Homemade 35mm Adapter

[Bob Hart]

Brainpick Time.

In regard the Sony FX1 / Z1P PAL camera family, there is a function known as peaking. In the exposure I had to these cameras in getting an AGUS35 to work, I tried the function whilst setting up SLR lens backfocus after disturbing the appliance. I understand peaking to be a focussing aid.

Does peaking artificially enhance the apparent resolution of the image or does it represent the true output of the camera CCD before processing to HDV codec?

I ask this because when the peaking function is selected, the current groundglass I have battled with yields a defined return from the horizontal 850 TV line block on the Lemac test chart, this time without flicker.

When peaking is off, then a faint moire pattern is apparent in its place.

Which represents true resolution at the CCDs, peaking on or peaking off.

Any advice would be much appreciated.

[Bob Hart]

My experiments suffered a bit of a setback tonight or maybe I found a reason for the resolution wall I have hit.

I have up until now reasoned that the limit on the image area off the groundglass had been determined by the available aperture of the prism path at the front face mounting point and true this can be.

However I have since discovered that the optical arrangement I use causes the aperture edges at the rear face prism mounting point to encroach into the image.

By the time I zoom past it, the recovered image off the GG is only about 22mm wide. Ironically, this ends up close to what I understand the P+S Technik to be which is 21mm corner to corner. So I have been chasing shadows for some considerable time and not knowing it.

The arrangement as it is remains quite usable and is a close couple to the camcorder bayonet mount which enables handheld work.

If I use a 4+ dioptre in place of the +7, I get back most of the 28mm at penalty of having to add 45mm to the body to move the GG furthur forward. this adds an uncomfortable leverage to affect the front of the camera body.

[Sheldon Schwartz]

camera: dvx100 original
GG: old scratched frosted cd I found in the trash on scrap cd-motor
macro: Generic macro lens from .45x wide angle lens
approx distance from macro to GG: 60mm
lens: Nikkor 50mm Micro Lens

Here's the footage: http://www.schtm.com/cheap35/cheap35.html

You need flash to view it.

I shot it at night in my bedroom so don't expect pro lighting.

Everything is inside a project box I got at Fry's.
Going to start working on a DIY rod system next..

[Michael Maier]

It's always good to see this thread brought up :)
I think somebody should bump it up at least once a month or even make it a sticker so the newer DVinfo generation can see how it started and who started it before people started to run away with his concepts and efforts, which were a fruit of generosity, innocence of sharing and group collaboration, and turn it into enterprises.

Ave Agus!

[Bob Hart]

Back to the honest original AGUS35 and probably still the best in terms of cost benefit and personal satisfaction, with yet 85% or better of potential performance from scratch.

The Micro-Nikkor may be a bit tight if it is a f3.5 but is otherwise a good lens with nice close-up ability and well chosen for a starter project.

Welcome to the obsession and enjoy.

(Probably about time somebody made a documentary because the subject surely now has a life of its own.).

[Sheldon Schwartz]

Is the easiest way to find frosted plastic cds still searching many different cd-r packs?

[Bob Hart]

Sheldon.

I think you are better off getting a clear one and putting the groundglass finish on it. The frosted CDs may have the diffusion effect for the full thickness of the disk therefore resolution and low light performance may be disappointing.

For clear blanks or the frosted ones, try duplication houses or local video production outfits who burn a lot of DVDs for wedding videos, commercial TV advertisements and the like or CD-Rs for multimedia.

Clear DVDs and CD-Rs out of retail packs these days seem to be two types, a special moulded spacer or partially completed disks diverted from production which can be seen to have a fine pattern of lines on them.

Diverted disks will run true but are now resistent to good groundlgass textures being ground onto them as they have a scratch resistant quality to them.

[Sheldon Schwartz]

Alright, I don't have access to a tumbler- but I can get sandpaper up to 1500 grit from an auto store. What grit should I get? Can I use any blunt hard object to sand it down? How long should I rub it?

[Bob Hart]

Sheldon,

The good news is a tumbler is only a help for lazy people like me. It enables you to conserve and not waste the abrasives as they are contained in use and can be poured off afterwards into a pasta sauce jar for storage and re-use.

Hand-finishing nearly always wastes the entire abrasive solution but you need much less of it at a time.

The tumbler is also useless for the newer scratch resistant blank or clear disks.

For a start, I would probably go with a 600 grade if you are going to use an abrasive sheet. A 1500 paper will probably clog and it will be difficult to get a good uniform graded finish across the entire disk area.

Wet sanding would be the method. Dry sanding will clog the paper and then a big piece of grit will come off and dig a long scratch across your disk.

Sanding with a sheet in any event is going to give you lots of scratches not small pits.

The sanded disk will give you good diffusion but lots of light loss and inferior definition. To get pits you need to use a loose abrasive in a water slurry.

If you can find a big enough piece of double-sided adhesive sheet to glue the disk down onto a flat surface, it is helpful to avoid bending the disk and protecting the clear surface. You need to remove the ridge in the centre section of the disk for this to work if you are fixing the disk down.

Otherwise, stick-on plastic material like schoolbook covering or cheap thin wood pattern style plastic sheet will last long enough in the water to protect the clear surface.

To avoid localised areas of varied finish, it is best to mount the disk onto a firm surface and use the whole disk like a sanding block. You will find progress is painfully slow compared to being able to add pressure to smaller areas on the disk.

How you rub the disk is up to you. I think most hand-finishers are moving the disk on a flat surface rather than fixing the disk and moving an abrasive surface over it.

To get a good grade across the disk you will also need to shave off the ridge which is near the hub centre on the disk. You will find a small piece of break-off parcel knife the handiest for this task used almost upright as a scraper.

Work on the ridge from the opposite side across the disk - more easily controllable.

If you use a loose slurry to dress the disk, the base surface on which you grind it can be sheet glass. You can get abrasive material from lapidary suppliers (gemstone hobby suppliers) as silicon carbide grits.

There is another dry method you can use to get a pitted finish and is not grade dependent. You could use 80 grit paper if you wanted but with care to avoid scratching.

You need to have a stick on backing to protect the clear surface of the disk. You place a sheet of abrasive paper on the disk which sits on a hard flat surface. You then use something to press the grit on the paper hard into the disk to cause pits.

This can be the back end of a BIC pen, but better is the hard round end of an automotive pushrod, either engine valve train or clutch, engine valvetrain pushrod is better.

You have to prevent the paper from sliding on the disk which will cause scratches. You have to periodically move the paper so the pressed pattern is changed.

The rubbing action will eventually wear away the paper. Wet and Dry silocon carbide paper is more robust in this regard.

Another method of applying localised heavy pressure is to get an old bearing race which remains free, fix some sort of axle through it and to use this arrangement like a wheel to roll across the paper. You have to use it raised onto on the corner to generate enough pressure.

Another method is to steal the kid's marbles and place them onto the paper and roll them about with a thick piece of hardboard. They will scratch and chip under pressure so a bunch of steel bearing balls is better.

They also need to be contained by someting like a small steel pie tray or cutdown metal can.

It is a long and arduous process before all the very narrow tracks drawn across the disk evenutally join together to form an even grade, but an acceptable result can be had. This pressing method also deals with the problem of scratch resistant disks.

Blow off but do not wipe off the loose dust on the disk. If you touch the surface at all it will be spoiled and will flicker like crazy.

[Sheldon Schwartz]

Before I saw your reply, I picked up a palm sander on sale for 9.99 at Kragen's, attached some 1000 grit sand paper, sprayed water, and appled pressure to the side of a clear disc that I wanted to grind. I set the disc on a big piece of double-faced adhesive paper. The results were great!

The only problem is a flicker at 1/48th shutterspeed-- if I move it up to 1/24th, then its flicker-free/crystal clear.

I'll try one of your methods (most likely the BIC pen method), or at least refrain from touching the ground side after sanding it-- maybe I can reduce the flicker at 1/48 shutterspeed.

[Bob Hart]

Your wet sanding method may yield an easier result than the back of a BIC pen. The pressing method is really long, hard and arduous and you will still get some flicker.

When wet sanding, try to keep the motion in a short circular pattern so the pattern of scratches is a uniform angle across the image frame at any point around the disk.

I gave up on prressing the disks because of shoulder soreness after two disks and used a alternator bearing with a bolt stuck through it for the third then went to dressing in a grit slurry.

Ways of minimising if not eliminating flicker entirely are :-

Set camera automatic gain or automatic exposure levels to manual or slow so the camera does not hunt for the exposure as the disk turns through brighter and darker segments. It makes the flicker look worse.

Shutter speed at 1/60th sec in NTSC land for 60i?

Try to run the disk close to if not exactly on 3600rpm. With a normal CD motor you will probably need about 4.5 volts to get this and the life of the motor may be shortened.

They normally run in continuous duty at lower rpm driving the disk or if used in load-unload actuators or tracking systems, they run faster but in short bursts.

On or very close to 3600rpm, the same piece of disk will pass the camera viewpoint or advance or trail very slowly which will minimise the flicker effect which may only be seen as a slow cyclic rise and fall of brightness, depending on how out of sync with the frame rate the disk rpm is.

If the cyclic rate is really slow, you might try automatic gain on the camera which might then improve things.

You could try 1800rpm but you will likely see a flicker nearly in phase with the interlace fields which may make it look worse.

With 24P I'm not sure how this will work out. My guess is to try as close as you can get to 1440rpm. 1.5 volts will get you close. If there is flicker in 24P try doubling the disk speed to as close to 2880rpm as you can get it.

Flicker tendencies are aggravated by high outdoors contrasts and lighting from behind. Light bright overcast really makes it look bad.

[Bob Hart]

Wayne and Dennis.

If you get a chance to get your hands on one, try the Sigma 50mm-500mm f4 - f6.3 zoom on your devices. With your good groundglasses able to go tighter than f5.6, I think you will be well pleased with what you see.

Up until now, I have used the Sigma into the camcorder with the groundglass removed for ground-to-air shots of aircraft in flight. The image is sharp but I have had to zoom the camcorder right in to get inside the vignette of the big lens in aerial image mode. The big lens also has to be used wide-open which reduces sharpness.

Additionally, the ND filter has to be constantly ridden as things seem to be more sensitive to this feature. The PD150 and FX1 camcorder are best left on auto which is not the ideal way to do things.

In aerial image, the lens interacts conveniently with the autofocus but the autofocus can run away unpredictably if a bird or insect flies through the shot at a close distance. The autofocus then goes for the nearest sharpest object which is the back of the Sigma lens.

With the groundglass fitted, the vignette goes away. The shot can be wider. Corner falloff occurs but furthur out in the image than the vignette, but the bonus is that the other problems all go away as well.

The little bit of resolution loss you take with the groundglass is offset by being able to back off on the camcorder zoom a little and being able to close the Sigma lens down one or two stops to restore sharpness without provoking grain on the groundglass.

I have yet to try it against high light bright overcast which most provokes flicker from my groundglasses.

Except for having to cart this heavy assembly around, these things could be handy implements for wildlife work and sports videography. A tripod of course is a must unless you are built like big Arnie.

[Bob Hart]

Furthur to above.

Some nice glary overcast and intermittent roll clouds came over so took the thing down to Jandakot and shot some real-world tests with light from behind against the cloud.

In these conditions, a little edge falloff is observed when camcorder zoom for relay is taken back past about 48mm.

The Sigma 50mm - 500mm lens at f11 will still yield a flicker free image but against a uniformly dull white glary background, groundglass artifacts appear in the form of faint whiter concentric arcs, no doubt due to inconstencies in my disk grinding method.

Going to tighter apertures on the Sigma and opening the camcorder aperture correspondingly to compensate, does not confer noticeable added sharpness to the image.

When the disk is turned off, the groundglass texture goes really dark brown like burned coffee powder.

There is little apparent difference between imaging through the adaptor with or without the groundglass except the reduced ability to pass light with the groundglass installed. An inspection of the images on a large screen is yet to happen and a different story may emerge.


Imaging path :-

Sigma f4 - f6.3 50mm - 500mm SLR lens >> AO5 moving GG >> 2 x right-angle prisms >> Century Optics 7+ Acromatic Dioptre >> Sony HDR FX1. Settings manual, shutter 1/50th sec, db video gain, relay zoom 48mm - 54mm, camcorder focus - auto. White-balance - manual to white card.

[Sheldon Schwartz]

http://www.schtm.com/cheap35drew.html :)

[Bob Hart]

I have attempted to upload some short demo shots from recent experiments including today at youtube. I have no idea if they successfully got where they should have. They seem to have and can be found at these addresses :-


http://www.youtube.com/watch?v=0CXz4oluTpA

which is a test of AGUS35 - SONY FX1 SIGMA f1.8 20mm @ f4


http://www.youtube.com/watch?v=EfC4V1iE-kk

which is a test of AGUS35 - SONY FX1 SIGMA Ff4-6.3 50mm-500mm @ f8


I don't think the resolution is going to be anything to write home about by the time the internet has finished with it.


FOOTNOTE:

I just managed to open them. don't waste your time. They look dreadful.


Sheldon.

I shall have to take some instruction from you on how to make these autoplay videos appear here.