Does Letus Extreme lose more light than Brevis

C

Cinemano

Active member
I wondered if the Letus extreem loses more light and detail than then Brevis. Seing as it has a prism to flip the image right side up and the brevis kinda goes directly to the lens then yu flip it in post..
 
There are many tests here on the forum. Unfortunately, some of them conflict with others, so an absolute answer is difficult to find with certainty. However, I'd feel confident saying that they lose approximately the same amount of light and deliver approximately the same sharpness.
 
I've owned both and would agree with Barry that they both lose about a half stop of light. The hands down winner in sharpness is the Letus EX though.
 
And the Letus is Flipped and loses that much light. Add a flip to the Brevis and that changes thing.
 
That is true. I owned the "pre-flip" system and it lost .5 stops and just wasn't very sharp. Add the flip module and who knows.
 
With the brevis stopping down one stop on the 35mm lens does not always equal one stop.
How is the letus with that?
 
It's pretty spot on with my lenses. The F1.4 50mm Nikon, going from 1.4 to 2 doesn't see anything but a change in the Bokeh Rendition. 2 to 2.8 responds accordingly. Edit: You're supposed to come out and mess with the LetusEX! Stop writing and get o'er here. =P

Jbed -- The Brevis + Flip looks to be a lot sharper than the Brevis alone. Makes for a good reason to buy the flip unit ASAP.
 
Well the more you read the more you'll see people have different experience with these adapters. I wish I could explain why.

In my tests a Pre-Flip Brevis with the CF1L diffuser was definitely faster than the Letus or the SGPro Rev 2 (also pre flip). However it was different with the 35mm lens at f1.4 or f2.8.

The Pre-flip Brevis saw no change in Boken or exposure from 35mm 2.8 to 1.4. It just didn't seem to see that light. The other adapters saw a gain as we opened to f1.4 though less than 2 stops. Thus in my tests the Brevis was only slightly faster than the others at f1.4 , but nearly a full stop faster at 2.8 and beyond.

Matty g is right about the Brevis not being linear with respect to light loss. I didn't find any of them to be, but some people say the SG and the Letus are.

Don't know how the flip changes this. I didn't see any significant sharpness difference between the Letus & Brevis but others have.

Note in my tests the Letus is the slowest which surprised me - keep in mind though that others have found the Letus to be faster than the SG so your mileage may vary.


with an 85mm/f1.4 Nikkor on my HVX:

@ f1.4 Brevis lost about .5 stop
SGPro .6 stop
Letus Ex 1 stop (if you corrected for the extra zoom-in due to being offset it was maybe .85)

f2.8 Brevis .5 stop
SGPro 1.2 stops
Letus Ex 1.6 stops

Lenny Levy
 
Lenny, you have no idea how refreshing your approach (based on real testing) is to us :-)

All of the demo footage currently featured on our website was shot on non-flipped Brevis units, and you won't hear much in the of complaints regarding sharpness! You'll start to see many reviews as folks get and use their flip modules this week...but Paul Nordin had some very positive first comments. You will see an in-depth technical review of the flip system with charts etc. published likely this week.

The Brevis with CF1Le or CF1 (flipped or not) was shown to be as much as 3-5 stops more efficient than the M2 and SGpro shooting at F8 in Phil Bloom's review last year. So there is a big difference in the adapters as you stop down. I do end up shooting at f4 to f5.6 a lot, and the fact that we can stop down a lens to it's sweet spot while losing only a stop or two of light is very, very cool.
 
Last weekend I shot some pickups for a feature I DPed late last year. We shot with two HVX200s both with Brevis, PL, and Zeiss Superspeed cinema lenses. I was lucky enough to test out the flip module on the B-Camera and can say unequivocally, that it rocks. The image was noticeably sharper on the edges with less chromatic aberration. In a couple of configurations I had both cams setup in opposite over the shoulder angles for dialog coverage, so there are some good apples-to-apples comparisons of the flipped and non-flipped images.
Click to expand...

From that same linked first user comment. And it further goes on to talk about using spacers. Part of the reason you can't use those Canon k-35 lenses on the M2 and Brevis is because the GG is too close. You can use them on the SGpro just fine.

Sorry, but that First user comment pretty much mirrors what I said: The Brevis' image sharpness increases with the flip unit attached.
 
There's no question that the Brevis flip/optics improves our image quality because that was the goal of a year's worth of development :-) However, there are plenty of folks out there who have done truly amazing work with the non-flipped unit (again, referring to the demo clips). It's true that our flipped configuration is more flexible with regard to framing 16x22 format lenses like the ones Paul is referring to. Cinema lenses have always been fully supported on our PL and OCT 19 mounts, but some camera/lens combinations required using a $20 spacer between the unit and our 72mm achromat. Given the number of PL/OCT19 mounts we've provided to our customers, suggesting that cinema format lenses cannot be used with the non-flipped Brevis is incorrect. In fact, Paul has been shooting PL mount cinema lenses almost exclusively for the last year.

In any case, I think most will agree that the flipped image, increase in edge sharpness, and reduction in CA balances nicely with the extra weight and .2 stops or so of light loss :-) Lenny's observation that at f2.8 the system is a stop faster than the units tested bodes well for folks using slower wide angle primes and zoom lenses.
 
Dennis Wood said:
There's no question that the Brevis flip/optics improves our image quality because that was the goal of a year's worth of development :-) However, there are plenty of folks out there who have done truly amazing work with the non-flipped unit (again, referring to the demo clips).
Click to expand...

How does the flip improve the edge-to-edge sharpness? Is it because of the space between the ground glass or achromat to the camera? Could a user extend the space and achieve better edge-to-edge sharpness with the Brevis?

Adding extra glass shouldn't improve sharpness, it's another layer for light to travel through. However, the space could/would, am I wrong?

It's true that our flipped configuration is more flexible with regard to framing 16x22 format lenses like the ones Paul is referring to. Cinema lenses have always been fully supported on our PL and OCT 19 mounts, but some camera/lens combinations required using a $20 spacer between the unit and our 72mm achromat. Given the number of PL/OCT19 mounts we've provided to our customers, suggesting that cinema format lenses cannot be used with the non-flipped Brevis is incorrect. In fact, Paul has been shooting PL mount cinema lenses almost exclusively for the last year.
Click to expand...

I named a specific cinema lens, and did not generalize. I know that PL lenses work with the Brevis. Please, re-read my post and note the specific lens set mentioned.



In any case, I think most will agree that the flipped image, increase in edge sharpness, and reduction in CA balances nicely with the extra weight and .2 stops or so of light loss :-) Lenny's observation that at f2.8 the system is a stop faster than the units tested bodes well for folks using slower wide angle primes and zoom lenses.
Click to expand...

It's good to know that I'm not crazy in seeing that the Brevis Flip improved the image enough to be mentioned. While I know that people have been fine with the image from the Brevis unit without the flip, would you suggest adding a Flip Unit to the package to increase the unit's ability to deliver sharper imagery in conjunction with your available screens?

I have seen the Brevis in action, in person, once before and had trouble with the clarity on either the left or right side of the image. I could see, when paired with the flip unit, considering using one because of the footage posted showing improvements.
 
Ok, guys, please slow down for me cause my head is running slow tonight... :)
maybe I need to read this again tomorrow morning with mah cup o' kofey

Does it seem that the Brevis is significantly faster than the Letus at smaller apertures? Cause that's what I think I am gathering... and if so, it seems the benefits start to show at 2.8f already...? I am hoping to get two 2.8 zooms.... maybe this is the selling point for me?

I need a head to head between the flipped Brevis and Letus Extreme with at least 720p footage uploaded and a chart or at least some numbers on speed...
 
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That is correct. Lenny is saying that at f2.8, the Brevis is 1 stop faster. That's half the amount of light required :-) The gap widens as you stop down the lens.

I regularly test with inexpensive f3.5 to f4.5 zooms (not everyone has a 20K lens collection at their disposal), and at this aperture, the Brevis is likely between 1.5 and 2 stops faster than everything else out there.
 
Dennis Wood said:
That is correct. Lenny is saying that at f2.8, the Brevis is 1 stop faster. That's half the amount of light required :-) The gap widens as you stop down the lens.

I regularly test with inexpensive f3.5 to f4.5 zooms (not everyone has a 20K lens collection at their disposal), and at this aperture, the Brevis is likely between 1.5 and 2 stops faster than everything else out there.
Click to expand...

If both units lose the same amount of light, how can physically chopping light out (shutter blades) make a difference?

I need someone with a Brevis in LA to show me this phenomenon where you stop a lens down and see NO change in how much light is hitting the lens. While 1.4 - 2 you BARELY see a light difference, you still see the difference if you're looking. I'm just completely confused on how the Brevis manufactures light.
 
I hope that people reading this thread are smart enough not to take everything that is said here as the absolute truth. Specially by companies and their reps that without proof claim that one is better than the other.

Anyone with a little technical knowledge knows that if you close a lens by 1 f stop you need twice the amount of light regardless of the adaptor.
 
But I have heard of this before... and NOT from the guys at Cinevate. I just want to understand what is this whole thing about the Brevis not being linear... not losing as much likght as you stop down on the lens and so on... because I have heard it from two guys now... one a Brevis non-flipped owner and the other an SGpro owner who only got to use a Brevis!

Barry, Kholi, you guys know WAY more about me, please look into it if you are curious about this.
 
Philip your Piccadilly Circus shots were on a Letus right?
Do you have these sharp images on the Brevis hosted somewhere?


And Barry, could you please elaborate a bit on the physical impossibility of the non-leniar'ity of the light loss of the Brevis? I mean how come people that don't even know each other are saying this?
 
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