I'm building home made mini-35 Relay Lens, XL1S + Relay lens?
 

I'm considering building a mini35 "dof machine" for my XL1s but I don't like the idea of stacking lenses. I've heard that I could mount the mini-35 adaptor if I use a relay lens. But what is it and what does it do? Where could I get one? does anyone have expirience with this setup? help would be grrrreat!! Thanks, Dave

Buy a Letus relay setup. There's your solution :)

Why buy when he can make it, before you encourage sales, remember this is a diy community. I do not know myself exactly how to caculate the placement of lenses to allow the 35mm frame to fill the ccd frame but i do know that you can use c-mount lenses. which are pretty cheap and come in a variety of focal lengths. you just have to find the correct placement infront of you xl1s sensor, and then build a housing for it to keep it at that distance

Is it possible to use the P+S technik relay lens with say a letus adapter or a DIY adapter.

I have an HD100, and attaching an adapter onto the stock lens results in a ludicrous length. I am curious if this or any other set up is possible.

The relay for a P+S is a few hundred bucks, whereas the adapter is like 7000...

Also, what about the ZOERK adapters? I know they make something whereby you can mount an SLR lens directly to the body - this doesn't achieve the characteristics of a regular SLR lens though - but could this be used as a relay for something like a letus or a DIY?


Anyone?

David,

The relay is any lens that focuses the image projected from the ground glass into the cameras CCDs. This could be a lens specifically designed as a relay, or it could be any 35mm still lens... or some other variant. The point is, if it focuses the GG onto the CCDs, it's a relay lens.

So, how do you go about making one?

The simplest, easiest, cheapest way (I believe) is as follows.

Use a 28mm lens (for a 35mm still camera). An old Canon FD lens, or any other decent fast lens you can get on ebay will do.

The lens must be positioned about 16mm in front of the XL lens mount on a camera, and the ground glass must be positioned about 19.5 cm in front of that lens. This will resolve a frame slightly smaller than 35mm (to help with vignetting). We were talking about this in another posting recently, but if you multiply the relay lens focal length by the desired magnification (7.2x for the XL1), you have the distance between the GG and the relay. For example, 28mm x 7.2 = 201.6. That's 201.6mm between the GG and relay to for a 35mm frame.

The cheapest and easiest way to attach the relay lens to the XL camera is to epoxy or bolt a body lens cap for the XL camera to a back lens cap for your relay lens at with the appropriate spacing, and drill a large enough hole through them both for the image to get through.

You'll notice that 20.16 cm spacing isn't an improvement in size over the 16x stock lens that comes on the XL1. The way relay lens setups usually get around this is by having an image flipper built into the adapter. Besides the advantage of in-adapter flipping, the verticle and lateral space between the mirrors (space that doesn't contribute to the adapters length) eats up the 20cm spacing. Alternativey, you could design your own relay lens from scratch, or use a shorter focal length lens. If you use a shorter focal length lens than 28mm, you have to start worrying about barrell distortion.

If you can afford it, the new Letus IS an amazing adapter... but I'm a do-it-yourselfer as well, and there's no reason to sell your self short. If you think you can do it, you can make as good an adapter as anyone, for potetnially a lot less money. And once you've made the first one and have an established design, the second and third etc are worlds easier.

I'd also like to point out that a lot of people feel that a built-in image flipper is a bad thing as it introduces light loss and potential quality loss, but the light loss of good mirrors isn't even noticeable, and as long as you keep them clean, quality shouldn't be an issue either.

Just look at the new Letus footage, and tell me an image flipper is a bad thing.

If you want more specifics on any of this stuff (like image flipping), just shoot me an email.

The problem with lens adapters like that is that they have the proper flange focal distance. That might sound a little silly, but to be able to focus on a 35mm frame close enough to the camera for it to be worth while, the relay lens has to sit farther in front of the camera than the published flange focal distance for that lens. Basically, with an adapter like that, you wouldn't be able to scale and focus a 35mm frame in a 35mm adapter.

David, after You read Justins last post(thanks Justin, it was very clarifiyng - makes me think again about dvinfo's - wiki). You may have a look Quyen Le's lens distances and overall the thread. This touches very much the subject at the end.

I was recently wondering the same thing, (as justin will attest to) and came to the realization that it can't be done unless the Adapter has an image flipping system. Sad, no?

For the record the P+S relay lens doesn't cost a few hundred bucks. Try a few thousands. Second, I don't think it will work with the Letus or any other adapter because it's made to work at the distances that the mini35's prisms are set at.

I'm talking about the P+S technik relay lens, which has a MSRP of 2500, which is 25 hundred... so that's sorta a couple hundred... really... if you think about it... in a certain... sense.

But hold on now... the actual P+S adapter is 7000, and that's only like... a couple hundred too. Holy shite, it's only...

...numerator goes here, then I...

...round to the nearest tenth and...

...carry the 7...

...do something with pi...

70 hundred! Problem solved.

Actually, if I think about it, it's a couple thousand.

I talked it over with my wallet. Definately thousands.