Are the Internal filters for the Alexa XT any good?

Mathew Rudenberg · October 28, 2014

I haven't used the Alexa XT and I'm debating internal vs external filters for an upcoming project. I would love to hear thoughts and opinions from ACs, Ops and DPs. Also if I have my facts right.

As far as I can tell:

Pros

- no reflections

- light weight

- more space in the matte box

Cons

- Hard to access

- have to take the lens off for each filter change

I tend to change ND filters fairly frequently as I prefer to maintain a consistent stop and I'm concerned that the extended time necessary to change a filter would outweigh the benefit of not having reflections.

Thanks,

Satsuki Murashige · October 28, 2014

Haven't used the internal NDs, but I hear they are IRNDs and completely color neutral. I feel they are designed to be used in combination with normal ND filters in front of the lens. Think of the internal ND as changing to a different ISO film stock for day exterior, day interior, and night work.

So for example, use the Internal N1.2 to get down to 50 ISO equivalent (while setting the camera to 800 ISO) for day ext, then use normal N3,6,9 in the mattebox to get to your shooting stop. Switch to Internal N3 or N6 when going inside for 200 or 400 ISO equivalent. Losing the light or moving to a stage? Pull the internal filter. The design makes a lot more sense when you think of it this way.

David Mullen ASC · October 28, 2014

As Satsuki suggests, I would not think of the internal filters as something to keep changing on every shot or take. Think of it more as allowing you to work outside with a 50 ASA film stock instead of an 800 ASA film stock. I'd probably use the internal ND to get to a base ASA that I like and then use an ND3 or ND6 (or adjust the ASA and/or shutter) if necessary to tweak depth of field, or live with the same ND level for big stretches at a time.

Mathew Rudenberg · October 30, 2014

Thanks for the tips guys.

As I feared they sound useful, but not that useful... I'll probably ask for them but then drop them quick if I get any push back.

Marc Shipman-Mueller · October 30, 2014

Our Full Spectrum NDs, as used in the XT cameras (but also available as an upgrade to the Classic ALEXAs) are totally color neutral. While it is a bit more cumbersome to remove the lens, most of the DPs that I know who have tried them have stuck with them for that reason. Here is a comparison of regular ND filters and our FSNDs:

http://www.arri.com/fileadmin/media/arri.com/camera/35-format-digital/ALEXA/IRND-FSND_Comparison.jpg

Marc Shipman-Mueller, ARRI ALEXA Product Manager

Mathew Rudenberg · October 31, 2014

hmm, that is very compelling - the color shift from ND filters, and IR filters in particular, is usually extremely annoying and compromises the image.

Edited October 31, 2014 by Mathew Rudenberg

Marc Shipman-Mueller · October 31, 2014

Indeed. As I said, all the DPs I know of that have tried it have loved it. And one (apologies to all ACs) has told me that he happily uses them, since he gets the better picture and changing the filters is what the AC is for.

Now - if you have an Optimo 24-290 with matte box and three motors on there, it will take a little while to remove all that stuff and then change the filter, granted. This is why some DPs will set a base ND with the ARRI internal FSND, and then fine tune with NDs in the matte box. The beauty of this approach is that you can use external NDs lower than ND 1.2, which is where they usually start showing color balance shifts.

Satsuki Murashige · November 1, 2014

No offense here, Marc! I heard you used be an AC yourself for several years. :)

Have you tested the latest ND filters from Mitomo (True ND) and Formatt (Firecrest)? The Mitomos are very neutral up to N1.5 and the Firecrests are supposed to be just as good. Right now, I would be very happy using True NDs in combination with Alexa internal NDs.

Marc Shipman-Mueller · November 3, 2014

None taken. Yes, I used to be a first AC for some years, which is really helpful now when negotiating with customers. A film (or digital) set is a strange beast and unless you have worked on one, it is difficult to understand. No, I have not tested those filters yet. On my to do list (sigh).