Homemade 35mm Adapter

[Alex Chong]

The piezo actuator method to vibrate the screen as suggested by someone in this thread is good but unfortunately not possible as you need an amplifier to drive the actuator. This amplifier thing is too big to fit into the mini35. I think the best solution as rightly suggested by Brett is to absorb any vibrations by mounting the screen on a rubber mount. Well! back to the drawing board. Does anyone on this thread know how P+S vibrates their GG? Somebody must know or is it suppose to be a company secret?

I am checking out a solenoid instead. I hope there is one that vibrates rather than just pushes buttons.

[Bob Hart]

FURTHUR INFO ON THE ROLLING DONUT/TUMBLER FOR
DRESSING AND POLISHING GLASS DISKS.

Since last post, I have removed the concentric grooves from the face of the rollers (donuts) and kept only the radial grooves. This has fixed the rings on the groundglass problem. The donuts tend to hang up on the glass more and have to be taken off and cleaned more often, not a big chore.

The performance between the full roller and donut version seems identical but the full version wears way at the edges leaving a very slight dome shape whereas the hollow version seems to self-correct.

I also found that the drum (cement mixer barrel) made from a 100 x CD-R cover needs to be fastened centrally on the hub of the water pump or whatever might be used as a bearing and axle. At the 70 rpm I am using, if the drum runs out, there is enough loft to the roller with each turn to cause an uneven cut on the glass disk.

The fine AO powder is also fatal to oilite type electric motor bearings. The bearing is fine but the shaft is gone in 10 minutes, so care is needed when adding more powder to a used mix.

An alternative source for small induction electric motors is older overhead ceiling exractor fans as used in kitchens of bathrooms. The open style motors have a smaller diameter drive shaft. The newer enclosed motors have larger drive shafts and generally these motors have been removed due to failure whereas the older motors have been removed purely because of noise from worn bearings and are still perfectly usable.

[Bob Hart]

FURTHUR INFO ON THE ROLLING DONUT/TUMBLER FOR DRESSING AND POLISHING GLASS DISKS.

Am now getting good results for frosted finish on gg side of disks using 300 grade AO using the tumbler machine. I allow the grit to literally wear itself out which seems to bring it down to a finer grade. A better result may come from the 5 micron which is on its way from t'otherside of the country with the prisms for the image erector. The texture of the frosted finish is probably still not down to the fineness needed for the Aldu35 developments but is finer than by the hand dressed method. The finish is fine enough that a dome lamp can be just barely seen through it. any finer and it may be too transparent with the hot spot problem occurring.

Polishing the frontside is another matter. The tumbler barrel is too small and the amount of movement (friction) across the outer half-inch of the disk is insufficient to get a polish. The tumbler barrel will need to be wider so that there is a good wipe of the polishing roller face across the entire disk. I will also experiment with floating the disk in a holder across a fixed polishing surface on the bottom of the tumbler barrel.

I have tried using felt-like materials and these when glued to the roller faces with contact adhesive ( "sniffing glue" for the youthful among you ) give a good result. The felt has to be a hard grade and thin. Its hard to find and I discovered that a local Oates brand felt-like cleaning/polishing cloth works well. It is about 1mm thick.

[Bob Hart]

FIRST TEST WITH OHARADISK WITH 5 MICRON GRIT.

Looks good so far in night time low light conditions. The 5 micron seems a little fine on the machine and I could see through the glass so had to hand dress it to make it more opaque. No hot spot in low light. How it fares in daylight is yet to be seen. My version of the AGUS35 with CD-R disk was not good in bright light.

The image through the glass disk subjectively seems a little sharper but the grain when the disk is stationary is more evident.

The prisms look good on initial handholding tests but the 4:3 academy frame is going to be very tight. Have yet to design the mounts.

[Bob Hart]

SECOND TEST WITH OHARADISK WITH 5 MICRON GRIT.

The 5 micron groundglass disk was tested in late afternoon conditions against the sun and with sun behind and later against the sun at sunset.

The results seem superior to the CD-R disk. There seems to be better contrast.

The light loss seems to be about two and a half f-stops.

In grinding and dressing the disk I used a holder which included a stub engaged in the centre hole. This caused the centre hole to become larger and loose on the spindle centre. The disk runs out enough to cause a periodic tremor in the image when a 130mm Nikon lens is on the front of the plastic case.

With the Nikon 55mm lens stopped down to f8, a tendency to a hot spot develops.

The glass disk and CD-R disk appear to confer more tolerance in the camcorder for pinpoint highlights. The glass disk seems to hang onto contrast better. With both there is less tendency for vertical bars. I expect the fixed groundglass would confer a similar benefit.

The glass disk was worth the effort and can be furthur improved.

[Bob Hart]

Furthur to above, I have sent some images to Chris Hurd with a request for favour of them being posted at www.dvinfo.net/media/hart

The images can be identified by the filename "ohara001.jpg" or similar.

The optical path was as follows :-

Micro-Nikkor 55mm SLR lens for Nikon > Groundglass disk Ohara optical glass - 5 micron groundglass finish > 2 element SW5042 50mm telescope eyepiece lens set (similar apparently to an achromatic diopter) (for Tasco) > Sony DSR PD 150P.

There are no improvements such as condenser lenses or fresnels so the defecits from not having these are evident in the images. Until I can improve the groundglass image itself, I won't be sending good money toward a result that may not be satisfactory to me.

[Bob Hart]

Furthur to above, I have emailed some furthur .jpg images to Chris with request they be posted at www.dvinfo.net/media/hart.

These are of a test pattern via the 5 micron AO finished oharadisk whilst stationary and a split image of test pattern via spinning disk and direct to the camcorder. These are named oharatp1.jpg and oharacomp.jpg

There are also three images of the disk tumbler with captions. These are named tumbler1.jpg to tumbler3.jpg and illustrate the basic principle.

[Chris Hurd]

All of Bob's most recent images are now online: see http://www.dvinfo.net/media/hart.

Sorry for the delay there, Bob...

[Alex Monita]

My 35mm experiment

I started it about two months ago when I saw the Marla rig the first time.>>>http://img20.photobucket.com/albums/...ma/35mmCam.jpg

The bottom image:
This is what I currently have built. Its just My GL1 fliped upside down and shooting the film gate where I have my static ground glass. The whole platform can be mounted on a tripod, and is made of thick plastic and aluminum.
Having the camera upside down fixed the whole "flip it in post" situation but its a bit tricky to shoot on location... nothing a little LCD couldn't fix though.

The top image:
The top image is a 3D model of what I'de like to end up with. The lens would be mountable directly onto the camera and then the camera put upside down on an all aluminum rig. The ground glass would spin like a record to maximize the film grain look.

And here are some test pictures. This is my friend's car>>>
http://img20.photobucket.com/albums/...FlamerPics.jpg
By reading this thread I've come to realize that I need a condencer lens BADLY, and would like to know the best place to get one.
also, has anyone tryed getting a 55mm condencer lens and grinding the flat side to project the image on?

Alex

[Bob Hart]

Chris.

No worries or grief felt. It's one of the issues of today's I-want-it-all-now consumer world that many people have lost their ability to let things just flow as they will and focus on the important matters.

Alex.

You've probably already read through it. There is another thread on the Aldu35 which deals comprehensively with the fixed groundglass option you employ including condenser lenses. The Brett Erskine posts discuss the condenser optics extensively.

Upside-down with a separate small monitor works up to a point. You nearly always have to use some sort of shield so that you can see the LCD screen in bright daylight. You however need to pay strict attention to camera hygeine as turning it over will liberate any loose bits of dust back into your tape cassette.

[Brett Erskine]

Bob Hart-
Great frame grabs. Your really making the effort to make a pro adapter. I like the shots of the chart. BTW I noticed your just a hair soft near the edge of frame. This could be cause by a few things but the most common is either the quality limitations of some optics along their outer edge or your GG may be mounted too close to the video camera. Yes there is such a thing as too close. Its only half of the solution to have a camera that has a short minimum focus. Something unique happens when you focus on a flat object and your too close - the whole frame isnt in sharp focus. You can set focus for the center of the frame and it will be in focus but if you look closely the out side of the frame will be alittle bit soft. Changing your focus to bring the outside of the frame in focus will only make the center of the frame soft. Technically speaking this is happening because the distance between the center of the GG and the camera's CCD is slightly shorter than the distance between the outer edge of the GG and the camera's CCD. A mm at these extreme short distances and wide aperatures makes a difference.

The solution:
Increase the gap between the GG and the video camera just a bit (ie: a inch or two) until you can keep everything in focus.

Hope that solved something for you - and for everyone else thats making a adapter.

Also, if its not too much trouble could you sketch the design you described above. Im changing my design to allow for both 35mm and medium format lens and going with a micro oscillating GG. Im coming to realise that grain is only one of the problems. The highlights glow too much because of how light diffuses when it hits GG. The smaller the GG the larger the highlights bloom and the less detail you can see over all. I've seen some crystal clear results from larger, more professionally made GG. Not to mention its alot brighter. There are other reasons too. I made a great little 35mm adapter with static GG. Its small as hell and has no grain except in the highlights of the image but its time to make one with no compromises.

-Brett Erskine
www.CinematographerReels.com

P.S. Thanks for the credit

[Bob Hart]

Brett.

The test pattern was shot with the SW5042 lens set which is a bit small at 50mm for the PD150. It was wide enough for the TV safe area but on the full scan frame grab I caught the corners.

A little more zoom through and it tidies up but remains a bit soft on the left corners in part due to the offset 3xCCD array in the camcorder which puts the optical centre to right of the chip centres as viewed.

With the SW5042, pincushion or barrel distortion occurs within a millimetre or 1/16" either side of the ideal position which resolves best at just under the 4:3 academy frame size, which verifies what you mention above.

Once I get the definition and prism erector sorted I'll probably go for the Century Optics 4x achromatic lens for PD150. 4x or 5x is all that is needed due to the longer path through the prisms.

[Bob Hart]

Brett.

Furthur to above, I have sent you an .pdf email attachment of the "plumbers version" in its current evolution as a side view. I have not published it here as I have to dimension it.

You will notice the image tube I refer to goes right through the appliance. The lens mount of choice is a PVC pipe cap which has been machined and filed to replicate the lens mount, in my case the Nikon lenses for FM2. For the Nikons and most others, about 8mm has to be taken off the open end of the cap to get close enough to the GG.

This detachable adaptor arrangement should suit your mixed use of 35mm SLR and medium format lenses as inexpensive joiners can be bought to extend the tube if extra distance from the focal plane is needed. I have marks filed on the tube to maintain backfocus for different lens types and their adaptors.

The material is quite adequate as to wear if lenses are not changed too often. The tube has to be dressed slightly to make it a slightly looser fit in the cap. The normal fit is a slight taper which is glued in its normal plumbing use. If I was making in metal, I would thread the tube and adaptor for attachment and fine backfocus adjustment.

[Rai Orz]

Look at our (internal) details (it´s 99,5% like the original).

http://de.geocities.com/raiorz/vibro_old/vibro1.jpg

Next days you will found more details and also a different and more simply way to vibrate the GG...

[Bob Hart]

Furthur to above, I have decided to ask Chris Hurd to post two separate .pdf files of the side-view which have been page setup for A4 and US letter pages. This hopefully should preserve 1:1 scale on the printout which should be adequate for getting the general idea. Also sent were three jpg images ohara010.jpg to ohara012.jpg which in conjunction with ohara001.jpg demonstrates what a little bit of filmlook in post can do for an AGUS35 origination