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Old January 13th, 2005, 07:47 AM   #16
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Bob, couldn't you just duplicate the footage on the timeline then from a single camera for the same effect?
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Old January 13th, 2005, 07:47 AM   #17
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I made a quick drawing with the setup from te top view:

http://s01.picshome.com/52a/double35mmadapter.jpg



http://s01.picshome.com/52a/double35mmadapter.jpg
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Old January 13th, 2005, 01:13 PM   #18
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Bob Hart wrote-
"In the same way you get a seemingly better resolution if you blend or layer four or five frames of standard DV, would not two cams framed on the same actual image through a splitter prism achieve something similar, though probably not to same degree as a joined frame?"


Yes this will increase your resolution. In fact I've heard of software that does just that. People sometimes use it to make higher quality photo prints from the combined resolutions of a short series of images from a video camera that are extremely SIMILAR. So yes this works sometimes BUT my point was that we loose all of are efforts and are back to standard definition when we finish the project to DVD because of DVD's current limitations on resolution.

Now if your shooting 60i you might be able to make some form of 30P from Oscar's device when you make the final DVD BUT once again you can NOT make it higher resolution than that and 60P isnt possible either when it comes time to make the DVD. Basically I believe you will only see your efforts on your computer or some HD format tape.


Aaron wrote-
"Bob, couldn't you just duplicate the footage on the timeline then from a single camera for the same effect?"



That will give you a higher pixel count but not higher resolution/clarity because your not giving the image any NEW data to make up its total image - just more of the same. Having a HD camera or two different cameras making up a larger image introduces both more pixels and new/different ones.
Hope I made sense.

What do you think of the 3DVX rig. I know I want one.
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Old January 13th, 2005, 04:18 PM   #19
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DVD, Standard TV comment...

I DON'T think you lose "all" of the benefits of the two camera recording system when it is compressed to standard size for DVD on a television. My understanding is that starting with more pixels equals high resolution and more color space. Compression of sorts is part of every form of presented video, whether its for a dvd, cable tv, or a streaming video. Without going into a technical discussion, my thought is that to get your best "looking" final result, you need to start with the highest resolution and colorspace you can achieve. Consider a cool car commerical that you can stream from the companies website, they no doubt used the highest resolution (maybe film) they could afford to shoot the content, even though it would would be presented on tv and even more compressed on the web. I think the two camera concept has merit even if its for dvd.
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Old January 13th, 2005, 06:05 PM   #20
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I didnít want to start a tread on DVD quality. Anyway, if you double the resolution, the video noise is two times less (or smaller, really) and the detail is twice as high. And that would also remain in DVD.

The system I'm currently building is possibly just good enough for a transfer to 35mm film. Thatís just a dream for me of course, but still, that's also the thing I would like peopleís opinion on. What resolution and quality would be a minimum for a transfer.

Note that I have two 'consumer' camera's. Not HDV or anything.
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Old January 13th, 2005, 07:34 PM   #21
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Ocar,

a 1040X720 image is pretty close to a 4X3 aspect ratio. Your frame looks 16X9. Did you letterbox the image for the widescreen look, if so, your losing about 20% of you vertical resolution and colorspace, leaving you with 1040X580. Another question is how are determining that two consumer camera's turned on there side will add up to 1040X720? I guess that would mean each camera had an effective 720X520 lines of resolution. I dont think consumer camera's have nearly that high of
"effective" horizontal or vertical lines of resolution. Anyone else know more about this?
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Old January 14th, 2005, 01:47 AM   #22
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Donnie-
Take another look at all of my post and you will see that we agree. Look what I said about film, compression (and its relationship with color space). My argument is simple. When all things are the same EXCEPT resolution (as is the case here) you will loose that extra resolution when you down res it to DVD. Film is different. Take a look at my links. It proves this is true for video (when compression, color space, latitude etc are the same but one is HD and one is SD). This isnt true for film that has been telecined to video. 35mm will looks sharper than 16mm even though 16mm has much more relative resolution than a TV can show. So when it comes to the basic concept of starting with a higher res format than the ultimate format - Video and Film just arent the same and dont follow the same rule. Pixels vs. organic shapped images.

Anyways none of this matters if your not making DVD's out of your work and instead plan on doing a film out. For a film out your definately going to see a HUGE improvement if you use twice the resolution than SD (two cameras). As to what resolution do you need for a quality film out...? Well when they do a digital intermediate of a 35mm print they say that scanning it at 2K is pretty damn good but at 4K you have a "perfect" digital copy of a 35mm print. But in reality how many people shooting DV end up doing a film out...seriously. If its extremely unlikely then making something like this 2 camera rig wont be of much benefit. Thats why I brought up the whole DVD thing in the first place - save you alot of headaches, money and time. But dont just take my word for it. Look at the link I posted and read up. Also run a test yourself. Remember to look at the final DVD NOT the combined image on a PC. Let us know.
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Old January 14th, 2005, 06:32 AM   #23
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The test image I posted is a quick test, so I squeezed it a bit to get the idea of the final aspect ratio. I don't know how I will do this for real, I made a very big anamorphic lens some time ago, it works very well, but not when light hits the glass. I'm also thinking about a smaller anamorphic lens inside the camera, between the GG and 35mm lens. But I don't know if that's possible. Another way would be to put the cameras not on their sides, but that would give a very widescreen 1400 X 576 pixels.

I would like to end the discussion about resolution and DVD, maybe it's mathematically correct, but it's also about what you compress, DV has a lot of artefacts like staircase on edges and ugly color noise.
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Old January 14th, 2005, 02:21 PM   #24
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Sure thing. So to answer your question about rear lens mounted anamorphics - yes they exist. They are somewhat of a rare thing these days. They used to be more popular because they could create a unique effect. They often could be rotated behind the lens while shooting to create a "drunk" or "dazed" pov shot. When you dont rotate them they act like a traditional anamorphic lens but mounted in the back like you want. I dont know for sure what they are using for elements but my guess is a achromat cylindrical lens. But using a film anamorphic lens will give you a 2.66 image in the end due to videos CCD aspect ratio being different than a anamorhic film print. Im not sure if you want a traditional 2.35 image in the end. If you do then for video your going to have to have a anamorphic lens that squeezes the image by 1.78X in order to end up with a squeezed 2.35 image on the CCDs. Good luck with your project.
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Old January 14th, 2005, 02:29 PM   #25
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Brett's right if you use a premade rear anamorphic. You should be able to set this compression yourself though if you build your own system. The compression depends on both the 35mm lens, the cylinder lens, the distance between the two and the focal length.
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Old January 14th, 2005, 04:59 PM   #26
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So, everything changes if you put another 35mm lens (like a zoom or wide angle) in front of the rear anamorphic lens?
That would be bad, because I like the 35mm adapter to use different lenses.
Thanks for the replies. Some time ago I made a (two triangle) water prism as anamorphic lens, but those would be way too big for a rear lens.

Isn't it possible to make from a lens protection glass (or UV) with curved sides and glue a piece of acrylglass curved on top and fill that with water or transparent oil. Or is another lens needed besides one curved.
These are just my stupid thoughts.

I've made a firm construction today with a lens-mount and plate to put the cameras on. I'm testing a GG: a CD dipped in an oil that attacks the plastic. One side protected with tape.
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Old January 14th, 2005, 05:21 PM   #27
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Sorry, I wasn't very specific. You should be able to use any 35mm lens without trouble if you were to build such an adapter.

It depends on you using 35mm lenses that is to say. Using a 16mm cine lens for instance will give a different result. Now if we were to use an anamorphic adapter which went in front of the 35mm lens then we would have to focus both the adapter and the anamorphic lens for any given focal length - in both the horizontal and vertical planes. Since we are talking about a rear system (called in its simplest form a bravais system) this is not a problem.

Now all a bravais system does in increase the image size while maintaining the images position. In our case with cylinder lenses this gives an anamorphic image (expansion in one plane). You can either compress the image horizontally or you can expand the image vertically. With the compression technique you end up with an even smaller image area than a normal 35mm on its own would give. This is bad for our purposes. The expansion would give a larger area in the vertical direction. Not very useful but it allows us to retain our 35mm image area on the GG at the cost of a little bit of light.
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Old January 15th, 2005, 06:53 AM   #28
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I recently read somewhere, that Canon may have an anamorphic product which goes between the front lens and the CCD. I can't recall where now unfortunately.
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Old January 15th, 2005, 01:20 PM   #29
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Besides possible visible seams due to the lens distortion on the edges of the frame, color difference etc, there's one big problem with this concept:

Synchronisation of the left half and right half of the image. Of course you can line up the shots in your compositing app, but since the clocks of both camera's aren't genlocked, there can be 1/60th or 1/50th of a second timedifference between the left half of the image and the right half of the image.

No problem with static shots, but if there's fast moving objects across the frame, or even worse: camera movement, you'll get very visible seams where you stitch together the images.

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Old January 15th, 2005, 03:15 PM   #30
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Possibly, but I'm not so sure, because the difference may not come up in regular times of a take. You don't show one camera position for two minutes mostly.
And if Barend means the time difference also mentioned by Matt, I'm sure this (less than a 30th of a second) difference can be dealt with in after effects or whatever.

I have a setup with GG and lens, so maybe tomorrow I can make some tests with two cameras.
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