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posing a thought ...and asking a question ....
isnt there some sort of material out there ...like wax paper .....that you could put in the place of the GG ........like ..the translucent screen in an SLR camera. ......that way ..you could have a clean enough image ..without having to spin the projection screen (ground glass) my question is ......what percentage of the original picture ...(720 X 480) are you losing.......by zooming in to the image close enough to eliminate vignetting. for exampe ...are you ending up with ....a 680 X 420 image?? .... chris |
OK I'll take a stab
# 1 even a very pure frosted (Wax Paper) type substrate is going to have issues because your taking 24-30fps it going to look like your filming thru a screen because the grain will not change overtime, unlike film who's grain is organic like due to changing it's pattern every frame. at least thats my take on it. and #2 your not losing any resolution because you have not hit the cameras CCD's yet they are going to take a 720X480 sample of what ever they see. I'm working on my plans right now, I really look forward to seeing what everyone comes up with. Luke |
heres my version,
im still experimenting with having to zoom slightly. I think that I can get the camera closer to the gg. the gg is adjustable by moving the fan frame along the guide bolts. I have a fresnel lens 1/8" away from the gg mounted on guitar wire. I am using a Sima wide angle lens that I got at Bestbuy for $30 then removed the WA lens portion leaving the macro in place, If I just move the cam 1/2" closer I have a great picture without zooming, but I dont have a good way to secure it properly so I left it alone for now. I also noticed that the final image is very dark, I might need a lighter gg http://www.imagestation.com/picture/...4/fa531005.jpg http://www.imagestation.com/picture/...8/fa531004.jpg http://www.imagestation.com/picture/...c/fa531009.jpg http://www.imagestation.com/picture/...c/fa53082e.jpg http://www.imagestation.com/picture/...8/fa528f0c.jpg gaspain |
<<<-- Originally posted by Jon Yurek : Interesting. VERY interesting. I may have to steal your idea of using the fan casing when I make mine. And is that a fresnel lens in the shot where the CD is off? -->>>
ya thats the fresnel, im still unshure of the proper distance away from the GG, rit now its about 1/8" away (1/4" would be better) Im pretty happy with using the fan. Its quiet and smooth. I used a part from an old DVD player to hold the CD, gluing that on center of the fan was a pain to get it centered. I also had to trim alot of plastic of the shroud with a mill so the GG wouldnt rub. |
Quote:
For those of you using the CD motor -- I noticed my portable CD player uses two "AA" batteries. Would upping that to a 9v stress the wiring or motor itself? Also...my latest trip to Home Depot had me looking over the sandpaper section. I've already used 150 on my GG, and 600 was nowhere in sight. Agus, and others who've experienced success with their design -- can we see close-up, clean shots of your GG? - jim |
On my trip to HomeDepot the finest grit sandpaper I could find was 400 grit. It seemed to work well.
Mike |
If not using sandblasted or chemically etched glass, I would be inclined to get hold of some 600 grade lapidary grit (silicon carbide), clamp two clear CD disks back to back with a firm seal around the inner hub and outer diameter edges, put a bunch of bearing balls into a gemstone tumbler barrel with the grit and water, turn it on and leave it to its own devices for a few hours.
As long as the two disks have not moved against each other or grit got in between them, you should end up with two clear disks with a translucent surface on one side and smooth on the other. I would do only one pair in a barrel at a time as sliding edges will cause long scratches not short pitts. Just a thought. |
i am using 2 AAA batteries (1.5 volts each) on the cd motor and I think thats going too fast and making more noise then it should... not nearly as much as the radio shack kiddie motors but noticable noise... any suggestions?
BTW: What project box size you guys using? |
Bob, you're actually close to the mark on how to create real ground glass. You basically take the grit, add a bit of water, and rub two pieces of glass together for about 20 minutes. Using that method you can create better-than-professional-grade true GG, if you take your time at it :-)
paulb |
<<<-- Originally posted by Peter Sciretta : i am using 2 AAA batteries (1.5 volts each) on the cd motor and I think thats going too fast and making more noise then it should... not nearly as much as the radio shack kiddie motors but noticable noise... any suggestions?
BTW: What project box size you guys using? -->>> 7x5x3, its takes a bit of heat to make the GG fit without rubbing |
Using a 9v battery....
may burn the motor out if it doesn't it will spin REALLY FAST!
I took the motor/CD holder out of an old portable CD player, snapped a CD into it and connected it to 3v. WHOA! It spins too fast. The gyroscopic effect was very pronounced and I was concened if my"Agus35 Mark 12 Pro Rev 1.0" was jerked to quickly the CD might come of holder! I then connected it to a single 1.5v cell and its much better. It still spins at a good rate. Tom |
www.elpez.com/agus35test.mpg linked
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Here are two pictures of my quick-and-dirty attempt to make one of these things. It works! Now I'm going to spend a few dollars and make a nice one.
The lense was biult into a 35mm camera and by the time I wrestled it out it could no longer be focused. I changed the motor on it and had to mount the lense backward to get it far enough from the GG. The big gash in the side is from only having 100 packs of CDs and having to cut a huge hole to shove my camera into. http://vistatheater.org/~rhenry/agus...35-1-front.jpg http://vistatheater.org/~rhenry/agus...s35-1-side.jpg |
For those looking for fine grit sandpaper, try the auto parts store in the paint section. They usually have really fine grit wet/dry paper for doing touch up or other paint/body work. I have gotten 1000 grit at auto part stores before. They should at least have 600...
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I added an adjustable fresnel lens
http://www.imagestation.com/picture/...8/fa528f0c.jpg edited to say: HELL YEA! thats what i needed! its adjusted out a little over 1/4". This fixed any vignetting. |
<<<-- Originally posted by J. Clayton Stansberry : John,
A couple of questions: 1. Where did you get the freznel lens? 2. Where did you get the fan? 3. Is the box the one from Radio Shack? 4. When are we going to see some footage with the fix? 5. Plans? Agus, How are your plans coming? Thanks in advance... Clay -->>> 1-Walgreens $1.50 2-computer store 3-radio shack 4-I need a better GG, so in a while 5-Just look at the pictures for now |
<<<-- Originally posted by Paul Bettner : Hey John, what tool did you use to cut such perfect holes in the box? -->>>
I used a hole saw attachment on my milling machine, a drill should work tho |
<<<-- Originally posted by Peter A. Smith : John what's the size of the fresnel lens 2x3? -->>>
it was 2x3 :) then I cut it up into 2x2 |
http://scientificsonline.com/search.asp?t=ss&ss=fresnel+lens
Here's are several decent Fresnel lenses you can get and then cut down to what size you need. Here's another place as well: http://www.3dlens.com/fresnellens.htm Do you see the lines from the fresnel lens on your recorded image? |
To invert the image you could also inster a dove prism in between the GG and the camcorder lens or fresnel:
http://www.optosigma.com/miva/merchant.mv?Screen=PROD&Store_Code=OS&Product_Code=pg137&Category_Code=Dove+Prisms |
John,
Thanks for the answers. I am going to try to get started this weekend. Is the fresnel lens used so that you don't have to zoom in so far? And, how much does it help the problem of not having enough light? Thanks again... Clay |
So is the fresnel a good replacement for a macro adapter? Which would be better?
Thanks |
Fresnel and Macro
The way I see it, the fresnel is placed between the SLR lens and the GG to focus the light more directly onto the GG.
1..2.3....4..5.6.7......... [| < |==== | [|[|CCD 1.SLR lens 2.Unfocused light rays from SLR lens 3.Fresnel Lens (about 1/4 inch from the GG) 4.Redirected Light Rays (reduced vigneting) 5.GG 6.Macro Lens attatched to Video Camera's lens to allow it to focus on the 35 mm negative sized image on the GG while zoomed in. 7.Video Camera Hope this helps some ppl out...excuse my terrible ascii art skills, Spencer |
Re: Re: Fresnel and Macro
<<<-- Originally posted by Agus Casse :
Have you even tried that ? cause i believe it wont work, the fresnel have to be after the GG and before the Camera. -->>> I've tried it and its the only way i belive it will work. Also take a look at John Gaspain's design: http://www.imagestation.com/picture/...c/fa531009.jpg I don't think the fresnel is accomplishing anything optically if you place it after the GG. By then all is done in terms of vignetting on the GG, nothing you can do to change it from the Camera side besides zooming past it. Anyone else try out a fresnel? Spencer |
I am experiencing a high flicker... anyone have any idea why?
here are two pics (after film look post) from video i did today http://www.orfilms.com/luke1.jpg http://www.orfilms.com/luke2.jpg |
Agus, John, and anyone else who has made one,
How do you know where to cut the holes? Obviously, one hole has to be bigger than the other. Do you just guess as to where they should be? Is a fresnel lens the same thing as a magnifying glass? I went to Walgreens and got a bausch and lomb "magna-thin" magnifier as it is the closest thing they had that resembled what John used. Is this it? John, I bought the bigger box (8X6X3) and the GG clears it fine...just a little more bulky. I have all the stuff ready to go, but don't want to mess anything up and have to start over. Also, John, how did you connect the camera to the box? Ok, can't wait to get started. Thanks in advance for the advice! Clay |
To Peter Sciretta.
High flicker. My guess is you are getting an intensity strobe effect which might be related to variations in density or texture of your groundglass surface and the disk rpm coming close to the frame rate of your camera which means that although the texture of the surface will be moving fast enough past the frame to average out all the small defects, larger patches of say quarter to half a disk size will phase in and out of your frame. The scratches on your groundglass disk - are there some which go straight across the disk or uniformly circular in an even finish? Your 35mm lens centreline axis is also bent off-centre to the left in your second frame so I guess you are at very early prototype stage yet. |
According to this link from what i understand: http://www.camerascreens.com/PDF/Ins...ew_Cameras.pdf
You put the fresnel lens between the gg and the lens. Here's a difinition from B&H photo: A fresnel lens is an accessory for a groundglass focusing screen. It helps "even-out" the brightness of the groundglass image and make the image appear brighter. The effect is more noticeable with wide angle lenses. Fresnel lenses are essential when using reflex housings. I haven't tried this out, but i'm going to assume it should be place between the gg and lens. Clay just know the size of your SLR lens and Camcorder lens, then get a hole saw or a mill and drill the holes. You need to convert the millimeter sizes to inches e.g. 37mm = 1 1/2 inches 52mm = 2 1/8 inches, 58mm = 2 3/8 inches Friendly advise from a fellow Texan Peace Peter |
My bad
My bad Clay you asked where to put the holes. You have to be careful aligning the lens hole and camera hole. I goofed once and had the lens hole lower than the camera by 1/4 inch. So one side of the film can became useless. Just measure and mark each placement of your holes including your motor and thay should lessen the degree of the vignetting.
More friendly advise from a fellow Texan |
Hey Peter,
Thanks for the advice. I got out the ol' trusty tape measure and got the inch readings. I hope to find center of both and somehow line them up and get them centered. I just didn't know if anyone else had any tried and true methods. I am still wondering about where to drill the holes on the box (CD spindle)??? I guess that's what makes this so great...fly by the seat of your pants! Well, we'll see what I come up with if I don't hear from anyone else... Clay |
Just tested my frosted CD with the lens, was surprised it looked very good and it wasn't even in a casing. Will try and get this done over the next week and post some footage.
I put the scratched cd directly infront of my GL2 and it went into macro mode and focussed on the cd, would I still need a fresnel lens or a macro adapter? I'll test some more when I have a casing. |
Alright, some questions on tightening up the design...
I put mine together tonight, after having received my macro zoom yesterday, and it's functional, but there is a noticable haze around everything. I used 600 grit sandpaper, and did my best to put down an even surface. I've got my apertures wide open, and setting the 35mm lens to an infinite focal plane, I've set my DV camera's manual focus. So: how do I remove the haze, or cut it down significantly? Agus -- in your experience, was haze a problem? If so, do I need to up the speed of my motor? (I'm using a CD motor, but have a Radio Shack 18,000rpm motor at hand...) Jesus this needs light :) - jim |
Dunno what is haze ....
BTW.. tip for all, i found a little teasure... look for fake cds what are already translucent... they are 100% perfect GG !!!!! I found 2, and i have a 20% image improvement... |
what do you mean fake cds?
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<<<-- Originally posted by Danny Tan : what do you mean fake cds? -->>>
They are the CDS that protect the CDR in the 50 spindle packs, they are useless, and they are crystal clear. but some have a traslucent texture in one side that works a like a perfect GG |
Agus,
Are you saying do not sand the translucent CD we get in the case? Fake CDs, this is all I can think of. "ook for fake cds what are already translucent." Then, what is the purpose of spinning them? I have all the stuff sitting in front of me to make the AGUS35, but want the best results...that's why I haven't made it yet! Spill the beans Agus! We need detailed news! You are the man.... Clay |
No no no ... most spindles comes up with fakes cds that are absolutely clear, but some of them in one side have a sanded texture just like a real Ground Glass, those are not needed to be sanded... cause they have a sanded texture already made..
i have been trying to build a baseplate with rods similar to http://www.jbkcine.com/i-1.JPG i made it, but still isnt too rigid. need to work more... ANOTHER TIP.. when painting the Agus35, be sure to paint the inside side, cause if you dont, any scratch could ruin your paint and you dont want any outside light to ruin the image in the GG |
Agus,
What brand of CDs are you buying that have this "already grounded glass?" The two I have are clear, so I must frost them myself (man I hope I don't screw both up!). As for the support, I am hoping to get some long rectangular aluminum brackets that create a mount to both my camera and box (I plan to use lots of washers). We'll see what old Lowe's (a hardware store here in Texas) comes up with! The more the better...keep posting everyone!!!! Clay |
By "haze" I mean that the image has some crisp details that are obscured as if they're shot through a fog. I'm re-attempting my initial design today, using the Radio Shack motor instead. If increasing the disc's rotation doesn't help, I'll assume it's the ground glass that's causing my problem.
Agus -- what kind of motor are you using to spin your GG? |
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