35mm Adapter Static Aldu35

[Rob Scott]

Back on page 56 of this thread, Damion Luaiye mentioned that if we got 50 orders, we might be able to get custom focus screens made.

Has there been any more news about this? I'd love to see some tests -- I'd even send someone a few bucks via PayPal to help pay for materials -- because if it looks good, I'd be interested in buying several of these.

Specifically, I'd like to see how it looks on a 720p HD camera like the one that Obin Olson is working on.

I'd love to build one of these adapters, but I have back and neck problems, so grinding a piece of glass for 2+ hours does not sound like fun. :-)

[Damion Luaiye]

The present hurdle: Beattie screens use fresnel lenses and the Beattie folks need a focal length spec (distance from eye to screen). With all of the distance variations and diopter configurations we have in our rigs I was unsure what length to give - any suggestions?

Meantime, today I mounted a Nikon type D, unmarked matte screen into a 55 mm ring. It's the only completely unmarked view screen I've been able to find - $22. The grain is finer than anything I've yet produced and is completely uniform, but the screen is a bit of a pain to mount and presumably will need frequent slight adjustment to maintain alignment.

A filter ring sized screen would be great. I haven't had a chance to try to test a full size Beattie screen in the hopes of determining the appropriate focal length - hopefully next week.

- Damion

[Bob Hart]

RE: DRESSING AND GRINDING DISKS.

I have been scheming and planning for means of cheaply automating the process. The machine is yet to be completed and the following is all unproven theory.

So far it looks like being a gemstone tumbler style thing :-

1 x washing machine AC pump motor.

1 x automotive engine water pump. - or -
1 x automotive power steer pump.

1 x oversize elastic band or flat drive belt.

1 x 50 disk CD-R case outer cover.

1 x 25 disk CD-R case outer cover.

1 x 25 disk CD-R case inner spindle. (Pillar cut off).

Several scrapped CD-R disks for spacers.

One custom brass donut shaped roller, with deep concentric grooves cut in it about 2mm (1/16") apart.

1 x door hinge.

3 x pieces of chipboard or scrap ply panel.

Assortment of screws gutter bolts etc..

METHOD:

Water pump or power steer pump is mounted by its bolt-holes to a wooden panel. A clearance hole may have to be cut out for the impeller.

The 50 disk CD-R outer is mounted to the pulley with bolts or screws. Use sealer or contact adhesive on the heads to lock them.

The washing machine pump motor is mounted to drive the water pump or power steer pump with a flat belt straight off the motor shaft like a flat belt turntable. (The plastic pump housing, seal and impeller will have to be removed. The plastic seal retainer may be an integral part of the motor and have to be retained for mounting purposes.)

The timber panel is mounted to a base plate with the door hinge. The third piece of timber is a prop. Another door hinge could be used and nails or screws used to make a ledge for the edge of this to hold the main panel at the correct angle.

The whole thing will look like a small cement mixer.

The CD-R 25 disk outer case will slip inside the 50 disk outer case. They are handily tapered. It needs to be removable as it will wear out. The spindle with its pillar cut off is now a lid.

The spacer disks may have to have the centres cut out and stacked until the centre hub of the CD-R case no longer touches an entire disk and the disk will sit flat and steady. These might best be glued in place.

The glass disk sits on top of them.

The brass donut rolls along the face of the glass disk in a polish slurry. The tilt angle has to be adjustable for best pressure versus the disk continuing to roll smoothly. The tilt must also be there to keep the slurry pool inside not on the floor.

My version uses a Ford 6 cylinder automotive water pump. This yields about 70 rpm with an AC 50hz electric washing machine pump motor driving off a 4mm approx shaft. For 60 Hz motors, the larger power steer pump puley may be need to keep the drum speed down. Buick V6 water pumps have a larger pulley but may be more awkward to mount.

All the automotive water pumps are doing is providing a bearing, a pulley and something with bolt holes in it to mount it with.

For the Aldu disks, a much smaller drum, maybe a small plastic food jar with a pressed lid and a smaller donut would be needed. For contact pressure the donut might have to be thicker for weight. In both examples the donut should not cover more than about 5/8th of the disk diameter otherwise the rolling action will become erratic.

The motor and pumps should be found in waste bins at repair shops. Whilst components essential to their function as pumps may have become completely ruined, often the bearings and the electric motor in the case of the washing machine pump remains serviceable. Do not wire the motor up yourself but have a qualified electrician do it for you.

No warranty of satifactory performance is made either express or implied.

[Wayne Morellini]

<<<-- Originally posted by Damion Luaiye : The present hurdle: Beattie screens use fresnel lenses and the Beattie folks need a focal length spec (distance from eye to screen). With all of the distance variations and diopter configurations we have in our rigs I was unsure what length to give - any suggestions?
- Damion -->>>

It might be better to discuss that with there engineer. I imagine that a standard screen could be made but custom interfacing optics might be needed for each rig (as presently is done from camera to camera). But does anybody here know allready, and has anybody bought that SLR Beattie focus screen to try out?

I have some good news (but I am too snowed under to look it up). I seem to remember in the information on Sony's HAD/hyperhad?? that they use a small microlense screen over the sensor to concentrate light on the pixels. Somebody was talking about this in the formum recently, that reminded me. If they can build them this small we should be able to get this finess too, even HD. So who makes them for Sony (Beattie could probably match this).

[Brett Erskine]

Damion-
Post frame grabs from your setup with the Nikon D screen

Wayne-
Is the "Sony Had/hyperhad" screen made up of a layer of micro lenses or is it simply super fine ground glass?

Bob-
You crack me up. Carry on man!

[Bob Hart]

Brett.

I try to please. As to the tumbler idea, in another lifetime, I did once polish gemstones (lapidary). Using junked autoparts might be one of two things, intellectual laziness or inspired genius. The washing machine pump motor comes from a Hoover Premiere, the original fitted. The replacement is an altered design.

Once I get the polishing trick sorted, I want to use the tumbler with small loose bearing balls and dry 5 micron powder or 3 micron if I can find it, to attempt to create a finer frosted glass surface, ie., light contact pressure, hopefully a stamping action instead of a scratching action and hopefully a finer groundglass.

[Obin Olson]

FYI I just took a normal cd-r NOT the spacer type and sanded the top layer off...now it's a better then spacer-type GG because the cd-r is a higher quality then the cd-r spacer! I took my small orbit sander and did away with the top coating..works great

[Richard Mellor]

Hi everyone


I am posting a link to the finished agus 35 . I made it with 1500
grit ground glass, purchased from a optical company. www.dvinfo.net/media/mellor

[Richard Mellor]

this is a link to the ground glass
this may be good enough for high def
http://www.optosigma.com/miva/merchant.mv?Screen=PROD&Store_Code=OS&Product_Code=pg211&Category_Code=Filters+%26+Apertures





the part number is 099-0160

[Pat Worrell]

just took a quick look couldnt find any previous answer to my question so here it goes...

Im shooting a movie this summer with the static lens attached to my camera, i would like to use it in conjuction with a glidceam, has anyone done this? I do not have the glidecam to test right now, but i was wondering if the added weight to the front of the camera made it impossible to do. (obviously i would need to counterweight it in some fashion, but with all this additional weight it makes me think it may make it extremely difficult to operate) Any thoughts much appreciated.

Thanks

Pat

[John Heskett]

If you are using the hand held version I would start working out. It is not for the out of shape.

[Nicholi Brossia]

1500 grit actually isn't as fine as it sounds. This webpage provides a grit-mesh-micron conversion chart that shows how 1500 grit is only about 10 micron. Many users have ground their glass with 5 and even 3 micron (equivalent of 4500 and 8000 grit) and can still see grain using a static adapter and standard definition camcorder.

[Bob Hart]

Obin

Sanding off the top layer. That option works fine except for the disk having a green tint which has to be manually white-balanced out. Not a big deal but it is there.

Pat.

You might examine finding the new centre of balance point with the Camcorder/Aldu assembly, then getting a piece of 3/16" aluminium flat bar, for fastening to your camcorder's tripod bolt-hole, then drilling and tapping a new threaded tripod mount hole and keyhole in the flatbar at the new point of balance. This also may enable you to also get a better lateral balance point. Some cams have tripod mount holes offset to one side.

[Richard Mellor]

I made three pieces of ground glass all handmade , and one acid etched, this is the best one so far. It cost 23 dollars

[Filip Kovcin]

<<<-- Originally posted by Richard Mellor : I made three pieces of ground glass all handmade , and one acid etched, this is the best one so far. It cost 23 dollars -->>>

maybe i'm confused - but WHICH ONE is the best so far? 1500 or acid etched?

filip

[Richard Mellor]

Hi everyone
this is the link to the ground glass. the part number is 099-0160


http://www.optosigma.com/miva/merchant.mv?Screen=PROD&Store_Code=OS&Product_Code=pg211&Category_Code=Filters+%26+Apertures






this is link to the agus35 with the optosigma ground glass
www.dvinfo.net/media/mellor

[Obin Olson]

Pat I have shot with our steadycam and the mini35 on the front that I made with the spinning cd works great BUT you need a focus puller to get any good shots at all unless you dont move aobut much and shoot the subject the same distance from the camera the whole shot

[Dietmar Zonewicz]

have a look at: http://arco.acromedia.de/ than go to projekte and select mini60 - filmlookadapter

tell me what is your opinion about the system - except of that the last shot was much too dark.

dietmar

[Richard Mellor]

thank you dietmar for the clips. does the boscreen reduce
the light or was it shot that way? as we always want to know.
what was used for the ground glass

[Michael Moore]

WOW this is one of the longest threads I have ever seen. I was trying to search through the post but there are just too many. What I am looking for is instructions. If any one has a step by step how I would love to see it.

Thanks in advance
Michael Moore

[Dietmar Zonewicz]

the bosscreen did reduce the light that much, but I think I can reduce this an the vignetting by usung a fresnel or a condensor behind it.
The groundglass was a mediumformat gg from Mamyia, the markers on it where removeable with aceton. It isn't as fine as your self grided may be, but at this big size it really doesn't matter. Remember the gg is 6x6cm!

dietmar

[Obin Olson]

<<<-- Originally posted by Bob Hart : Obin

Sanding off the top layer. That option works fine except for the disk having a green tint which has to be manually white-balanced out. Not a big deal but it is there.

Pat.


it's not green it's clear

[Jim Lafferty]

Hello all...

I'm just popping my head in here to note a finished adapter that works very well.

I did a tutorial on building the Agus35 originally, and then followed it up with an Aldu35 tutorial shortly thereafter, and then got submerged in life's distractions and demands. I finished the adapter recently and took it to NYC for some random tests.

Here are the images. I'm currently working on encoding some footage as well.

This adapter is built from instructions in this tutorial, for the GL-1. It's not the cheapest adapter, but it is simple and effective. The only notable exception to the instructions -- as they currently stand -- is that in the most recent iteration I ground one side of the GG by moving the GG ontop of the grinding glass, instead of the other way around. By doing so, it was easier to ensure that the side that was to remain free of scratches would do so.

The main problems I'm having to overcome now surround keeping dust off the elements, and keeping my shots steady while pulling focus handheld. I sometimes worry that spray paint might be flaking off the interior and settling on the glass -- in the future, I'm going to see if I can dye the plastic of the PVC tube instead of painting it.

When proper time and care is given to callibrating the adapter I've built, there's no vingetting/blooming of the image. I don't use any condensor lenses, and attribute the image quality of my adapter largely to the use of the Century Optics achromat.

I've taken note of James Ball's acid-etching instructions and have ordered etching cream -- thanks for the extensive notes, James. As it stands I'm not sure if I do or don't like the grain I see in footage, but there's always room for improvement and it's nice to have a choice.

Thanks for everyone's who has been contributing!

Anyone know what's up with Agus these days? He had stills back in the day from a short using his adapter that I've wanted to see...

- jim

[Bob Hart]

Obin

Good news if there are clear ones around. Could you advise which brand of CD-R it was.

[Obin Olson]

not sure jsut some random disk at work :) I will look today and tell you

[John Heskett]

Bob the color in many CDR discs is from the foil on the top. You are grinding the top off anyway; therefore you will end up with a clear disc.

[Obin Olson]

Yes, John that is/was the deal with mine

[Wayne Morellini]

<<<-- Originally posted by Obin Olson : FYI I just took a normal cd-r NOT the spacer type and sanded the top layer off...now it's a better then spacer-type GG because the cd-r is a higher quality then the cd-r spacer! I took my small orbit sander and did away with the top coating..works great -->>>

I got a cheap obital sander some time ago for this pupose too (only about $10US) but have yet to get around to it. How much better is it than hand grinding, or chemical etching?

[Jim Lafferty]

It's not better than grinding with AOx -- I don't understand why people are regressing to the original project -- the results simply aren't there.

I've got an original Agus35 that hasn't left the shelf since I made the static solution pioneered by Aldus -- and while it's a nice relic, and has some aesthetic potential, the investment needed to get it working properly outweighs the benefits.

- jim

[Brett Erskine]

Jim you really have to change your tutorial to say "grind only ONE side of the UV filter's glass" not BOTH. If they do both they are sure to have very soft images. Not to mention it take twice as long to gind both sides. I only mention it because I know you agree but havent changed the tutorial yet.

[Jim Lafferty]

Actually, Brett, quoting the tutorial:

You may find it to your benefit to cover one side of your filter with strips of scotch tape in order to avoid scratching, while still allowing you to see through it completely. Ideally, you're going to want to frost only one side of the glass, but if you scratch both sides, grinding them until they're uniformly frosted will be your only recourse.

I've since placed some emphasis on this part of the tutorial, but it's been there for a while now.

In the future, once I get the time to grab more shots of myself grinding, I will change this area of the tutorial to demonstrate grinding by moving the GG over the grinding glass, rather than how it's currently demonstrated...in this way I found it easy to keep one side free of accidental scratches.

Still waiting on my etching cream :D

- jim

[Kaushik Shridharani]

Hi all,

I've been reading this forum with great interest for the past few weeks. While I start putting together the components for an Aldu35, I'm also waiting for the design to "settle".

I'd like to help out, so I've done a little more research into optics and home-made cameras and have dug up some useful stuff, I believe. (It's hard to read every post, so apologies for repeating and any wheel re-inventing).

I think it's also important to start identifying the trade-offs so we can make our own choices and learn how to better use the adapter. There are LOTS, especially with regard to:

Peripheral Illumination Loss
=================

After reading up, I'm learning that there are a lot of sources for the loss around the edges. Please correct/add on to these.

a) angle of view
Your choice of lens might contribute to this problem. The wider the angle of lens you mount, the greater the light loss on the periphery relative to the center. No escaping this because it's physics. Unfortunately, choosing a longer lens means losing a few stops.

b) aperture setting
At f2.8, the illumination at the edge of a 35mm image is 40% less bright than the center. At f8, the image edges are 90% as bright. By keeping our lenses wide open, we'll get more light onto the GG but we'll contribute to periphery loss. (I'm guessing this is also why people have reduced peripheral vision at night.)

c) coarseness of GG
Hand-made camera makers seem to find that, all other things being equal, the coarser the GG (ie, less scattering) the brighter it is; however, the more the edges of it will be dimmer compared with the center. Everyone here seems to be going for a fine grain, which helps keeps the GG evenly but not as bright overall, which causes us to want to open up the 35mm lens as much as possible, which contributes to light uneveness! Ugghh!

d) off-axis condenser mounting
This is the principle behind those traffic lights you can only see straight on. If you mount a condenser and it's not right on the optical axis of the adapter, you'll make a real mess around the edges of your images.

e) mis-specified condenser lens
Condensers can sometimes contribute to peripheral illumination loss. There are at least three ways: the wrong focal length, wrong position and/or the wrong orientation. More in the next section.

Condenser Lens Issues
==============

Whether or not to put in a condenser has been debated quite a bit. I'm putting myself in the must-have-condenser camp. I found this to be a really good discussion of condenser/fresnel issues for home-made medium-format camera makers: http://medfmt.8k.com/bronfresnel.html

a) focal length of condenser
Hand-made box-camera makers (who place a GG as a focus screen on the film plane before replacing with film and exposing) suggest a focal length for the condenser that is a little longer than the focal length of the prime lens assembly. This makes sense, because that's the only way to get the condenser to focus on the same point that the front lens is working on (aka, the lens's "rear principal point"). Note, though, it's not possible to get it perfect since that point shifts (and the focal length of any 35mm lens changes from its specified focal length) as you move it away from infinity focus.
The worse thing you can do, I'm reading, is use a condenser lens whose focal length is much longer than your 35mm lens, ie "overshoot" the rear principal point. In other words, if you've got a condenser whose FL matches your standard lens (say ~50mm) and you use your 28mm WA lens insteads.
But it seems to me that it should also be bad if you "undershoot" the rear principal point. Think of a Fresnel light: when you move the bulb away from the lens, it goes from flood (wide, less light in center, gentle falloff) to spot (narrow, more light in center, hard fall off). Flooding the light is like the focal point has "overshot" the light bulb. Spotting the light is like the focal point has "undershot" the light. It leads to a spotlight effect and hard edges.
Both types of peripheral illumination falloff show up in some of the test images I've seen so far. Using the wrong focal length for the condenser can sometimes be worse than having no condenser at all. This might explain why some people have ignored the condenser. I think that before you give up you should try to get focal length and position right at the same time. If you can't get one with a focal length approximately the same as the 35mm lens and position it butt up against the GG, then get another condenser whose difference in focal length makes up for the difference in position.
Re an earlier post, where Jonathan measured the focal length of a condenser element from this Canon AE-1. His was 155mm; but it was actually part of a multiple thin lens element (with a GG/fresnel combo). If that fresnel's focal length was 70 or 80mm, then the combined focal length would be about 50mm, which would sound right. It's the combined focal length that counts and where the condenser is relative to the front lens.

b) orientation of condenser
If you use a planar-convex condenser, the orientation matters. The flat side should ideally face the 35mm lens, the convex should face the direction of convergence. If you put it in backwards, you introduce spherical aberrations or over-convergence. That over-convergence might even contribute to peripheral image loss. I haven't read that specifically however. (Check out this website for a good applet that shows it: http://www-optics.unine.ch/education/optics_tutorials/plano_convex_lens_aberration.html

c) condenser position relative to GG
Putting the condenser after the GG seems most practical for us home-brewers. But, in theory, it's supposed to be better to get the light rays to converge just before they become diffuse as they strike the GG. Getting them to come in parallel helps to reduce diffusion (relative to the coarseness of the grain) and thus loss of brightness, apparently. This might be why in some SLR cameras, the designers put a condenser lens before the GG. But it also adds a little to the light path and means the GG has to be placed a little further back. (Apparently, it needs to be pushed back about 1/3 the thickness of the condenser if it's glass). Getting this right might be tricky if you're building a rigid assembly and you don't have a caliper to measure the thickness of the lens. If you've got a variable spacer between your lens and your GG, it shouldn't be a problem to make this adjustment.


Sorry for the length. Hope it's useful, especially to the people who are trying to catch up.

[Richard Mellor]

thank you kaushik for your informations on lens .


I have a link to my finished aldu35 . I wonder if you could look at the design and give recommendations to design changes.

I t was made with 52mm lens filters, 1500 grit ground glass, from opto sigma, and a plcx lens


www.dvinfo.net/media/mellor

[John Heskett]

Richard,

How do you like the 1500 grit ground glass form Opto Sigma? I was going to order some but they never called me back.

[Richard Mellor]

the agus 35 was made with 52mm lens filters the 50mm piece of ground glass fits perfectly. the filters threaded spacers allow fine tuning of focal length. as to the ground glass I,ts the best I have found or made so far. the part numer is 009-0160

http://www.optosigma.com/miva/mercha...+%26+Apertures

[Kaushik Shridharani]

<<<-- Originally posted by Richard Mellor :
I have a link to my finished aldu35...

It was made with 52mm lens filters, 1500 grit ground glass, from opto sigma, and a plcx lens


www.dvinfo.net/media/mellor -->>>

Sorry, Richard. I didn't see a jpg for an aldu35. First question I think is if you know the focal length of your PCX lens and how close is it to the length of your 35mm lens.

[Richard Mellor]

kaushik- the first three files ,35mm lens adapter are the aldu35
- need to rename them - the pclx lens is 50mm with a focal
length of 50

[Kaushik Shridharani]

richard -- i wish had the knowledge to do more than take a stab, but i'll take a humble stab:

i take it your pclx is not up against the GG. i would think that having a condenser with approximately the same FL as your 35mm lens also requires it to be as close as possible to the GG. if it's far back from the GG (a 6mm spacer ring is already a hefty 12% of the FL), then its focal point will also be short of the lens "rear principal point" (the imaginary point inside the lens that we want to stay targeted on).

thinking back to the fresnel light analogy, if the light bulb is moved beyond the focal point (ie, the focal point falls short of the source), then it acts like a spot light. this might explain why your peripheral illumination loss has such a hard edge to it (to my eyes).

i guess you have two options: use a pcx lens in the same position but with a slightly longer focal length. or get your current pcx lens right up against the GG.

the other source might be the aperture. if you've got it wide open, light from sources that are off-axis have a greater chance of getting lost compared to light from sources in the center. stop the lens down and you'll get less light overall, but there won't be as much waste of off-axis light sources compared with the center.

[Michael Ogasawara]

I've been busy with school and other things lately, but I've got back on track with my adapter, and I now have a working prototype.
(large image files)
www.edwardflinch.com/images/mini35.htm

I also have a short clip here: (2.6MB)
www.edwardflinch.com/images/testshot.mov

The ground glass is ground with 5 micron grit, and the condenser lenses are from Surplus Shed. All of the components fit together very snugly. I chose the two condenser lens approach after doing some experimenting. I found that it reduced some spherical distortion I was getting.

[Frank Ladner]

Michael: Nice images!

I too am using a GL2 w/ my adapter so I am glad you posted your prototype design for us to check out.

I notice a small amount of grain and maybe some color fringing on the sides, but the frames look good.

By the way, about how much do those PCX lenses run?

Thanks!