Does the Letus Extreme fix the flaw of all vibrating adapters?

[Dennis Wood]

Barry, that's my point. If he rents those lenses, he will get exactly the FOV he's used to, whether they're cinema or still lenses. And if he wants to squeak a wider shot, he can do that too! All the framing is done at the video camera end...so the shooter decides to limit the FOV...not the adapter design.

 

[Barry_Green]

If someone's properly instructed to set it up that way, then yes. I mean, the L35 Extreme does the same thing -- you can zoom out to get a full-frame 35mm-sized image if you want, with its attendant shallower DOF and wider field of view. Or you can zoom in to the proper field of view for a movie lens. Both choices are available.

 

[marco0782]

Barry, correct me if I'm wrong, but you're saying that ideally we should all operate at the same field of view as a Super 35 motion picture camera. I disagree.

If we are using still photo primes that were designed for a larger field of view, we have the option to take advantage of that. There are no negative consequences in doing so, except the extremely hypothetical example you gave that a professional cinematographer (who takes his/her craft seriously) might get confused with the field of view difference vs. Super 35. I say that a cinematographer needs to know his/her tools and how to exploit them. I know that I can achieve a wider field of view with my Brevis and if that suits my needs I can make that choice. I know what the difference is and I know what results to expect from my lenses at different focal lengths.

Earlier you were suggesting that I take off my Brevis and attach a Century Optics .6X converter instead of just using my 20mm still prime. Your suggestion is even further from Super 35 terms than what I'm doing, not to mention is has more distortion.

Also, you are incorrect in stating that depth of field changes with a larger frame size. A 50mm lens has the same depth of field characteristics whether the frame size is 16mm or 35mm. The only difference is that a 50mm becomes a telephoto lens on a 16mm camera whereas it is a normal lens on a 35mm camera. On a 16mm camera you would be using a 25mm as your normal lens, hence you get more depth of field than a 50mm normal lens on a 35mm camera. So when I choose to use a 50mm on my Brevis at the VistaVision-like frame size, I know that I am getting a wider field of view than if I was using a Super 35 frame size. It is a conscious decision and with practice I have become familiar with what results to expect, and frankly, the results are beautiful. People love the look I am getting because it's different than what they're used to.

People shouldn't get confused by your statements and think that they absolutely have to zoom in more on the ground glass. The main purpose of 35mm adapters is to let us achieve shallower depth of field than we can with small 1/3" or 2/3" sensors which restrict us to shorter focal lengths. The main purpose is not to simulate the exact frame size of Super 35, however if you are using cine lenses you should obey this since those lenses were not designed for a larger frame size. With still photo lenses, you can do whatever you want.

It is also important to note that depth of field varies between adapters depending on the ground glass being used, so there is no direct correspondence between the depth of field characteristics on film vs. using an adapter. I know, for example, that the Redrock M2 ground glass produces a shallower image than film, whereas the Brevis using CF1/CF1L is not as shallow as film (and hence why it loses so little light).

If the Brevis is one of the few adapters that let you use a larger frame size, that is a huge selling point in my opinion because you can get amazing results that you can't if you are restricted to a smaller frame size.


Marco

 

[Barry_Green]

Barry, correct me if I'm wrong, but you're saying that ideally we should all operate at the same field of view as a Super 35 motion picture camera. I disagree.

I'm saying that if you want to emulate the look of "the movies", which is what I would wager 95% of people using these adapters is trying to do, then yes you should use the same field of view as a 35mm camera.

You obviously have the option to use wider if you want -- but you will not be getting film-style depth of field at that point. You can't have it both ways, either you'll get wider FOV (and shallower DOF), or film-style FOV and film-style DOF.

If we are using still photo primes that were designed for a larger field of view, we have the option to take advantage of that. There are no negative consequences in doing so

Yes, there is -- the depth of field and perspective will not match what a movie camera would have shot. If you don't care about those elements, then there's no negative downside, so go right ahead. But please don't say there are no consequences when there most definitely are.

You're telling me to take my Brevis off and attach a Century Optics .6X converter instead of just using my 20mm still prime. Your suggestion is even further from Super 35 terms than what I'm doing!

No, I'm not. I'm telling you to do whatever you want, just understand that there is a difference. You can always zoom out on the adapter if you want; the Brevis isn't the only one that does that though, the L35 Extreme can do it too. I just wouldn't, in most circumstances.

Also, you are incorrect in stating that depth of field changes with a larger frame size.

Well, no, you're incorrect -- in stating that I'm the one who said that. I wasn't. I have always pointed out that imager size is not a factor in what actually determines depth of field.

I don't know why you're so insistent on trying to prove me either incorrect, or misunderstanding, or whatever...

So when I choose to use a 50mm on my Brevis at the VistaVision-like frame size, I know that I am getting a wider field of view than if I was using Super 35. It is a conscious decision

Then we have no disagreement. I disagree with it when it is not a conscious and active decision, as I believe the manufacturers do their users a disservice by not pointing these things out.

People shouldn't get confused and think that they have to zoom in more on the ground glass.

And yet they do, if they want to emulate the look of the movies.

The main purpose of 35mm adapters is to let us achieve shallower depth of field than we can get with small 1/3" or 2/3" sensors. The main purpose is not to simulate the exact frame size of Super 35

Er, says who? Do you speak for all adapter users and manufacturers?

The first adapter on the market, the mini35, was specifically designed to simulate the exact frame size of 35mm movie film. Actually, maybe this question could be answered with a poll, where we ask the users what they want: do they want the shallowest DOF they can possibly get, or do they want their footage to look like it does in the movies (DOF-wise)? You, or I, may be surprised by the poll results.

It is also important to note that depth of field varies between adapters depending on the ground glass being used

No it doesn't.

, so there is no direct correspondence between the depth of field characteristics on film vs. using an adapter.

Depth of field is established by the optics in the lens, not by what it's projected onto. For any given focal length, iris, and distance from the subject, the DOF is fixed. The optical image is fixed. You could project that optical image onto a wall, onto a piece of ground glass, onto a CCD, onto a CMOS sensor, or onto a piece of film, and it won't make any difference to the optical image. It doesn't "know" what it's being projected onto and somehow magically change the depth of field. The image is established by, and fixed in, the lens.

I know, for example, that the Redrock M2 ground glass produces a much shallower image than film, whereas the Brevis using CF1/CF1L is not as shallow as film (and hence why it loses so little light).

I sincerely doubt that this is what's happening. There is no way that the depth of field is actually shallower on one ground glass than another. DOF is fixed by the lens, not the ground glass. There may be some other factor at play here, but it certainly isn't changing the actual depth of field.

If the Brevis is one of the few adapter that let you use a larger frame size, that is a huge selling point in my opinion because you can get amazing results that you can't if you are restricted to a smaller frame size.

The Brevis allows that. I don't know if it's "one of the few" because I don't know how many others allow it as well. I know the L35 Extreme allows it. Maybe most or all of them do, I don't know.

 

[marco0782]

Yes, there is -- the depth of field and perspective will not match what a movie camera would have shot. If you don't care about those elements, then there's no negative downside, so go right ahead. But please don't say there are no consequences when there most definitely are.

I said that there are no negative consequences, which is what you were implying previously.

I sincerely doubt that this is what's happening. There is no way that the depth of field is actually shallower on one ground glass than another. DOF is fixed by the lens, not the ground glass.

Then how would you explain the differences in diffusion between the three ground glasses available for the Brevis? The CF3 is clearly shallower than the CF1.

 

[marco0782]

do they want the shallowest DOF they can possibly get, or do they want their footage to look like it does in the movies (DOF-wise)?

Barry, the depth of field on a 50mm lens is the same regardless of frame size. It's just that with a larger frame size you will need a longer lens to achieve an equivalent field of view, but given the differences between ground glasses and the option to stop down your lens, you are not necessarily going to get a shallower image. One thing is for certain, though: you will get a flatter image.

The real question is, "Do you want a wider field of view or a narrower one?"

Ask yourself, why do we want to make our images look like the movies? It's because "the movies" are considered to be beautiful. Not because there is a specific frame size we all hope to achieve. I find that the VistaVision frame size is beautiful, in fact potentially more beautiful. Have you seen Hitchcock's Vertigo? Here is a great opportunity to do something that's less common and less obvious. If you want to be like every other movie you certainly have the option of zooming in to the typical Super 35 frame size.

The first adapter on the market, the mini35, was specifically designed to simulate the exact frame size of 35mm movie film.

In order to achieve what? To let us get what we can't with our small sensor cameras: Shallow Depth of Field! That's why they're also called DOF adapters.

P+S Technik chose the exact frame size of 35mm film to maintain compatibility with cine lenses, but when using still lenses we should be able to use larger frame sizes.


Marco

 

[Barry_Green]

I said that there are no negative consequences, which is what you were implying previously.

Again, that depends on what you consider a negative. If someone's trying to emulate the look of film, and they get results that are different, then that would be a negative consequence.

It all depends on what their priorities are.

Then how would you explain the differences in diffusion between the three ground glasses available for the Brevis?

Ah, the $64,000 question. I don't know, I'd have to fiddle around with it to see. But the way to get through the truth is to weed out the impossible, and it's impossible that the image's actual depth of field is being manipulated by the ground glass.

I'm tempted to order one just to experiment with it to get to the bottom of all these claims and questions, but I really don't feel like spending $1900 (Brevis HD bundle + cinefuse2 + cinefuse 3 + flip module) just to satisfy some curiosity.

 

[Barry_Green]

Barry, the depth of field on a 50mm lens is the same regardless of frame size.

I know that. I was one of the first to state that and try to break people from the mantra that they've been hearing for decades, which is that DOF is determined by image size. It isn't.

It's just that with a larger frame size you will need a longer lens to achieve an equivalent field of view

I know that as well; remember I'm the one who brought FOV into the discussion in the first place! :thumbsup:

But if someone uses a 50mm lens to achieve a certain shot on a mini35, and someone else uses a 36x24 frame size at the same shooting position, they're going to have a very different shot, so now they have to make a choice: either they move the camera closer (which exaggerates perspective and shortens the depth of field) or they put a longer lens on (which will also shorten the depth of field).

The real question is, "Do you want a wider field of view or a narrower one?"

You can have either. But you have to factor in that choosing the wider field of view is going to dictate shallower DOF for any given composition.

In order to achieve what? To let us get what we can't with our small sensor cameras: Shallow Depth of Field! That's why they're also called DOF adapters.

I didn't know people called them DOF adapters. I'd always heard them called 35mm adapters (like the name of this forum!)

P+S Technik chose the exact frame size of 35mm film to maintain compatibility with cine lenses, but when using still lenses we should be able to use larger frame sizes.

And you can. But not without consequences. You may like or even prefer the consequences, but someone else may not. They're there, either way.

 

[marco0782]

I'm tempted to order one just to experiment with it to get to the bottom of all these claims and questions, but I really don't feel like spending $1900 (Brevis HD bundle + cinefuse2 + cinefuse 3 + flip module) just to satisfy some curiosity.

There are stills and photos on Cinevate's site that should illustrate the differences.

I was a little misleading when I said that depth of field changes. What I meant is that the effect of shallow depth of field (bokeh) varies greatly between ground glasses. And in fact when you compare CF1 to CF3, CF3 looks significantly more shallow.

This takes place independently of the actual depth of field that the lens produces but either subtracts from or complements the "bokeh" effect.

If someone's trying to emulate the look of film, and they get results that are different, then that would be a negative consequence.

There are different types of film. Super 35 is one type, Anamorphic is another, VistaVision is another, Techniscope is another, etc.

I think we're both saying the same thing but remember that you have a lot of influence on this board and you might be dissuading people from trying something different because you make it sound less desirable. It's not less desirable, it's different, and some people may like it more. I know I do.

 

[Jason Ramsey]

Barry, you'll save a few hundred... you won't need the achromat with the flip module, so you don't need the HD bundle, just the regular one heh...

Jason

 

[jgastelb]

Guys! Please take a chill pill and call it a day. This is worse than a re-run of Jerry Springer.rogar-KnockedOut(D

 

[Lenilenapi]

While I will avoid weighing in on most of this conversation, i will have to disagree with Barry about the diffusing screen having no affect on DOF.

It runs counter to everything we know about lenses and the concept of DOF but the results are clear to the eye if you compare a Brevis with say a Redrock or a Brevis CF1 screen with a CF3. Theory should follow observed fact here not the other way around.

If you want you can make up a new term - call it "Apparent Depth of Field", but it is clear that the same lens, with the same field of view and the same f-stop when seen through different rear screens can exhibit strikingly diofferent DOF.

I imagine , and Dennis at Cinevate also surmises that it has something to do with how the screen scatters light that is already beyond its sharp focus point. Certain things seem to be true. The screens with more depth of field are optically denser - i.e. they require more light ( which probably means they scatter more light. They also tend to appear a bit softer though whatever is in focus may still be quite sharp.

My guess is that everyone of these adapters has a slightly different "apparent DOF " as they are all using different diffusion materials. People here are often calling this bokeh.
I've tended to assume that the Brevis CF1L is closer to film since it is scattering light less in the diffuser itself, but alot of things get weird in these adapters. Very little attention has been paid for example to the fact that in many of them the f-stop exposure changes are not linear as they would be in film.

Lenny Levy

 

[marco0782]

The screens with more depth of field are optically denser - i.e. they require more light ( which probably means they scatter more light. They also tend to appear a bit softer though whatever is in focus may still be quite sharp.

I think you meant the screens with less apparent depth of field. I agree with what you are saying though. The way a ground glass represents depth of field through bokeh is completely different than the way film does. The bokeh using a Redrock or SGpro is more exaggerated than on film. I have seen footage from a 50mm f/2.8 lens on the SGpro that appears to be as shallow as the Leica 50mm Noctilux at f/1.0.

Dennis correct me if I'm wrong here, but to me it seems that ground glasses (or diffusers, as Cinevate calls them) have millions of little particles inside that catch light and become illuminated. The finer the particles, it seems, the less bokeh (more appears in focus) but also the most light transmission. Then when you get larger particles as with the CF3, you get more bokeh (less appears in focus) but less light transmission.

This might be overly simplified because density (the number of particles) most likely also plays a role.


Marco

 

[marco0782]

Guys! Please take a chill pill and call it a day. This is worse than a re-run of Jerry Springer.

If Jerry Springer had arguments about this kind of stuff I'd be watching all day, lol.

 

[Lenilenapi]

Yes Marco I meant screens with less DOF - actually you see that mistake all the time on these pages.

What Barry said about cine lenses being closer to the look we identify with 35mm was interesting. My guess is however that the increasingly shallow DOF of many of these adapters is a more significant difference between the look of the adapters and 35mm. That's why we see alot of (to my eye) bad out of focus images coming through these pages. Often its beautiful and striking though, and actually a different kind of look than 35mm might yield.

Lenny Levy

 

[marco0782]

Yes Marco I meant screens with less DOF - actually you see that mistake all the time on these pages.

It's not a big deal, I just wanted to make sure nobody gets confused since we are making somewhat of a breakthrough here. Didn't mean to come across like I was nitpicking you.


Marco

 

[jgastelb]

Yeah. But then instead of cheating with her sister you would be sleeping with a Brevis while secretly betraying your Letus Extreme. Adapters would be flying left and right while the crowd asked for more depth of field and better edge to edge sharpness. Huh?

:2vrolijk_08:
Jgastelb

If Jerry Springer had arguments about this kind of stuff I'd be watching all day, lol.

 

[TimurCivan]

I think a good friend is buying one. im looking forward to using his.....

 

[Lenilenapi]

No nitpicking, you were right to clarify it. Thanks

- Lenny

 

[Dennis Wood]

Your observations are correct regarding the CF1/L CF2/L and CF3/L. Although physics dictates circles of confusion and DOF, it's true that every adapter is a diffusive/transmissive device, and this changes things. We have invested heavily in R&D so that Brevis users can achieve full frame performance with virtually any lens/camera application and then choose/quickly interchange the imaging element that makes most sense for their applicaton.

For a shooter with fast lenses, and a lighting kit, looking for max shallow DOF, we have CF3/L. Richard Darge posted "Symphony", an ad done with an HVX/CF3/L. Alternatively, for someone looking for max sharpness shooting at f5.6 we have CF1/L with has incredible light efficiency, and a wider usable aperture range than CF3/L. The important thing is that like film stock, you have a choice which will depend on light, look, and lens choice.

A critical issue that is never discussed is simply how adapters work with the myriad of choices out there for cameras. Look at the optical path on the little HV20 with 1 CMOS sensor, then look at the comparitive path of the HVX with a large lens, and trichroic prism array splitting off light to 3 CCDs. This consideration is built into every unit we sell, and it's why it works as well as it does.