If you actually had been following the thread carefully you'd know that the ground glass is the one part that this entire adaptor revolves around. It is because of the ground glass that we get such short depth of field. The image from the 35mm lens gets projects onto the ground glass and then this projection gets taped by your dv camera. Without the ground glass, the depth of field we are attempting to get with this adaptor would be lost.

This may kick off some debate as I know that the working theory is that you need the ground glass... but I, for one, think that you could do it without the GG, but you would need a relay lens in its place.

In the 80's Panavision did exactly this with their first Panacam EF cameras... they took Panavision 35mm Cine lenses and projected the image from them onto a 2/3" tube. To accomplish this with the same DoF and image characteristics as the 35mm lens, they just had a relay lens which changes the image size from the 27mm diagonal of a 35mm film plane down to the 11mm diagonal.

As I understand it, they stopped making these because the abberations created by the relay lens become unacceptable at high-resolutions (like HD), but were perfectly acceptable for standard resolutions. I'm not sure where this stands by today's standards of optics manufacture.

I've got a couple of bi-convex lenses (curved outwards on both sides) lying around. I held my SLR up and positioned the bi-convex lens behind it at about focal flange distance - looking into this at the right angle, and from the right distance, I see a big bright fat inverted image. Seems like it should work.

Others?

--- references:
http://www.dvinfo.net/dv-l/869.htm (search for Panacam)

http://www.cinematography.net/[cml-h...%20cameras.htm (no real resolution, but an interesting discussion)

that was my intention to have the condenser lens acting as the gg until i see the result given wth the gg and the condenser with the flat side towards the video lens (no vignetting) from Alain.
as i got only one lens for instance, i would be happy to hear what is the result with a condenser lens that is reversed.

<<<-- Originally posted by John Gaspain :
I havent been all-stop though. Here is what ive done in the meantime. I made this rail dealie., this thing is rock solid.

pic
http://aequantum.com/DSCF0003.JPG

John -->>>

I like the look of the adapter, what materials did you use? That doesn't look like the PVC pipe they sell @ my home depot

about relay lens, you skip the most important of your references.
quote:
In conclusion, even an excellent cine lens, combined with a theoretically perfect relay lens, will produce a relatively poor image on a 2/3" CCD camera when compared to even an average quality video lens.

Yes, but if you continue reading that article, the guy in the very next post completely disagrees - and so on and so on - back and forth. This is what I meant by "no real resolution"

Unfortunately, none of us (lurkers notwithstanding) are qualified to understand the optics of this. I am continuing with the ground glass idea because its easy and works pretty well. I just threw out the thought and links because I don't believe its set in stone that you couldn't make it work without the GG if you had a good understanding of optics and a very high-quality relay lens. I have neither, so its GG for me :)

Just a'waitin' for my grit. (there's a tune in there somewhere).

Any lurking optical-degree-holders care to join in the fray and set us straight?

<<<-- Originally posted by Ari Shomair : <<<-- Originally posted by John Gaspain :
I havent been all-stop though. Here is what ive done in the meantime. I made this rail dealie., this thing is rock solid.

pic
http://aequantum.com/DSCF0003.JPG

John -->>>

I like the look of the adapter, what materials did you use? That doesn't look like the PVC pipe they sell @ my home depot -->>>

Its a Lowes model :)

1200 Grit Aluminum Oxide
 

I don't know if this has been brought up before, but I found a source for 1200 Grit Aluminum oxide powder -
http://www.whiteabrasives.com/aluminum_oxide.htm .

Only problem is they sell in minimum quantitys of 10 pounds. Are there 9 of you out there which want to split some with me? Email me if interested, or if you know a place to get smaller quantities.

http://www.gotgrit.com/default.php/cPath/2_7 has aluminum oxide powder that sells by the 1/4 lb. According to this chart http://www.facetingmachines.com/grit-mesh-micron.shtml, 1200 grit is the equivalent of 15 micron. Dick Dokas's article on making your own ground glass (http://www.phototechmag.com/previous...kas/dokas.html) speaks of going down to 3 micron/8000 grit. Gotgrit doesn't sell that small, but they do have 5 micron/4500 grit. I plan on buying some from here soon.

sTRANGE IDEAr
 

WHIT CANON XL1 CAMERA

YOU REMOVE THE LENS

iF YOU PUTT VERY STRONG CONDENSER LENS (after GG) THAT CONCENTER LIGHT RAY DIRECT IN TO 1/3 " CCD SIZE ????

what about this ????

Nicholi-
I know there is a point when choosing the right grit that if you using something thats TOO FINE it acts as a polisher and not a grinder. In other words it wont make ground glass. Im not totally certain what that grit number because I keep getting conflicting info on this thread. But I can tell you alot of the suppliers on the net seem to put the cut off point just after 9 microns. For this reason I myself decided to use 9 micron Aluminum Oxide powder.

A interesting note is Canon uses lasers to etch/pitt their ground glass for some of their still cameras. The process promises not only finer grain ground glass but brighter as well. The problem is that their GG always seems to have some type of focusing assist marks on them making them useless for our needs. Still looking though.

-Brett Erskine

Canon type C
 

Brett this link about what you hare talking

All mate GG is type C, J, K

look
[url]http://www.mir.com.my/rb/photography/hardwares/classics/canonf1n/metering/screens/screens.htm

Thanks to all
 

I say the best part of this thread is all of the great, hard to find links. Thanks to Nicholi for the gotgrit link.

Brett, did you notice a great difference in performance using the 9micron GG vs. the 1000 grit GG? I've been pleased with the GG I created with 1000 grit but am always striving for more.

One more thing, Paolo Rudelli posed a great question earlier today and I would love to read a respnse from someone who's already corrected for hotspotting and vignetting. (I'm still waiting for condenser lenses to come in so I can experiment)


My questions are similar to his:
1. has anyone tried to grind the flat side of the condenser lens?How did it work?
2. has anyone tried to place the condenser between the SLR lens and the GG? It would be great if anyone who has already done condenser placement experimentation to share their findings and the steps taken to get their results.
If it has already been posted and I simply missed it, could someone please post a link? Thanks, Joe

Stuck testing condensers
 

I've got a variety of cheap lenses that I got from American Science Supply. Of interest are:

1) A larger-than-35mm-film-size diameter biconvex lens with a large radius (it's a fairly thin lens, about 4mm at its thickest point).

2) A larger-than-35mm-film-size diameter biconvex lens with a smaller radius (bigger curves). Probably 15-20mm at the thick part. However, the 'thin part' is still a good 5mm across, feeling like two plano-convex lenses which have been put back-to-back - but I can't see any seam.

3) A larger-than 35-mm-film-size diameter biconvex lens with a large difference in the two sides... One side is slightly convex - but nearly flat - the other has a serious curve. This is about the closest thing I have to a usable single-element condenser.

4) A smaller plano-convex lens - truly flat on one side, curved on the other. Too small to use though.

5) A rectangular exactly-the-same-size-as-35mm-film plano-convex that was the condenser from my AE-1. Very thin at its thickest point - probably 3mm.

6) A couple of small achromats. These seem like plano convex in their entirety because their flat on one side and curve out on the other - but they are actually two elements cemented together - a plano convex cemented into a concave/convex lense, like this:

The tough part is I haven't yet come up with a good way to mount these odd-sized lenses such that I can get them into my actual PVC adapter assembly. This makes it very difficult to guage their effects on vignetting, because this really only gets visible when you're all locked down and light-tight. The best I've been able to do is hold them up in some open-air experiments. ALL lenses seem to significantly brighten the image on my GG, regardless of whether they are between the SLR and the GG, or between the GG and the macro - and the direction (curved vs. flat) also doesn't seem to affect brightness at all - they're all the same.

Any tips from you builders out there on how to get one of these held in place and locked into a PVC assembly near my GG? I'll be happy to measure the focal lengths, and radii more accurately, but frankly, without some measure of the difference in their effects in a real 'lightless' environment that displays various amounts of vignetting, it doesn't seem like it will help much.

Additionally, I'm still waiting for my real grit to show up, so I have some ground glass I got from American Scientific Supply - which works and is fairly even, but has large visible grain. I also have my quick/ugly, but mountable GG with I made with (choke) sandpaper and steel wool. I also see an image - but it has large scratches and shows even more vignetting due to the unnevenness of the surface.

In short - I need to complete my real ground glass and figure out a way to mount these odd-shaped condensers before I can do any definitive testing. I'd love to hear mounting suggestions for the condensers.

Jonathon Wilson-
While you wait to get better GG you can fake a lightless situation and swap out the different condensers but simply shuting off all the lights in the room your in at night and point the 35mm lens thru the crack of a door to another room that has all of its lights on. If its day time try cuting a small hole in a thick black plastic trash bag(s) and put your 35mm lens through it - making sure to use tape to seal any possible light leaks around the outside of the lens. Get your head inside the bad (both like a large format photographer and...a idiot) and test your GG/Condensers.

As far as the Canon laser etched GG the other problem is that I believe they decided to have the GG and the fresnel on opposite sides of the same piece of glass so - no good.

-Brett Erskine

Good idea Brett, sounds fun climbing into a hefty bag.

I'll try that and report back... Probably not until at least tomorrow night - looks like I'm pulling yet another all-nighter at work.

Joe Holt: Thanks for that advice! Yep, I played around with it some more and it seems to be working better now. When it's just a thin layer of primarily water with an even, thin spread of aluminum oxide, that seems to work best.

I took it out for a test yesterday (we're having some beautiful weather down here) and was impressed with the results - especially since I don't have an achromatic diopter or a condenser.

Basically, I have the ground glass, 35mm lens, and a regular curved lens, in this arrangement:


35mm Lens -----> Ground Glass -----> Lens ------> Canon GL2

The regular lens is right against the back side of the ground glass, with the outwardly-curved side facing the camera. This cuts down on the hot spot I was getting with just a 35mm lens and ground glass.

I will try to get some images up in the next couple of days.

,Frank

Aldu35 for Xl1/XL1s
 

I have successfully made an XL1/XL1s version! I haven't even begun to perfect the design or address other simple issues-but still, lacking these improvements-my images are, easily, as good as, or superior to what I have seen so far.

All I can say is wow!!!
D

Sounds exciting, Dino! Congratulations! It'd be nice to see some of your footage if you can find a place to put it.

thanks jonathan, i'll start posting up some samples as soon as i get a second of breathing space from work-jeez, these 70 hour work weeks are starting to get to me...
-d

good news in deed for the xl1/xl1s people
 

geaux Dino, good news for you is also good news for the rest of us. keep up the good work.

My framegrabs
 

I have uploaded 9 test frames. They can be found here:

http://www.frankladner.com/testpics.htm

Thanks!

Frank, I bet if you got a Condensor AND Macro it would help out the vignette and how close you can get to the gg with your camera.

for a bit of theory see

http://www.cartage.org.lb/en/themes/Sciences/Physics/Optics/Optical/Lens/Lens.htm

and

http://homepage2.nifty.com/optas/lore-e.htm

look like we can have the condenser lens act as the gg because the way you mount the flat side has no effect on the picture.
a positive meniscus would be even better according the text, as projection of the picture on a curved plan would increase quality versus flat plane. problem is then to gg a concave surface :-)

Thanks for the links Giroud! Very informative.

Another problem I see with using a concave surface would be getting a clear focus from your camcorder. At the close distances we are dealing with, I believe you couldn't get an exact focus on the entire concave surface. (different focus planes) If I'm wrong and focusing isn't an issue, then the ground glass could be made comercially using the laser etching Canon is using for their GG mentioned earlier in this thread. I know most of us don't do laser etching in our basements but if we are all still talking about putting together a standard/manufactured version, then it might be feasible to contract a company to do it for a limited run. What would be ideal at this moment would be to have a supply of laser etched GG/condenser elements (50MM dia.) That sure beats grinding our own. Does anyone know who is doing Canon's laser etching?

Frank,
Nice images but I did notice a good bit of grain, dust and the scratch in the top right corner(or was it a hair?) Did you shoot that in the evening, in low light? I think you've proven that we need to do some finer grinding to reduce the grain. I believe a brighter image would help too. What was your video camera's iris setting? Did you try slightly over exposing the GG image to "burn out" a little of the grain. I'd be interested in your results with a bright scene. I also noticed during my own tests that opening my camera's (PD100A) iris really made the hotspot stand out but the image overall was more acceptable (sharper focus, less grain). I too am waiting for a set of condenser lenses to begin experimenting. I look forward to seeing your next set of images. Joe

Joe: That was shot in the evening. I turned my shutter speed up to around 100 and had the iris about half open. You're right about the hotspot. I tried to keep the center from being blown out, so that way, I'd have some detail throughout the frame. One trick I have done (not with these images) was to create a 720x480 black and white radial gradient in photoshop, which I would import over the footage in After Effects, setting the mode to Overlay. This would balance out the image some. I do believe, though, that if the hotspot problem gets fixed with the condenser (or some other solution), then recording a brighter image would help the grain situation.

Yeah, there are a few nice little scratches I managed to put on the ground glass. I had absolutely no problems with the 600 grit, but the 1000 seems to clump together, requiring lots of water, as you mentioned before.

Joe, where did you order your condensers from? I have not been able to find an old SLR body to get one from.

Thanks!

Condenser source
 

Frank,
I ordered the below products from Surplus Shed. Here is the link.
http://www.surplusshed.com/pages/category/educationaloptics_1.html

They have a large selection of optics at greatly reduced prices. I called on the status of my order today and the guy said that my stuff shipped on Friday (1 week after I placed my order online GRRRRRR!) I should get my lenses today or tomorrow. I'll let you know how they are as soon as I can get my eager paws on them. I ordered these initially to have a broad range of types for testing.
SKU: L1875D
EDUCATIONAL SET OF 50MM LENSES 1 12.00 12.00
SKU: L1961D
EDUCATIONAL DCV 50MM X -50MM 1 2.00 2.00
SKU: L1951D
EDUCATIONAL DCV 38MM X -50MM 1 1.50 1.50
SKU: L1574
RECTANGULAR PLANO CONVEX LENS 1 0.50 0.50

These are educational quality lenses. That means they are not of consistant enough quality for manufacturing purposes. (focal lengths vary slightly from lens to lens) But for our single unit applications, I believe they'll be perfect for testing.

Great Idea about the overlay in AE. I'm going to give it a try.

BTW, Has anyone made any progress on correcting the image orientation? I shoot a lot of sports footage and following action and focus with an inverted image would be impossible. How about a rectifying lens like in a spotting scope? I was considering a large pentaprism and mirror set up(like SLR system for a medium format camera) I personally would be willing to loose an F stop or two to gain a correctly oriented image. Anyone know where I can find an old medium format pentaprism viewfinder? (35mm is too small) Edmond Optic sells large enough pentaprisms but they're outrageously expensive. I'm willing to spend $20-$50 to experiment but not $500.
Joe

moinitor
 

Forget prism and mirror
i did whit upside down 5"6 monitor
(119 $ )
is working perfect even on a steady-cam

Joe: Thanks a lot! I'm headed over to their website to look around.

I was just thinking, and - don't scream at me if this sounds ignorant :-) - can't you rig up a system that basically projects an image onto a solid surface, enclosed in a light-tight box, for the camera to pick up? (You know how you can hold the 35mm lens over a piece of paper and see the image projected?)

Basically, the whole idea is to pick up an intermediate image - thus the Ground Glass. But......if you can use a system of mirrors or a prism and project the image on a plain, solid surface (not sure what'd be the best surface, but the grain wouldn't be a problem any more.)directly in front of the DV camera...wouldn't that be the same principle?

Also, in the manner that the image is relayed, would it eliminate the inverted image problem?

Again, forgive me if this sounds crazy, but I was just thinking about it as I was typing this post and thought I'd throw it out there.

Thanks!

,Frank

Corrected image
 

First off, I know using an inverted external monitor is an option but I would rather save myself the time and effort of fixing orientation in post. I think a correctly oriented image is doable. Saying this,I must point out that I am not an optical engineer. In fact, I've learned almost everything I know about this subject from you all and the articles you've posted here in this and the Agus35 thread. Experts, please chime in.
Frank, I don't think you're crazy! I gave your idea about projecting onto a reflective surface with a mirror some serious thought. We Southern Boys must think alike! I didn;t throw the projection idea out completely but I do have a few concerns about it.
1. We would be talking about a front projected image, right? Well, you would have an issue with left to right orientation when compared to a rear projected image (GG) A front projected image is really a reflected image just like a mirror so left to right orientation would be reversed while vertical would remain the same. I bet that is why SLR cameras use a GG element the viewfinder assembly instead of simply focusing on a projected image.

2. I haven't come up with a simple way to orient all of the elements to make using a projected image practical

Here's my stab at a simple correct oriented image. Sorry for the poor diagrams.

Basicall, I'm proposing an optic quality mirror mounted at 45 degrees to the light path from the slr lens. The GG and condenser lens are mounted above the mirror. (which comes first GG or CL is still under debate) The video camera is mounted vertically and is focused on the GG. I have a nice short camera 9.5" from lens tip to battery pack, so the vertically mounted camera wouldn't be too awkward. My adapter wouldn't need to use a round GG or round tubing either as I would house the whole thing in a compact, lightproof black box. In a nutshell, this is identical to a top view viewfinder on a med. format camera. In fact, you could use a med. format camera body and just add your own GG and condenser. Watcha Think? Joe

_________
' '
' '
' DV '
' Camera '
' '
'--------------'
/____\

CL (___)
GG ====
' /
' /
[ SLR ] ---------'/ 45 degree mirror
Lens /
/




_______
| | |
| | |
| | |
|____ | |
/___\ | |
--------------| |
I | |
I CL (___) | |
I GG==== | |
________ I / | |
_ _ \ | SLR Lens I / | |
/ |________I / | |
______I_/_______ | |
|__________Mount_ __|
[ ]
/ / \ \
/ / \ \
/ / \ \

YIKES!!! Well, I guess my ASCI art leaves a lot to be desired. Never tried it before. Sorry. Guess my written description will have to do. Joe

LOL

Actually, Olivier and Sebastien used that same idea for their first prototype and the video turned out great. They posted pictures of that setup at http://www.originalversion.net/temp/makingof01.jpg. Also, you can check out their movie thread at http://www.dvinfo.net/conf/showthrea...threadid=21567. If you haven't already seen "Marla," its very worth the download.

to Frank Ladner
 

frank,

you just "stoled" my idea, he, he...
i was thinking about the same thing, but never tested it in practice.
some time ago i saw slide portable projector, and i was inspired from it. the original device looks like this:

PLEASE, IGNORE THE DOTS! i was unable to "draw" it wihtout...


.....................\
......................\ <----- your eye
.......................\
........................\ big frosted GG
.........................\
..........................
small ...\.......
mirror ... \...... <------ ray () <------!! <----- lamp
..............\.................... lens.......slide

small mirror is parallel to big GG.

so if i'm right - you can use certain flat grainless surface instead of big GG. and use "system" like this...


.....................\
......................\
camera POV.......\
----------> ........\ grainless opaque surface
...........................\
..........................
small ...\.......
mirror ... \...... <--------- ()
.............\.................35mm lens



what do you think?

filip

Joe: Ha ha! Yeah, that ASCII art is quite difficult to pull off. I do understand what you're saying, though. That sounds pretty good to me, but I'm not an expert. I like the idea of using box/square stuff, because it's easier to line parts up correctly whan they're not circular.

Filip: Whew....I feel better now that some of you guys didn't laugh at my idea. What you are illustrating is exactly what I'm thinking about. Actually, it's better, because I was adding a few too many mirrors to the equation while envisioning it. :-)
That looks doable! Nice!

,Frank

he, he i was designing the whole asci drawing during yours replies...
nice to see that everyone is thinking here!

So my next question is......are mirrors just mirrors? ie. Are there certain mirrors that are better than others as far as quality? How are they rated?
Thanks!
,Frank

mirrors
 

in my opinion (i'm not a mirrorist :),

the mirrors used must have reflecting surface on the TOP ...

(so called venetian mirrors, hm, well at least in poland)

... surface, not the bottom.

in that case you do not have reflection distorted by glass itself.

just a thought.

since projecting the image on a solid white surface seems a good idea, i am afraid that the loss of light in such process would be too big.
What about projecting the picture on a surface mirror ?
I am not sur that in that case we get the same result than with the gg, but in theory, the picture would be build the same as on the GG and in the same time reflected (and inverted) so we get the economy of several parts.
We could use the mirror of the SLR body that is just the right size.
the only problem i see with using mirror before the gg is that we could create a light path that could exceed the about 46mm that is required to focus properly.
On the other hand we usually have plenty of useless space after the GG due to the requirement needed by the macro lens.
So using here a kind of zig-zag path could be usefull to build a compact adapter.
My best guess would be to have the light comin out of the SLR lens to a 45 deg surface mirror (inverting picture) to an horizontal plano convex lens with the flat side acting as GG.
This still require to have the camera mounted vertically and the picture inverted a 2nd time.