Extreme Vs Brevis

ProjX v2.0 said:
You mean like a locking pin? I don't see one on my base plate.



Says me too. I really don't like how the weight of the camera is held up by horizontal screw pressure so I'm flipping the adapter instead.
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I have it, and I see your point. Though I must say that it is really secure.... albeit at the expense of screw marks on the riser tube. If that bothers you.
 
Just a thought;

Maybe this overexposure is being misinterpreted possibly do to some form of halation like affect. The scattering of light when slammed into a opaque surface could be just that. Then maybe NOT. Just a guess........

Pappas

Barry_Green said:
Just because something's accepted as "commonly known", that doesn't make it true.

I've disproved this notion, anyone with any knowledge of optics will know that this "overexposing the ground glass" stuff is inaccurate, and Lenny and I have been asking for someone/anyone to offer any evidence to the contrary. None has surfaced.

Don't know much more what we can do. The notion is wrong, it's been disproven, so now it's up to you guys to start challenging those who say/repeat it.
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hey all, haven't seen this in any of the posts in the thread so i figured i would ask. Hopefully there will be some responses to the question.

In comparison of light loss between the Brevis Flip ( lets say either CF1L or CF3L GG screens ) and the letus extreme, which one loses less light?

I don't want to know based on the adapter itself, but how much light is sacrificed by the lens, with the adapter, with the lost light from the camera itself being stepped down due to the zooming in factor.

Right now with the letus extreme, a lens stepped down to F2, and my camera zoomed in to Z80 ( canon A1) which closes the iris to F2.6

Therefor the camera alone is losing a stop and a half, the adapter another stop, and then the lens which is about a stop as well? So almost 4 stops in total?

Has anyone evaluated the final light loss with the brevis and flip unit?

Thanks guys!

( generally i like keeping the gain at -3db, but at 0db, and a 1k softbox only a few feet fro ma subject is really cutting it close in terms of propper exposure and i can't plug in stronger lights! )
 
i did a little test this morning and it seems to me that the total light loss of the adapter + F2 lens + closed camera iris = 2.5 stops.

not too shabby! so i was way off with 4 stops. 2.5 in total.
 
.. are there any brevis flip owners yet? Is this the reason why no one is responding?
 
The flip will be out around the end of this month, I think... So, it's too soon for those comparisons to have been done yet.

Later,
Jason
 
Barry_Green said:
Just because something's accepted as "commonly known", that doesn't make it true.

I've disproved this notion, anyone with any knowledge of optics will know that this "overexposing the ground glass" stuff is inaccurate, and Lenny and I have been asking for someone/anyone to offer any evidence to the contrary. None has surfaced.

Don't know much more what we can do. The notion is wrong, it's been disproven, so now it's up to you guys to start challenging those who say/repeat it.
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A ground glass has no ASA or Sensitivity Rating. It's just a relay for an image, no image is actually retained on it. The overexposing the ground glass notion makes about as much sense overexposing a movie screen. A ground glass is essentially a rear screen projection. You cannot overexpose a movie screen because it doesn't burn an image. When the projection bulb is real strong, our eye's iris closes and when it weak it opens. This would be analogous to the iris in the DVX or its nd filters. You can also monitor projection brightness by an iris on the actual lens or put an ND on it. This would be analogous to the iris on the still lens of an adaptor system or ND on a matte box.

I can't think of anything more ludicrous on this entire forum than the mere suggestion that ND's after the ground glass, risk over exposing it. It's got to be the most dumfounded illogical clap trap I've ever read on this forum. Stop the madness.
 
Yup!

I've said many times I'm open to their being something surprising in the adapter set-up that might prove us wrong - so show us an example. That was months ago. No examples have ever surfaced.
 
P, the Brevis with 50mm lens attached, and flip module will lose less than one stop of light when measured with a scope. As of right now, we're the only one using the flip, therefore the lack of opinions out there. This will change in 2 weeks or so :-)

Tim, regardless of the discussion on imaging screens, and overexposure, I believe the correct way to discuss the issue is simply light control. Light that is not required for imaging, or extraneous to it, is best kept under control to at lease reduce flare and hazing. This makes a mattebox and external NDs very desirable to use, particularly when combined with graduated ND filters, and polarizers which increase image quality, contrast and apparent exposure range when used properly.
 
dennis, the letus extreme is also advertised as losing .5-1 stop of light, but personally i would find it much better to advertise complete light loss. The camera has to zoom in to the GG and as a result, loses light due to closing the cameras iris lens down.

Have you had a try to test the brevis with,, lets say CF3L, with your flip unit, on a canon XH A1?

My extreme only loses about a stop aswell, but then my caemra has to zoom in, closing my apature from F1.6 to F2.6, which is a stop and a half. So the total light loss is almost 2.5 stops! adapter + camera lens.
 
You have to keep in mind the fact that the light loss from zooming will vary from camera to camera. These are "universal" adapters for the most part and can not be advertised with particular data such as that. The XH might lose 2.5 "total" but a HVX might only lose 2 "total". Catch my drift? I figure that is a big factor in their decision to advertise the light loss the way they do.

Going back to this ND external vs internal issue. You guys are saying the best way to adjust exposure is to first fine tune INTERNAL settings (camera ND and Fstop) rather than external filters and stopping down the 35 lens?

Basically always try to expose open or less than 2.8 on the 35 lens rather than stop down that 35 lens and leave the cam settings always the same?
 
Avenger007 said:
You have to keep in mind the fact that the light loss from zooming will vary from camera to camera. These are "universal" adapters for the most part and can not be advertised with particular data such as that. The XH might lose 2.5 "total" but a HVX might only lose 2 "total". Catch my drift? I figure that is a big factor in their decision to advertise the light loss the way they do.

Going back to this ND external vs internal issue. You guys are saying the best way to adjust exposure is to first fine tune INTERNAL settings (camera ND and Fstop) rather than external filters and stopping down the 35 lens?

Basically always try to expose open or less than 2.8 on the 35 lens rather than stop down that 35 lens and leave the cam settings always the same?
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very true, and i did think of that. but i also understand that zooming in on any camera will result in the camera to step down, be it a dvx, canon, or what not. That being said, it wouldnt take very much to take some of the main leading cameras for indi makers, canon XH A1, panasonic dvx and HVX and get the figures of light loss for the widely used models.

so more specifically, the question would be related ot how much one must zoom in to get the 35mm frame size on their GG. Does the brevis require less zoom than the letus extreme, and by how much if any?
 
But the zoom-in factor is variable depending on whether you're trying to emulate VistaVision, or 35mm movie film, or whatever. And you may not be running your camera wide-open anyway (at least, not with some of the more light-transmissive adapters!)

Factoring in the zoom demands may be important, but has to be kept separate from the adapter itself's light loss issues. The adapters should be tested for light loss with no lens attached, since that's the only way to guarantee a known scenario. If you test it with a lens attached, you should test it with the exact same lens attached; my f/1.4 lens may not transmit as much light as your f/1.4 lens, for example (hence the whole issue of T-stops instead of f-stops).

There's validity in what PaPa's saying, which is to show total light loss as per each camera, but there's so many models that any data calculated will quickly become obsoleted. Still, if someone has the time, inclination, all the cameras and all the adapters, I'm sure we'd all find it very interesting to know how they all compare once they're all configured on an HVX or XHA1 and all using the same lens and the same field of view.
 
Dennis Wood said:
Tim, regardless of the discussion on imaging screens, and overexposure, I believe the correct way to discuss the issue is simply light control. Light that is not required for imaging, or extraneous to it, is best kept under control to at lease reduce flare and hazing. This makes a mattebox and external NDs very desirable to use,
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Yes, keeping flare off the lens is vital to avoiding hazing and washing out the image, and is a key reason why a mattebox is such a good idea. External or internal ND filtering is completely irrelevant, but shading the lens properly is vital.
 
whats best for shading a spinning/moving Nikon... imagining the matbox/sq. sunshade spinning like a prop.
 
Barry_Green said:
Yes, keeping flare off the lens is vital to avoiding hazing and washing out the image, and is a key reason why a mattebox is such a good idea. External or internal ND filtering is completely irrelevant, but shading the lens properly is vital.
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theo nly reason im asking is to evaluate the total light loss of the letus extreme versus the brevis with flip.
 
Yes, but be aware that the "total light loss" is dependent on your camera and particular lens as well. So there's too many variables for such a test to have any real relevancy except to you or someone who has the exact same camera and exact same lens as you. See what I mean?
 
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