GH5 Vlog color shifts with variable fader ND?

[filmguy123]

I've read that GH5 vlog is very sensitive to color shifts, so using a variable fader ND can be problematic. Why is this? Are there subtle color shifts as you fade the VND one direction or the other? Should one re-white balance after any rotations of a fader ND? Are there are any higher quality variable NDs that avoid this?

 

[Thomas Smet]

ND filtering can be affected by IR pollution because it blocks regular and UV light but not infrared light. So the more you raise the ND strength the more the camera is balanced for the IR light you had before, this can cause a color shift when you adjust the ND a lot. Typically white balancing with every ND change is a solution but even that doesn't always eliminate color shift, there are special IR ND filters that help a lot, Tiffany makes an IR variable ND as well to help reduce the color shift from IR pollution.

 

[TheDingo]

I've read that GH5 vlog is very sensitive to color shifts, so using a variable fader ND can be problematic. Why is this?

This has NOTHING to do with the GH5 V-LOG L profile, and EVERYTHING to do with crappy variable NDs that change color as you adjust the amount of ND they produce.

I own a couple of expensive variable ND filters, but have gone back to using solid single density NDs to eliminate any color casts and polarizing effects.

The better solid ND filters will also block IR pollution which can make some black items appear red. ( currently working with the new Hoya SOLAS ND filters that combine ND and IR )

 

[filmguy123]

Ok, so I have been using the Tiffen 77mm Variable ND. I just recently picked up an SLR Magic 77mm Variable ND to see if that solves any issue, but not sure if that is IR blocked:

https://www.bhphotovideo.com/c/prod...r_77vnd_ii_77mm_variable_neutral_density.html

Is the Tiffen crappy? What's better? How's the SLR Magic? I had read good things about it (on this forum).

I may also want some solid state NDs but that isn't always possible in run'n'gun scenarios... what brand should I pickup for the solid state NDs?

 

[TheDingo]

s the Tiffen crappy? What's better? How's the SLR Magic? I had read good things about it (on this forum)

Tiffen sells different grades of variable ND filters. I tried their low-cost version years ago that would shift from green cast to brown cast as you adjusted the amount of ND.

A simple test of any variable ND filter is to shoot a white wall with different amounts of ND dialed in and see if there is a color change when you look at your footage in post.

I don't want to have to keep rebalancing my color in post because I changed the amount of ND applied with a variable ND filter. Also the polarization from variable ND filters is not great for skin-tones. ( the same way a polarizing filter can be bad for skin-tones )

 

[Zak Forsman]

I did a comparison between the SLR Magic and Tiffen variable ND without IR cut and threw the Tiffen in the garbage afterward. ��

https://vimeo.com/125507165

 

[filmguy123]

Thank you Zak. I have noticed the haziness with my tiffen, too. Not always, but on brighter days the footage really seems to have degraded. Thanks for sharing such a thorough test, this literally saves me hours running through it myself. Looks like I may be ditching the Tiffen's as well...

Anything worth snagging OVER the SLR Magic that is even better, then?

 

[Imamacuser]

The SLR Magic has a slight warming affect at darker densities, but the ability to dial in the amount of polarization is invaluable. You might be able to squeeze some more life out of your Tiffen by adding a rotating filter ring from a CPL, it might cause vignetting though. I don't think that anyone has come out with a variable ND that's as good as standard NDs, but variable ones are fast, convenient, and versatile, so it's worth the compromise in my opinion.

 

[Thomas Smet]

https://www.bhphotovideo.com/c/product/1055201-REG/tiffen_77irvnd_77mm_ir_variable_neutral.html

This is the Tiffen you want and not the "cheaper" one. Yes it costs more but thats for a darn good reason.

I use the Tiffen hot mirror with my regular ND filters and would never consider using a non IR filter ever again. Have not used the Tiffen variable so cannot speak how well it does compared to other IR variable ND filters. I just know IR really is a must for video.

 

[joe12south]

This has NOTHING to do with the GH5 V-LOG L profile, and EVERYTHING to do with crappy variable NDs that change color as you adjust the amount of ND they produc.

The issue *is* related to V-LOG L in that the shifts introduced by the ND filter are exaggerated when the compressed V-LOG image is expanded back to a "normal" curve. Any LOG capture scheme is more susceptible to revealing problems than profiles that only require minor adjustments.

 

[TheDingo]

The issue *is* related to V-LOG L in that the shifts introduced by the ND filter are exaggerated when the compressed V-LOG image is expanded back to a "normal" curve.

I can see LOG formats slightly exaggerating color shifts, especially when shooting in bandwidth limited 8-bit color depth. Any color problems I've experienced with variable ND filters were almost entirely caused by the VND. I've heard that the higher end VND filters have virtually no color shift, but I've since gone back to solid single factor IRND filters.