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    #21
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    Quote Originally Posted by Beat Takeshi View Post



    BOING!!!!
    LOL! Hey Dennis my flip never did arrive


     

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    #22
    DVXuser Sponsor Dennis Wood's Avatar
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    K, now that we have the retail enclosure done, we'll be doing a new series of tests regarding light loss. At this point, a decent estimate is 0 stops from the adapter/flip itself, and .9 to 1.2 stops lost with a 50mm f1.4 attached, and CF1L installed. The bare Brevis adapter shows about a .5 stop gain with no lens attached. Although no tests have been done on the Letus with a lens attached, we're still projecting a .5 to 1 stop advantage in light efficiency.

    Setup is still possible in minutes. Once lens mount micro-collimation and rear XY adjust is done, expect to be shooting in seconds...just like now. We've got a quick release system in the works which will make attachment even easier that it is now. You'll be able to go from fully rigged on rails, to bare cam in about 10 seconds.
    Last edited by Dennis Wood; 10-12-2007 at 01:59 AM.


     

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    #23
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    Wow ! Why the camera sits so high ?
    I can't wait to see the first sgpro owner that tried this.
    I think sgpro with this flip unit is too much adaptors on 1 camera.
    Why can't we make some digital converter, that flips the image? In the jvc hd200/250 and xl h1 they have this option in the menu.


     

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    #24
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    Dennis,

    Are you saying the flip adapter won't reduce the light at all !?!

    I don't think there is a full stop loss with the Brevis and even a 2.8 prime, but I should check my test numbers again. Its actually kind of tricky to measure, because if you just go by say the f-stops on the video lens, those can be quite inaccurate in my experience.


     

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    #25
    Director of Photography TimurCivan's Avatar
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    Dennis, we keep going back and forth about this.. there is a variable in your test your not accounting for. ITS PHYSICALLY impossibly for the bare brevis to amplify light by ANY stops..... Newtons law of the conservation of energy says so.

    ITs actually impossible for it to lose 0 stops... i accept your .5 stop adapter loss claim. If the brevis did amplify light by half a stop, you my friend should recieve a nobel prize.
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    #26
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    It is absolutely impossible for there to be more light exiting an adapter than there is entering it, that's completely true and Timur's spot on with that observation.

    But it is possible to measure the amount of light exiting the adapter and come to the conclusion that it's 100% of the light entering it, or even more. And while that's technically possible, it'd just be extremely undesirable, and mistaken. You can magnify the amount of light hitting a certain point, making that point appear brighter, but it'd happen by concentrating the available light into a small hotspot. Think of a magnifying glass -- it can amplify the amount of the sun's energy to the point where it can start a fire, but the result is that you get a small pinpoint of hot light.

    What would be technically impossible is to magnify past (or even preserve) 100% light transmission while maintaining an even field of light distribution. All lens surfaces are going to cause light transmission loss, that's just the way the universe works. You cannot gain energy by shining light through an adapter -- if you did, as Timur said, you'd win a Nobel prize and create a perpetual energy machine -- heck, we could solve the world's energy needs just by stringing adapters together in a six-mile-high chain and shining the results onto a solar panel...

    If an optical path appears to be magnifying the amount of light, it'd have no choice but to be producing a hot spot in the center and vignetting in the corners. If you measured the hot spot through a light meter you could maybe show a gain, but you'd really have to throw the unit up on a waveform monitor, shooting a white card, and look at the light falloff at the edges. If you're seeing a flat line that's good, if you're seeing a "hill" (higher in the center, lower at the edges) then that's bad and an indicator that there's vignetting going on.

    Having a vignetting hotspot wouldn't be gaining light, you'd just be moving it around. The only way to actually gain light would be to add a light source inside the adapter.
    Last edited by Barry_Green; 10-12-2007 at 12:51 PM.


     

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    #27
    lOwEr CaSe Member ryan brown's Avatar
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    Quote Originally Posted by Barry_Green View Post
    create a perpetual energy machine -- heck, we could solve the world's energy needs just by stringing adapters together in a six-mile-high chain and shining the results onto a solar panel...
    In an absolute world.


     

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    #28
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    regardless in my eyes it appears the brevis 35 with flip will cost about $1300 but allow for different focus screens and more lens adapters than the letus.

    The letus is also a limited time offer at $1200 too AND includes a rod support.

    I think if these systems stick around $1200 then theyll be a great offer at only a stop or two of light loss
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    RED ONE cameras, HPX/HVX cameras, 35mm Adapters, EFP/ENG Audio, Steadicam, Jib, Dolly, and Grip/Electric Packages Available.


     

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    #29
    DVXuser Sponsor Dennis Wood's Avatar
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    I've always described the light loss issue in terms of what shooters would expect to see on their camera with and without the adapter given the same lighting, distance and framing. How/where that light loss get's attributed is a matter of mathematics, but the fact remains that with a 50mm f1.4 lens attached, users can expect to see a relative difference of .5 to .7 stops with the non-flipped Brevis. I agree with the solar panel analogy 100%, however what we're comparing here is a bare camera vs a camera with a 35mm lens projecting onto a small screen (a break in the convential chain of optics), which is then relayed to the video camera lens. If you project an LCD projector onto a 20 ft screen, then compare it to the same LCD scaled to a screen 10 ft across, the smaller screen will look much brighter. It's the same amount of energy, but over a smaller area...so it appears brighter when viewed from the same distance. From my research here, it seems very clear that the light loss equations work as expected after the imaging element, but to impose them before is to suggest that the ground glass/spinning disk/imaging element has an aperture and an f stop value...and it doesn't.

    What we're seeing here with the retail flip module + CF1L is 10 to 14 IRE using a 50mm f1.4 lens mounted, (HV20) and with the XHA1, about 20 IRE drop with an 85mm f1.8. In other words, framing the same scene with and without the adapter attached on those two lenses would show an average drop of 13 and 20 IRE respectively. That equates (and correct me if I"m wrong) to .7 of a stop with the HV20/50mm f1.4, and a full stop with the XH-A1/f1.8 85mm attached. This is better than we had modelled optically.


     

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    #30
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    I find the ways in which people are measuring the amount of light loss quite a bit tricky.
    Among the variables
    1. the gamma of the video camera is not linear from 0 to 100 ( so if you are measuring say a white between 70 - 100 a 15 IRE change may be quite different than at dark grey below 40.
    Best to measure movement in the middle of the Grey scale but even that's inaccurate because:

    2. the various gammas have radically different slopes. Probably Cine D is the flatest but to tell the truth all my tests have ben done with HD Norm because that's where I keep my camera. But either way they will throw the measurements off.

    3. If you look at the IRE response to opening up the 35mm f stop, I have seen (odd as hell) that wider openings get less response and as I close the iris it gets more and more pronounced. 1 stop between f2 and f2.8 is much less than between 4 and 5.6. Often opening up wider than f2 or even f2.8 has little affect.

    My guess is that this varies from diffusing screen to screen and perhaps may depend also on the video camera, the adapters optics and the distance to the diffusing screen. But i can't say i've tested the variables - I just know they are weird.

    I say this just to caution everyone not to get too caught up on light loss numbers . They are general aproximations and very valuable at that but only aproximations - your mileage may vary.

    I trust the shutter speed more than anything else as an objective measure. If I can get the same IRE reading say from a naked HVX @ 1/60 and then an adapter (at a given fstop & lens) at say 1/30. I know that they are 1 stop different all other variables are silenced for that moment at least.

    But it might be possible for one adapter to be faster with a 1.4 primes and another to be faster or equal at 2.8.

    Take it all with a grain of salt because being really precise can drive you nuttty.

    The best test is the same lens on the same HVX using different adapters side by side. But those tests have to be extremely careful. Actually I would do them all at f2.8, f2 and f1.4


    Having said all that mouthful. I do find Dennis's numbers for the CF1L in the ball park.


     

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