IR filters do we need them?

[charles lim yi yong]

Ryan Walters did this test . [h=3]IR ND Filtration + EPIC[/h]
And I was wondering if the RED epic needs IR filters, how come the RED filter in front of the sensor is no doing it's full job?

 

[Milan Spasic]

I have no answer to this question but I find Ryan's test very true to my real world experience. Anything up to ND9 works fine with IR and Epic, but ND1.2 is unusable in most situations. I wasn't brave enough to use a ND1.5 but amazingly the 1.5 seems to have less pollution than 1.2 in Ryan's test (???).
What gives?

 

[charles lim yi yong]

shouldn't we just get a better filter in front of the sensor?

 

[Uli Plank]

It's not possible to make an IR-cut filter in front of the sensor strong enough for all cases. If it were, why do all cameras show similar problems?

Since no filter will be free from blocking some visible red too, you'd get greenish vignetting on wide lenses. Red has already improved that filter over the R1, where I tended to use an IR-filter in front starting from 0.9 ND. I'm sure they used the best solution available without degrading image quality. But from 1.2 I'd definitely use one.