Questions re Letus Ultimate.

Great discussions happening. One thing to add in the "design" debate over lightloss is that light travel also occurs in the flip/optics and barrel of the adapter. We can't solely go by the thickness/coating of the ground glass for light transmission and comparatively use the SG's glass or the Extreme (or any other for that matter). A super thin/clear GG at the end of a 1 foot tube is more likely to lose more light than a thicker/more frosted GG only a few inches from the Achromat/Camera lens.

I think some of the Ultimate's improved Bokeh AND good lightloss can be attributed to the physical size of the adapter along with the GG changes. This is all speculation of course, but I don't think we should discount any of this if we are to use the SG glass and others for comparison based solely on their current performance.

Honestly, I think that having accurate, linear stops is a major advantage to an adapter. Its the same idea behind accurate collimation. Sure you could just eyeball from a monitor, but having the capabilities of once again working within a proper professional manner and using measuring tools is a great addition for pulling the tape out from the GG and nailing the shot.

So, with accurate light transmission comes the ability to properly meter a complex shot, repeat specific details, match shot for shot, and actually having a basis for communicating with the gaffer/key regarding lighting rather than just "make it about this bright". I've gone plenty of times without a meter due to the innacuracy of the adapter being used then, but sometimes it doesn't work out for specific projects. For example macro work can get rather specific and SFX work, particularly in commercial projects. You could go by foot candles but why change the system we've been using for film? I try not to live or die by the technical details, but knowing the limits always helps.
 
hey I'm jumping in this convo here just to say in my own tests the brevis affect on the brevis stops at 2.4-2.8 and not at 4.0 as some have stated here. Also I finally was able to see some kind of change between 1.4 and ~2.8.. I was aiming directly at a desk lamp bulb and as I stopped down the glow from the bulb lessened! woooweee something actually does happen.. lol.
 
i agree with you avenger. but a huge problem is that for the adapter to behave in a linear fashion, the GG needs to be more diffused. and that means more light loss, more visible grain patters, less DOF and softer images.

i think the M2, being the most diffused, is going to be the best we get. i haven't seen any tests on the M2 though. it might perform linearly up to f1.4 but then f1.2 is only 1/20th of a stop different... who knows. any one care to test?

what i would do is rate the ISO of the camera at specific apertures...

for example my DVX/sgpro is ISO 300 at f1.4, 290 at f2, 180 at 2.8, 120 at f4 etc (not the real numbers...)

then chose an aperture for your scene and light to that ISO as a reference for your key grip. and use the cameras aperture as your adjustment, not the taking lens. but that means you're max aperture is f2.4 at zoom 74 on the dvx.

so say if i shoot an interior and chose f2.8 on my sgpro's taking lens as the DOF for that scene. then my camera is now ISO 180 with a max aperture of f/2.4... that's what i'd tell the key grip/gaffa.


it's pretty easy to rate your camera's iso with an adapter. all you need in a grey card and a light meter.
 
Avenger007 said:
Great discussions happening. One thing to add in the "design" debate over lightloss is that light travel also occurs in the flip/optics and barrel of the adapter. We can't solely go by the thickness/coating of the ground glass for light transmission and comparatively use the SG's glass or the Extreme (or any other for that matter). A super thin/clear GG at the end of a 1 foot tube is more likely to lose more light than a thicker/more frosted GG only a few inches from the Achromat/Camera lens.

I think some of the Ultimate's improved Bokeh AND good lightloss can be attributed to the physical size of the adapter along with the GG changes. This is all speculation of course, but I don't think we should discount any of this if we are to use the SG glass and others for comparison based solely on their current performance.

Honestly, I think that having accurate, linear stops is a major advantage to an adapter. Its the same idea behind accurate collimation. Sure you could just eyeball from a monitor, but having the capabilities of once again working within a proper professional manner and using measuring tools is a great addition for pulling the tape out from the GG and nailing the shot.

So, with accurate light transmission comes the ability to properly meter a complex shot, repeat specific details, match shot for shot, and actually having a basis for communicating with the gaffer/key regarding lighting rather than just "make it about this bright". I've gone plenty of times without a meter due to the innacuracy of the adapter being used then, but sometimes it doesn't work out for specific projects. For example macro work can get rather specific and SFX work, particularly in commercial projects. You could go by foot candles but why change the system we've been using for film? I try not to live or die by the technical details, but knowing the limits always helps.
Click to expand...

This is a huge reason why I'm weighing the option of HVX200A+Ultimate or RED for my short. There's gonna be greenscreen and tracking and both systems have some flaws built into them that will affect the greenscreen footage. Not too stoked about that but understanding is the first step to conquering.

I guess for the adapter's case it's another trade-off that we have to live with, if the ground glass has to be diffused heavily then I would rather take the inaccurate light loss measurement under 2.8 or whatever it is.
 
OK, Hope you don't take this too personally, but Kholi why should a guy who doesn't even own a lightmeter care about this.

On a broader note I don't know a single DP who trusts light meter readings to set video exposures. I'm talking about people like myself who made the switch form film to video and that's virtually everyone I know in the business. i've had this discussion many times with colleagues.

Its great for lighting though and that does allow you to be repeatable and to communicate with the gaffer. For exposure though it only gets you in the ball park, and if you are careful you always check a waveform.

BTW I did measure a Redrock once and it was much closer to linear.

Lenny Levy
 
I'm talking about Greenscreen work. For that controlled environment we usually have waveforms and a VFX guy on set that'll be working in post.

Lightmeter doesn't really have anything to do with it.

Outside of greenscreen work I actually don't care about linear response. I use Zebras and such and make out just fine.

By the way: No offense taken. xD I know people say LightMeter's are important. I think my take on it is just from the perspective of a noob being that there are so many tools built into the technology to judge exposure I kinda feel that I don't need it. I'm sure I should invest in one, but for this particular project I'm only concerned about greenscreen work being close to accurate and it goes beyond lighting. RED's rolling shutter has plenty of potential to mess up my tracking marks.
 
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A lightmeter is more critical for me on a greenscreen shoot than probably anything else.
Its how I set my levels and determine whether my lighting is even. I can't imagine doing one without it unless its a just a simple head and even there I use a meter.
The waveform is the secondary tool and of course for determining final exposure.

lenny
 
Different strokes, s'all. With all the greenscreen work we've been doing (see reel at the Rainfall link below) it's always been minus a light meter. Usually waveforms and IRE reading.

Never had an issue with it and we do quite a bit of VFX/Greenscreen stuff. Not negating the importance of a Lightmeter to some. Just hasn't been in my arsenal. Sure I'll get one soon, though. Just not on it at the moment.

Naturally, I do appreciate the advice and I know I ought'a get one asap.
 
jenningsp said:
what i would do is rate the ISO of the camera at specific apertures...
Click to expand...
Exactly. That's been my approach since the early days with M2 units. The SG is pretty much always consistent thus a cheat sheet basically lives on the side of the unit. It assures that the DP, meter, and crew are all on the same page.
 
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