Sigma FF cine prime threads for 85mm focal length is 86mm instead of 82mm diameter

[Noah Stout]

Hi all,
I've got my eye on a set of Sigma FF primes but haven't used them yet. I know to rent before you buy but this question would apply to a rental or purchase.

Having filter threads seems handy for more run-n-gun situations and for international travel, etc. I just noticed in the basic 5-lens set the oddball here is the 85mm, which has a thread size of 86mm instead of 82mm. This means if I want to ditch my matte box I'd either have to have 2 sets of screw in filters (ND, diffusion options, closeup filters, etc) or I'd have to get a step-up/down situation going. Moreover, there are filters I want that don't come in 86mm so I'd have to figure something for that 85mm anyway. Does anyone know if with the build of these lenses you can put step-up filters to make them all common? I imagine a step-down filter on the 85mm would not be possible or they would have made it an 82mm thread in the first place. I'm a bit surprised there'd be vignette issues on the 85mm but maybe I'm missing something. I'll actually usually be using these on an Alexa Mini so maybe that vignetting on these FF lenses won't be an issue with a step-down. Anyone have a solution or tried these out with screw-ins?

thanks

 

[Matt Uhry]

Hi Noah,

I've got a step down ring 86mm to 82mm on our Sigma 85mm Cineprime and it seems to work fine for the infrequent times I need screw in filters.
I don't see any vignetting on my Dragon or A7R2 in "FF" video mode, I'm sure you'll be more than OK on the Alexa.
There probably is a small loss of light but i'd guess it's less than 1/3 stop when wide open and probably lessens as you stop down.

Hope that helps.

Matt Uhry
www.mattuhry.com

 

[Noah Stout]

Very helpful, thanks Matt!

 

[Alexander_Klose]

I have the 85mm Sigma and tried a stepdown from 86mm to 82mm. That causes vignetting for FF on my a7riii. I always use a mattebox on the 85mm but I can try it if you need to know.

My Problem was to even find a good 86mm vari ND in general. Like to use the tiffen for run&gun on the 24-35mm but as I said its 82mm. Thats the biggest one from Tiffin.