Hi all. . .

I have an HVX and both an M2 and Brevis systems with Nikon primes. For outdoor shooting, I'm going to need some neutral density filters. I am told that the stock ND filters inside the HVX are of inferior quality. If this is true, and I shouldn't use them, what ND filters would you recommend I use? I will be placing them in a Cavision mattebox. It has filter holders for both 4x4 and 4x5.65 sizes. What densities would you recommend?

Thanks very much.

Stephen

Contary to what you've heard we've found the internal ND's to be more "neutral" than the matte-box drop-ins. So far I've only used 2 brands, Schneider and another (I can't remember) and both were actually very warm rather than neutral including the Cir-Pol's.

I've been wanting to test Formatt filters but so far nobody carries them in my area and they are special-order only from B&H (or were) so I haven't been able to try them yet.

However, here's what I've been doing for the HVX: I use my Heliopan photographic screw-on filters instead. They've been much more neutral than any of the square filters and the Cir-Pol is especially neutral. It's less convenient than drop-ins for sure and it means that in your setup you'd have to purchase filters for every thread size of lens you'd use, but so far I just haven't come across another 4x4 filter set that is really "neutral" density.

Robert,

Did you test B+W's?

Actually you shouldn't need to buy different size filters for every lens you own, just buy the largest and then get step up adapters.

I'm still not convinced that there i s anything wrong with using the internal ND filters either with the HVX by itself or with a 35mm adapter.
Has anyone actually seen image degardation from the internal filters in either situation?

I understand not wanting to use the internal 85 since that is electronic and could introduce more noise by effectively adding gain to the red's.

- Lenny Levy

Stephen,

If you are using any of the 35mm adapters (M2, Brevis) you will want to use the ND filter ahead of the adapter (in a mattebox) and avoid the ND filter from the camera. Because if the image is blown out on the adpater, it doesn't matter what the camera's ND filters do.

Schneider does makes very good filters (I'm buying a few myself).

Todd

I keep hearing this stuff about the image being blown out on the adapter so you need ND's in front of the lens. Dennis at Brevis has told me this as well.
However, has anyone actually seen this happen?

I did some quick tests looking out the door of my garage and didn't see any problems with using the internal HVX filters. Looked the same as with ND in front of the lens to me. Maybe the scene itself wasn't bright enough or backlit, but so far no one has actually told me they have observed this as a problem - and I have asked repeatedly on these forums.

In theory it doesn't make sense that it would matter where you put the ND, but i realize that these adapters behave in unusual ways.

I'm very willing to believe it is a problem and appreciate being forewarned, but i sure would like to hear an actual documented description of someone's experience.

A separate issue would be what Stephen mentioned, that the stock internal filters were inferior quality. I haven't heard this before. Anyone have anything to say about that?

Lenny Levy

Leonard,

Keep in mind that when using a 35mm adapter (and I have seen one 'blown out') you are basically recording the image projected onto the GG or diffuser. If that image on the GG/diffuser is already over-exposed you really are just trying to compensate by using the camera's ND filter.

Here is something to try:

Over expose a shot and then try to properly adjust it in post in your NLE. Sure you can drop down the exposure, but you'd never gain back the detail that was lost by overexposing it in the first place. Plus you want to control the amount of light going into the 35mm lens (so you don't have to stop it down too much) so you can still maintain the DOF you desire. This really pertains mostly to exterior/daylight shots anyway.

Basically when you are using the camera's ND filter, you are adjusting it 'in post'. Getting the proper exposure projected onto the imaging element of the adapter will give you better results.

As far as the HVX200 ND filter being inferior. I haven't heard that one.

Oh, man. . . this is getting complicated!

I'd love more opinions. I'd really like to save money and use the internals, but I don't want to cheap out, either. I guess I just want to use what's best to use and be done with it. Apparently, there is more than one solution.

Stephen

Stephen, Todd is correct.

Todd and David,

This issue was debated on DVXUser awhile back and both Barry Green and I disagreed with that analogy. The diffuser is not (in principle at least)analogous to an exposed image on a negative or a chip. Those have a very limited dynamic range and the exposure has to stay in that limited range. There is no reason I can think of why the diffusion screen should have any limited dynamic range. If more light is put on it, then it should be perfectly adaquate to compensate by lowering the camera's exposure down the line.

For example, say you were shooting a front or rear projected image from a slide projector. Would it matter if you used a brighter or darker bulb?
You wouldn't overexpose the image, you would just compensate on your camera.

I repeat that its very possible I'm wrong. I am open to learning that these diffusing screens behave in unexpected ways, and eager to hear the experience of someone who has seen his picture blow out so much that its not salvagable, but my own (admittedly limited) experience was that it made absolutely no difference if i used the HVX's internal ND.

So far no one on these boards has testified to the contrary. It seems people just don't bother to report back. Do a test and report your findings please - or explain what happened (in detail) when you saw one blown out. I'm not trying to argue with your experience, I'd just like to hear it described.

-Lenny Levy

Leonard,

I actually think using the word 'diffuser' will confuse some people when referring to 35mm adapters (I know Brevis calls it a diffuser while M2 and other spinning adapters call it a Ground Glass). Lets keep the camera out of it for a bit: the image that is projected onto the diffuser or GG comes only from the 35mm lens attached to the adapter. Whatever the 35mm lens is 'seeing' is what the camera then sees. If you open up, say an 85mm 1.4 lens to it's widest aperature you'll get a washed out (over exposed) image on the GG or diffuser. Then the camera will capture that image (so if you use your camera's ND filter, you are compensating for the 'blown out' image. Again, manually over expose the camera in daylight without an adapter and see what the image looks like: this is 'blown out'. Of course you could stop down the 35mm lens to say 4.5 or 6 but this actually will affect the DOF the lens can get (all lenses have a sweet spot). Stopping down the lens this much defeats the purpose of even using the 35mm adapter. This is also why most people prefer to put the ND filter ahead of the 35mm lens. The Brevis35 is more light sensitive than the M2 and by stopping down the lenses too much you'll start to see grain (again a good reason to put the ND filter ahead of the lens). I know this is slightly off topic, but to help everyone out I'm just mentioning it.

When dealing with a 35mm adapter it can be a bit tricky (do I leave the 35mm lens wide open, stop down the aperature on the camera, or do I find the sweet spot for both the 35mm lens and the camera?). I hope this helps a bit with some confusion.

Once I get a mattebox (once Redrock Micro makes it available) I'll try to shoot a test to show you what blown out looks like. I'll do a test with my M2 (which has the edge in exterior daylight shots mainly because the Brevis35 is more light sensitive) and my Brevis.

Todd

Todd, I understand what you are saying, but I disagree with it, and I have not seen the effect you are describing. No one else has ever actually described seeing it on these forums either, at least not that i've seen.

I don't understand why you are describing the 35mm image on the GG (let's stick with that term) as overexposed. It is simply an image. Exposure , (under or over) only happens when that image is projected onto a light sensitive surface like say 35mm film or a video chip that has a specific sensitivity or ASA.

If you look at it with a human eye it won't look blown out, it will simply look an image because your eye will adjust to the exposure. Take a 35mm SLR out into the sunlight. You're looking at an image on a GG - same as the adapter. It will never look blown out - only brighter or darker.

If my 85mm lens at f1.4 as seen through the adapter to the HVX looks blown out, I have a choice - I can stop down the 35mm lens , but you start to see grain above 5.6 - or I can stop down the lens on my HVX which will have very little if any affect on the image.

If I'm in daylight and I need to stop down more, I add ND to the HVX. I see no difference between this and stopping down the HVX iris. Either way I haven't seen any affect on the image (except that there may be better corner focus with HVX apertures closed to at 2.8 or 4).

Maybe something else is operating here but no one has demonstrated that.

I don't understand why you are describing the 35mm image on the GG (let's stick with that term) as overexposed. It is simply an image. Exposure , (under or over) only happens when that image is projected onto a light sensitive surface like say 35mm film or a video chip that has a specific sensitivity or ASA.


I just did a search over at the Redrock Micro forums and Brian Valente (one of the creators of the M2) stated that "That is a bit of a religious argument, but the M2 does not affect use of camera ND filters one way or another". In other words, you are probably right. I believe the reason there is a problem with the blown out or smeared image is the fact that most cameras use electronic ND filters as opposed to actual glass ND filters. Using a camera that has electronic ND filters will/can cause smear (blown out) images which is why it is suggested to use the ND filter ahead of the 35mm lens (so when I said the image was blown out it actually was a smear from the electronic ND's in the camera and NOT from the 35mm lens).

It seems the HVX uses glass ND filters (according to Barry Green). If the HVX does in fact utilize glass ND filters internally, then you have nothing to worry about.

Thanks for making me check into this because I think I now have a better understanding. I still believe you should try to use the sweet spot of the 35mm lens (to get edge-to-edge sharpness) and then go from there.

Todd

Thanks, Todd.

That may be the source of this misunderstanding.

The 35mm lenses are probably at their best b/n 2.8 and 5.6 generally.
Also you should get better corner to corner focusing on the GG with the HVX not wide open. Sometimes you have to pick which will be a bigger problem.

Okay. . . so we're agreed that the GG on the adapters won't "blow out." The original question remains somewhat on the table (at least to me): Use the internal HVX NDs or external ones? The HVX has, of course, two NDs. Are BOTH of these filters actually glass?

If I SHOULD be using external NDs, which ones do you folks like to use? I'd like to see more opinions and merits/disadvantages.

Thanks again.

Stephen

Stephen: I'm curious about the source of your information that the internal filters shouldn't be used... I haven't personally used the HVX (although I bought one as a backup camera 2 days ago - it's still in the box) but I've used virtually every other camera out there, with and without 35 adapters, and I've always used internal NDs... glass is heavy, tends to cause flares when shooting toward light sources (which I do regularly) and takes up valuable tray space in my matte box.

Shooting with the HPX500 I regularly flip filters as I walk from interiors to exteriors and back, while shooting.. changing 4x4 filters would be out of the question. With my Canon A1 and the M2 adapter I use internals all the time, same scenario.

I could be wrong, weirder things have happened, but I would doubt there are any serious issues with the HVX's NDs...

I don't know, as a matter of fact, if the internal filters are glass, gel, or electronic... Probably not glass... gel would be fine (cinematographers always use gel rather than glass BEHIND lens elements - less refraction problems)... electronic, maybe, it is a switch rather than a wheel - but since I haven't used the camera yet, I don't know...

If you open up, say an 85mm 1.4 lens to it's widest aperature you'll get a washed out (over exposed) image on the GG or diffuser. Then the camera will capture that image (so if you use your camera's ND filter, you are compensating for the 'blown out' image.

Not exactly compensating. It's more of the order of operation. Once the GG is over exposed, the camera will do nothing to fix it. I'm a firm believer that you need externals.

Stephen, you definitely will want external ND's. Even if it's only a single .3 it will only help that much, which might be enough to at least remove most of the blown out light for your particular circumstance. It can only help if anything. For bright sunlight and a fast lens you will probably want at least a .9 and a .3.

"Once the GG is over exposed, the camera will do nothing to fix it. I'm a firm believer that you need externals."

Gene, Have you actaully seen this happen, or is it simply something that you believe in? Please don't take this as condescending, its a genuinely curious question. I really do want to know about when this might happen and don't want it to be a surprise on a shoot.

If you have seen it please describe the circumstances.

- Lenny Levy.

Actually after I posted that I went onto my balcony to quickly shoot an example. The sun was out but for some reason it wasn't as bright and hot as normal. I think there was a thin layer of haze or clouds that were horking the sun. Either way it wasn't happening for me. I'll try and shoot an example soon and post it here.

The only thing I know is that when I use external ND's, my images are noticeably better looking. So whether or not it actually blows out the GG or something else happens, externals are better imo.

The discussion of external vs internal ND's is always a lively one :-) Like Gene, I do use external ND's and nearly always shoot in this mode these days when shooting with the adapter. However, there's no question that I would (and do) use the internals in a pinch.

There are a few positives to using external NDs:

1. In many cases, they are used in matteboxes, which also shade the35mm or camera lens from non-image forming light. Lens flare, lens hazing and internal reflection are therefore minimized at the start of the optical chain. Nd's positioned downstream of the lens optics cannot help with this.

2. Reducing internal light levels (either in a set of lens elements, or a 35mm adapter) will coincidentally reduce internal reflection/flaring/hazing that may be introduced at the 35mm lens, imaging element, or achromat.

Add in some of the benefits of other filters (like polarizing filters to reduce glare) and the expense of an external mattebox/filter system becomes a bit more palatable.

I never use the internal NDs when using my adapter.

Expose for the GG as best you can, then use the camera's iris for minor adjustment. Yesterday I had an ND .9, a CP, and the taking lens was stopped to f4... the most I stopped the camera down was 3.4, but it was usually open.

Okay, Jon. . .

Stupid question time. What's a "CP"?

Stephen

And, Jon, while we're on the subject, what external NDs are you using??? Brand, that is. . .

Thanks!

Stephen

I believe CP means 'circular polarizer'. This is great when shooting through windows; cuts down glare and enhances contrast.

Jon,
I hate to keep beating a dead horse , but did you see anything in tests that led you to prefer exterior filters to the interior?
I'm not questioning your decision, just wondering if it was based on tests or general principles. I'm really seeking to learn from someone who has seen problems from the interior glass.

I assume you're using very good quality multi-coated filters if you are stacking them since that can create its own problems with internal reflections.

It is simply not possible for a ground glass to "overexpose", because a ground glass doesn't "expose" at all. It's glass. It's like a window -- can you "overexpose" a window? Windows don't expose.

(and yes, I've tested this, by taking a shot with a ground-glass adapter at one light level, and then at 256x that light level, compensating with internal ND filters and internal iris -- the results were identical).

The HVX's ND filters are not "electronic", they're physical filters that slide into position with the clunking of the ND filter switch, just like on a bigger broadcast camera. As to whether the ND filters are glass or gelatin I don't know.

Well Barry, I'm with you on this all the way. We beat this death over at DVXUser and I just keep asking those people on this forum who tell you not to use the internal filters if they've ever actually seen any problems.

So far nothing has come up. I making my offer now - Free Pizza to anyone who can document overexposed ground glass or any other significant image problems from using the internal HVX filters as opposed to external ND's.

Go Barry! Go Leonard!

SAVE ME SOME MONEY!

:-)

I simply don't want to buy external filters if there are no issues with the internal ones.

I've spent enough of my "hard earned money" at this dance.

:-)

Stephen

Well I use both and I have to tell you it's like night and day.

Use 1/8 internal ND filter and split the difference w/an external B+W filter.

(seriously, for my 24hr Timelapse shots I use the B+W and click off the internal ND's as the light fades to achieve proper exposure from daylight to ambient city light)

Brian,
I'm not sure what your saying here. Is this relevant to the question of image quality with a 35mm adapter, or is this just a way you have figured out to do timelapses efficiently?

it would seem to me that if the image is "overexposed" on the GG, that it would be overexposed coming off of the subject, so ND filter placement doesn't really matter. As Barry said, the GG never holds the image, it simply refracts the light again from a set distance of a previously refracted image.

Either way, I use my internal ND filters and I've never had a problem with them.

It is simply not possible for a ground glass to "overexpose", because a ground glass doesn't "expose" at all. It's glass. It's like a window -- can you "overexpose" a window? Windows don't expose.

(and yes, I've tested this, by taking a shot with a ground-glass adapter at one light level, and then at 256x that light level, compensating with internal ND filters and internal iris -- the results were identical).

The HVX's ND filters are not "electronic", they're physical filters that slide into position with the clunking of the ND filter switch, just like on a bigger broadcast camera. As to whether the ND filters are glass or gelatin I don't know.

Barry, the thing you are either unaware of, or forgetting is Sub-surface Scattering. You simply can't compare GG to perfectly crystal clear glass with an IOR of 1.0.

http://en.wikipedia.org/wiki/Subsurface_scattering

It's directly dependent on the material properties of the GG.

Cheers

I'm not forgetting it; it's inherent to the way the ground glass "holds" the image. It's the very nature of the ground glass, and it's primarily the difference between ground glass and a window.

But it has nothing to do with the concept of a ground glass "exposing" or "overexposing". A ground glass can no more "overexpose" an image than, say, a projection screen could. I don't think I've ever heard anyone claiming that a rear-projection screen "overexposes" an image, but it's vaguely the same technique.

Except for the thickness, the material and the physical size of the screen. If you say so though. All I know is how my images look with and without.

Ciao

the fact that most cameras use electronic ND filters as opposed to actual glass ND filters.

What cameras are you talking about? An "electronic ND" would be the same as negative gain - I don't think any camera with an ND filter switch/wheel would not have actual glass ND filters (on the DVX/HVX for example you can even see it's mechanical when you set the switch in between the right position).

I don't know about the adapter issue, but my experience with filters is that any filters in front of your lens might cause blurriness in full zoom, while I have never seen any image degradation with the built-in filters of either a DVX100, HVX200 or Sony DXC-D30/35/50. I don't think this would be any different with the HPX500 (that I haven't seen yet, but maybe soon)

Gene,
You have not described a situation where you've compared with and without an external filter and explained the difference. I'm honestly eager to hear it.

On the last post you went on to your balcony and the effect didn't happen, but you thought maybe it wasn't bright enough.

- Lenny

There are some properties of our imaging elements that I can't discuss...and having said that, even if there was no difference on the imaging element side of things, I'd still do my shading/exposure control at the front of the optical chain where practical. Here's why.

Of the forms of lens flare (most being obvious) out there, hazing is the one that gives me the most grief. It's hard to see when you're shooting, can be unpredictable, and is easily taken care of by properly shading/exposing and in some cases stopping down the 35mm lens. Internal ND's will do nothing in this case. It would be extremelty difficult to predict bare lens behaviour in the field with incident light...there's too many variables. Also, AFAIK, no camera has an internal polarizer, and for me, that's a staple filter when shooting outdoors. On my list of things to do...a visual (with examples) guide to best practices on shooting with the Brevis.

So although imaging systems in adapters vary (I believe Barry was testing the Letus) and will predictably vary in behaviour with technology differences, no one can argue that proper shading/exposure control out front will never hurt your image quality, and in most cases will improve it. As a still photographer enthusiast for some 23 years, I am a firm believer in keeping non-image forming/unnecessary light off of my optics :-)