Be careful with the 85mm Art specifically because that 86mm thread size creates a lot of surface area for flare. I would suggest looking at high-index glass to avoid the green cast you mentioned.

• PolarPro 86mm Peter McKinnon Variable ND 2-5 Stop Edition II
• B+W 86mm XS-Pro Digital MRC Nano 810 ND 3.0 Filter Make sure to get a slim profile mount or you will definitely see vignetting at f/1.4.

Late to the party but @Reply #2 - good point! Unfortunately, I have been pretty disappointed with some filters lately. Even expensive ones can be unreliable with color shifts on the Art series.

• NiSi 86mm Nano IR Neutral Density ND64 6-Stop : Great IR suppression but the glass feels fragile.
• Hoya Solas 86mm IRND 1.8 6-Stop : Very accurate color tho the build isnt premium. I'd suggest the Hoya for reliability.

Just saw this thread and honestly I went through the same panic when I first got my Art lenses. I was super worried about that green cast everyone talks about because I am definitely not a pro at fixing colors in post yet... I just wanted something that worked right out of the box without making my photos look muddy or weird. I ended up playing it safe and going with some fixed filters instead of variables because I heard variables can be finicky on big glass. I have been really happy with how these perform on my 85mm:

• Breakthrough Photography 86mm X4 ND 6-Stop Fixed Neutral Density Filter
• This one is basically my favorite piece of gear. It is super neutral and I havent noticed any sharpness loss even at 1.4. It is right at the top of your budget but totally worth it for the peace of mind.
• NiSi 86mm Nano IR ND64 6-Stop Filter
• These are great because they have that IR coating which basically stops the infrared light from messing with your colors in harsh sun like the Mojave.
• Hoya 86mm SOLAS IRND 1.8 6-Stop Filter
• If you want to stick with Hoya but avoid the cheap stuff, the Solas line is way better for color consistency than their basic lines. The 6-stop is usually perfect for keeping that aperture wide open in midday light without blowing everything out. I mostly use the Breakthrough one tho... it just feels really sturdy and reliable which is what I need when I am out in the dirt.

Regarding what #1 said about "Be careful with the 85mm Art specifically because that 86mm thread size creates a lot of surface area for flare."

• I totally agree. That massive front element is basically a magnet for stray light when you're out in the open sun. I have been super satisfied with my current setup after trying a few duds. It is all about finding glass that can handle the resolving power of the Art series without shifting colors or losing contrast. I've been using these for about a year with zero complaints on the reliability side.
• Get the Formatt-Hitech Firecrest Ultra 86mm IRND 1.8. It is probably the most neutral glass I have used. No green tint at all, which makes post-processing way faster since the colors stay true to the Sigma profile.
• If you want a slim profile to avoid vignetting at wide apertures, the Haida NanoPro 86mm Slim ND 1.5 works well. I dont see any darkening in the corners even at f/1.4. Quick tips for the Mojave:
• Keep a hood on. Seriously. 86mm glass catches side glare like crazy and will wash out your blacks.
• Watch for sand in the threads. Desert wind will jam those big diameter filters fast if you dont wipe them down constantly.