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Old March 23rd, 2006, 10:05 PM   #16
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I'm pretty sure Jamey has this on his mental plate. There has been much talk of it on the Redrock forums.
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Old March 25th, 2006, 07:04 AM   #17
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Yes, I would love a redrock XL relay lens provided it reamined relativly cheap. I think the usability of the rig (Expecially the XL2 comapred to the JVC or any other cam cause the XL lens is humungous) would be vastly improved with a much shorter relay lens. Provided it has an iris and ND filter, it should be good!

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Old March 27th, 2006, 09:23 AM   #18
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Has anyone tried using a Nikon marco lens as a relay lens? I'm new to this forum, but it seems like many folks would like a shorter lens to use as a relay lens with the xl1/2. For example, a 55mm nikon macro is designed for close focus (such as the distance of the ground glass on the Mini35) and it has an adjustable aperture, but I don't know if it is otherwise suitable. These lenses are high in quality and readily available.
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Old March 27th, 2006, 09:28 AM   #19
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a macro lens would have no focusing abilities or iris control. It couldnt do the job of a relay
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Old July 7th, 2006, 02:55 PM   #20
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M2 + XL2 sample footage (wide angle)

Hi Matt - I just found this thread and was wondering if you had any sample footage taken with your XL2 using the M2. How are you liking the results. I am looking for a wide angle alternative to the Canon 3X lens. How do your wide angle shots with the M2 look?
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Old July 7th, 2006, 08:57 PM   #21
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Andrew: Macro

What we commonly call "macro" lenses are often close-focus diopters which don't, infact, have focusing abilities or iris control. However, what Craig was suggesting, I believe, was that we might use Nikon (or Canon, Pentax, etc.) lenses designed specifically for macro work (there are several extremely good ones out there, and all but one have both iris-control and focus, one has a fixed 0.95 iris, I believe).

The thing that I can't answer for him is how much space it takes to get from a Nikon mount to an XL Mount (1/3") and how that would affect backfocus-- whether this is a usable solution or not. As I recall there was a company that strictly made XL to film-style adapters (before the rage of the DOF adapters). They may have a second life, as a relay lens adapter source.

-Jack
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Old July 8th, 2006, 08:26 AM   #22
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I was considering this, but I am having some trouble getting things together.

My biggest problem is focal length. Can anyone guess what focal length in MM, multiplied by 7.6, would give a frame size of 36x24 mm? Once that can be established, I will rent the appropriate Canon EF lens and EF adapter to check it out and post my findings here. If it works out, I will conduct the same experiments with a Nikon SLR lens and Nikon to XL adapter.
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Old July 10th, 2006, 05:29 PM   #23
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Update:

I am finding it difficult to find an EF adapter for sale. If anyone has one and can do the tests, that would be awsome.

Thanks.
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Old July 11th, 2006, 11:11 AM   #24
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I'm absolutely wild-wild guessing here so ignore please.

A 28mm focal length lens, set about 5mm - 8mm forward of its normal mounting flange. Groundglass about 180mm - 200mm from lens. Might get you close to a 35mm x 24mm frame, might be a bit tighter.

Repeating above. Ignore. Don't go out buying in lenses on my say so.
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Old July 11th, 2006, 12:20 PM   #25
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I think the way to do it is figure out what percentage of full zoom must the 20X be on to facilitate a 36x24 frame? As chris hurd points out in his artilce on the watch dog, at full zoom, in 16:9 mode, the XL2 20X IS lens has a 35mm equivelent of 846mm (it's a 108mm lens in 35mm terms, multiplied by 7.6 to compensate for the 1/3" CCD). So... When I set the Zoom on my lens to match the M2, it is usually at about "12". (If you dont know what I am tlkaing about, zoom your 20X in, click on "position preset" and then select zoom and set it. You should see a number near the Zoom indicator...)


Now, whatever, this arbitrary number means, it seems that "12" is almost fully zoomed in. I would say fully zoomed is probably "15"?

Okay... so, lets divide 846mm by 15... then multiply it by 12, so we can see what 12/15th's of 846 is.
I get 676.8mm... now, let's divide that by 7.6 (For the chip size)... I get 89.05. Therefore, the closest prime lens capable of getting around 36" by 24" would be an 85mm lens. Your image might be zoomed out a tad.

Someone check my math...

Thanks
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Old July 11th, 2006, 04:25 PM   #26
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To get full 24x36 frame, you would need to do some calculation. I believe it's 7.2x not 7.6x.
whatever your SLR lens is, multiply the focal length by 7.2x and you will find the distance between the center of the lens and GG. For example, the 50mm lens will need 360mm distance. 28mm will need 201mm distance. If you use 85mm lens, it's 612mm.If you don't mind the distortions of the 24mm or 28mm, they are the best for your need. In fact
24mm lens need 195mm
28mm lens need 229mm
50mm lens need 400mm
85mm lens need 697mm
Hope this info helps.

Quyen
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Old July 11th, 2006, 10:18 PM   #27
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Queyen,

Seening as how you have built relay lenses... can this not be shortened using an Achromat lens? Also... what is, technically, the focal length of your lenses?

So, a 28mm wold work, but the GG would have to be exactly 22.9 CM away?

Doesnt seem like much of a savings on space! How does the Relay in your set up manage to be so short?
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Old July 16th, 2006, 01:00 AM   #28
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I can't speak for Quyen, but with the adapter I'm finishing I found that the space is eatan up after the light makes it through the flipper mirrors. For this reason, I think making an adapter without image flipping could wind up being more complicated if a relay is to be used.
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Old July 16th, 2006, 07:54 AM   #29
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If you operate in defiance of the original designed geometry of the lens, move it forward of the focal plane, the position of the object can be brought closer to the front of the lens to restore sharp focus. This could mess some other things up.

To experiment, I drew a target the size of the pixel area of a 1/3" CCD upon a damaged groundglass. (However, there is such a thing as "effective" pixel area so all my assumptions are now wrong.)

I then cut a 24mm x 18mm hole out of a piece of Weetie packet. I positioned this against a smooth background light source then adjusted distances between the Weetie panel, my selected lenses and the groundglass until I was able to frame the hole sharply in the 1/3" rectangle.

There are other complications relating to video camera like "on-chip" lenses which make my assumptions invalid. Beyond casual playing around with things by hand I did not set up a proper experiment.
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Old July 16th, 2006, 02:21 PM   #30
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Sorry, bob. Not following you... I am not well versed in the world of lenses and optics, so I need a hand understanding this.

1: A 36mm X 24mm image is projected onto the GG.
2: The GG now becomes the focal plane.
3: An XL2 lens, zoomed through an Achromat, reads the 36mm by 24mm image, and relays it to the 1/3" (8.3333_mm) chip (albeit upside down)
4: This is a function of how far the lens is Zoomed in.
5: Could and SLR lens, attached to the camcorder body, with a proper focal length (when multiplied by 7.6) not give you exactly the same image? (A macro lens could focus close enough, no?)

Please explain!
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