Hello everyone
As more and more LC filter products are announced/launched throughout this year, I would like to learn more about this technology.
Although this tech has been around for quite some time - remember RED's Motion Mount or Tilta's TE-ND, which, if I remember correctly,
never made it to market (color shift?) - manufacturers seem to have only recently solved the issues from seven years ago.
RED's eND PL Mount and Sony's built-in automatic eVND are among the latest developments in this area.
Tilta's announced 4" x 5.65" matte box friendly eVND solution is also worth a look.
...and just in case you missed it, electronic diffusion filters (repeatable, exactly adjustable diffusion) have been announced as well.
While searching for an LC filter solution for EF-mount lenses, I was quite surprised to see KipperTie announce three new filter products,
two of which use LC technology:
LCminiND (eVND) for Canon's EF-RF drop-in filter adapter,
Revolva LC cartridge (clear + eVND)
Strata Electro (compact, motorized clear + solid ND swap)
Actually, my favourite is the Revolva LC cartridge as it makes Revolva extremely versatile. Kudos to KipperTie for developing
new products for Revolva.
But coming back to the topic of this thread - as good as this technology may seem nowadays, I found it difficult to get information about
how these products work and more important - what the downsides of eVND filters are (so, when not to use an eVND).
AFAIK, Liquid Crystal Tunable Filters (LCTF) are being used in scientific narrow-/broadband imaging applications
(to block unwanted wavelengths), so I assume that eVND filters are based on the same technology (maybe different designs)
to equally tune/regulate the transmittance to prevent color shifts and IR contamination.
The light passes a (linear or circular?) polarizer to uniform the angle of the light hitting the liquid crystal fluid.
The alignment of the LCs can be changed by the voltage applied, so in our case, if no voltage is applied,
the LC fluid is absorbing the light (no transmittance) and the more voltage is applied, the higher the light transmittance.
And for the diffusion filter mentioned above, the glass looks clear at no voltage and the diffusion gets stronger the more voltage
is being applied. Apologies for mistakes and misinterpretations, corrections are welcome.
The advantages (especially in regard of KipperTie's upcoming products) are:
- 2-7 stops of ND in one filter
- repeatable, seamless and precise tuning of the optical density
- fast switching time = near zero delay
- very consistent color rendition through the whole range of optical density
- only a minor color shift towards magenta between clear and the eVND
- remotely controllable via app
The disadvantages...
...well, I didn't find any information about when better not to use electronic VNDs.
It would be really helpful if manufacturers like RED / KipperTie and/or people who have experience e.g. with RED's eND PL Mount could
share their knowledge, findings and recommendations in this forum.
So, my concerns/questions are the following:
- Since LC tech works with polarized light, can light sources (e.g. sunlight) entering at certain angles cause (partial) color shift
or a sort of vignetting??
- Color shifts when filming LCDs at certain angles?
- Possible artifacts and color shifts in conjunction with other (CPL-) front-mounted filters?
- Do LC fluids deteriorate in neutrality / optical density or transmittance after time and if yes, in what timeframe?
- Can LC fluids take damage when pointed at the sun sporadicly?
- How does the filter behave when using below the recommended operating temperature (slower switching time or not uniform density?)
and can the LC fluid take damage in such cases?
- Can dead pixels/segments occur, or are eNDs one big adjustable segment? I suspect that eDiffusion filters are divided into
several segments to obtain a homogeneous diffusion pattern.
- Are the LCs being aligned at a certain frequency and if so, could this cause flicker issues (shutter speed / artificial light)?
...and here some KipperTie eVND related questions:
- As these filters are powered separately and not through the lens mount (probably to avoid issues in camera/lens communication),
is there a power priority cirquit, e.g. if the tiny internal battery dies, can the filter still be powered via USB-C only?
- Is the internal battery user-replaceable?
- In terms of back focus shift, I expect KipperTie is putting a lot of effort into getting it right for the Revolva LC and Strata Electro,
but what when using LCminiND and Canon's clear drop-in filter? Is the LCminiND "optically matched" to Canon's clear filter to some extent?
Many thanks in advance to everyone who helped clear things up.
As more and more LC filter products are announced/launched throughout this year, I would like to learn more about this technology.
Although this tech has been around for quite some time - remember RED's Motion Mount or Tilta's TE-ND, which, if I remember correctly,
never made it to market (color shift?) - manufacturers seem to have only recently solved the issues from seven years ago.
RED's eND PL Mount and Sony's built-in automatic eVND are among the latest developments in this area.
Tilta's announced 4" x 5.65" matte box friendly eVND solution is also worth a look.
...and just in case you missed it, electronic diffusion filters (repeatable, exactly adjustable diffusion) have been announced as well.
While searching for an LC filter solution for EF-mount lenses, I was quite surprised to see KipperTie announce three new filter products,
two of which use LC technology:
LCminiND (eVND) for Canon's EF-RF drop-in filter adapter,
Revolva LC cartridge (clear + eVND)
Strata Electro (compact, motorized clear + solid ND swap)
Actually, my favourite is the Revolva LC cartridge as it makes Revolva extremely versatile. Kudos to KipperTie for developing
new products for Revolva.
But coming back to the topic of this thread - as good as this technology may seem nowadays, I found it difficult to get information about
how these products work and more important - what the downsides of eVND filters are (so, when not to use an eVND).
AFAIK, Liquid Crystal Tunable Filters (LCTF) are being used in scientific narrow-/broadband imaging applications
(to block unwanted wavelengths), so I assume that eVND filters are based on the same technology (maybe different designs)
to equally tune/regulate the transmittance to prevent color shifts and IR contamination.
The light passes a (linear or circular?) polarizer to uniform the angle of the light hitting the liquid crystal fluid.
The alignment of the LCs can be changed by the voltage applied, so in our case, if no voltage is applied,
the LC fluid is absorbing the light (no transmittance) and the more voltage is applied, the higher the light transmittance.
And for the diffusion filter mentioned above, the glass looks clear at no voltage and the diffusion gets stronger the more voltage
is being applied. Apologies for mistakes and misinterpretations, corrections are welcome.
The advantages (especially in regard of KipperTie's upcoming products) are:
- 2-7 stops of ND in one filter
- repeatable, seamless and precise tuning of the optical density
- fast switching time = near zero delay
- very consistent color rendition through the whole range of optical density
- only a minor color shift towards magenta between clear and the eVND
- remotely controllable via app
The disadvantages...
...well, I didn't find any information about when better not to use electronic VNDs.
It would be really helpful if manufacturers like RED / KipperTie and/or people who have experience e.g. with RED's eND PL Mount could
share their knowledge, findings and recommendations in this forum.
So, my concerns/questions are the following:
- Since LC tech works with polarized light, can light sources (e.g. sunlight) entering at certain angles cause (partial) color shift
or a sort of vignetting??
- Color shifts when filming LCDs at certain angles?
- Possible artifacts and color shifts in conjunction with other (CPL-) front-mounted filters?
- Do LC fluids deteriorate in neutrality / optical density or transmittance after time and if yes, in what timeframe?
- Can LC fluids take damage when pointed at the sun sporadicly?
- How does the filter behave when using below the recommended operating temperature (slower switching time or not uniform density?)
and can the LC fluid take damage in such cases?
- Can dead pixels/segments occur, or are eNDs one big adjustable segment? I suspect that eDiffusion filters are divided into
several segments to obtain a homogeneous diffusion pattern.
- Are the LCs being aligned at a certain frequency and if so, could this cause flicker issues (shutter speed / artificial light)?
...and here some KipperTie eVND related questions:
- As these filters are powered separately and not through the lens mount (probably to avoid issues in camera/lens communication),
is there a power priority cirquit, e.g. if the tiny internal battery dies, can the filter still be powered via USB-C only?
- Is the internal battery user-replaceable?
- In terms of back focus shift, I expect KipperTie is putting a lot of effort into getting it right for the Revolva LC and Strata Electro,
but what when using LCminiND and Canon's clear drop-in filter? Is the LCminiND "optically matched" to Canon's clear filter to some extent?
Many thanks in advance to everyone who helped clear things up.