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.