WHat size macro should I use on the agus35?

[Ben Gurvich]

Just wondering what rating i should use for a macro lens for the agus35, i was thinking +7 ?

Cheers,
Ben Gurvich

[Bob Hart]

If eventually you go to a prism version, any more than +7 between the camcorder and the groundglass will bring you too close. +7 on a non-inverter will put the disk approx 5 inches away from the camcorder, depending on the cam. Don't take this as gospel. These numbers relate to a PD150P and a 4:3 projected image frame on the groundglass of 18mm x 24mm, which is the standard motion picture academy frame.

For a non-inverter (the original Agus35), I have used an after-market telescope eyepiece lens set 50mm 2" out of mainland China, the generic part number is SW5042, sold in Australia to fit Tasco scopes but possibly for other brands of the same spec elsewhere. This enables a very close couple to a PD150 and cams with smaller diameter optics but probably is no good for larger ones like XL1&2 and DVX-100 with their 72mm filter mounts. The eyepiece case has to be scrapped and a new one made to hold the glasses and provide the filter mount, which is a machine shop job. A store bought macro will be a lot cheaper than this option.

For best resolution and no rainbows on hard edges in the image an achromatic diopter is pretty much mandatory if you are serious about image quality. Do it right with a 5 micron spinner and you should be good for up to standard definition TV, probably better but not for HDTV.

[Ben Gurvich]

Thanks Bob,

Im actually jsut thinking of trying this on my single chip first before i go to the big boys. Maybe ill just use a +4 or +5, should be enough.

You seem to know a lot about all this stuff, id be interested to see some of your footage, is any of it on the forums here already?

Cheers,
Ben Gurvich

[Bob Hart]

I am by no means any sort of expert but have played around with this for a while. You propose a sensible course, trying it out at a low cost level first.

www.dvinfo.net/media/hart has a whole lot of files, either .pdf or .jpg which if downloaded or viewed by date, gives a hint of the evolution of one project which I called the Australian Plumber's Version because it is built using PVC pipe parts and caps. These are not in any sensible order.

None of the diagrams you find there should be built to as they are not the final designs and have some errors. The images will demonstrate early low quality attempts and a gradual improvement.

If you use a simple single element close-up lens (macro) for a +5 you should achieve an acceptable result. Achromatic dioptre is better but that comes when you have committed to getting into that last 15% of perfection.

Achieving a good groundglass finish is the most critical factor at this stage. I assume you will be using a plastic CD-R spacer disk from a retail CD-R pack. This disk is best roughened by rubbing it gently by small orbital movements by hand in a water based slurry of an approx, 1200 grade or 5 micron abrasive. This should happen on a smooth perfectly flat dressing surface. Most people seem to have used a sheet of glass. Cleanliness is essential to avoid scratches from large pieces of
environmental grit (in other words common household dirt).

Plastic disks almost inevitably will end up with an unwanted scratch. With a spinning disk, it is not too much of an issue. It may show up in bright conditons if your camcorder shutter speed cannot be manually controlled. Then you might need to use some neutral density filter gel in the optical path to force the camcorder to choose a slower shutter speed.

The abrasive which seems to get most mention is aluminium oxide. If the disk becomes too opaque for adequate light transmission, the advantage of a plastic disk is that you can restore it somewhat by backpolishing briskly with a clean soft cloth.
Don't backpolish too much otherwise you end up with a mix of projected image on the groundglass and aerial image which the cam will see directly through the disk. This effect is like a ghosted TV image. Whilst it is not the true MINI35 style of getting things done, a little aerial image coming through seems to confer slightly better detail sharpness. It falls over badly however when highlights in soft background are very bright. Try to keep fingerprints off the groundglass surface of plastic disks. They are almost impossible to remove and inevitably the polishing which occurs when cleaning is attempted causes areas of less opacity on the disk which causes flicker unless the disk is rotated faster than 1500 rpm.

In meantime you will be pleased to be able, as well as playing creatively with narrow depths of field, to be able to connect a range of SLR lenses to your cam via the adaptor.

[Ben Gurvich]

thanks for the info mate,
will do