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

[Adam Bowman]

Dino,

As has been stated in this thread and all over the forums, the CCD sees 7.2x less than a 35mm SLR camera does through the SLR Lens. So a 55mm lens on the XL1 will give the same FOV as 400mm lens on an SLR and a 24mm lens on an XL1 will give 170mm equivalent.

Where exactly are you getting this 1.7-2x multiplier effect number from?

[Dino Reyes]

here be a brief description...
http://www.lonestardigital.com/multipler.htm

and, sadly, a partial article here...
http://www.digitaldingus.com/articles/fov/fov.html

but surely a 24mm to 170mm is a sea of difference
making my aldu35 impossible for use, but it seems
to work well!

7.2x seems rather extreme, but the EF adapter does
come with a small, 30mm condensor lens, perhaps
that little guy is the culprit(!?). But if you use a canon to
nikon or pl adapter they don't contain those lenses,
what they do do is that push away the lens around
3/5 of an inch, something like an extension tube you
would use for macro photography, only just a bit, so you
have the tinyiest "magnification effect." like not quite
100% but more like 50-70%.

I've been struggling with this problem as it is a big
xl1 issue. i was considering consulting with an expert
but the costs were astronomical for the amount of
effort i considered...

or something like that,
d

[Jeff Donald]

Dino, both of those articles in the links reference dSLR chips which are much larger than the 1/3 inch chips used in the XL1. The 1.5x to 2x magnification (crop) factor quoted in the articles is in reference to the larger chips.

[Dino Reyes]

hmmm, well I know for sure the xl1 CCDs pick up only a portion of the image, like so:

http://www.dinoreyes.com/images/frame-comparison.jpg

this is a given. so it is my reccommendation to go as wide and fast as possible for the relay lens, because you are really just shooting the gg about 1.75 inches from glass to glass, you wont have any trouble with vignetting because using a 52mm filter setup, there is plenty of "wiggle" room on the gg.

[Adam Bowman]

If you can focus the image of the groundglass onto the CCD's the system will *work* regardless of the focal length of the lens, but the depth of field qualities of the 35mm imager size will be lessened the smaller the area of the groundglass the CCD's see.

If the focal length is so long that you only see a very small portion of the groundglass you'll effectively be doing nothing put putting more glass between your subject and your CCD's and gaining no depth of field shortening (not to mention the loss in stops).

The Canon EF adaptor does indeed have a 7x magnification effect (Canon state this) and any mechanical adaptor will inflict this same penalty.

Really, as far as relay lenses go for the XL1, projecting the entire 35mm groundglass imager to the CCD's will be tough, you'll either need to use very wide and fast lenses (<24mm), like you said, or have a very long adaptor with longer more affordable lenses. The later not being a very usable alternative. We can of course compromise and still have a system which works by capturing less of the groundglass image.

As I've said before, with a 24mm relay lens you'll need about 14cm distance between the front element and the groundglass to capture the full 35mm frame (less for a 35mm motionpicture frame). Compressing the system length and optical path will leave you with less field of view and more depth of field, you can shrink it physical and retain the same optical pathway distance if you use mirrors however (you can also erect the image killing two birds with one stone).

We don't have to build these systems to any standards but what we personally think is good enough, so if you don't capture the full frame and it still looks good enough for you, then it's a job done!

[Anders Floe]

Thanks for all the great info guys! But now I'm REALLY confused! How do you think the Mini35 relaylens works?? It has to be a really wide and fast lens - or what? Anyways it must be possible to make something similar somehow!???

Their relay lens costs about 1500 Dollars and the other solution could easily end up costing the same! I really don't know which way to go now!

Thanks

[Brett Erskine]

Put the UV on the right side of that extension tube so that you throw any dirt COMPLETELY out of focus to the point of disapearing.

-Brett

[Brett Erskine]

Left side (next to the PL mount). HA HA Whoops

-Brett

[Adam Bowman]

I don't know what FL or speed the mini35 lens is, but I expect it's probably a around 15mm <f2.0.

Remember the stock Canon lens will do this in a full 16x zoom lens and making a prime is much easier.

Using wide angle SLR lenses as the relay lens is overkill really, since they are designed to cover 7 times the image area that we're using. A professionally designed prime lens made especially for the job will do it much better and that's what the mini35 uses.

If you can afford the 1500 for the relay lens, buy it! It'll do the job perfectly :)

I have yet to find an alternative which is perfect for the relay lens, the best options are wide-angle and fast SLR lenses. The problem is the FFD of the XL1 is similar to that of an SLR but the multiplication effect makes SLR lenses a poor choice for wide angle work. And at the same time most CCD based camera systems use the C/CS mount system which has an FFD completely incompatible with the XL1. There are plenty of very wide CCTV camera lenses which can never be used with the XL1 despite the fact the cameras uses the same size CCD's.

[John Jay]

Further to my earlier post, I dug up the macrophotography formula as

u = F.(M+1)/M

where
u = distance of object from lens
F = focal length of lens
M= scale of reproduction

for the full frame 35mm gg, M~1/7

which means that

u = 440mm for a 55mm lens, and
u = 200mm for a 24mm lens

neither of which lends well to a short form factor, furthermore a f1.4, 24mm will eat money

which leads me to a better solution ???

1 buy a broken Nizo 2056 S8 camera from German ebay (they have tons of them) with a clean working Schneider 7-56mm f1.4 macro zoom lens and carefully remove it

2 buy a cheap Canon standard lens with a mount compatible to your existing adapter and remove the bayonet mount from it

3 find someone (maybe a good camera technician) to fit the Canon mount to the rear of the Schneider


total cost should be under 250 euro and would allow the gg to be within u=50mm of the Schneider and the image would be razor sharp


good luck

[Dino Reyes]

So maybe i'm not really good at talking about all this lens stuff. but after sometime of thinking about it i figured out how to build an adapter that seems to work well, (haven't had time to really test fully yet). it requires almost no cutting which is amazing and allows for screw adjustment. so i finally got around to taking some pics of the Aldu35 for xl1/xl1s so it goes like this

here is a pic with the unit mounted...
http://www.dinoreyes.com/images/cam1.jpg

it's still all unpainted pvc with simple hot gun glue...

this pic has the parts broken down and exploded out with another model i'm building that will be using a hologrpahic diffuser and a condensor lens.

http://www.dinoreyes.com/images/cam2.jpg

above you will notice a complete one all screwed in and glued, with the lenses dismatled

below are the parts (2 inch pvc connectors) roughly numbered in the order they are arranged, those filters are 52mm. on connector #9, the dotted line shows where i cut it to glue on the prime lens mount. all you need is a cheap dremel tool and it will cut through that plastic like a hot knife through butter. notice the relay lens on the upper right has a sleek black connector at the end. that is the canon to nikon converter.

i'll try and post some video in the next 24 hours...

get to work!
-d

[Dino Reyes]

because the image will be upside down, to invert the image, all you have to do is flip the eyepiece to the opposite side of the camera. notice here...

http://www.dinoreyes.com/images/cam1.jpg

[Adam Bowman]

That looks like a significantly lengthy piece of equipment (your adaptor :p).

How's it like to operate with the focus ring all the way out at the front like that?

[Dino Reyes]

true, the unit put together starts taking on the appearance of a 16mm camera, so far handling the focus is not bad at all, you have to get used to the flipped eyepiece, but it starts making more sense because you can actually work the controls much better because you can finally see them all.

the real key is the "relay lens", that's where the added length in the piece is, the rest of the unit, from the front lens to the white plastic is probably as short as the other units for the standard dv cams.

my main goal was to make something very strong and if need be adjustable, notice the steel 52mm reversal ring (#1) i'm using to connect to the front part of the relay lens. i'll put the rails on for secondary support later, but i'm envisioning this to be my primary camera for shooting. i'll make another for a standard dv as a secondary camera as those are way cheaper and simpler to make once you have a nice lens collection.

-d

[Anders Floe]

Could this work as a relay lens : Dallmeyer F1.5 15mm wide angle ‘C’ mount lens? Like Adam Bowman wrote earlier in this post "the mini35 relay lens is probably around 15mm <f2.0"! Or am I mistaken?

Thanks