Consolidated XL1 35mm Adapter Thread

[Stephen Birdsong]

Dino,

Definately makes sense.

My question is, with the 24mm lens, are you able to capture the 36x24mm portion of the image on the gg? Or are you going in farther? What I want is to be able to know that when Im using a 35mm or 50mm prime lens, Im actually getting that focal length. If your primary (or relay) lens isnt capturing the correct size off the gg, not only do you lose DOF but you increase your focal length (basically the same thing happening). which for me is a significant drawback.

So, can you figure out what size (in mm) your 24mm lense is capturing off the gg?

Im thinking Im going to scrap the 16mm cine lens and go with a wide 35mm still lens as the primary (relay) lens. I just dont know how wide I need to go.

Barrel distortion? Wide angle lenses less than 20mm or so start to have significant barrel distortion, is it noticable in this application?

Do you have any actuall pictures of your adapter? If not, could you try to get some... Mounted to camera, and then in pieces.

Do you have any frame grabs or clips to show?

Stephen Birdsong

[Sarena Valilis]

its not anodized yet to i dont want to post it on the web page...

but for this board check out:

http://www.xl1adapters.com/prototype/prototype.html


that is a photo of the straight adapter w/o any lenses inbetween
the standard arriflex lens...

check out the samples.... if you can get this good of results with
just a small chunk of aluminum and NO EXTRA lenses, then why complicate life....


there is nothing here that you cant do yourself.... if you have to take the photos to a local machinist and for 100 - 200 dollars worth of his time you can have the same results....

like i said this is the setup that shot the demos.... the aluminum cost around 20 bucks, the lens around 50, and the results are comparable to any other prime lens method....


KISS principle should apply here...

there is still significant control of the depth of field, and the low light capabilities exceed the stock canon lens... and YOU can make it yourself for less than the 800 dollars that most places are asking.....

[Brett Erskine]

Sarena-
I hear ya. That Ziess reducer is expensive and has 12 elements in it. WAY too complex. A focus reducer is one way to go and I agree its pretty tight in there on the XL1. You really seem like know what your doing never the less I feel I should caution you that heading in this direction will not change the DOF and it sounds like thats what you want to do. By having one of these adapters you open yourself up to using longer lenses which will give you shallower DOF but thats true if you simply screwed on a teleconverter to the front of the video cameras lens. Basically without the use of some form of intermediate image plane (ie. GG) your DOF will aways remain the same for any given FOV no matter what kind of lens you put on the camera (35mm, 16mm, whatever). Either way a "image plane reducer" would be very useful for other reasons. Let us know how it comes together.

[Dino Reyes]

stephen, so you've seen the schematics, here is

the camera with it mounted sans rail system or support - using metal threads keeps it strong
http://www.dinoreyes.com/images/cam1.jpg

broken down - the top row is basically connected together the botton is it broken down into elements... check out the pvc connectors i'm using, they are cheap and help with adjustments
http://www.dinoreyes.com/images/cam2.jpg

movie sample (8mbs and compressed through cleaner, i keep forgetting to rightside in post sorry... but the idea was to show a raw file)
http://www.dinoreyes.com/images/test11B.html

notice the amber coloration is because my test uv lens which i made into a gg had a slight tint on it so it looks ultra warm, my next gg has no tint but still seems to have amazing dof

i was using a superfast 55mm f1.4, but i was shooting in brookly the other week and broke it by accident so it gave me an excuse to take it apart and refine it again... this will be my 3rd model.

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

you know i know what you mean when your asking about coverage of the ccd's but since i've been continually improving my model i haven't had time to do a "proper" measurement. because i built my model with connecting pvc pipes it gives me the advantage to adjust distance between the acromat and the relay and again from the master to the gg, thus whatever master i put on, i can adjust on the fly and the adjustments stay amazingly, at least to my eye the lens stays tight/accurate - i'm still really just amazed it all works... once i get this version going, i probably should do some more tests to get better measurements...

-dr

[Sarena Valilis]

Brett-

you realllly sound like you know what you are talking about...

if you would do me a favor and check out the clips on the site in my first post i would appreciate it.... i thought that i was getting a much SHALLOWER DOF with the adapter and the arri lens than i was able to attain with the stock canon lens...

if nothing else, it is just nice to be able to get and use lenses on the xl1s that are not as expensive as the canon manual lens...

but, unless im wrong, the results seem to me like what everyone here is after. by using the focus you get a highly selective DOF and get that "cinema look" ... due to a shortage of time and resources i just focused on a picket fence and adjusted the focus so that it would be clear how the DOF was behaving... i also focused on the fence, then a flower a few feet beyond, then another flower a few more feet beyond, and then a rose about 12 feet away, and each came into focus seperately....

am i wrong or is that the desired effect here??? the drawback is that you would have to manually prepare your own DOF charts for each lens, (but at least we would be doing it on video and not film)

thanks,
sarena

[Bob Hart]

I did some rough tests with the Kampro camera. This uses a Sony Exview chip. It is claimed to be 1/3" but the effective image area looks to be just over 1/4" corner to corner.

With this camera, the Tamron C-mount zoom on wide angle 12.5mm, spaced 2.2mm forward of the mount face, will frame the 24mmx18mm 4:3 academy frame within the 4:3 TV frame safe area viewable in the LCD screen of the PD150 I patched the Kampro into. The distance from front of the lens to the test card was 27mm.

The same arrangement for a 16mm F/L prime lens needed 60mm between front of lens and the test card.

The same arrangement with the Cosmicar 25mm lens was not in the game at all.

There is a reference in the other XL1 thread here about the prism path in the camcorder.- It may not be possible to mount a C-Mount lens in an adaptor close enough to the camcorder's focal plane.

[Stephen Birdsong]

Serena:

If you did not use some sort of ground glass element, then you do not acheive shallower dof.

Now, It may appear that you have a very shallow dof (i saw your clips), but how far away from those bushes were you? My guess was pretty far. If the standard xl1 lens was long enough to match that focal length, the dof would be identical. The only way to decrease dof is to eaither decrease the fstop or increase the size of the "film plane" that the front element lens (prime lens etc..) projects the image onto, which in your case is the actual ccd (which hasnt changed). To keep the focal length of any given prime lens, while maintaining the dof, requires a ground glass element.

Dino:
With your 24mm lens, you mentioned that you can adjust how far away the gg is from your primary (relay) lens. Can you measure the smallest and largest amount of the gg image you are able to fill the frame with? Ideally, I want to capture exactly 36x24mm so that when I use a certain focal length prime lens, I KNOW that I'm getting that focal length (and proper dof).

The reason this is so important to me, is that I already know how to achieve a somewhat shallow dof with my current manual 16x. I iris all the way open, I zoom all the way in, and I back up untill I have the framing I want.
It sucks. Especially when I'm in close quarters.

If Im not capturing the gg image at 36x24mm, then Im effectively doing the same thing with a still, prime lens. Not preferrable.


Stephen

[Sarena Valilis]

stephen-


how far away from those bushes were you?


the fence post is about 2 feet or less away from the front of the camera...(two of the bogen tripod legs are actually touching the fence)... the clips along the length of the fence give the best view of the performance of the lens (again, the tripod legs are touching the fence)... YES, gg would give i slightly different selective focus, but i can afford this and it does seem to work OK without compromising lens quality by adding a bunch of extra lenses.

you said:
The only way to decrease dof is to eaither decrease the fstop or increase the size of the "film plane" that the front element lens (prime lens etc..) projects the image onto, which in your case is the actual ccd (which hasnt changed).

this is true and NOT true.... those taking portraits have long used a lens that has a selective depth of field characterized by manipulating the elements of the lens.. The concept of the Mini35 is a great one... it is the best way to simulate film... BUT since many of these cinema lenses are designed for selective focus with shallow depth of field then we can still benefit from the lenses characteristics even though these will not be exactly the same as the lens if we used gg...(using a gg method would enable you to use focus pulling charts)....

.......ie- i dont have an arriflex camera to test it on but the performance of the lens seem pretty cool to me even if it is not the same as it would be with a mini 35. ,



you said:
To keep the focal length of any given prime lens, while maintaining the dof, requires a ground glass element.


??????
true...

as i said a simple straight thru adapter will not have the same
fl and dof, but if it still shoots cool video that looks cinema like
then who cares???

[Patrick Wright]

XL1 Static Adapter
This adapter consists of a canon 1.2 50mm FD mount lens and adapter on a Radioshack 4.5x6.5inch project box. the GG is a Linhof 4x6inch micrograin obtained from B&H. Next step is to make a platform for the whole setup to rest on. Perhaps a mattebox & support rod setup. I used the stock 16x auto lens and the Macro is a 5x single element. when money and time permit I'll replace it with an Achromat, perhaps more powerful although with a little more tweaking I think 5x should be enough to fully eliminate the vinetting.

the clip is about 1mb and is a fairly low bitrate so pardon the compression artifacts. It doesnt like to stream so download before viewing.

www.quicktel.com/users/archamian/candletest.wmv

[Patrick Wright]

Stephen, please refer to this thread http://www.dvinfo.net/conf/showthrea...5&pagenumber=3 in which I discuss an arri bayonet adapter I designed to use 16mm lenses on my xl1. In it I found that with arri bayonet mounted lenses the distance between lens flange and camera body is 22mm or not quite 7/8th of an inch. If you are setting your lens at 3 inch or so then you would have nearly zero ability to focus with it.

I would recommend that you find a way to mount the lens stabily by itself say on a table with the lens at the proper height for the camera. Set up an object to image and make sure it is a set distance, say 3 feet or 1 meter, from the lens measure this carefully. Slowly move your camera towards the lens until the object comes into focus. That will help you determine the focal lenth for your lens to the CCD plane. Again, do not move the lens , only move the camera.

My adapter webpage is www.quicktel.com/users/archamian/adapter.html

Sarena, you may also find that post interesting as what I did is about the same as XL1 solutions products just for a different type of camera mount. I too noticed better control over depth of field but it is still a little too video-sharp so I am proceeding to finish my own GG based adapter. What I especially liked about my adapter and a 16mm film lens is that I have total manual control and that has made life easier in many shoots, though the auto lens also has its benefits.

--Patrick

[Brett Erskine]

Sarena-
If you want to test your theory and varify that you are indeed getting shallower DOF simply do this test and post the resulting frame grabs.

One frame grab with your adapter and 35mm lens shooting a shot showing off its DOF characteristics. Record what you used for a f/stop.

-------dont move the camera at all. Not even a little----------

Now shoot without the adapter and just the standard video lens. Zoom to match the same FOV EXACTLY and dont forget to check that your f stop is the same as in the first picture.

Post the resulting two frame grabs.

In fact this test should help you as you finalise the adapter.

Once again even if you come to realise that the DOF hasnt changed you still have a very valuable tool there. Think of it as a low lux adapter. News and wedding videographers will eat it up.
Or market it as a cine lens adapter.

Let us know when you have some pics to show. Good luck.

[Kevin Burnfield]

Hey Pat, do you have any pics of your set up? would like to see it and more details... thanks

Also can you put up your vid in some other format? That film bombs on me every time...

[Patrick Wright]

... a quicktime file, hopefully Adobe Premiere encodes it properly.
http://www.quicktel.com/users/archam...dletest001.mov
and a pic www.quicktel.com/users/archamian/flower.jpg

I'll try to take some pics of my setup asap and will edit this post with the links.

--Patrick

[Anders Floe]

I can't get my relay lens to work:

http://www.edmundoptics.com/onlinecatalog/displayproduct.cfm?productID=1281&search=1.

Seems like it has to be mounted closer to the CCD than possible (canon xl-1 ccd is protected by a piece of glass making the distance to big)

Well...What to do now??? I don't think that the idea is far from right. I just didn't know how to do the math to prevent buying the wrong one..hmm it is kinda small though.

[Dino Reyes]

anders,
for your relay lens, what kind of lens are you using? also, what kind of connector/adapter are you using also to attach the lens to the canon body also?

-dr