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Old August 10th, 2007, 01:50 PM   #1
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Neutral Density filters for use with the HVX

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
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Old August 10th, 2007, 02:07 PM   #2
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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.
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Old August 10th, 2007, 02:19 PM   #3
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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
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Old August 10th, 2007, 02:22 PM   #4
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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
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Old August 10th, 2007, 03:26 PM   #5
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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
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Old August 10th, 2007, 04:06 PM   #6
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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.
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Old August 10th, 2007, 04:56 PM   #7
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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
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Old August 10th, 2007, 06:49 PM   #8
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Stephen, Todd is correct.
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Old August 10th, 2007, 06:55 PM   #9
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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
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Old August 10th, 2007, 09:49 PM   #10
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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
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Old August 10th, 2007, 10:11 PM   #11
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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.
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Old August 10th, 2007, 10:31 PM   #12
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Quote:
Originally Posted by Leonard Levy View Post
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
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Old August 10th, 2007, 10:41 PM   #13
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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.
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Old August 11th, 2007, 08:44 AM   #14
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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
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Old August 11th, 2007, 10:15 AM   #15
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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...
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