Canon XL-1 Relaylens (original, now merged w/ consolidated XL1 thread) at DVinfo.net

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Old March 21st, 2004, 01:08 PM   #1
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Canon XL-1 Relaylens for use with the 35mm adaptors

I really want to get started with building a 35 mm adaptor. But I have the canon XL-1 and I believe that using another lens than the original one would be the way to go. Both considering the cameras length and quality of image. It would be really nice with a relaylens which is made for the focusdistance to the GG.

Have anyone found a relaylens that works? - or a better solution??

Thanks
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Old March 21st, 2004, 03:41 PM   #2
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Hello Anders

I guess what you need is a macro lens which can focus on a ground glass

try this

Optex UK make a Nikon lens mount adapter (LMNIKXLC) to which you cound attach a 55mm Nikkor Macro lens plus maybe an extension tube (say PK13) so that the image size is about right

that should do it
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Old March 21st, 2004, 04:39 PM   #3
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Hey John - thanks for the quick reply.

I actually got a Canon-EF adaptor with the camera when I bought it. But it has the 7x magnification . Do you think it would work anyway?
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Old March 21st, 2004, 04:44 PM   #4
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If anything that 7X will work to your advantage. Remember you need to be able to focus on a section of ground glass measuring at the most 36mm X 24mm.

-Brett Erskine
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Old March 21st, 2004, 08:15 PM   #5
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There is no 7x magnification in the Canon adapter.

There is also no lens in the Canon adapter.

The Canon adapter lets you put Canon still lenses on your XL1. The idea of the 7x magnification comes from the fact that the 35mm still-camera frame is about 7x as large as the 1/3" CCD's in the XL1... or, in other words, you'll see 1/7 of the full frame. So the "equivalent" focal length of mounting the Canon lens on your XL1 would be like as if it was 7x as long... i.e., a 100mm lens, when mounted on the XL1, will provide a field of view equivalent to a 720mm lens on the 35mm camera.

But there's no magnification going on. It's just seeing a smaller window through the lens.

A 24mm still-camera lens, for example, when mounted on the XL1 using the Canon adapter, will give you the exact same field of view (and depth of field) as if you just put the Canon 16x zoom lens on, and zoomed it to 24mm.

Now, back to the original question: yes, you want and need a relay lens. That's the way P+S Technik designed the mini35, and it's the best way to go for what you're talking about. A dedicated optic that closely focuses the 24x18mm frame will give you the best results.
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Old March 21st, 2004, 08:32 PM   #6
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I have the Canon EF XL adapter and it does indeed have optical elements. The adapter does impose a 7x image size change and it may impact your DOF. If I want my subjects head to be the same size I will need to be further from my subject, and that will effect DOF.
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Old March 22nd, 2004, 11:41 AM   #7
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Fascinating -- I should have said "I don't think the EF adapter has a lens..." Sorry for the mistake.

But: I still question the idea of 7.2x magnification being a property of the adapter. If you use equal zoom length on your stock lens, or on your still-camera lens, the field of view and distance to subject should be the same. A 50mm lens is a 50mm lens, regardless of whether it originates on a still camera or a video camera.

Your point about matching subject size is perfectly valid as to why it would affect DOF, IF you're trying to match subject size between a still camera and a video camera. The still camera has a much wider field of view, and needs correspondingly more telephoto optics to provide a similar field of view.

What I'm saying is, does the adapter have any effect on the still lens itself? I don't believe it does... but nothing beats verifiable testing...

Let's take the longest end of the lens as an example. The 16x maxxes out at 88mm, so an XL1 at max zoom, or an XL1 with the EF adapter and a 90mm lens, should deliver the same field of view, the same subject size, and the same depth of field. Do you have an 85mm or 90mm lens that you could test that supposition out with?

Thanks!
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Old March 22nd, 2004, 02:21 PM   #8
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I've bought an F2 24mm SLR lens for use in the adaptor I'm developing, distance from the front element to the 36x24mm image is around 14cm, I'm hoping this is more than workable (prism and mirror should cut down the physical size).

If you've got the money, try finding a 20mm F2 SLR lens. Fully wide-open these fast ultra-wide angles will be a bit soft, but the more stops of light you can salvage the better considering the nature of these adaptors.
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Old March 22nd, 2004, 07:58 PM   #9
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the relay lens

the is the toughest part to figure out for the xl1s. and this is the reason, any of your lenses you use goes through what is called as the multipler effect. That is it icreases the lens properties to somewhere around 1.5-1.7 roughy. so say you, take off your factory lens (16x or 14x) put on canon xl1 mount to, say a nikon fitting (going nikon is the cheaper route like $180USD right now at Les in the UK). so you get a fast cheap 55mm lens that opens up fast (f2), when you put it on your camera it will act like an 80mm lens-this focuses in much to far on your ground glass. so what you want to get for your relay lens is get the widest and fastests you can afford. like a 24mm f2.8, when this is put on it acts more like a 35mm because of the magnifyer effect. you will also want to try and get one that can fit a 52mm lens filter. as you will see how useful it becomes later as a connector to the rest of the unit.

the ideal meduim you'll be housing will be 2inch diameter pvc connectors, they fit 52mm filters amazingly well and centered.
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Old March 22nd, 2004, 08:11 PM   #10
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oh and...

for the magnification at say, 24mm, you only need +3
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Old March 22nd, 2004, 09:13 PM   #11
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Dino has been working on an XL1 solution for a while now but hopefully those of us with them can put our heads together with the rest of the folks here and come up with a less expensive option.
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Old March 22nd, 2004, 09:17 PM   #12
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Barry, the magnification comes from the size difference between 35mm film and 1/3 inch CCD. the difference as measured horizontally is 7.2X. Why does this change DOF? Think of the lens as projecting a circle of light on to the CCD or 35mm film. The circle has excess coverage when the CCD is placed in it's path. Compared to 35mm film, the CCD only sees the very center of the circle. When the image (either captured on film or electronically) is enlarged to a fixed size (TV monitor or print) The smaller format will show a higher degree of magnification. Why? Remember the smaller format only captured the center portion and when enlarged to fixed size the center portion is enlarged a higher percentage to fill the fixed size (size of screen etc.). In the case of the Canon XL1 with the EF Adapter, the degree of enlargement is about 7.2X This is a problem when you try to fit a subjects head into the fixed size. You end up having to back up to get all the subject in the frame.
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Old March 22nd, 2004, 10:39 PM   #13
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this one is pretty close to accurate

as far as how mine is built, although i have an extra filter protecting my gg, and i'm not using a pl mount (nikon still), but it's adjustable from the relay to the achromat and from the gg to the prime lens... i've got a holographic diffuser model i'm working on next. the quality is already pretty damn amazing, esp. in low light, i just picked up a fast 17mm i want to try as my prime lens and see the results, but here are schematics i've kindof updated...

http://www.dinoreyes.com/images/xl1_deluxe_aldu35_new.jpg

the most expensive are the two lenses then the canon lens mounts that attach, everything else can be bought for less than $175 and put together with very accurate but not extensive cutting then cementing and painting...
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Old March 23rd, 2004, 02:26 AM   #14
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Design

I noticed that you have, what you call a "achromat" behind your GG where most people are using condenser(s) (also known as a plano-convex lens - PCX). Would you please decribe the shape of the glass your using. Is it flat on one side and curved on the other? Or is it curved on both sides (at equal ammounts)? Thanks. Nice looking diagrams by the way. May I recommend you add a plain UV filter between the PL mount and the adjustable focal length tube. The reason being is it will keep dust and hairs from coming in contact with your GG and ruining your shots. Of coarse there are many other changes if you want to add EXTRA features like tilt/shift and anamorphic glass but as a "base model" it is a very accurate representation of the design I've been describing in words on this thread.
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Old March 23rd, 2004, 01:30 PM   #15
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even more accurate image

this is closer to what i've made

http://www.dinoreyes.com/images/lens_xl1_v4.jpg

what i am using instead of a condensor lens is an acromatic diopter (50.8mm), it originally came from newport optical? reg. like $140, but i got it off ebay for $40 new. condensors lenses (also, i believe called singlets/simple lenses below) are around $30

go to this article:

http://www.edmundoptics.com/TechSupport/DisplayArticle.cfm?articleid=267

now read Application Primer #5 at the VERY bottom....

What is an Achromat?
An achromatic lens consists of two optical components cemented together, usually a positive low-index (crown) element and a negative high-index (flint) element. The additional design freedom provided by using doublets allows for further optimization of performance not possible with singlets. Therefore, achromats will have noticeable advantages over simple lenses

Achromats have better accuracy and color correction but the are more expensive. But for sizing make sure for either condesor lens or achromat get a 50.8mm. Find also, an extra 52mm filter with the glass broken or popped out, they are good frames to hold these lenses in. It is flat on one side and slightly curved on the other

As you notice Brett, i also got the UV filter to protect the gg as you had previously suggested...

-d
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