Formatt Hitech ProStop IRND filer flare - what is acceptable?

[tadas1]

I've just received Formatt Hitech ProStop 4 stops IRND for my matte box and noticed heavy orange flares when sun directly hits the filter. Even though flares are normal to some extent, I would like to know your opinion if this example is still acceptable (currently I don't have many different filters to compare the results). Lens without filter has few flares with minimal color shift. Both frames were shot with filter, but in the second one matte box shades the sun rays.

 

[Aegis]

That's pretty normal - adding filters plays havoc with flares unless your lens has a hood or matte box - so long as the Firecrest isn't affecting the colour-cast of your image then it's working for your sensor.