Homemade 35mm Adapter

Filipe Helder · October 31st, 2006, 07:07 PM

new 35mm adapter..., WDR35 italian
http://www.wdr35.com/
370€

Sam Jankis · October 31st, 2006, 09:20 PM

Looks bulky. Any footage or large grabs?

Bob Hart · November 1st, 2006, 05:06 AM

A DivX file of 12Mb of the Peleng fisheye footage can be downloaded at this address.

http://www.filefactory.com/file/c6a42d/

Bob Hart · November 14th, 2006, 07:18 AM

Just a short note to shove this thread back up to thetop of the heap for a while. Also, the Peleng footage referred to above is due to time-out from filefactory in the next few days.

Phil Bloom · November 14th, 2006, 01:07 PM

bob, i sold my letus in the end. i hope the buyer makes it work better than me!

Bob Hart · November 16th, 2006, 11:21 AM

Last night, I got to cast my greasy fingerprints and stray DNA all over a P+S Technik Mini35 JVC HD100 model which has immigrated to W.A. and is believed to be the only known specimen in the state.

What a change it is to be able to offer a camera up to precise mounts and lens fittings and have them go on without obfuscation and my reversion to the red mist and foul language.

The thing works, no argument about that. Except for a bit of misunderstanding which comes from my practice of momentarily autofocussing a PD150 or FX1 to get initial relay focus, I found it simple to manage. The HD100 of course is direct relay.

The objective lens mount for Nikons is precise, locks the lens in place and best of all, no back focus of the Nikon lens mount is needed.

It helps to have built and have spent some hours using a home-made as once the basic operating methods have become instinctual, everything on the MINI35 falls into place where you expect it to be including the offset.

I am confident that any competent camerman who has constructed and made a lot of use of their own Agus35 or similar emulation would be able to step into a Mini35 with all the ease of putting on an Armani jacket.

It is patent that once set up correctly, the Mini35 will function solidly, not drift off-axis, spoil the sound or display any of the other vices my own home-made gadget will have me on constant and distracting vigilence for. The motor is very quiet and no vibration can be felt.

It uses the camcorder batteries so no worries over remembering to bring spare torch batteries.

The construction and finish are excellent, a welcome change from hacksaw marks in PVC sewer pipe, dags of blueglue on joints and brushmarks in blackboard paint.

Best of all, it doesn't creak or groan when hand-held. It is smaller and not anywhere near as heavy as I expected it to be.

The owner had the good sense to buy the additional front extension arms with handgrips on them.

On the shoulder, with these, I would feel confident in being able to stay on subject with up to an 85mm prime lens hand-held, with a focus puller of course and not be crippled after an hour of using it.

Best practice of course will be tripod or other stable camera supports.

I hope to be tagging along when furthur tests are done and the first project is undertaken with it.

In meantime I shall have to plug along with Agus's best as the real thing is well over my available and justifiable budget but at least I know now what to aspire to.

Chris Barcellos · November 16th, 2006, 12:33 PM

Bob:

We talked about achromats in another thread I started. I'm still awaiting delivery of my 72mm achromat from Cinavete... hoping that will improve the footage I get on the FX1 Micro35 DIY project I built. Will advise you what kind of luck that has brought. Hope to get where you have gotten already, at a minimum.

Bob Hart · November 16th, 2006, 06:12 PM

Chris.

I think that you will find that you shall get there. Whilst the 58mm lens will work, things can only get better if you are shooting through a wider one of equal quality.

There may be a sweeter spot in terms of how close to the camera the GG has to come versus how far the zoom goes in.

I cannot over-emphasise how important having the centre axes of both the camcorder/achromat and the SLR correct and all the faces parallel is.

If the centres are off, whilst you will get adequate coverage of the GG with your SLR lens's projected image, some interesting assymentic distortional things happen if you choose to use ultra-wides like 14mm or Peleng 8mm.

You can of course cheat a little by applying a bit of correcting pressure to skew the axis before you tighten the camera and adaptor to rods or other bracework. You risk edge softness with the wide lenses by doing this.

Bob Hart · November 17th, 2006, 08:28 AM

DAY 1 OF RED BULL AIR RACE in Perth W.A.

Amazing stuff. I am covering it as best I can for my own aviation archive which is another story I won't go into for the moment.

I am using the Agus35 with groundglass removed for the long lens and found it works this way just fine for the fisheye lens as well with thecamcorder zoom in all the way and the Peleng lens wide-open.

You can actually get away with f4 but I am skewing the axis slightly to bring the flat horizon down to the lower third of the image frame for better, more natural composition. With f4, this offset picks up the iris in one corner on underscan.

There were two helicopters doing airbourne coverage. One of them flew the actual competition course. It had a gyrosphere?? hanging off the front. The pilot of the helicopter wasn't bad at what he does either.

I couldn't get media accreditation so I had to be satisfied with looking in longingly from outside of a link mesh fence.

I tried for some 8mm shots of the take-offs from head-on outside of the fence. The rate of climb and angle of these aircraft is mindblowing. Fisheyes for ground-to-airs of aircraft are a bit difficult. The aircraft has to be really big or really close to fill the frame.

The redbulls are small aircraft so we are talking blowflies visually.

The long lens wll come out tomorrow for some more head-ons and the landings which are equally spectacular. Sunday will be more long lens of the actual competition and the air displays.

There were four other FX1/Z1P operators passed by. I lost a few opportunties when people wanted to know what was on front of the camera.

Nearly all serious cameramen who stopped by knew exactly what it was and what it was for, so it seems there is a lot of general knowledge out there now about adaptors.

Chris Barcellos · November 17th, 2006, 10:09 AM

Quote:

Originally Posted by Bob Hart

Chris.

I think that you will find that you shall get there. Whilst the 58mm lens will work, things can only get better if you are shooting through a wider one of equal quality.

There may be a sweeter spot in terms of how close to the camera the GG has to come versus how far the zoom goes in.

I cannot over-emphasise how important having the centre axes of both the camcorder/achromat and the SLR correct and all the faces parallel is.

If the centres are off, whilst you will get adequate coverage of the GG with your SLR lens's projected image, some interesting assymentic distortional things happen if you choose to use ultra-wides like 14mm or Peleng 8mm.

You can of course cheat a little by applying a bit of correcting pressure to skew the axis before you tighten the camera and adaptor to rods or other bracework. You risk edge softness with the wide lenses by doing this.

After the first version with a $5.00 Radio project box, I recognize I have to be a bit more exacting. So I've already purchase a new box, and will probably change my design a bit. I won't do that until the achromat arrives.

In the meantime, with what I have got, I am learning more about the alignment issues. Nothing really great coming out of the +10 close up lens, so the achromat is my next big step. Then, I should no better what to blame on my poor alignments in the first build.

Other issue is I am using some old Pentax K mounts lenses as the prime lenses, using the glued on rear lens cap technique.. May look at ordering adapters from Redrock before I do rebuild...

Bob Hart · November 19th, 2006, 11:26 PM

Chris.

A quick and dirty way of getting the axes near correct is to take care of the camcorder end of the adaptor first, then once this is fixed, drill a small pilot hole in the case where the SLR lens mount is be in the spot where you think the centre will be.

Mount the device to the camera, look through your camera viewfinder for the pinhole with your camera zoomed to its correct position. If the hole is off-centre, use a small keyhole file or hotwire to widen the hole to move its centre.

The hole must remain circular, just larger, otherwise some optical bads happen which misinform you whether it is centred or not.

Once you have the hole centred in your camcorder view, mark out your lens mount hole from it. Don't use an electric drill powered hole saw with this hole as a centre for the arbor bit. A hole saw simply is not precise enough.

FOOTNOTE: ( with PD150/PD170 cams there is an optical issue which will work against the option of direct aerial imaging without the GG installed if you use this construction method ).

GENERAL INFO:

For anyone using the AGUS35 or similar as an aerial image relay (with the groundglass removed).

When using camcorder autofocus in bursts with long lenses to track dynamic subjects moving towards or away from camera, best practice is when opportunity permits, to reset the SLR lens to its infinity mark, sight the lens on an infinity subject which has lots of texture and contrast, then trigger the autofocus to reset the camcorder lens.

There is a tendency when using short bursts of autofocus, then trimming with the SLR lens for the next action, for the aerial image plane to creep towards the back of the SLR lens.

This makes more apparent, any soft blemishes from dust which settles onto the back of the lens during the day, increases the likelyhood of an autofocus pull to the back of the SLR lens when soft plain objects like clear sky come into the frame, such as momentary loss of an aircraft or bird out of the frame when the autofocus has been left on to track the movement.

I know cleanliness is next to godliness when it comes to optics however some consumer longlenses by nature of their design are not sealed against environmental dust and cause by the zoom function a lot of air movement in and out through the adaptor which if it is not cleaned out frequently will pass dust onto the back of the SLR lens.

While doing some imaging of the Red Bulls Air Race, with the Sigma 50mm-500mm and a doubler, at the 1000mm end, this became a real, almost unmanageable problem.

Red Bulls = a very enjoyable event by the way. It's coming to Perth again over the next two years I believe.

Alex Chong · November 20th, 2006, 07:30 AM

Quote:

Originally Posted by Bob Hart

Julius.

I can't speak for the Canon lens with authority as I have not used it. Comments on the web favour this lens in terms of quality for the task it is intended, a high quality close-up lens for still-cameras.

I did find comment on one website that the lens was in effect 4+ lens or thereabouts.

If it is a 4+, for the 24mm x 18mm 35mm movie frame, I don't think it will be powerful enough. The camera on full zoom may not frame tight enough and you will likely get an image with a hot spot because the frame may be in the ballpark of 40mm x 30mm but I am really only guessing here.

In my original testing for the PD150 which is optically similar to the VX2000, I used an inexpensive three lens in one pack set. This was a 1+,2+ 4+ and stacked you got 7+.

The stack was the only magnification power that worked for my setup.This stack of lenses however causes a real problem with chromatic aberration because they are only single element optics.

The front element of the VX2000/PD150 lens is 52mm diameter. I used the optics out of a 50mm 2" telescope eyepiece which had a diameter of 44mm which just worked with the camera at about 80% zoomed in but these don't come cheap either.

If you can't find a cheaper 7+ acromatic dioptre which will mount to the 58mm filter tread, you may find one with a smaller diameter. As long as it is no smaller than the 44mm I used, it may be okay with a step-up ring to the 58mm.

There is a chance however that there may be a ring shaped defect out towards the corners of the image as the telescope lens set does this with the FX1 which uses more of the groundglass image width than the PD150.

I am not a lens technician so my thoughts on the matter have no validity beyond what lenses I have offered up to my camera and find worked or not.

A 5+ may get you coverage of the 36mm x 24mm??? still-image film camera frame. This size is favoured by the builders of static grounglass devices as the grain or texture of the groundglass is smaller in proportion to the size of the image so resolution is better and the grain artifact is less evident.

At this groundglass image size, builders start talking of hot spots or edge falloff and condenser lenses which even out the lighting across the frame.

I'm sorry I cannot help you with this beyond what I have found is workable for me.

Iv'e done a bit of hunting around and it seems the Century Optics +7 may be the only game in town though the beta 72mm +10 achromatic mentioned on this site looks interesting.

Hi Bob,

Was just reading some of the old posts and I came across this one. Just asking for some advice from you if you don't mind. My MX500 (PV953) needs a +7 diopter to get the image grabbed at around 4X zoom. I tried +4 and +3 individually and they just don't work. I know some camcorders don't need any macro. But for some that do, is +7 diopter the only one to use? Thanks.

Alex

Bob Hart · November 20th, 2006, 06:21 PM

Alex.

A general rule of thumb might be that for a 1/3" CCD 16:9 camera, you might need at least 54mm zoom-in, for +4 to work onto a patch of GG 24mm wide, from about 120mm away from the groundglass.

A 1/4" sensor, with the same setup might cover a smaller patch of the GG. The camera zoom might be able to be pulled back a little.

Distance of cam from GG, magnification power of the dioptre, camcorder CCD size, maximum zoom-in of the camcorder lens, ability of camera to focus on close objects, all interact to set the limits.

4+ is right on the bottom limit of magnification power which will work for 24mm wide off the GG. This 24mm is about the widest image on the GG which will not give you problems with variations in light diffusion through the GG which gets called variously hotspot, edge falloff, dark corners etc..

A wider size image will get you better apparent resolution, as the groundglass texture is scaled smaller relative to the total image size.

The balance is tipped away from uniform light diffusion which has to be cured with condensers or coarser groundglass texture. Both of these workarounds affect resolution to some degree and add complication for the home builder.

My first device was not a flip version. The power of the 2" telescope eyepiece I used came out at more than 12+. It included in effect its own BCX condenser only I didn't know it at the time.

It only had an entry diameter of 44mm. Fortunately the PD150 zoom-through at maximum was enough to get inside the rim of the lens.

I have to leave the discussion at this point as work beckons and have rushed this a bit.

For non-flip adaptors, +7 to +10 seems to be the more common dioptres of choice. For a flip adaptor, the options are narrowed by the flip path and some cameras may simply not work.

Alex Chong · November 20th, 2006, 06:55 PM

Bob,

So you are saying for flipped adaptor, it is only limited to a few camcorders in the market and not all even with different diopters magnification strength in the market? An easy way i guess to test if a camcorder can zoom in to see if it will frame a 24mm wide GG is to have the camcorder positioned at the correct distance away from the GG, i.e if the adaptor has a light path of 120mm say. Then place a GG size rectangle on a white sheet of cardboard and zoom in using different diopter strength. What do you think?

Bob Hart · November 20th, 2006, 11:22 PM

Alex.

To get an image off a groundglass into a difficult camcorder, anything is possible depending on the will and means to get it done. But the reality is that most home-builders are hoping to come in at sub AU$1,500 which takes the more elegent solutions off the table.

Beyond a certain point, even factoring in the labour savings of doing it yourself, a person would be better served buying in or renting the real thing and converting their own labour into an offsetting profit to pay for the commercial device.

Your method is the way to go and a path well proven by others.

A handy jig is to get a piece of wood about 40mm long, about 80mm wide, about 15mm thick, - doortrim or architrave is fine. Screw or glue underneath, two cross pieces to get it up off the table and stop it from falling over.

If you can find a friendly woodworker with a router, have him cut a slot about 10mm wide for most of its length.

A dummy camera, (block of wood) with a centre axis accurately marked and a tight string or rubber band (even thin cutting from inner tube strip) going from a small curtain wire hook to another fastened to another piece of wood on the opposite end can help set up centres.

Cut a whole lot of scrap pieces of plywood of varying thickness to use for spacers or packing pieces and drill holes through the centres for bolting through to camcorder tripod mounts.

Cut up some automotive or motorcycle inner tubes. These make handy instant straps to temporarily hold things in place.

Prism erecting or flip devices have a practical minimum camcorder to GG distance as the prisms themselves take up space in the path and shorten the distance from camera to GG by bending the path back and forth. Mirrors do the same.

A non-flip device can be a lot shorter. In the case of my telescope eyepiece, the usable distance from the dioptre to GG was 12mm to 18mm which enabled a handy close coupling of the camera and device for handheld operating.

This handyness is what I have tried to copy with the prism device and have gone with the 7+ which was about as close as I could get to the groundglass and still be able to fit everything in.

With an adaptor, within reason, the closer you can get, the better you will be because you can then back off the zoom to preserve more light transmission. Most consumer/prosumer cams lose some light zoomed right in and sometimes the edge or corner sharpness is less than impressive.

Some cams also have their own corner falloff issues before you add more by fitting an adaptor which aquires a wide image off the GG.

Once you start going as close as I did with the non-flip version, things like pincushion and barrel distortion and chromatic abberation (rainbows) start to become a real headache.

Tripod mount holes and lens centre axis are rarely on the same line in most cams I have dealt with. The Sony PD150 family lens centre and centre of CCD also do not co-incide. The Canon GL1/XM1 family is said to share this trait but I have not confirmed this myself.

This is not a huge issue unless you are relaying aerial image without a GG to attach really long lenses such as the Sigma 50mm- 500mm with doubler, then things get interesting.

Hope I have not added to confusions.

November 14th, 2006, 01:07 PM	#1475
Phil Bloom Trustee Join Date: Aug 2006 Location: London UK Posts: 1,939	bob, i sold my letus in the end. i hope the buyer makes it work better than me! __________________ Philip Bloom Cinematographer, Director, Filmmaker www.philipbloom.net

November 16th, 2006, 12:33 PM	#1477
Chris Barcellos Inner Circle Join Date: Nov 2005 Location: Elk Grove CA Posts: 6,838	Bob: We talked about achromats in another thread I started. I'm still awaiting delivery of my 72mm achromat from Cinavete... hoping that will improve the footage I get on the FX1 Micro35 DIY project I built. Will advise you what kind of luck that has brought. Hope to get where you have gotten already, at a minimum. __________________ Chris J. Barcellos

October 31st, 2006, 07:07 PM	#1471
Filipe Helder New Boot Join Date: Oct 2006 Location: PORTUGAL Posts: 9	new 35mm adapter..., WDR35 italian http://www.wdr35.com/ 370€

October 31st, 2006, 09:20 PM	#1472
Sam Jankis Major Player Join Date: Jun 2006 Location: St. Pete, FL Posts: 223	Looks bulky. Any footage or large grabs?

November 1st, 2006, 05:06 AM	#1473
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,477	A DivX file of 12Mb of the Peleng fisheye footage can be downloaded at this address. http://www.filefactory.com/file/c6a42d/

November 14th, 2006, 07:18 AM	#1474
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,477	Just a short note to shove this thread back up to thetop of the heap for a while. Also, the Peleng footage referred to above is due to time-out from filefactory in the next few days.

November 16th, 2006, 11:21 AM	#1476
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,477	Last night, I got to cast my greasy fingerprints and stray DNA all over a P+S Technik Mini35 JVC HD100 model which has immigrated to W.A. and is believed to be the only known specimen in the state. What a change it is to be able to offer a camera up to precise mounts and lens fittings and have them go on without obfuscation and my reversion to the red mist and foul language. The thing works, no argument about that. Except for a bit of misunderstanding which comes from my practice of momentarily autofocussing a PD150 or FX1 to get initial relay focus, I found it simple to manage. The HD100 of course is direct relay. The objective lens mount for Nikons is precise, locks the lens in place and best of all, no back focus of the Nikon lens mount is needed. It helps to have built and have spent some hours using a home-made as once the basic operating methods have become instinctual, everything on the MINI35 falls into place where you expect it to be including the offset. I am confident that any competent camerman who has constructed and made a lot of use of their own Agus35 or similar emulation would be able to step into a Mini35 with all the ease of putting on an Armani jacket. It is patent that once set up correctly, the Mini35 will function solidly, not drift off-axis, spoil the sound or display any of the other vices my own home-made gadget will have me on constant and distracting vigilence for. The motor is very quiet and no vibration can be felt. It uses the camcorder batteries so no worries over remembering to bring spare torch batteries. The construction and finish are excellent, a welcome change from hacksaw marks in PVC sewer pipe, dags of blueglue on joints and brushmarks in blackboard paint. Best of all, it doesn't creak or groan when hand-held. It is smaller and not anywhere near as heavy as I expected it to be. The owner had the good sense to buy the additional front extension arms with handgrips on them. On the shoulder, with these, I would feel confident in being able to stay on subject with up to an 85mm prime lens hand-held, with a focus puller of course and not be crippled after an hour of using it. Best practice of course will be tripod or other stable camera supports. I hope to be tagging along when furthur tests are done and the first project is undertaken with it. In meantime I shall have to plug along with Agus's best as the real thing is well over my available and justifiable budget but at least I know now what to aspire to.

November 16th, 2006, 06:12 PM	#1478
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,477	Chris. I think that you will find that you shall get there. Whilst the 58mm lens will work, things can only get better if you are shooting through a wider one of equal quality. There may be a sweeter spot in terms of how close to the camera the GG has to come versus how far the zoom goes in. I cannot over-emphasise how important having the centre axes of both the camcorder/achromat and the SLR correct and all the faces parallel is. If the centres are off, whilst you will get adequate coverage of the GG with your SLR lens's projected image, some interesting assymentic distortional things happen if you choose to use ultra-wides like 14mm or Peleng 8mm. You can of course cheat a little by applying a bit of correcting pressure to skew the axis before you tighten the camera and adaptor to rods or other bracework. You risk edge softness with the wide lenses by doing this.

November 17th, 2006, 08:28 AM	#1479
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,477	DAY 1 OF RED BULL AIR RACE in Perth W.A. Amazing stuff. I am covering it as best I can for my own aviation archive which is another story I won't go into for the moment. I am using the Agus35 with groundglass removed for the long lens and found it works this way just fine for the fisheye lens as well with thecamcorder zoom in all the way and the Peleng lens wide-open. You can actually get away with f4 but I am skewing the axis slightly to bring the flat horizon down to the lower third of the image frame for better, more natural composition. With f4, this offset picks up the iris in one corner on underscan. There were two helicopters doing airbourne coverage. One of them flew the actual competition course. It had a gyrosphere?? hanging off the front. The pilot of the helicopter wasn't bad at what he does either. I couldn't get media accreditation so I had to be satisfied with looking in longingly from outside of a link mesh fence. I tried for some 8mm shots of the take-offs from head-on outside of the fence. The rate of climb and angle of these aircraft is mindblowing. Fisheyes for ground-to-airs of aircraft are a bit difficult. The aircraft has to be really big or really close to fill the frame. The redbulls are small aircraft so we are talking blowflies visually. The long lens wll come out tomorrow for some more head-ons and the landings which are equally spectacular. Sunday will be more long lens of the actual competition and the air displays. There were four other FX1/Z1P operators passed by. I lost a few opportunties when people wanted to know what was on front of the camera. Nearly all serious cameramen who stopped by knew exactly what it was and what it was for, so it seems there is a lot of general knowledge out there now about adaptors.

November 19th, 2006, 11:26 PM	#1481
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,477	Chris. A quick and dirty way of getting the axes near correct is to take care of the camcorder end of the adaptor first, then once this is fixed, drill a small pilot hole in the case where the SLR lens mount is be in the spot where you think the centre will be. Mount the device to the camera, look through your camera viewfinder for the pinhole with your camera zoomed to its correct position. If the hole is off-centre, use a small keyhole file or hotwire to widen the hole to move its centre. The hole must remain circular, just larger, otherwise some optical bads happen which misinform you whether it is centred or not. Once you have the hole centred in your camcorder view, mark out your lens mount hole from it. Don't use an electric drill powered hole saw with this hole as a centre for the arbor bit. A hole saw simply is not precise enough. FOOTNOTE: ( with PD150/PD170 cams there is an optical issue which will work against the option of direct aerial imaging without the GG installed if you use this construction method ). GENERAL INFO: For anyone using the AGUS35 or similar as an aerial image relay (with the groundglass removed). When using camcorder autofocus in bursts with long lenses to track dynamic subjects moving towards or away from camera, best practice is when opportunity permits, to reset the SLR lens to its infinity mark, sight the lens on an infinity subject which has lots of texture and contrast, then trigger the autofocus to reset the camcorder lens. There is a tendency when using short bursts of autofocus, then trimming with the SLR lens for the next action, for the aerial image plane to creep towards the back of the SLR lens. This makes more apparent, any soft blemishes from dust which settles onto the back of the lens during the day, increases the likelyhood of an autofocus pull to the back of the SLR lens when soft plain objects like clear sky come into the frame, such as momentary loss of an aircraft or bird out of the frame when the autofocus has been left on to track the movement. I know cleanliness is next to godliness when it comes to optics however some consumer longlenses by nature of their design are not sealed against environmental dust and cause by the zoom function a lot of air movement in and out through the adaptor which if it is not cleaned out frequently will pass dust onto the back of the SLR lens. While doing some imaging of the Red Bulls Air Race, with the Sigma 50mm-500mm and a doubler, at the 1000mm end, this became a real, almost unmanageable problem. Red Bulls = a very enjoyable event by the way. It's coming to Perth again over the next two years I believe.

November 20th, 2006, 06:21 PM	#1483
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,477	Alex. A general rule of thumb might be that for a 1/3" CCD 16:9 camera, you might need at least 54mm zoom-in, for +4 to work onto a patch of GG 24mm wide, from about 120mm away from the groundglass. A 1/4" sensor, with the same setup might cover a smaller patch of the GG. The camera zoom might be able to be pulled back a little. Distance of cam from GG, magnification power of the dioptre, camcorder CCD size, maximum zoom-in of the camcorder lens, ability of camera to focus on close objects, all interact to set the limits. 4+ is right on the bottom limit of magnification power which will work for 24mm wide off the GG. This 24mm is about the widest image on the GG which will not give you problems with variations in light diffusion through the GG which gets called variously hotspot, edge falloff, dark corners etc.. A wider size image will get you better apparent resolution, as the groundglass texture is scaled smaller relative to the total image size. The balance is tipped away from uniform light diffusion which has to be cured with condensers or coarser groundglass texture. Both of these workarounds affect resolution to some degree and add complication for the home builder. My first device was not a flip version. The power of the 2" telescope eyepiece I used came out at more than 12+. It included in effect its own BCX condenser only I didn't know it at the time. It only had an entry diameter of 44mm. Fortunately the PD150 zoom-through at maximum was enough to get inside the rim of the lens. I have to leave the discussion at this point as work beckons and have rushed this a bit. For non-flip adaptors, +7 to +10 seems to be the more common dioptres of choice. For a flip adaptor, the options are narrowed by the flip path and some cameras may simply not work.

November 20th, 2006, 06:55 PM	#1484
Alex Chong Regular Crew Join Date: Jun 2004 Location: Brunei Posts: 140	Bob, So you are saying for flipped adaptor, it is only limited to a few camcorders in the market and not all even with different diopters magnification strength in the market? An easy way i guess to test if a camcorder can zoom in to see if it will frame a 24mm wide GG is to have the camcorder positioned at the correct distance away from the GG, i.e if the adaptor has a light path of 120mm say. Then place a GG size rectangle on a white sheet of cardboard and zoom in using different diopter strength. What do you think?

November 20th, 2006, 11:22 PM	#1485
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,477	Alex. To get an image off a groundglass into a difficult camcorder, anything is possible depending on the will and means to get it done. But the reality is that most home-builders are hoping to come in at sub AU$1,500 which takes the more elegent solutions off the table. Beyond a certain point, even factoring in the labour savings of doing it yourself, a person would be better served buying in or renting the real thing and converting their own labour into an offsetting profit to pay for the commercial device. Your method is the way to go and a path well proven by others. A handy jig is to get a piece of wood about 40mm long, about 80mm wide, about 15mm thick, - doortrim or architrave is fine. Screw or glue underneath, two cross pieces to get it up off the table and stop it from falling over. If you can find a friendly woodworker with a router, have him cut a slot about 10mm wide for most of its length. A dummy camera, (block of wood) with a centre axis accurately marked and a tight string or rubber band (even thin cutting from inner tube strip) going from a small curtain wire hook to another fastened to another piece of wood on the opposite end can help set up centres. Cut a whole lot of scrap pieces of plywood of varying thickness to use for spacers or packing pieces and drill holes through the centres for bolting through to camcorder tripod mounts. Cut up some automotive or motorcycle inner tubes. These make handy instant straps to temporarily hold things in place. Prism erecting or flip devices have a practical minimum camcorder to GG distance as the prisms themselves take up space in the path and shorten the distance from camera to GG by bending the path back and forth. Mirrors do the same. A non-flip device can be a lot shorter. In the case of my telescope eyepiece, the usable distance from the dioptre to GG was 12mm to 18mm which enabled a handy close coupling of the camera and device for handheld operating. This handyness is what I have tried to copy with the prism device and have gone with the 7+ which was about as close as I could get to the groundglass and still be able to fit everything in. With an adaptor, within reason, the closer you can get, the better you will be because you can then back off the zoom to preserve more light transmission. Most consumer/prosumer cams lose some light zoomed right in and sometimes the edge or corner sharpness is less than impressive. Some cams also have their own corner falloff issues before you add more by fitting an adaptor which aquires a wide image off the GG. Once you start going as close as I did with the non-flip version, things like pincushion and barrel distortion and chromatic abberation (rainbows) start to become a real headache. Tripod mount holes and lens centre axis are rarely on the same line in most cams I have dealt with. The Sony PD150 family lens centre and centre of CCD also do not co-incide. The Canon GL1/XM1 family is said to share this trait but I have not confirmed this myself. This is not a huge issue unless you are relaying aerial image without a GG to attach really long lenses such as the Sigma 50mm- 500mm with doubler, then things get interesting. Hope I have not added to confusions.