35mm optical adapter (No GG)

Super8 said:
Dan:

I did get DOF...if i had to rate the different DOF's I was getting (and I did the comparisons) with 10 stars being the best and 1 star being the crappiest DOF I would say:

Adapter with GG = 10 stars for DOF
Adapter with no GG = 6 stars for DOF
Stock Lens = 1 Star for DOF
Click to expand...

When you compared the stock lens to your adapter with no GG did you make certain the stock lens was at an equivalent focal length and field of view?
If so - you shouldn't see any difference in the DOF.
 
i brought this up months ago over at dvinfo and here about the GGless solution which i came across with i just attached a lens onto the front of my camera with a achromat.

http://www.dvxuser.com/V6/showthread.php?t=110687

the thread is there with a video you can check out. there's also an optical taper but i can't find the link he provided. the thread is over here

http://dvinfo.net/conf/showthread.php?t=87243&page=2

you quickly find out the dof is there, but on medium close ups which is still nice considering no grain. the bokeh isn't as good as you want it to be or could be with a 35mm adapter.



edit: it only had a link to one of the videos. the first link is my fav of the 2
right click and save as for these please:

http://www.fileden.com/files/2007/1/8/612706/Optical%20Video1.mov
http://www.fileden.com/files/2007/1/8/612706/Optical2.mov
 
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I've been thinking about this some more... I don't have an adapter to mess with so I can't really even try this but, I wonder what would happen if you switched the GG for just plain old NON ground glass.

It might not do a single thing, but you never know till you try it right?
 
"Estimated cost of Zacuto DOF system: $12-$15K including 4 Zeiss prime lenses (25, 35, 50 & 85mm), 4 Zacuto Zip gears, 4 Zacuto ZLA's (20, 35,50 & 85mm), 1 Zacuto ZCA (pick camera), 1 Zacuto Lens Support (ZLS), 1 set of 10" rod extensions, Zacuto custom cut foam insert & case. In development."

Just keep saving up for that Red One.....
 
I messed with this a while ago when the motor died on my Letus Flip. I thought it was doing something but I got a new motor and forgot about it. Today I pulled the GG again and tested it with a FD 50 1.4 and 28 2.8 and the DOF is less than the GG but still better than the HVX alone. With the plus of no grain at all and the fact that I try to avoid extreme DOF other than FX shots, this might be the way to go. I'll get outside tomorrow and shoot some more. It looks really good in the basement with 2k of light. Seems too simple, am I missing something? I've spend 100's of hours looking at plastics for a static adapter (movie tube) but this seems promising.

I hope there is no math in this class.
 
cardmaverick said:
Just out of curiosity, why are you using the term stop in your explanation. Do you simply mean doubling of sensor size or something to that effect? Sorry, I just don't hear that term outside of the exposure world very often.

Thanks
Click to expand...

I was using the term 'stop' in reference to use in the equations for DOF calculations. For example, a lens set at F4 on a 2/3" camera has a certain DOF. If you have a 1/3" camera and you use a lens that gives the same FOV, then the DOF will be the same as the 2/3" at about F2.4 (2.5 stops open from F4).

To clarify a little more on the No-GG adapters, think of them as a "black box" system. Say for example you put a 20mm lens from a 16mm film camera on the JVC device, set at F2.8. According to the specs, on your 1/3" camera, you see the same FOV that you would see on the 16mm camera, and you have the same DOF as the 16mm camera with that lens.

If that is true (and I'm sure it is, or reasonably close), then you can work backwards from the FOV and DOF and establish exactly what is going on. If the FOV is the same on the 1/3" camera as it was on the 16mm camera, that DEFINES the effective focal length of the black box. In this example, the focal length of the black box is 20/2.5 = 8mm. That is an absolute--it is a function of the imager size and FOV--you can't change it. Now, for this 8mm black box to have the same DOF as the original 20mm lens, the f-number of the SYSTEM has to be 2.5 STOPs wider than the original f-stop, in this case F1.0.

I think maybe that's why no one goes beyond a 2.5 stop conversion, because the limit of any system may well be F1.0. If that's true, then the maximum usable aperture for a 35mm cine to 1/3" camera would be F4.6, which would not be very helpful to achieve shallow DOF.

Regarding "apparent" shallow DOF without GG, careful testing will reveal what we already know from the laws of optics--unless the overall F-number of the system is decreasing as with the JVC and Angenieux, you don't get shallower DOF.
 
kplo said:
Brett,
If you're simply rephotographing a projected image, whether it's on ground glass, the wall, or existing in an aerial plane of 35mm film size, the DOF effect of the 35mm lens will be recorded.
Ken
Click to expand...


I think what the posters on this thread are missing is the overall purpose of the ground glass: to collapse the many vectors of photons onto a single focal plane.

If you envision the light vectors that go through the center of a lens they tend to be very straight through the lens. If you envision the vector through the edge of a lens the glass does a good bit of bending to get the vector to strike the focal plane in the right place. There are some errors in this bending that can limit the depth of focus, causing bokeh. The more you open the iris the more edge glass you use, the more bending errors are introduced, the more bokeh you get. But until you introduce a focus plane to collapse the vectors to a plane, you are dealing with VECTORS.

The question becomes: what happens to a *desired errant vector* (a photon that adds to bokeh) that is sent through a second lens before being collapsed onto an imager? From the JVC review it would seem that these vectors are further bent (or even refracted away) by the camera's lens to the point of missing the imager entirely. If this were not true than opening the iris on the mounted lens would create a softness on the entire image.

Ground glass lens adapters are a stopgap technology that will be around until larger imager-ed cameras with lens mounts (like the Red One) become more affordable. I am very curious to see what Canon brings out next in its XL line as they have a lens adapter for their SLR lenses that adapts the EOS to the XL mount, replacing the delivered lens.

As far as removing grain, why would you want to? We have been viewing film for 80 years now and grain has always been present. When using the HVX, my personal obsession is reducing noise (color and luma errors) because I know my Micro35 will bring a certain amount of grain (luma deltas) to the image. If I *swing for the fences* in making a feature length film that does not make it to theaters but does make it to DVD retail and rental, I don't want to have to pay to scan in my film print when my computer can output the proper format, complete with film grain a-la Micro35...

Bob
 
oh well, tried some more and then put a GG in half the image and you really do need the gg. there is some increase in DOF but the comparison between GG and no GG is huge.
oh well now for my hangover.
 
Bob Gruen said:
As far as removing grain, why would you want to? We have been viewing film for 80 years now and grain has always been present.
Bob
Click to expand...

I should be more clear, its both the grain and the sharpness of the image. Projecting onto a GG will always soften the image. You are essentially shooting threw a promist filter really, and I just don't want my image to constantly look soft focus. As for grain, my camera (Andromeda) producers a very very tight low noise (some would say grain free) image, and I want to keep it that way.
 
Grain will go the way of the Dodo.

When the average person has 60"1080 120p+ monitors at home (probably within the next 5 years) they will indeed be turned off by the grain. They will be use to Discovery HD et al.
 
Does anyone know what would or could happen if you tried making an all optical adapter using MEDIUM format lenses instead? Or does it not make any difference?
 
This portion of a chart test didnt come from a straight optical but from a gg based adapter. The gg image size were bigger on the mid format at 42mm x24mm compared to the 35mm lens at 29.6mm x 16.6mm.

My point in the test was to campare grain.

I found the difference minimal. I dont know if this would still be the case in a straight optical path.


Ted


1199258371.jpg
 
The medium format looks much more sharp. Are you sure the FOV is correct? Thats one thing I don't like about these adapter tests... how far should you really be zooming in on the ground glass? Anyhow, I'm sure this affects every adapter test out there in some way or another.
 
I try to capture as much FOV as i could based on the original film image from each lens category, 6 x 4.5cm for the mid format and 36 x 24mm for 35mm. But doing so produces light falloff and corner softness. This is the case with an image travelling from still cam lens to GG to achromat then to cam lens.


The zoom recommended in most adapters is even slightly smaller in image width than what i did. for the 35mm gg image, its wider than the crop factor of a digital SLR. The benefit of the med format is outweight by flexibility and economy.
If grain is compared, at first I was expecting a dramatic difference. But it wasnt the case in my tests.

But then again its an observation based on GG based adapter's image. I dont know about the straight optical path proposition, I read somewhere here that the attached still lenses, wether 35mm or others lose there DOF and the FOV is smaller without GG but it must be clearer and cleaner.

Ted
 
Hoy! Pare!

Kumasta ka na Ted!

Paumahin na ako ay huli sa ibang sinulid.


Your grab from the adapters look nice.

I hope we can get some footage of some of your comparison shots!
 
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