'm just concerned if using only the back element would result in something I wouldn't want to see. Preview looks clean.

[hijodeibn]

Most probably the back element will perform just like a fixed ND filter

[manueldomes]

As little report, I did end up trying the DIY solution -- bought a cheap-ish Walimex circular polarizer, which didn't have any effect when I screwed it into the broken Tiffen's front thread. But alas, flipping it and then taping it to the leftover piece did the trick

It looks and feels seriously DIY, but seems to work fine, at least as a backup filter. Here's some highly unscientific (and not necessarily the sharpest - camera was moving) screen grabs of the improvised vs the Tiffen filter which I bought again. At first glance, the difference seems to be mainly the lower contrast of the DIY, which isn't necessarily a bad thing. ND value was close to maximum on both filters.

 

DIY:

 

Tiffen: