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Roberto,
It looks like you dont have a 36x24mm frame inside your adapter. I think this should be your next step, as it will serve as a reference point to determine what lenses you need, a macro, a PCX or both. Without it, you are trying to setup the unit blindfolded, not knowing if you are zoomed in enough or not. Dont use the vignetting as a reference for zooming, use the 36x 24mm frame/window. Vignetting should be eliminated via a PCX lens, not by zooming in more. So, first thing i think you should do, is forget about the vignetting for a second, and concentrate on getting your camcorder to zoom in and focus on a 36x24mm area of the GG. Best way to do this is as i've said to put in a 36x24mm frame/window in front of your GG. If you can't zoom in and focus on this area, then you will need a macro as you say. Once you can get focus on this frame area, the next step is to avoid vignetting, if any. And this is where the PCX comes in. Either way, the aim is to zoom in only enough to fill the LCD with this 36x24mm frame, and not to zoom in more to avoid vignetting, as this will loose your FOV and it will no longer be a true 35mm image. |
Quote:
something like this ? http://www.fdivisions.com/portion.jpg ...and then i have to try to focus on that portion, right ? |
Yes that is exactly it. Reason i asked this, is i was not sure if you were zooming in blindly, and simply trying to zoom in until the vignetting has gone. If you were, you would probably zoom past this 36x24mm image, which is not good.
So yes, first step is to get the cam zoomed into the frame area and focused regardless of vignetting. As you have said you probably need a macro close to your camcorders lens to do this, depending on what camcorder you have and its distance from tthe GG. After you have got this far, it is then that you start to tackle vignetting, if any. Ofcourse this is just my system of doing things. |
Roberto.
Your cam seems to have a similar zoom range to the PD150. If it has a 1/3" CCD then it should behave in a similar manner. Before you go to the trouble of putting a frame inside your adaptor, try a little experiment first. Draw a 36mm x 24mm frame on a card. Inside that frame, draw a grid of crossing lines. Put this in front of your camera and try to focus on it and frame inside it. If you can't get inside the frame without losing focus, you will need a close-up lens or adaptor. The camera on a tripod and the card sitting upright on a table may be the best simple way of doing this experiment. The 36mm x 24mm frame is the 35mm still-camera image size. For best sharpness off a groundglass, especially a fixed groundglass, then this is a better size image. This image size is fine for still-camera film, but in a rear projection process which is what these adaptors use, there is a problem. The outer corners of the image are darker, the centre brighter. f1.8 aperture lenses help solve this problem but it does not go away entirely. Many builders use condenser lenses or PCX lenses to solve this problem. I have taken a different course for my adaptor. I have chosen to use the smaller 35mm motion picture film image size, which is 24mm x 18mm. This image is more faithful to the theatre motion film image an audience views but has problems of its own as well as advantages. Chief is a reduced potential sharpness of image. It requires a groundglass to be of as fine a texture which can be had and still relay an image without the hotspot problem becoming worse. The best texture seems to be the finish created by dressing with 5 micron aluminium oxide. This material is used for dressing glass. I have experimented with CD-R plastic spacer disks, DVD+R clear spacer disks and split DVD+R disks and some special CD sized glass disks I imported from Ohara in Japan. I have settled on the glass disks as they are the only ones I have been able to achieve a consistently predictable finish on. They require some machinery not available to the average home-builder, so for practical reasons, the plastic CD-Rs or similar will be your most likely option. The smaller image frame fits inside the hotspot of f1.8 aperture lenses so the condenser element can be deleted. The smaller image size will almost inevitably require a close-up lens or macro to enable the camera to frame inside of it. As far as I am aware and I could be wrong, the P+S Technik uses an even smaller image size of 21mm corner to corner. This would eliminate entirely any hotspot problem but require a very good groundglass indeed. My setup flips the image. The path is :- SLR still-camera lens >> Groundglass >> 2 right-angle prisms >> Century Optics 7+ Achromatic dioptre for PD150 ( a very good quality close-up lens or macro ) >> camcorder. If you don't use prisms, with the 7+ dioptre, the groundglass will have to be about 5" or 125mm from front of the close-up lens. A stronger close-up lens will enable the camcorder to be closer to the groundglass and make a non-flip adaptor shorter. To experiment to find the best power of close-up or macro lens, you could buy cheap close-up lenses made from a single piece of glass but for good images you need an achromatic dioptre which is made of two pieces of glass. The motion images at www.savefile.com were created using this setup. At www.dvinfo.net/media/hart, there are a lot of still-image .jpg frame grabs which were made on successive improvements from the very first adaptor I made. My personal preference would not be to position the frame along the disk radius as your diagram illustrates but across the radius line. This reduces the possibilty of part of the image showing the groundglass texture as there is less of the inner portion of the disk area used. The linear speed of the disk surface is slower the furthur towards the disk centre you go. |
Ok, everything is more clear to me now. Thanks a lot guys.
I did some experiments, and i've just realize that i can get pretty close to the GG. So close to the glass, that i can touch the lens and i'm still in focus. It seems that my problem is between the photo lens and the GG: Quote:
I drawed a 36x24mm square in the glass, and I can't fill the complete square. It gets darker in the corners. So, in this case, the PCX is the way to go ? I'm using an (Auto Rokkor-PF, 1:1.8, f=55mm) from a Minolta SR-7. http://www.fdivisions.com/front.jpg http://www.fdivisions.com/back.jpg |
Grab yourself a PCX lens, and it will even out the vignetting.
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Glass Disks.
Some info for anyone who is making glass disks from 1.3mm thick centre-holed blanks from Ohara in Japan using a free platen in a tumbler style machine. The blanks are thin slices off a large diameter glass rod. It is the nature of the cut-off process that they will have a very slight simple bend in the cut. It is essential that the first grind to figure the disks true is allowed to proceed right to the centre on the groundglass finish side which is the hub mount face, even if the outer rim starts to get a bit thin. It is okay for the fine dressing and the polish stages to be limited to the outer image area provided the fine dressing removes the coarser texture in this area. The free platen tumble process has a defect in that the outer edge dresses down faster because the rubbing action is not a true circular orbit. This can be offset by another smaller diameter free heavy metal disk being added to bear weight against the platen carrying the glass disk so that pressure transfers from the high surface velocity area. Failure to allow the dressing to continue to the disk centre will result in a disk which will not run true. The platen and the added metal disk should be brass or bronze. There is wear between the two metal disks which roll at differing rpm and also from the rolling contact with the barrel. The metal particles which come off brass or bronze are not injurious to the glass. Castiron or steel rusts and these particles or hard particle inclusions in the steel itself which come free as it wears down will damage the glass. This damage usually shows as narrow elliptoid coil patterns in a band around the groundglass. This will also occurr if contaminants are allowed to get into the mix. Rotation speed for a 160mm diameter tumbler barrel should not exceed 65 RPM, otherwise there is a tendency for the slurry to throw to the outside and leave a dry spot about 10mm inside the outer edge of the glass disk which may cause non-lubricated glass to glass contact. This may result in pickup of glass from the disk onto the dressing surface which will then cause gouges in the disk. It also helps slurry circulation to have a centre-hole drilled through the platen so that slurry can feed up through this hole and the disk centre hole and let worn mix out instead of it remaining in a zone in centre of the disk. |
my latest agus35 clip + rundown
Hi there here is a link to a short clip i made today that shows my agus35 in action
http://www.filefactory.com/?62cac1 I have experiemented today with the following set ups: 1. pcx lens between gg & slr lens (my usual set up) 2. pcx lens between gg & camcorder lens 3. pcx lenses either side of the gg I also use a 10x macro lens on the camcorder PLUS i am using the nivea creme on the disc which has been sanded with 320 grit sandpaper (then washed) - thank you Ettorre!. When i had the pcx lens between the gg and the camcorder the image to my eyes was far too grainy. When I had a pcx lens either side of the gg I could not get a sharp enough image. The set up i have come back to is with the pcx lens between the gg & the slr lens. Keeping in mind that green is one of the 'noisiest' colours, to my eyes I find this image the most acceptable. I think for what i want to do with the adapter, this will be A ok! I plan to do a short movie in the next week or so that combines dof adapter footage with std camcorder footage so will get a better idea of how it all blends then. I am still planning on trying a 'achromat lens' which may or may not improve things. incidentally I have used a free plug in in 'virtualdub' called MSU denoiser on this footage which i quite like the look of. I also applied an 's' curve, some contrast and some saturation to the footage as well cheers Jamie |
Day 1 to report on the set of "The Cage", an independent martial arts based movie being created principally in the old Fremantle Prison in Western Australia.
I have participated in order to get some AGUS tests in on a real world shoot when moments permit and to get some hands-on with an action based project. (I get to assist the cameraman and clap the slate and hopefully not my finger instead). It is looking much better than I had expected. The people are very professional, there's industry experienced people among them and all are putting their heart and soul into it. So far I have not been able to take any matching AGUS footage of actual takes as my tasking on the project does not allow this. I have managed to do some tests during run throughs and rehearsals but the lighting setup was not completed and the images are a bit dark. It's 12-hour night shifts until they move on to the dialogue driven scenes where I may have more opportunity to try it out. I won't have time to get any stills up for the next few days. It's a good gig as they say. |
Day 2 of the shoot "The Cage".
They have got more of the fight scenes in the can. From the outside tey are looking quite good and I got some AGUS shots which I hope to get some copied JVC matching footage for. The old Prison according to an urban myth is haunted. There was a legend at the prison during its occupancy that if a white dove was seen to be flying nearby someone was about to top themself. (suicide in custody). 3-30am yesterday and in a fully enclosed area of the building as sudden chill drift came through. This morning about 3-0am and two different HDV cams, the Sony and the JVC, both on manual settings, spontanously lost sharp focus. - As you say in the US-"Go figure". I am a cycnic when it comes to the creepy stuff but I ope to get some interviews on it for the "Special Features" for the DVD. As soon as I have some useful stuff, I put it where it can be seen. |
spooky!
soundss like alot of fun. i will look forward to seeing some 'in focus' footage! jamie |
Day 3 on location "The Cage".
All is well. "The Bull" fight scene. Lot's of fun watching it done. Cameras being nice to their operators. The lights are not. One is burning out its globes frequently and the other is tripping the overload frequently. We assume the lamps' excuse shall be "The Ghost made me do it." I understand that a few of the key crew on this one were also involved with "Ozzie Park Boys" which is apparently doing well in direct to DVD-Video distribution. |
Day 4.
More interesting times. Some very good performances today. Watching actors reach what you think is their limit, then their coach works them up another level, you think that's it, then it goes up one more notch. Very educative. We innovated some focus stops for the JVC for focus pulls when handheld. The camera is light and the operator can be pulled off the shot if somebody like good old heavyhanded me gets fingers onto the focus ring. So, three bits of aluminium for limit stops, a rubber band on the focus ring, another rubber band hanging off that - crude, rude but reasonably effective. A doorbell went off spontanously in the place today. At one point, a loud call went out to turn the house lights off so the set was lit by stage lights only. The lights went out. As I understand the story, no one admits to actually turning the lights out and one crewman came up to the cage after lights went back on, quite animated and apparently shaken. Tried to get some demo footage done, but it was mostly a case of one-handing the camera/Agus combination , operating the slate with the other and picking off what I could get in the meantime which is not a lot. Still, I have a few and will post them once I have clearances and the time to code them to something the internet can handle. The Agus system is not ideal in a run and gun situation like this as any focus errors are very apparent. I suppose the same goes for the genuine 35mm filem camera. |
DAY 5 or is it DAY 6.
Overnight shoots have left me a little confused. Whatever, they shot some fight sequences today which really worked, the main one being Justin Versus "Bull". They have coverage shots on one particular fight scene and despair of not being able to use them all. Kenny Low - (Justin) is martial arts trained and is well in tune with where his body is in space and time in split seconds. Lee Jankowski - (Bull) is a professionally trained actor who went to W.A.A.P.A here in the west which is regarded as being up there with the best. Lee is a big guy but has impeccable timing and ability to move around. The both of them worked off each other and had trust and confidence in each other's ability. One shot in particular was a launch and bounce off the cage wall straight to a head kick which had a close clearance. They shot it four times and each time was a winner and was convincing to the point of one feeling compelled to call for the ambulance until the big guy sat up with a big grin on his face after cut was called. Yet to see how the dialogue driven scenes shape up but the action scenes have wrapped safely. This little project looks like it may punch well over its weight in terms of the budget and resources available. They screened some of the JVC HD 25P footage tonight and the images from that camera are remarkable, clear, colourful with deep blacks and no gain noise in the low areas whatever. Last day of this part of the shoot tomorrow and hopefully some time after that to put a few clips together. |
DAY 7 and the first schedule of production has completed and there is now a three day break.
One of my 500watt lights failed. The globe (actually a bar) still looks good so probably a quality issue with the switch or internals. The production Senneiser 816 broke down today so they have switched to a Sony C74 which I by chance took down today for interviewing a retired prison officer about the Fremantle Prison ghost stories. It is made of brass and is a heavy brute on the end of a long pole.The Senneiser has been increasingly picking up stray AC fields into the sound. If anyone has any hints on what might be wrong with the Sennheiser, any advice will be appreciated. Apparently it has been dropped twice in its lifetime. They shot three good short actions today and I got good Agus35 equivalent shots lighting wise, over the shoulder of the camera op. As soon as I have clearance to use them, I'll process and post the clips in H264. I'm still not sure whether Premiere Pro is acually capturing high def or not. Much of what I am shooting indoors looks grainy like pushed Super16mm film. I tried the Sony flavour of 25P (cineframe??) using the default preset 4. It actually doesn't look too bad. The production footage is JVC HD 25P. The AGUS35 stuff I am shooting is intended for a behind the scenes "Special Features" or "Bonus" section on the DVD as well as perhaps a short promotional clip. |
Off topic. I have posted details in the sound forum of dvinfo but here goes a short version.
Sennheiser 816 after four days of varying degrees of AC interfence penetrating the audio, finally died completely. Another mike on the same lead does not admit the AC interference so this hints at an internal earthing/shield failure in the Senneiser as I think the cable shield may provide part of the phantom power supply conductive path or be connected to it. Any advice on tracing the fault and repairing in-field would be appreciated, especially any previous similar experiences on other Sennheiser 816s. |
DAY 9
First new location other than the Old Fremantle Prison, the top floor of the Playhouse Theatre in Pier Street, Perth. This is serving duty as the "boardroom". They shot a scene today which demanded greatly of the two actors playing "Terrence" co-owner of the illegal fight club and trotting track and "Leelu", widow of "Jonathan" and who now has a renewed bond with a principal character, "Justin". I shot some AGUS35 shadow footage of the reverses and will post these shortly to the new project at savefile I have generated relating to "THE CAGE" the movie. The lighting was plenty for the JVC HD but only just enough for the FX1 via the AGUS35 setup. A full 18db of gain was needed. I shot it with the factory default PP4 selected which gives "cinelook" and an ersatz 25P. The images are grainy in this lighting environment with the 18db selected. Lighting as I remember it consisted of a 1000w "blondie", 2 x 500w halogen bar lights on stands ("Lowell" I think?), with masks and a coloured flouro tube for a blue cast from one side. I have the blessing of the director to post samples from my footage of the shoot. This is limited to Windows .bmp frame grabs for the present. These can be found at :- http://www.savefile.com/projects/618011 |
DAY 11
I got to try the system out in an exterior lighting situation. It works quite well in an organised lighting environment. Despite +18db gain selected, there was no video noise? It seems a high contrast environment keeps the video noise down. Lighting was 1000w "blondie" key, 2 x 500w industrial halogens fill, 500w Lowell backlight. I will be trying to get a half-size H264 Quicktime file of an assembled scene uploaded tonight and will edit this post or add another if successful to advise the savefile address. FOOTNOTE: Furthur to above, the clip was successfully uploaded and can be found directly at the following address :- http://www.savefile.com/files/4071292 This clip as shot as shadow footage via an AGUS35 motion picture film emulator on a Sony HVR Z1P. I do not have current HDV edit-assmebly software so the clip is derived from DV standard transcode and capture as MiniDV. Viewers are warned that whilst the video clip does not itself comprise of events of injurious physical assault or contain obscene language, it does credibly depict a situation of duress and threat. The clip should not be regarded as representative of the actual production camera footage or the intended style, edit and final production values of the movie project. "The Cage". Appreciation is expressed to the director, Morton Willoch and actors, Dein McAskil and Tracy Baker for permitting me to harvest and present shadow footage of their performances. |
For anyone building PVC pipe versions, I received the widescreen prisms today. I have yet to make up the new mount plate and to bond the prism pairs. Once this is tested, the altered design will be posted at savefile.com
Slightly Off-topic PS Go to TOTEM POLE at the bottom of the main dvinfo page and look for :- "The quest for a Century Optics CE-AD5870" |
An interesting phenonomen observed last time I was shadow shooting at the Cage location with the Sony HDV.
The lighting environment was indoors, fairly confined space so everything was lit fairly evenly. Lighting was 1000w key, 1000w masked fill, two x 100w relector downlights in photoflood housings. The lens was Sigma for Nikon f1.8 20mm prime. To get acceptable exposure from available lighting, the camera gain had to be +18db for a shutter of 1/50sec. I discovered that compared to operating outside in bright daylight, the camcorder zoom can be retreated furthur and pick up a larger area off the groundglass without the hotspot becoming apparent. This gives some flexibility for framing and also allows by zoom-back from the GG, a better resolution for wide shots where sharpness matters. Unfortunately, it is not a consistent feature one can rely on. I am totally confounded with this one. All I can assume is that the camcorder's internal aperture as something to do with it. |
Bob,
I had to click cancel cancel cancel to get the pop ups off the way, could you please use something else instead of File Factory, it's very annoying. Besides, still couldn't find the file .. sorry. |
Savefile.com was the only site which would accept the uploads from my sorry excuse for an internet computer. If you were looking at File Factory for my stuff you would not have been able to find it there.
I think you will find most of the free file archiving sites will have advertising or pop-ups in some form or another as this is the only means they will have of paying their way. Like free-to-air television, there is no such thing as a free lunch. Advertisement is a hassle and chore to be rid of but we would not have many of these things without it. I've got to go on the Cage shoot again tomorrow. I'll see what I can find over the weekend as alternatives. |
Have just finished milling up a new block for the 62mm hypotenuse ( = approx 30mm usable half-hypotenuse ) x 32mm common thickness right-angle prisms. The material I have used is 10mm thick black phenolic board as used in electrical work.
On zoom-back with the FX1, there is clearance between the image of the peak of the rear prism and the gg frame but on zoom-in, this peak encroaches into the visible image path. It falls away out of frame to the left lower and on full zoom-in is well gone. So far it looks like this arrangement with the 7+ doptre will yield a blemish-free image width of 28mm off the groundglass with the opportunity of a small amount of zoom range for framing adjustments. |
On set of "The Cage" again today. The location is a 1920's vintage family home in Nedlands which is soon for demolition. As co-incidence would have it the building is a style which was known as a California bungalow.
We had to trim down a stuck door which hasn't closed in a long time. All the doors and a lot of the moldings have been done in oregon pine and the build quality is by hand and heaps better than anything you would see in consumer housing today. All the doors are still straight and the moldings and an overhad verander beam is as straight as the day it was put there. Leelu gets to terminate her man in today's scene. There was some good action. Tried the AGUS machine up againsat the JVC and the standard Funjion lens with the 7+ dioptre on front has plenty of zoom through. I also found that if one is prepared to live with the a little of the hot spot, light to centre or overlight the edges, zoom-back from the groundglass with the f4 12mm - 24mm Nikon lens on front, set to wide, yields an almost bizarre field of view especially when shooting down from a higher position onto action. |
Show us a screencap of that, love to see it!
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Bill.
In the hasty grammar of my post I have perpetrated a confusion. The wide-angle was on the FX1 not the JVC, but on the JVC it would have the same characteristic. The SLR lens was the Nikon 12/24mm f4 zoom. As an Agus lens it is only just good enough and needs a lot of light. It is one of those lenses (I momentarily have forgotten the correct definition)where lines along the edge of the image are straight and there is a sort of perspective stretch which confers an interesting effect when looking down into a room from the vantage point of a kitchen benchtop. I'll post a screen grab in about three days when time permits. |
Bill.
Do you want the frame grabs as email attachments or are you content to download them from savefile.com. If you want them as email attachements could you provide an email address. This email service here does not seem to provide for attachments. The DP on "The Cage" had a play with the cam between takes and was quite impressed with the wideangle ability with the 12-24mm on the AGUS35 into the FX1 despite its other faults. It would probably work a lot better with a condenser but my design does not permit a simple condenser to be added in as the prisms take up too much space in the available close-up (macro) lens to groundglass stage of the path. |
My Adapter
Finally, I've done mine based on the mediachance design. Here are the the screenshots:
http://img.photobucket.com/albums/v2.../Imagezero.jpg http://img.photobucket.com/albums/v2...rk8/Image4.jpg http://img.photobucket.com/albums/v2...rk8/Image2.jpg Shots were taken without any lighting set up. Only the flourescents lit the room. And No post processing was done yet. I'll post some pics of my adapter soon. |
Julius.
What videocamera are you using.? Pics look good. Could you describe the image path? My device is pretty much along the lines of Agus Casse's original with some enhancements. Image path description follows :- Nikon f1.8 SLR lens >> [ plus 46.5mm to ] >> CD-R sized groundglass AO5 finish >> 2 x 40mm x 40mm x 56mm x 40mm common thickness right-angle prisms in 90 degree opposition (to flip image) >> [approximately 120mm in prism path but shorter in real distance] >> 7+ Century Optics achromatic dioptre >> camcorder. [ FX1 lens focus comes in at about 1.6M as displayed in the LCD. ] |
Julius.
The project box. - People have had good results with home-mades based on this method, plus a stout piece of board as you have done to firm things up a bit to deal with any vibrations such as they are. The CD-Rs are generally trouble free for vibration, but a bit of mass dampening doesn't do any harm. I observe you have the disk motor above the lens centreline. This is a working solution for the non-flip version but might add to a sound problem as any motor noise is more in-line with the mike pickup pattern and also may tend to mask off the mike from your sound source. If you use a separate mike, then this is a non-issue. You may find that if you later add a prism path, you may have to bring the disk motor below, as the prisms also shorten the physical distance between the front of camcorder and the groundglass which may bring the case against the in-camera mike. The bridge support beneath the camera and adaptor is a good move as you can rebalance the whole thing central on the tripod by drilling and tapping a hole in the bridge support. This is the route I went for tripod work. There are two tripod mount holes, the standard small camcorder size and the larger and I tapped these into a 5" x 2" x 5/16" piece of aluminium flat bar which I fixed to the wooden bridge support with four corner screws. I don't know the Kenko but I suspect the rear lens used in the close-up (macro) mode is a single element (one piece of glass) as there is a slight colour smear in the image where the chair frame is in sharp focus. The colour smear (chromatic abberation??? somebody correct me here) is the signature of a single element lens when a high contrast edge is encountered in the image. An achromatic dioptre does not have this defect but you may not be able to get one of the same magnification power as your current lens so you may have to remake the camcorder-to-project box section if another macro lens is used. What you have works. Enjoy, as undoubtedly you will. |
An update on the slow progress of designing the larger prisms into the old device for a better 16:9 image for the Sony FX1/Z1P --.
Due to the greater depth of the rear (forward facing) prism (+3mm for the half-hypotenuse), the prism block has to be moved forward in the case about 4mm to maintain clearance of the +7 dioptre on the camera. The position of the rear prism in the block is about 1mm furthur back than in the older version because the block is thinner. Initial tests shooting the aerial image demonstrated that the vignette from the 28mm Sigma for Nikon f1.8 lens clears the allscan area in the viewfinder at about position 35mm on the zoom-in. For the recovered image from the groundglass, this should yield a usable image from a wider zoom back from the groundglass which in turn should assist resolution. The prism path remains limited to about 30mm width, not much of an advance over the 26mm from the old prisms however this area is clear of any internal reflections and ghost artifacts which were sometimes present with the older prisms under certain lighting conditions. It may not be necessary to relocate the groundglass backfocussed position as the front face of the prism block is about the same as for the original thicker block with the old prisms. The groundglass and motor have yet to be installed. Designing a reliable adaptor mount for the JVC HD100 standard lens is proving to be a headache. I endorse Quyen's committment to using a fixed relay lens in the JVC version. |
A quick hint for anyone going through the ordeal of cutting plastic pipe caps with precision.
A Dremel with a small drill bit of 1mm diam or thereabouts held backhand so that the shank end or upper part of the drill leads and the drilling end of the bit trails, inclined at about 45degrees works quite well as a fast precise cutter. Use the incline to lead the cut. Don't force too fast or the material will melt and widen the cut. Don't dwell too long in one spot or go too slowly or the same thing happens. |
Tests with the groundglass installed match the aerial image tests with the zoom range of the FX1 from about 35mm to 50mm+ available for subtle reframing of the subject.
Wider than 35mm on the camcorder zoom picks up the edges of the vertical prism and the edges of the lens hot spot. For some as yet unknown reason, this version seems more sensitive to dust and fingermarks on the groundglass. |
Furthur tests in daylight conditions at 4pm suggest that the usable camcorder zoom range can be from 28mm - the max of 54mm with the best of the f1.8 lenses, the Nikon 85mm.
This is a much larger image than the aerial image which is limited by the width of the port which the prism face rests against. At this point the disk edge in my current design comes into the bottom of the frame also the corners begin to darken. There is enough useful zoom range for the 20mm, 28mm, 50mm and 85mm lens images to almost overlap in framing. |
For the wider prisms, I found that in being able to go a little wider with the zoom, that the camcorder is now too low by about 1.5mm and picks up the edge of the groundglass disk in the corners.
Moving the camcorder lens axis 1.5mm to 2mm vertically brings the bayonet mount into the edge of the pipe cap which has to have a clearance cut away. The inner face of the cap also has to be kept about 2.5mm out from the image tube end otherwise the bayonet fitting fouls against it. The SLR lens mount may have to be moved the same amount downwards to compensate for the shift if the SLR lens centre is already too high. If the SLR lens mount centre was originally correct, the 1.5mm does not seem to make much difference unless you want to go really wide and live with the corner falloff or bury it with dark image areas. The disk in the new device is a rework of an old glass disk which got scratched on the end of a self-tapping screw in the prsim block which I forgot to trim off. The aluminium oxide 5 micron was overworked but this time no partial backpolish was done. This seems to cost apparent resolution but the return from the Lemac chart is the same for the backpolished version. I think this is due to the wider frame now available off the groundglass for the same framing into the camera of the chart. |
Bob,
I am trying to improved the image quality of my adapter by using an achromatic diopter as advised. Century Optics is too expensive for my budget but I found some Canon achromatic diopters which is affordable. Can you give an advise which one of these is best suited for my adapter set-up. Here's the bhphotovideo link: Canon 250D achromatic diopter: http://www.bhphotovideo.com/bnh/cont...ughType=search Canon 500d achromatic diopter: http://www.bhphotovideo.com/bnh/cont...ughType=search Thanks in advance. Julius |
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. |
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Sorry to ask this, but is there anyone in this "HDV room" that is picking their main audio from the on-camera mic position? Please don't tell me there are... But the motor noise may be an issue even if the mike is closer to the source and the room is really silent. |
Mea culpa.
Presently, I am shooting footage alone for the "special features" section for "The Cage" in between doing other tasks as crew. This means I have to put the camera down and pick it up as opportunity permits and use the on-board mike. At 1/50th second shutter and with the disk motor on 1.5v the speed is about 1200 - 1500 rpm, more than fast enough to dissolve the grain on a 5" 120mm disk but slow enough to keep things quiet. A glass disk may be more noisy as they are hard to balance. A plastic disk should be okay. If the motor rattles a bit, perhaps put a drop of auto-transmission oil on the bearing. If it rattles a lot, perhaps try to fit the thrust bearing from the CD player the motor came from. That is the part which drops down onto the CD after it goes into the CD player. The thrust bearing is only a nylon tit which bears against a smooth metal pressure plate under spring pressure. I didn't bother as it is a hassle to extract and fit exactly. It also interferes with my backfocus ajustment which on my device moves the entire motor/mount/disk assembly. An alternative is to remove the spindle hub from the motor without breaking the spindle. You have to do this by getting something underneath the centre of the hub right against the shaft and not pulling on the rim because this will bend or break. A piece may come off the inner neck of the hub but it will still be usable. I trim off this section anyway because I don't use the original spindle motor but instead use the tray actuator motor or the tracking motor. These motors have a shorter shaft. On the older CD players and DVD players, the motors are identical except for the shaft length. The tray actuator motors are best. Because they have not been in constant duty in the player, they are less worn and are quieter. The shorter shaft and trimming some of the neck of the hub off means the disk mass can be set closer to the front of the motor. Any out-of-balance state in the disk has less leverage on the motor therefore less vibration to the case. In a serious production environment, I would not use the on-camera mike except to create a reference audio track for syncing up later to a separate double-system audio recording. |
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