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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

Built in ND device for your camera: ND Slide

D

Douglas Underdahl

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Greetings Redusers:

Here's the ND Slide, a built in ND filter system for your Scarlet, Epic, Dragon, Weapon. It is shown in bare aluminum but please know that finished version will be black anodized.

It has two filter stages, each loaded with a different ND value, giving four settings:

1) no filter - no light reduction to the OLPF and sensor;

2) slide one engaged: ND .6 (two stops) light reduction:

3) slide two engaged: ND .9 (three stops) light reduction;

4) sildes one AND two engaged, giving a light reduction of ND 1.5, or 5 stops.

Filters used will have both ND and IR reduction. Phil Holland seems to think that Formatt Firecrest filters are the best and we will test them along with others. Also, other values might be used, for example, 3 stops, 6 stops, and the combo would yield 9 total stops along with IR attenuation. Or more?

Slides can be engaged and disengaged instantly - please see the demo video:

https://www.youtube.com/watch?v=sXC2foO9ULk

LENS MOUNTS - right now, I'm using this prototype with our Long Valley Equipment Posi Lock Nikon mount for Epic/Scarlet/Dragon/Weapon. This mount uses the Red One Nikon locking system and is very robust. The chassis is CNC machined from a single billet of 6061 aluminum. It offers manual iris control for G series Nikon lenses and other lenses that have no iris control ring. It does not have any electrical contact with the camera and offers no electronic iris or focus control from the camera - a "dumb" mount. I've tried about 10 different Nikon mounted lenses, old and new, and none of them protrude into the lens mount enough to contact the ND Slide.

I am sure that there will be interest in this built in filter system for use with other lens mounts such as the Red Digital Cine's DSMC Nikon, Canon, and PL mounts, but at this point, I'm not sure how compatible it will be. It should be clear that a slot needs to be cut into the top of the mount and I don't know if this will or won't be possible with these mounts.

FOCUS - It was Richter who said that anything placed between the lens and focal plane will shift the flange focus distance (some say backfocus) by about one third it's thickness. So there will be a focus shift when one engages the filters. This is not a problem for the vast majority of users who focus their cameras by eye; that is, viewing the subject on the monitor and turning the focus ring on the lens until sharp focus is achieved. For those who use a tape measure and set focus using the witness mark and focus distances on the lens, it should be noted that the focus marks will not be accurate when one or both filter slides are engaged. They will all be shifted slightly.

SHARPNESS - I've been doing some tests with my Epic at 5K, and I'm actually having trouble figuring out which image is with the built in ND and which is without. There is some reduction in quality but it is very slight and probably similar to using ND filters in front of the lens.

RUN AND GUN - Well, you know what this device means for run and gun - and other work. You can instantly switch on ND filters in the camera, so you can react to wildly changing light values without stopping to pull out an ND and place it over the lens. In many cases, this can mean the difference between getting the shot or losing it forever. Even for scripted narrative work, the ND Slide can speed up production and will prove invaluable, as built in ND filters have in other cameras.

CUSTOM FILTERS - not sure what other filters might find their way into the ND Slide, but if you have ideas for effects filters, etc, just let me know. I can imagine nets, UV, IR Pass, fog, double fog, low con, etc etc.

Douglas Underdahl
Long Valley Equipment
 

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Nice work, Douglas! This looks really cool!
 
Douglas,

this is looks great! I have a question. Did you consider having the slides from the operator or dumb side as well?

I dont think my rear focusing Leica R lenses (modded to Nikon mount) would work, but I pretty sure all my 10 or so other Nikon lenses would work just fine.

Very nice concept.
 
That is awesome, Doug!

Wow I hope this can be integrated some how into a Canon mount!
 
Thanks guys.

David: it could go in from the dumb side, but I think it might be hard to reach if you are doing one man, on the shoulder shooting and are right handed? Meaning, if you have the cam on your shoulder and you are using your right hand on a grip, how would you reach up with that hand to slide? It could slide in from the operator's side, but then I think it would cover some user buttons. Can't really go from the bottom because it would block/interfere with the fan. But maybe you have an idea for it to slide from the dumb side? Maybe you can reach up with your left hand?

Adam: I think it could work with a Canon mount. They are 2.5mm shorter so space is more of an issue. Also I think the best mount to put it in would be the OEM Red DSMC Canon mount since it has nice electronic controls, and I don't know if one could be easily modified. Hmm.
 
Very interesting although the final product would be matte black? If you could put this in a Canon mount whilst retainning the electronics you would sell alot. The changing focus marks is a bummer but as long as you could still hit infinity not a deal breaker although my first AC might think differently
 
Douglas, this is a VERY intriguing product. VERY.

Couple of things.


1) Would the drop in filters be 77mm? (which many of us own). That would be extremely helpful (ie same size filters we screw in front, could be "slid" in at back?). Though I'm guessing you may have to remove the glass and make the inserts yourself, to save space?

Other filters to consider are: Classic Soft, Schneider Streak Filter, BMP 1/8, Hollywood Black Magic, etc.


2) EOS mount I think would be HUGE (and a large part of your market, esp for run and gun) - even a non electronic one could be extremely useful for those of us using all manual Leitaxed lenses (esp if a non electronic cost less?)


3) PL would be useful for many I'm sure, too.


Can't wait to see more!!!
 
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The way you have designed this system, it can never be used on productions where you have a 1st AC pulling focus from distance marks on the lens. This limits it's use to EFP and ENG style production. I would instead suggest that you change the design to a Variable ND in the outermost slot 1 (with an 0.8 pitch gear for the rotating element protruding out of the mount on the operator side) and Optical Clear of the same thickness to slot 2 towards the sensor. You would use one OR the other. The purpose of the clear filter is simply to keep the same back focus adjustment. If desired, the clear could be replaced with diffusion and the back focus would be adjusted for 2 filters.
 
Nice
 
It's a nice concept but really the majority of users need that on a PL mount. We'll wait and see if that's possible, maybe with a third party PL like WC mount.
 
Yes, as I said in the text, it will be black anodized.

Filter size is 35mm x 16mm to fit inside the lens mount. I can cut this size from many different existing filters depending on customer request.

I think that very few users tape focus. Those that do can use another system. I stated this in the text above.

Yes, it could be used with PL or EOS mounts, just have to see how much interest there is.
 
Curious,
A few questions comes to mind. Cost vs motion mount, I guess for this you need to cut two filters to the right dimensions and also make the mounts. So it can not be so cheap in the end, but possibly more low cost than the flicker glass in the motion mount...or?

Then as the glass sits quite close to the mount, not flush to the sensor, I guess a lot of lenses will not fly with this as they would touch the ND glass if they portrude into the mount to much. So a lot of lenses would not work.

And the shift in light path that is different for no ND, ND and double ND would make backfocus correct at no ND then when one ND is in the slot the back focus moves... what way? I try to figure it out in my head, I think it is so that you can not reach infinte... or it´s the opposite you can not reach you normal near focus limit. I guess not reaching near focus limit is more ok than not being able to reach infinity. But I think if people find the motion mount to be a hack then this would probably be quite of a concern even when used with EF, or Nikon glass... but for PL and lenses with markings it would be quite a mess.

I think there must be some good reasons for the red sensors to be in a "gate hole" and not sit flush on the camera if the sensor could be seated flush then Red would have made all kinds of crazy filter wheel modules... I guess a fitting name for a red filter wheel would be... "the revolver" :)
 
Gunliek - yes, no loss of light when not engaged. I think that's important. I like my Epic to be as sensitive as possible for low light situations.

Bjorn - all good questions.

I don't know how many lenses will or won't work with the ND Slide. I have looked at all my Nikon mounted lenses and none of them protrude into the lens mount enough to contact the ND Slide. I think this would be true of EOS mounted lenses also. As for PL mounted lenses, my experience is that many of them do protrude into the lens mount and some would contact the ND Slide and not be useable.

The "gate hole" design of red sensors, as you put it, does seem to negate the idea of a filter wheel sitting right in front of the sensor, in place of the OLPF. So the ND Slide is an attempt to get "behind the lens filtration" as best as possible.

Of course, the thickness of the filter(s) will extend the flange focal distance (back focus) so your lenses will likely focus beyond infinity (that could be desired by some users) and increase the minimum focus distance, or Minimum Operating Distance (MOD). This extention of flange focal distance will be more apparent on wider lenses than telephoto. I'll do some tests. I would say that for a wide angle lens - about 18mm - MOD would increase from 3 feet to 3.5 feet.

Right now, I have two 1mm thick filters installed. The Firecrests seem to be 2mm thick. They have excellent IR rejection which is important.

Cost? Hard to say. Don't hold me to it, because I haven't gotten all the figures in, but I'm thinking $500 minus lens mount and the filters themselves. Filters would probably cost $50-$100 per unit.

What lens mounts? Respond here with what mount you'd like to have an ND Slide installed in.

Also, thanks for your responses!
 
Douglas Underdahl said:
Of course, the thickness of the filter(s) will extend the flange focal distance (back focus) so your lenses will likely focus beyond infinity (that could be desired by some users) and increase the minimum focus distance, or Minimum Operating Distance (MOD). This extention of flange focal distance will be more apparent on wider lenses than telephoto. I'll do some tests. I would say that for a wide angle lens - about 18mm - MOD would increase from 3 feet to 3.5 feet.
Click to expand...

I think that's backwards... Adding glass behind the lens is like adding distance, same principle as using a macro extension tube. You'll not reach infinity and gain some close focus. You can easily observe this by taking any interchangeable camera, focusing on a distant object and loosening the lens mount.

Mount looks cool otherwise and there are ways to work around / adjust to the FFD shift. I could see having my Red EF mount modded with a slide ND.

Matt Uhry
www.mattuhry.com
 
Douglas Underdahl said:
I think that very few users tape focus. Those that do can use another system. I stated this in the text above.
Click to expand...
Well, all 1st AC's tape focus so the issue is that in many cases a 1st AC is handed a camera body and told to make it work by the production company. Which according to the law of optics they cannot with the design of your current system. It's relatively simple to set flange depth for one setting in prep. It is highly impractical to set two or more throughout the shooting day. Also, no rental house is going to want a system where the back focus doesn't remain consistent. It is not a trivial issue that can be brushed aside. So why not fix it while you're still in the prototype stage?
 
No, not all A.C's tape focus. It's something that many do, and many do not. How many is hard to say.

Readers of this thread know which method they use. I think they can make up their own minds.

Any competent AC wanting to tape focus during production would compare tape and eye at checkout - as usual - and find that one or more filters from the ND Slide is engaged. Then he/she could simply disengage all slides in about three seconds. Or ask for another body. Then continue comparing tape and eye.
 
when shooting PL, a mattebox and the big-rig tools are usually available (to me at least). this seems like a great match for the nikon/canon mounts. and run/gun
 
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