Homemade 35mm -- Edited Copy for Reading

[Peter Sciretta]

both of the items have the standard tripod screw... so the shoulder mount is screwed into the telephoto lens mount which is screwed into the video camera.

[Peter Sciretta]

unfourtunately I do not know the brand for the shoulder mount, but I'm sure someone in another area of this forum could point you to a good cheap one like it... i know varizoom makes some stuff like it...

http://www.varizoom.com/pages/supportindex.php

EDIT: I think I found a model that looks to be the newest model of what I have at:

http://www.studio1productions.com/dvbrace.htm

its 149.99

you may be able to find something cheaper....

[Jim Lafferty]

Alright...questions for those of you in the know about optics and/or those of you with a GL1 or similar cam that has an Agus35 working:

1) I cannot pull focus with my 35mm lens. I'm talking both alone and with the adapter attached.

Upon investigating -- and here my ignorance of optics will show -- I found that I need to place the lens about 6 inches from the surface of the projection (in this case, my eye) in order for anything to come into focus. Which begs the questions: 1a) how do you shrink the distance between the 35mm lens and the GG, or 1b) am I stuck keeping the lens to a distance of 6in. or greater from the GG? (i.e. making my adapter larger?)

2) Anyone having success with a CD motor/clasp setup at a proper speed? By proper, I mean that I assume these motors have a max speed they're rated for -- with the typical portable CD player runningg off of 2 "AA" batteries (3 volts), I assume hooking one up to a 9 volt battery to be a mistake.

However, running through tests today, I noticed a palpable shimmer in my (as yet focused) imagery that was directly related to the slow RPM of the motor. Hooking it up to a 9v battery cured the problem, but I have doubts as to how long the motor will run in this mode.

- jim

[J. Clayton Stansberry]

Agus,

I think if you are going to make a commercial product and sell it that way, you need to flip the image. I personally would not want to spend around $1000 for an Agus35 and not have my image correct. Maybe you can offer a cheaper version that doens't flip the image? Give the people a choice!

Clay

P.S. I don't know any good way to do this, but I think it needs to be done. You might just study exactly how SLR cameras flip the image and then find some way to use that???

[Bob Hart]

To Jim Lafferty:

Could you tell us what 35mm camera lens you're using. If you have to place it so far from the groundglass there's something not right there - unless you are using a projector lens. Some sit off about 6 inches from the film plane.

Just for curiosity sake, take the groundglass out and see if you are getting the same result direct into the camcorder. I have observed in my tests, the camera aquires the aerial image.

To All:

I dismantled the VCR16B lens set and tried that last night. It underscans the 35mm image frame into the VX2000/PD150, by about 15% so it's not a viable option. It is about 7x power, 3x was too small so 5x may be about right.

[Paul Doss]

Here's a page I put together rather quickly about these adapters and the principals involved. Let me know what you think.

Paul

www.thecountrybulletin.com/dv_dof.htm

[Danny Tan]

nice page. but i think if you have fresnel lense, then you don't need the magnifier cause they just do the same thing. correct me if im wrong

[Paul Doss]

Danny <if you have fresnel lense, then you don't need the magnifier cause they just do the same thing. correct me if im wrong>

Things are just getting started on all of this. So I guess you could say that the jury is still out. See the links to the graphics showing the effect on the ground glass by the fresnel. It brightens the edges. The magnification is to allow your camcorder's screen to be filled with the image (24 x 36mm). I'm not trying to build that kind of adapter so I'm not sure. That's just my take on it.

Paul

[Jim Lafferty]

"To Jim Lafferty:

Could you tell us what 35mm camera lens you're using. If you have to place it so far from the groundglass there's something not right there - unless you are using a projector lens. Some sit off about 6 inches from the film plane."

This is a standard Nikon Nikkor 50mm lens with an aperture of f/1.4. The same effect can be seen from my Pentax 50mm lens with f/1.7. They're both standard lenses fitted for 35mm cameras. Neither of them can get a focused image on my GG which sits about a 1/2 inch from the rear of the lens, and three inches or so from my GL1's macro (which, incidently, can pick up the grain on the GG fine).

- jim

[J. Clayton Stansberry]

Jim,

I could be wrong, if so forgive me! But, I thought the GG must be closest to the video camera lens, and further from the Camera lens. It may be a whole different can of worms with the GL series. But from what I have seen, the GG needs to be really close (1/4"?) to the video camera. You might try reversing what you have already tried, or have you? Just a thought...

Clay

[Dino Reyes]

Working towards a solution at reversing the image the Agus35, I had already picked up one of these great gadgets http://www.zgc.com/zgc.nsf/active/6FA3DA5F0C16A24985256B82007B576D a little shock absorber/mic/eye-piece extender. So to right side the image all you have to do is flip the mic/eyepiece arm to the other side of the support T and turn off the evf display. I'm still awaiting a few key pieces to build out my Agus35, I will be on vacation for the next few weeks but I hope to show pics and tests of my mod the early week of january.

D

[Robert Knecht Schmidt]

I have no plans of my own for building an Agus35 yet and I'm not an expert in optics, but here are my thoughts on the subject just from having read through the thread--

- The name of the game in building one of these should be preservation of light. Additional generations of reflectance/transmittance are going to substantially reduce the amount of light that gets to your CCD.
- To that end, why fool with mirrors to invert the image. This is something best done in post. If you're having a hard time visualizing on the set, put the inversion apparatus outside the camera after the viewscreen/viewfinder.
- Similarly, it's hard to imagine the amount of light reflected from a built-in white screen (as in Paul's diagram on his web site) would be as good as what's being transmitted through a ground glass.
- Someone mentioned using something other than a frosted CD as a ground glass. The nice thing about the CD is that it's already very round. Use anything with a center of mass in a different spot than the center of rotation and your implementation is going to vibrate like the dickens.
- When's the XL2 coming out again?

[John Gaspain]

<<<-- Originally posted by Danny Tan : nice page. but i think if you have fresnel lense, then you don't need the magnifier cause they just do the same thing. correct me if im wrong -->>>

yea thats wrong.

The Fresnel lens is to even out the light recieved from the 50mm lens, so you dont get a really bright spot in the middle of the GG.

The Magnifier (macro lens) is so you can get your DV camera really close to the GG and be able to focus a clear image on the GG.

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Please people- read the previous posts, I know 28 pages is daunting but its really not that hard.

[Emmanuel Decarpentrie]

"- Similarly, it's hard to imagine the amount of light reflected from a built-in white screen (as in Paul's diagram on his web site) would be as good as what's being transmitted through a ground glass."

Indeed: at best, Paul could get a regular 1.0 reflection rate for his screen. Spinning disk implies he can't get any sort of gain for his screen, because gain would make the screen highly directional. "No gain screen" means the light is gonna end up being scattered everywhere, in every direction. So lots of photons are gonna be lost in the process of reflecting the picture.

Furthermore, I just can't see how he could possibly get a correct picture geometry with this setup... The adjusting process must be daunting. Paul must be ending with a very dim and somewhat distorded picture IMHO.

Paul, why don't you take the "KISS" approach (Keep It Simple, Stupid)?

[Bob Hart]

To: Jim Lafferty.

Jim.

Perhaps we should talk about two distinct functions which happen and call them stage one and stage two.

Stage one is in effect a camera and setup (= AGUS35 system). -- Object>>>lens>>>focal plane |, in this case it's the groundglass.

Stage two is another camera and setup. -- Object, in this case the image on the groundglass>>>relay lens or close-up lens if needed>>> camcorder lens>>>focal plane |, in this case, it's your camcorder's CCD chip.

It sounds to me like your problem is in stage one. You have your 35mm objective lenses too close to your groundglass. The rears of those lenses must be the same distance forward from your groundglass as they would be from the film plane (focal plane) if still installed to the cameras they came off.

This distance will be in the ballpark of about 1 and a half inches or so, not the half-inch of so you are using. To get the exact measurement, grab the camera bodyn dismount any lens you have on it and look for a mark on the top to left of the viewfinder prism enclosure for the Nikon (FM2).

The mark will be an "O" with a line drawn through it. This line corresponds to the focal plane (film plane) of your 35mm camera.

Put a straight-edge (a ruler is fine) across the lens-mount face of the camera so that you can then measure the shortest direct distance from the focal plane to the edge of the straight-edge. That distance is the space which needs to be between the mount face of your objective lens and the groundglass. Once you get that right things should start to look a lot better with a sharp image projecting on the groundglass you can see with your eyeball.

The issue from that point will be stage two, being able to frame and focus sharply upon the image projected onto your groundglass.

Between your camcorder and the rear of the groundglass is where any of the close-up lenses, macros etc talked about here will have to be placed if your camera cannot frame close enough and hold sharp focus on that projected image on the groundglass.

To initially set this part up, forget about trying to project an image onto the groundglass and use a barcode panel off a food packet to see if you can get your camcorder close enough. The barcode will show any distortion of focus defects.

Once you've got that sorted, then you can mate up stages one and two with a lot less grief, knowing each of the stages in themselves are working properly.

This leaves you with the task of rotating your groundglass and putting the whole thing inside a nice looking enclosure. Don't forget to paint the inside with blackboard paint to eliminate internal reflection which may cause a fogging effect.

If your groundglass is not opaque enough, the image into your camcorder will have a hotspot in the centre, most evident when your objective lens on stage one is stopped down.

To all:

Best frosted effect with the plastic CD disk is achieved by finding a flat surface, (sheet of glass on a benchtop) laying on it a piece of dense soft cloth which is not going to scratch the smooth side of your disk, placing face-down on your disk, a sheet of 500 grit silicon carbide (wet and dry) paper, using a short screwdriver handle or similar blunt object with both round and straight edges, then scrubbing away to press the grit against the disk. Do not let the paper scrub across the disk as you want pits, not scratches in your disk. For the broad surface of the disk you can scrub the ridged grips of the handle across the paper. Towards the edge of the disk you will need to use the rounded end of the handle to scrub with as the disk rim is slightly raised and the frosting effect will not reach the edge.

It will take you about 80 minutes of patient work. The job will be done when you cannot see through the disk but a lens will project an image on it.

Cleanliness is next to godliness and most importantly, do not touch the ground surface as finger grease will spoil it and no amount of furthur work will remove that smooth mark. Efforts to clean it will polish the groundglass pattern because the plastic is soft.