I have finished my Agus35! The CD motor is really noisy (I don't think I have it balanced). And, I get lots of Flickering, but no vignetting. And, for some reason, I can't focus on things more than about 4 feet away??? I do not have a fresnel lens installed, but the DOF is better than the tests I did without the spinning CD. I used 1000 grit paper and sanded in one motion across the disk (I don't know if this is the recommended way?). Haven't tested in the light of day yet, so don't know the real abilities. Anyonen have comments? I will try to get some footage tomorrow that is acceptable to post...until then, let me know of any improvements I can make...thanks in advance!

Clay

J. Clayton,

you are in the babies step yet, you have some problems with the distance from the SLR lens and the GG seens like it is too close or too far (my best guess is too close) the flickering is cause you probably didnt use a discman piece or it isnt well fitted, also remember that no all cds are perfectly straight some of them are bended a little.


About the shave machine and making this to vibrate... that is not a good solution, the noise is really high and you just cant get good results with it. if you are making this homebuilt the cd option is the simple and more effective way... and cheaper. And simplier to build.



BTW for everybody interested in the comercial version, i got some news... i got the prism and i can find more real cheap :) ... thanks to Guatemala cheap market.

heheheh no more info for now until i have some real pictures of this new baby. Also we are still working now in making an universal lens adapter. We have some ideas so stay tunned.

Hi Guys

I made a mock up last night using a 35m lens, a cardboard box and a piece of 6x4" satin glass (4mm) that I just shoved through 2 sides.

When I put my Sony DCR-TRV16e into the box and output the picture onto my 32" tv, the quality was great. I didn't notice any grain and had little to no vignetting and I also couldn't see a light spot. The TV probably masked what little grain there was. The camera was attached to the box using a 30-37mm step up ring connected to the Cokin A series adapter ring which was drilled and screwed onto the box.

I'm going to play with it over Xmas and see how much grain there is when I view the video on my pc and then blow it up using Spline pro. If there is very little grain then I will put the project in a 4x4" box. I'm going to try some thinner satin glass to see if that yields a better quality image.

Regards

Terry

A preliminary report on the pressing method of achieving a groundglass surface on a clear CD disk. So far, I get a sharp image on the screen, and it persists in low light. It is much improved when the disk is spun and flares from highlights seem to diminish. Getting a consistency of density across the disk is very difficult (Like I haven't achieved it yet.) With spindle motor speed at about 1500rpm, this causes a flickering effect which has been described here.

Microscope slides might be an option as raw stock for lapping fixed groundglass screens. It's a pity they don't still use large format glass slides for theatre advertising any more.

As a construction method, is anyone using a continuous length of PVC pipe 60mm OD or so with a slot cut in it for the groundglass rotary screen and adaptor pieces slipped into either end for the front lens and the camera mount or close-up camcorder lens. Some of this stuff is OD of 61mm, ID of 56mm and might have enough meat in it to support an external thread cut for the PD150/VX2000 camcorder family.

I propose using a short piece of PVC sewer pipe to align two PVC sewer end-caps for the groundglass enclosure. The 60mm pipe will go right through it hopefully preserving centricity of all lenses. It may be a bit large but may provide space for face mounting the switch, the spindle motor and a battery container.

Has anyone gone this route?

I have sent some captioned .jpg files to Chris (kennelmaster)which hopefully he can post if they don't take up too much room on his server. Three demonstrate the distance between a 50mm objective lens from 35mm still camera and the groundglass image plane. A fourth demonstrates the light transmission through a "groundglass" CD frosted by means of pressing pits into the surface with a 500 grade silicon carbide "wet and dry" paper.

All images were originated on a PD150P, captured into Adobe Premiere 6, exported to .bmp files, imported to Ulead Photoplus 4, captioned then saved as .jpg files. After export as .bmp images, the pics are darker than they appear in Premiere or in the camcorder viewfinder. The image agus4.jpg was inverted and flipped but they have not been otherwise adjusted.

The fourth image is intended to demonstrate the light transmission through the rotating pressed groundglass. The sharpness or rather lack of it should be ignored as all components, the CD + motor, wires onto battery, objective lens were all separate and handheld together in a very awkward improvisation.

Lighting was by way of the ceiling lamps which were 3 x 60watt incandescent globes inside frosted dome shades. The camera was left to run wild and free on full automatic settings for exposure but manually focused.

The objective lens was a Fujinon 50mm as illustrated in agus1.jpg to agus3.jpg

The camcorder close-up lens was the macro portion of an Optex wideangle adaptor. It has a 46mm filter thread which was stepped up by two adaptor rings to the 58mm of the PD150. This put it forward of the PD150 front lens element by about 14mm so there is some vignetting on the about 75% zoom used.

Strangely, the flickering effect I observed by eye is not apparent in the camcorder playback.

There is granularity apparent in the image via groundglass. I'm not sure if this is the frosted glass or low light noise from the camcorder itself. On the other images which were also low-light some granularity or noise is also evident.

We live in interesting times.

Re: Lens hoods
 

>>>>Originally posted by Jeremiah Rickert : Does anyone know a place to buy a lens hood for a GL-1?... It seems it would be easier to use something that basically snaps into place for a mount on the 35 adapter, rather than something clumsier... Of course, I don't want to use the only lens hood that I have, that came with it. I didn't see one on B&H...there was a GL2 hood on Ebay, but nothing for the GL-1.

- Jeremiah, check again. Look for one that uses a 58mm screw-on thread mount such as this one from CAVISION http://cavision.com/LensHood/for_58mm_dia__shade.htm or one from CENTURY OPTICS http://www.centuryoptics.com/product...s/dvshades.htm. You could even try Google for a "58mm lens shade" or "58mm sunb hood". You get the idea.

- don

Don - I assume he doesn't want to wear out his 58mm threading with the weight of such an add on... thats why he wanted to use the baymount connection....

but I could be wrong

Well I was thinking that it would be affordable that way. You could still mount it to the lens that way to have a firm "light-leak-proof" connection to the lens,,, but you would still need to use some rod support in any case - unless the adaptor created is very lightweight - at that point ity would be moot point.

If you need an OEM stock GL1/2 sunhood, contact Canon.

- don

There'some large diameter plastic plumbers fittings (sewer pipe joiners) which look a bit promising for disk enclosures. There is a reducer which has offset centres, a bit like a funnel to look at. It is about 1/8" too small to enclose a standard CD but might be useful as an endcap to hold a lens adaptor.

No GG at all! Is it just me, or has no-one else done this?
 

Ok, so as I said above I finally got my grubby little hands on a +10 macro adapter for my VX2000. I was fooling around with my new ability to gather close focus to the frosted cd when all of the sudden, to my delight, I realized that when I wasn't holding the cd in place a clear image was seen from just zooming right into the center of my 50mm lens. It's a 50mm 1:1.8 Olympus lens. So here's a design featuring literally no GG at all, just zoomed through the +10 macro's vignettes, and the 50mm lens' vignettes, and voila no grain, no fuss.

So, to exaggerate my point, I have a 50mm SLR lens placed about 4.5 inches in front of my VX2000 with a UV adapter and a +10 Macro adapter on it. THATS IT!

It's shaky due to the fact that nothing is mounted, its just sitting on my table...not light tight whatsoever. Notice the HUGE amount of breathing when focusing (the changing of size of objects when focus is shifted) Don't know what to do about that, pretty much a feature of inexpensive still camera lenses, but in general I'm really happy with this...

So please watch the short clip I've captured, it's under tests on this page:

http://www.par-t-com.net/media.html
(The image was flipped in post)

...and then bring me back to Earth as to why this won't work for some probably obvious reason.

Happily,
Spencer Houck

An interesting product available at the following web address,

www.scopetronix.com/maxview2.htm

conveys the image from a telescope to digital cameras with 58mm filter thread. May possibly work with the PD150/VX2000 camcorder family but may frame only the up to 18mm diameter image target my own adaptor does due to the smaller CCD area of motion video cameras compared to still cameras.

I thought there have been several people who have tried Spencer's method with no luck. Hey Spencer, could you post some more footage once you have the whole thing completed? Maybe having the +10 macro is the ticket. It's hard to believe that it's that simple.

Re: No GG at all! Is it just me, or has no-one else done this?
 

<<<-- Originally posted by Spencer Houck : Ok, so as I said above I finally got my grubby little hands on a +10 macro adapter for my VX2000. I was fooling around with my new ability to gather close focus to the frosted cd when all of the sudden, to my delight, I realized that when I wasn't holding the cd in place a clear image was seen from just zooming right into the center of my 50mm lens. It's a 50mm 1:1.8 Olympus lens. So here's a design featuring literally no GG at all, just zoomed through the +10 macro's vignettes, and the 50mm lens' vignettes, and voila no grain, no fuss.

So, to exaggerate my point, I have a 50mm SLR lens placed about 4.5 inches in front of my VX2000 with a UV adapter and a +10 Macro adapter on it. THATS IT!

It's shaky due to the fact that nothing is mounted, its just sitting on my table...not light tight whatsoever. Notice the HUGE amount of breathing when focusing (the changing of size of objects when focus is shifted) Don't know what to do about that, pretty much a feature of inexpensive still camera lenses, but in general I'm really happy with this...

So please watch the short clip I've captured, it's under tests on this page:

http://www.par-t-com.net/media.html
(The image was flipped in post)

...and then bring me back to Earth as to why this won't work for some probably obvious reason.

Happily,
Spencer Houck -->>>

NICE WORK!..I tried and failed. I have the same Oly lens too, Maybe if I try a macro lens with it.

<<<-- Originally posted by Peter Sciretta : What +10 macro adapter do you have? Brand? Model? -->>>

It's a "samigon" branded (1:1) Macro Close-Up Lens +10 58mm made in JAPAN. So says the little oldschool box it came in. I got it from a store called Campus Camera, at the local university. It caters to still photography, so I'm assuming most well stocked still photography stores would have something similar.

<<<-- Originally posted by Rob Hester :J ust wondering though, isn't the image also zoomed? -->>>

As far as I can tell the image is just as if you were using a ground glass. In essence I'm still taking a picture of a picture. The zooming by 7x happens with XL1's with 35 mm lenses adapted directly to them, projecting the 35mm negative's image right onto the camera's CCD. The 50mm lens I'm using must pass through my VX2000's lens, so the CCDs are not being projected onto directly, so it doesn't magnify.

Also with that direct coupling on the XL1 you don't recieve the DoF of the 35, so by default I don't think thats happening, cause i'm experiencing some "XtremE Shallow DoF".

One thing to note tho, is that for mine to work, the 50mm lens itself must be shifted 1 and 7/8s of and inch to and fro the VX2000 to achieve focus of 4 inches to infinity.

-Distance of 3 5/8 inches from the back of my 50mm lens to the front of my camera's housing(not the front of the +10) gives me a focus of infinity.
-Distance of 5 1/2 inches from the back of my 50mm lens to the front of my camera's housing(not the front of the +10) gives me a focus of 4 inches.

The lens' focus ring will not move the focus to this range, and therefore the whole lens must be mounted to some sort of moving platform. I'm hoping to be able to focus much like a telephoto 35mm lens with a smooth slide ring around a tube which moves the 50mm lens to and fro.

So, in short, this does indeed produce a much more optically perfect image, no grain, none of that, but introduces problems of allowing smooth focus adjustments on the fly. It would be easy to make an adapter that can change focus between shots, but to change the shallow focus while the camera is rolling when your character walks closer to the lens will require a more sophisticated structure.

Hope this helps, I'm going to continue testing housings to allow on-the-fly focus adjustment.

Spencer Houck

Actually what spencer is doing is all another thing to the Agus35,...

He is still making the image in the camera CCD, so you wont get the same DOF of the SLR lens in a negative, he is still need to full zoom this dv camera to open the iris to the max and then adjust the focus.

With the agus35 you are creating the imag first in a Ground Glass, and than you just shoot that image with your dv camera, making in other words that your CCDS either you have 1 chip, or 3 chip camera, to be as big as a 35mm one to capture the full DOF.

Ground Glass on Demand
 

I ran across this looking at lights.

www.arri.com/entry/ggc.htm

no GG tested
 

Spencer

I discovered that as well late afternoon when i stacked tiffen marcos up to +11. I have a sony trv 900, stacked the macros, rigged my version of the agus35. When i took off the GG i saw a full frame into the canon lens. Exicted, I started doing immediate test in my room using dolls for DOF and then compared pixels with the rig and without using photoshop and AF.

I found conclusive by,using a 28mm lens, i get the SLR len's angle of view, and DOF, but lose 1 1/2 stops.
However, when i tried to rack focus, i liked what i got from the TRV900 better. I know the 28mm is not great with narrow focus but i think it's more convienent without any lens rigged at all then what i saw.
When i deinterlaced and color corrected, I see a slightly diffused image from the SLR, but I have come to the conclusion that what creates much of the film look of the P&S and Agus's version is the GG. You need to have it because i was dissapointed in DOF and the quality was just the same as if I didn't rig anything at all but with light loss.
I have a Agus35 up and running but it cuts too much light and plan on making my own gound glass to shoot indoors. The quality of the GG is really important.

Peace

Agus, I may not be capturing the full DoF of a 35mm SLR, but if you've seen the video I linked to, I believe that the DoF is quite adequate. I'd rather have the clearest picture coming in...regardless of its "videoness" and "non-film" grainyness. Frankly if I want to degrade the image with grain, I've always got After Effects.

The two main steps, or barriers, I see between me and the almighty "film look" = lack of shallow DoF, and lack of 24p.

24p shall be achieved through post-pro (magic bullet, or vegas), and the DoF is seen in my test video, so theres the 2 barriers coming to a crashing end in my book. So i'm sittin' pretty at the moment.

Spencer Houck

If anyone in Australia is into roll-your-own groundglass, there's an outfit in Victoria named Abasco Trading Pty Ltd Unit 19/12 Edina Road, Ferntree Gully VIC. 3156. They have Aluminium Oxide grits which are mentioned in another website mentioned here. I actually thought they were here because they were listed in the city metro directory yellow pages under 1800 809 228. They have local phone 03 9752 2816 and a fax number 03 9752 2808.

Nevertheless the rep was very helpful on the phone and happy to send a small order of 500gms across Australia for $10-00 item, $10-00 mailbag and GST $2-00, all up $22-00. He apparently normally sells to industry in bigger lots but was good enough to hunt for a broken bag to send a smaller amount and got it here in 1.5 days which is not bad.

Some components and optical engineering principles incorporated in the Mini35 and Pro35 might not in themselves be furthur patentable individually.

The method and order in which all can be combined to produce a deliberate and new unique outcome is another matter. (I think the legal-speak word used in court the other day was "synergy").

A case alleging such an intellectual property is being used by a defendent without consent or licence, might be pressed by an aggrieved party as an enforcable right if that method is sufficiently unique as to not be a commonplace practice of combination of those components for any other purpose.

So be careful out there relating to patent rights as wisely suggested in preceding posts. There seems to be potential risk of liability both under national patent laws and under common law.

There are references being made to case law in the UK and Canada in a current matter in Australia so be aware the issue is very far from dead.

I am not a lawyer and am paraphasing from recollection some things I have stumbled across recently.

Another lowlight test with groundglass CD dressed on a glass sheet with loose 600 aluminium oxide grit in water. - Much nicer uniform finish. No flicker. Image seems slightly softer, maybe due to denser opacity. Light transmissability appeared to be not as good as the pressed version. Quality across image was uniform with screen stopped or spinning. Spinning removed any faults in the groundglass finish.

Has anyone done any tests with test patterns? Mine don't look too good so far with merging in different places in the image at between 400 to 450 TV lines. DVCAM normally gives about 500.

<<<-- Originally posted by Peter Sciretta : I'm lost in the past few pages of posts... we've gotten so far distracted from the original simplicity of this thread.

Some of these posts take someone with a lot of college science courses to figure out.

What happened to keep it simple??? -->>>

The principle has been the same, static GG or spinning CD. The simple version of the adapter is done, Agus has given everything you need to make one yourself. What Agus and some are working on is to improve the quality of the image and make it more useable, such as producing correct upright image, and hopefully will bring the result on par with mini35 or even better.

Technical problems:

1. Ground Glass. Quality is everything here, you need something not only fine, but also transmit more light.
2. Hot spot. Without solving this problem, you are limited to what kind of ground glass you can use and the image quality won't be good.
3. Producing upright image.

Let me state the progress so far (as far as I am concerned):

1. The 3 micron ground glass is at the border line of suiteable for the static solution. It's certainly suiteable for the spinning solution as well and using in the spinning solution will give you much better result. There is a good possibility that a material better than the 3 micron GG will be discovered in a few days, in that case this problem is resolved for static solution as well.

2. Hot spot problem. I consider this problem resolved. Refer to the static solution thread.

3. producing upright image. This one is solved in a few ways and the most efficient/economic way needs to be decided.

I think it's going well, and in a few weeks you should have something layed out with everything you need.

There is another solution to inverting the image. Some night-vision intensifier tubes have a very compact inverter built in to a tube measuring about one and a half inches long by about one and a quarter inches in diameter with a display screen of 18mm (about 2/3 of an inch).

It is military tech so they are not exactly going to tell how its done in detail. The principle is they use fine optical fibres. These are packed accurately together so that along the entire length of the path, each fibre remains in its correct relationship with its neighbor.

Both ends of the piece terminate as a pick-up screen at one end and a display screen at the other. At the eyeball end, as I can work out there is a form of opaque projection surface superior to anything we have been evolving, or it may just be the polished face of all the fibres themselves.

To erect the diplayed image, it is pure simplicity. They just twist the mass of fires through 180 degrees. The doing of it probably creates incredible challenges in just keeping those fibres from shifting about. If an intensifier tube gets a strong (for an intensifier) light into it and goes into clear display, you can sometimes see little imperfections where a clump of fibres has moved slightly in relation to the rest. It shows like an earthquake fault line.

The CP16RA motion picture camera viewfinder uses a little projection groundglass screen - not quite true. The screen is about the thickness of a circuit board. It is actually a sheet of packed optical fibres, stablilsed I guess with some sort of tough adhesive, thinly sliced and then polished on both surfaces. The light transmissabilily of the viewfinder is excellent on wide-open lens aperture. Detail and contrast is crisp. (After getting accustomed to one of these, tube or LCD video viewfinders comprehensively suck to extremity.) With the lens stopped down, there is a weird diffraction rainbow effect. As we are after a wide-open lens aperture for best depth-of-field effect, this would not be an issue for us.

Optical fibres have come a long-long way since the early seventies when the CP16 became the king of news gathering.

If sufficiently fine optical fibres could be accurately packed in a wide round, glued, sliced and polished flat on both surfaces, it would be the ultimate groundglass. Maybe that's what the Mini35 uses.

I doubt a full CD sized panel would be workable for spinning. A more compact arrangement like a Sarich orbital piston, which works something like an orbital sander, to move a smaller screen might be possible.

If the fibre screen could be made with sufficient resolution that it would not have to be spun, then a pack of fibres twisted 180 degrees like inside an intensifier tube might provide a solution.

As a custom job it might be horrendously expensive however there may be somebody here who messes with fibre-optics who could put us right. Even better, maybe somebody here works for Electrophysics Company in the US, Photonis in France and Delft in the Netherlands and might ask some questions on our behalf.

Here is a work around to inverting.
A monitor that will flip the image on all axis.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3065860805&category=14946&rd=1

Taylor Moore man, i've already suggested that idea!

not specificially that monitor in question but about using an external monitor flipped upside down OR using an optical device that will flip the view finder of the camcorder

Either way at least you do not disturb the incoming image.

I also suggested using a "project box" someones seems to have imlemented that to.

I think the race is on to make a pro version that does not need flipping in post and a static GG version may well be nearing reality.

One more idea for you guys :

If you wnat to vibrate as opposed to spinning try connecting the GG to a small speaker and apply a sine high frequency signal to the speaker. My guess is that a very high frequency will be needed in order to minimise the grain, and aslo if you use 2 speakers one in the x axis and one in the y axis then you will have the grain movement in total random fashion thus remaoving any "streakes" which appear from either spinning of vibrating in one direction

Groundglass disks. Been doing some homework and have found there are two types of precision glass disk made in numbers for industrial applications, a third if you count CD mastering disks but these are too big at about the size of an old 45rpm vinyl record.

Some advanced computer hard drives now use a glass disk which has an outer diameter of about 3 and a bit inches and an internal hole of about 3/4" Its thin stuff at 0.6mm. It is supplied as blanks ( hard disk substrates )to the industry. They offer toom small an image target between the inner and outer diameters for our purposes.

There is another product which is probably most promising to us if we could get our hands on it. It is a glass disk made for testing computer hard drive read heads. It is available in varying outer diamaters with varying internal diameter centre holes. It is a bit thick at 2mm. (You could probably get something made up as 2mm glass is fairly common.) This stuff however is made to spin.

If there were such items as rejected disks which don't meet the surface standards but would suit us to make our groundglasses, or worn out disks, buyable cheap???

Otherwise it might be necessary to form some sort of group to buy in a batch at economic prices.

This product is called a glass disk for flying height tester "GD-FHT". made by ohara of Japan. There is a US website www.oharacorp.com The Japan website is www.ohara-inc.co.jp

Anybody here involved in R & D or product quality control at IBM???

A couple of people have experimented with zooming straight into the rear of a 35mm camera lens. I've watched Spencer's video and think it looks like video, and accomplishes the same as attaching a telephoto/wide angle lens to the camcorder. Others feel that it is acceptable. Either way, if you like it, you like it. But, for experiment's sake, maybe it would be a good idea to get a controlled group of shots from both Spencer's setup and Agus's setup. Spencer's keyboard/note shot and the guy at the door could be easily reproduced with a ground glass adaptor for comparison. Unfortunately I don't have my adaptor completed to do a controlled experiment here, but if Agus or any of the other guys that have completed their adaptor want to try this, then it might help clear something up.

here's something to try...

1) Find out your camera's 35mm focal length equivalent. You can usually find this information on the internet. GL2's are 39.5mm, PC-101s are 42mm, PD150s are 43.2mm equivalent at their widest settings.

2) Use a 35mm lens with a close focal length. The lens that most people have been using on their adaptors have been 50mm focal length (35mm refers to the size of the film frame, not the properties of the lens). 50mm lenses should be close enough to the 42mm of the camcorders to work for this experiment.

3) Record identical shots with each of the two setups as well as the stock camera lens. Keep the camera lens front at the same distance from the subject with both versions. Depending on the length of the adaptor, you may have to move the camera back or forward a little to keep the 35mm lens front at the same distance from the subject. The shots should be framed the same. For test purposes, if you have access to both setups (that would be most controlled) get a shot with the 35mm ground glass adaptor, 35mm non-ground glass adaptor, and the camcorder's normal lens (you may try zooming in just a tad to match the other shots... but be precise).

4) Keep track of which shot is which and compare, taking note of the distance between objects that are "in focus" relative to "out of focus"

5) Post still frames (with no post production) of the different setups with descriptions of what the shot was. That way others can see your findings.

Unfortunately, not everyone has access to everything, and not everyone has identical camcorders. However, this can still be done in a convincing manner... if you have an adaptor, you can contribute. Just be sure to mention which adaptor, 35mm lens, distance from subject, and camcorder model.

Have experimented with a microscope slide using loose aluminium oxide grit 600 grade lapped on a sheet of glass. Glass is a much more controllable medium to work with than the CD disks which seem to get injured at the drop of a hat. The result across the glass is also totally consistent.

For those thinking of the fixed glass option and can't get the Zenit screens, the microscope slides are almost 16:9 frame. Used with a large or medium format camera lens and videoing the larger image across the whole slide, you could look forward to a good blemish-free result. I'm not sure how good the light from the lens will be as the image is spread over a larger area thus dimmer.

The frosting texture with 600 grade aluminium oxide might still be a bit course but the light transmission is heaps better than the plastic CD lapped with the 600 or pressed with 600 grade silicone carbide paper. With glass, the frosted surface is not injured by encounters with finger sweat or cleaning cloth.

Have tried the new groundglass as a stationary screen. Method = Pringles chip can, slots for glass slide to fit through it. PD150 videocam, with close up lenses x4 + x2 + x1 stacked, looking in from one end, 55mm Nikon f3.8 lens in other. Lens is crudely secured in end by rolled up sock cuff, video camera secured in end by rolled up sock cuff (True, the socks did have no heels left - honest and were washed).

In bright daylight which would require f16-f22 with ASA 320, the Nikon lens wide open, there does not appear to be any difference in the quality of the image at centre from that of image into PD150 direct. Contrast and colours remain the same though blue seems perhaps a little truer. This effect is reminiscent of late seventies 16mm Agfa neg stock.

There seems to be a slight diffusion of highlights. White objects like a flying moth seem a bit fuzzy.

There is a bit of a hotspot over 80% of the image from centre with the corners seeming about two f-stops darker.

Granularity becomes apparent in these darker corners. If the Nikon lens is stopped down, the granularity becomes apparent across the screen. The dark corners might be because I can not zoom close enough to the screen before focus crashes in the last 10% of the zoom range and I am covering an area larger than the 35mm camera frame.

There is a greater depth of field effect but nothing I cannot replicate with a close-up lens on the DP150 direct. However with a close-up lens, one cannot pull focus to infinity, so there is the bonus to using the Agus35 principle.

The PD150 will tolerate being operated upside down and the viewfinder can be positioned to display correctly if the combination is used at waist height like an old-fashioned box Brownie or medium format camera with top window viewfinders. With the eyepiece jammed into the stomach, the whole thing can be held quite steady. (An ample gut helps).

In low light levels, with the 600 grit fixed groundglass, I have shot a couple of comparative tests also one test in good light. I'll send these images to kennelmaster Chris to see if he can post them.

The groundglass test pattern seems softer yet on closer inspection, resolution seems to be the same across both test patterns in poor light. The groundglass image is about a half-stop darker, a slight lowering of contrast and there is a faint fawn coloured tint.

Camera gain was left on automatic for the low-light tests. It's probably not a valid test except it might be more representative of practical low-light conditions where you want every bit of gain you can get. Defects on the groundglass visible in strong light were not apparent in low light.

Some slightly darker streaks were apparent in some of the bright light images. These came from oils in the can lining from the crisps it once contained.

Dressing the groundglass surface with a hint of some sort of oil or wax might be an option for better contrast. The oily bits seem to contain light spill from adjacent areas.

I read on the large format camera forum that one thing to do is smear vasoline on the ground side of the glass, then wipe clean with a soft, smooth cloth. The vasoline will fill in the holes and provide a "wet" look to the glass, and improve brightness. I haven't personally tested it, but it might be worth a try.

GREAT NEWS!

I've discovered where to get pre-frosted CDR's like Agus uses -- Maxell's 48x/700mb 50 spindle has it!

I found this on sale at Tower Records today ($15.99), and since I just ripped the label in order to open the pack, here's an idea of what it looks like:

http://ideaspora.net/agus35/frosted.jpg

- jim

Daniel,

Are these the clips you speak of at bobflash.com.br:

Clip 1

(bobcam-natalbarrozo-01.wmv -- 4.07mb)

Clip 2

(bobcam-natalbarrozo-02.wmv -- 3.47mb)

?

For future reference -- when posting clips, please include the file name and/or size in your post -- that way we know we're getting the right material.

- jim

If having trouble getting the CD disk to run true, three solutions - (1) Use the whole of the CD spindle system including the pressure plate which clamps from the opposite side. This is supposed to let the CD find its correct position through gyro effect with the inner hub acting more like a clutch and centre rather than an alignment. The motor remains hard mounted. (

2) If this can't be done because of limited space and you have to mount the CD rigidly to the spindle, try making a diaphragm mount for the motor if the motor is of face-mount Mabuchi style construction. Make a little thin disk or square out of something really light and pliable. Shim steel would be best. Ice cream or milk container is okay but it will deform out of position in time. Face-mount the motor to this. You'll need to be able to precisely drill 4 holes through it, one for the motor spindle shaft, three for the screws.

( A quick and dirty cheat for making a template is to place an identical motor face down on the platen of a scanner or photocopier. The spindle shaft will have to have been removed though some photocopiers or scanners will accurately scan an object up to half an inch away from the platen. - So you'll probably have to have a second motor to dismantle for this. Slide-tray CD players often
have similar motors for tray and transport drives so these could be used. Print the scan and check the distance between the holes against the motor. Glue the print to the metal or plastic you want to drill, mark or centrepunch through the paper then drill through it. Printing to a sticky label makes the job even easier.) Mount the plate or glue it to the case. When the CD runs up to speed and straightens out, the motor will be seen to be vibrating slightly.

(3) Make a foam rubber sock out of hotwater pipe
insulation. Fix your spindle motor inside this and mount the foam inside a piece of plastic pipe glued to the case. It may be harder to keep the motor is position though as the material will slump in time.

For Aussie visitors, with Chris kennelmaster's help, there may soon be a .jpg of a partly assembled early prototype of the Agus35 non-inverter rotary groundglass principle, using Australian standard PVC plumbing bits for case and lens tube structure, plus a Decor potplant saucer as a soft motor mount. (Yes the sock will be there).

Once the motor and disk image plane positions have been tied down by testing, the lens tube will be shortened to accept a proper lens mount for the objective lens and some sort of attachment, probably 58mm filter thread for the PD150 at the other.

There will be observed a cut-out in the lens tube insude the enclosure. This provides assembly clearance for the motor and disk mount which clips into place. The enclosure case comprises two riser caps and a short piece of pipe inside one purely as an internal guide sleeve for case assembly.

The disk sits ahead of the orange saucer driven by the motor mounted behind - not fitted in this illustration. The battery holder will fit in the rear enclosure with the motor and the switch will be mounted to the rear cover which will be the removable cover for maintenance.

Fixing of the covers will be by long pillar nuts and screws as used to mount circuit boards.

Bob Hart's images now online at www.dvinfo.net/media/hart.

Note from Chris Hurd: This is an edited, locked version of the original "Homemade 35mm" thread located here. It has been edited by removing off-topic posts, meta-data (such as "great job!" etc.), repeated questions, and so on. This should make your reading of the entire relevant technical discussion a bit easier. If you'd like to add to this discussion, or post a question which has not yet been asked, please do so at the original thread located here. Hope this helps -- CH