Extreme Vs Brevis

i do, absoluteyl. which is why i was hoping there might be an XH A1 owner with a brevis, flip, and nikon lenses :)
 
bah, i mean in terms of half stops accuracy ... stop this :P

nikon 50mm at F2 ! lol
 
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.[/QUOTE]

Dennis, I respect you technical wizardry but I think we're now talking about separate issues here. Hazing and flare are the same whether you use the same power ND behind the lens or in front of the lens. So is exposure for that matter. There's a reason why Panavision have a wonderful behind the rear element filtering system. It's the size of the iris and direct light refracting off the glass that impact flare. This is different than saying you can over expose a ground glass.

I do agree with you completely a mattebox is absolutely a necessity if you plan on using an adaptor to block direct light and use control filters. The other reason I advocate it over the internal filters is that I don't think the internal filters are of a decent quality (I'm putting my flak vest on). I can see the difference between my Tiffens and the HVX's internals in terms of clarity. Try it some time. It's truly depressing to the point I use glass filters whenever possible even without an adaptor. It's not the same stuff as the ENG camera internals. Also, the HVX doesn't have the "in between stops".

Light blocking, quality glass, grads and the like are the reasons for a decent matte box.
 
Papa, our quote of the Brevis system losing less than 1 stop of light is total loss, including the Breivs, flip module, a 50mm f1.4 lens, and uses the same framing in both tests :-) Our testing is all done now with the camera tethered to a laptop running Adobe Onlocation. The captured footage is analyzed using the software's scope. We don't quote adapter loss alone as there are too many variables in measuring it, and I don't feel it means a whole lot to the end user. What does mean something is the difference on an identical scene with and without the adapter attached. We use a 50mm f1.4 lens as it's probably the single most popular lens being used on adapters.

In simpler terms, attaching a Brevis35 + flip + 50mm f1.4 lens to your camera will lose less light than stopping the bare camera down 1 stop.
 
but its not just a question of how much light is lost with the adapter.

i too have done a few tests that show with a 50mm F1.4, with the flip, letus extreme and canon XH A1, that the adapter loses about a stop of light. maybe 3/4 of a stop. But its the fact that my camera has to zoom in, and there, the camera loses a good stop and 3/4 that is the killer.

So unless you have devised some fantastic way to not have a camera zoom in, i fear that even the brevis will suffer from this problem
 
Dennis, how much does the flip itself add to the light loss?
By the way just to add another wrinkle. In my tests recently ( which i will report soon) I noticed that light loss on zooming in the HVX only happens on a wide open aperture. Shoot at f2 and its greatly reduced - at 2.8 its pretty much gone at least in the adapter range. Yet another reason why absolute numbers can be very hard to come up with on these things.

Lenny
 
Last edited:
Lenny, 0.2 of a stop. P, we always test with an identically framed scene so that the bare camera vs the camera+adapter+flip+35mm lens test is as relevant as possible. In other words, zoom is accounted for.

How did you test the Letus on/off your camera if you weren't zoomed in to frame the 35mm image?
 
Actually I don't know if you are talking to me there Dennis, but in my recent tests (which I haven't really reported here yet except very briefly) I zoomed in of course.

0.2 stop - is that for real? How much will this set me back?


I agree with you that the only way to test is with the lens on and zoomed in to full academy or vistavision. Actually I preferr vistavision but they don't all achieve that. My tests were to zoom in only to the point where I lost vignetting on each adapter. That might be a different framing on each one but is in reality how I would use the adapter.

But on the HJVX if I wasn't wide open the zoom-in affect on exposue was minimal.
 
Dennis Wood said:
Lenny, 0.2 of a stop. P, we always test with an identically framed scene so that the bare camera vs the camera+adapter+flip+35mm lens test is as relevant as possible. In other words, zoom is accounted for.

How did you test the Letus on/off your camera if you weren't zoomed in to frame the 35mm image?
Click to expand...

i guess my question more specifically is this. i dont know if you have the means to answer this but it will solve my query.

When using a canon XH A1, how much does one need to zoom in with the brevis adapter + flip to get full frame 35mm ?

What is the cameras final aperture reading? Right now, as i said, the light loss of the letus extreme is very minimal, but the only kicker is the camera zooming in.
 
Last edited:
Lenilenapi said:
I noticed that light loss on zooming in the HVX only happens on a wide open aperture. Shoot at f2 and its greatly reduced - at 2.8 its pretty much gone at least in the adapter range.
Click to expand...

That's to be expected. All the cameras work that way -- the maximum-open iris at wide-angle is more open than the maximum you can get at telephoto. An HVX is 1.6 at wide angle, 2.8 at telephoto, and as you zoom in you gradually lose that 1.6, so partway through the zoom it becomes 1.7, a little further in it becomes 2.0, then 2.4, and at full tele it's 2.8.

So if you stuck the camera iris on 2.8 you would have a constant light transmission from full wide to full tele. It's when you try to open more than 2.8 that you get issues. They all do this, I think the longer Canon zooms (20x, etc) max out at something like f/3.4 even. So if you want to avoid any brightness change during zooming you'd have to not open any wider than 3.4 on those.
 
Why not just test it yourself?
http://www.dvxuser.com/V6/showpost.php?p=1105730&postcount=3

Just substitute in arri 35mm instead of 35mm photographic in the format box.

Also, I found that with the HVX the Letus Extreme has to zoom in *much less* than my older Letus Flip Enhanced had to. I mean, on the FE I had to zoom into 44.0mm, whereas on the Extreme I think it's about 27mm. That alone makes the overall amount of light transmitted quite a bit higher.
 
i wish i spoke your language barry, unfortunately can't work my head around those numbers, all i can work off of are zoom numbers from the canon camera lol.
 
For emulating 35mm movie film, put a 50mm lens on the adapter and put the adapter's "film plane" exactly two feet away from the wall. Make a mark on the wall 10" wide by 5.75" tall. Zoom in or out of the ground glass until you're just filling the frame with that 10" x 5.75" image. Actually, IIRC the XHA1 overscans its LCD so you'd probably need to zoom in a little past until the marked area just clips off your frame.
 
i dont own a brevis, so i can't exactly test that out.

i tired your paper method on the wall with my letus extreme, and i found zoom 80 to be the mark on the xh A1, but not with the brevis.
 
darn, still no resonse.

( hope this question isn't being avoided :P )

i simply am curious to know what zoom one must use to get the 35mm field of view with the brevis and flip, on a canon XH A1 camera. regardless of the light loss of the adapter itself.
 
Pm Dennis and ask him. He's probably one of the only few that would know right now, since release of the flip is still a couple of weeks (I think) away.

The footage he posted of the flip was shot with the A1, so he should know.

All I can tell you about the Brevis is the non-flip and the zoom settings on the HVX. Which, the widest I can be is around 17.7mm or so (going from memory). 18.1 is very comfortable with room to spare. Irrelevant to this discussion though, as it's not flip and the A1 with the non-flip Brevis requires (I think) a spacer ring, which would add to the zoom in on that cam.... I don't know if the A1 uses a spacer ring with the flip or not though, obviously.

Later,
Jason
 
You must log in or register to reply here.
Back
Top