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Old November 30th, 2003, 06:08 PM   #46
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I am still not sure why you need the frosted glass if you are going from the 35mm lens straight to the DV Camera. I understand why it is necessary if you are going through the veiw finder, bouncing off of mirrors etc. It is further from the first mirror to your eye than it would be from the point of the first mirror to the film. So the frosted glass is there the same distance as the film and you are looking at it when you look through the veiw finder. Here is a diagram: http://entertainment.howstuffworks.com/camera7.htm

It seems like the light or image will be at the film plane with or without the frosted glass. It seems like the trick is to get the DV camera focused on that plane. Would it be possible to say insert a slide with a focusing pattern and a grid showing the area that should be covered, focus and then remove the slide and block off all light. If this worked it would cut down on the loss of light because of the frosted glass.

Agus, can you focus on the frosted glass and then remove it? If so, what do you get?

The image will still be upside down. Also remember focusing on the move or follow focus will still be a problem with still camera lens because of breathing. See Charles Papert's explanation here: http://www.dvinfo.net/conf/showthread.php?s=&threadid=7713&perpage=15&pagenumber=3

Still I'm sure we can all live with these problems for this kind of DOF. Add some color correction and 24p or 30p good enough for many projects.


Paul
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Old December 1st, 2003, 04:25 AM   #47
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Wouldn't frosted glass compared to clean glass affect the image quality?
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Old December 1st, 2003, 08:03 AM   #48
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IMO:

The frosted glass is used like a projection screen, and the camcorder "film" the image produced by the 35 mm lens on this "screen". A clean glass would not preserve the focal lenght of the 35 mm lens.
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Old December 1st, 2003, 11:06 AM   #49
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Ground glass v. aerial image

I'm not sure of the proper optical terms here, so I hope I amd able to convey this idea...

The ground glass essentially is acting as a rear-projection element and is re-establishing your depth of focus by reimaging what you are seeing through the 35mm lens.

If you used a condenser lens, you would simply be adding the 35mm lens to your DV lens and would not be gaining the same effect. Again, I don't know the specifics, but you wouldn't be seeing the 35mm image. By recapturing the depth of focus onto a flat screen, you are able to take advantage of the optical properties of that 35mm lens.

Also, the grainier the ground glass, the more contrast you will see. As you remove the grain, the contrast is reduced. Hence the spinning ground glass.
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Old December 1st, 2003, 12:29 PM   #50
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Agus35 vs Mini35

Unbelievable Agus, i'm very impressed, currently i've done some preliminary testing of your prototype which i hope to flesh out over the next many weeks. True the Mini35 is nothing new, just a different take on the "Camera Obscura" (http://brightbytes.com/cosite/what.html). But you are ingenious, daring and ABOVE all inspiring...! That's why I want to dub your creation the Agus35.

Some quick questions... Your using the clear CD from the 25-CD pack, correct? (or is there another component I'm missing which you refer to as the "ground glass"?)or did you aquire an actual circular cut glass which you have "sanded" on one side? Else, I'm also thinking of trying to aquire an actual circular glass and using some etching acid from an arts store to frost one side for a finer "sanded" finish. Would you think that makes a difference in quality? Technically it seems it might. Also have you found an ideal place to put the rotating motor? And another, once you have adjusted the image to appear in the ground glass, the sweet spot, have you tried other lenses to check on their results? Like a zoom???
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Old December 1st, 2003, 12:40 PM   #51
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Well, yeah, if you use a cutted groud glass, made of glass and not plastic, you will have more quality, and you will loose less light steps.

Also, the ideal place for me for the motor is in the center of the spindle, it even have te same diameter to fit those very popular chinese motor toys.

I love all that about calling this adaptor the Agus35 ... heheheh
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Old December 1st, 2003, 03:01 PM   #52
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Posted by Brandt<<The ground glass essentially is acting as a rear-projection element and is re-establishing your depth of focus by reimaging what you are seeing through the 35mm lens.>>

I understand all that. I just can't picture why the light isn't at that same place, plane or distance if you focus on it. I guess the light must actually strike something to be seen.

I see how there are advantages to using mirrors, prism, etc. so as to be looking at the other side of the frosted glass and not having to look through it. That has to really cut down the light as has been discussed. Plus looking at other side it's possible to flip the image. Good bit more involved to make though.
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Old December 1st, 2003, 03:20 PM   #53
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Ok, this is quite simple, it seens that you havent even tried up the adapter, and also you seen not to understand how it works.

The adapter is way to simple to use, to build and the picture quality is amazing clear and pefect DOF... now, if you want to build another adapter using no ground glass and mirros... well... i think that is another topic.

The challenge was to build an adapter which would cost less than 10 dollars, and you could get equal image to the mini 35... i have succeded, the image is clear, i have DOF control, no vigneting... no noise...

the mini35 offers many more really advanced features, but i have adchieved the simpliest ones and the most important.

You need the ground glass.. i dont know why you are putting that you can do it, when you havent even tried. When i look at the mini 35, ithought it was just as simple to put the SLR lens in front of the DV camera, NO... it doest work that way...

So, pick up an SLR camera lens, your dv camera, and tried like you said, to use mirros, and no ground glass, the point is that this topic is about this adapter, which was built only using a 25 cd spindle, and cheap toy with an electric engine...

no means to offend, just to continue moving forward with this project.
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Old December 1st, 2003, 03:29 PM   #54
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another test...

http://altoque.tv/35mmAdapter/kartfilm.mov

about the GG, i wonder about its weight... cause if it is too heavy it will force a lot the little engine.
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Old December 1st, 2003, 03:48 PM   #55
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Quote:
I guess the light must actually strike something to be seen.
Exactly. Without actually being projected onto the ground glass, you'll just be bending the light more, which will affect the DOF as if the camera was taking the picture itself. With the ground glass, it's more like your camera is taking a picture of a photograph, or of, say, a movie screen. The picture of the photo or movie screen will show the shallow DOF that the movie camera did. Your camera isn't actually getting real light that's passing through the 35mm lens, it's taking a picture of the image it's projecting, which is a completely different thing.

That's why you can get a shallow DOF on your DV camera using this even if you're zoomed in, with a small aperture, and your CCD is only 1/3"... the usual rules don't apply since you're taking a picture of a picture, not of actual things.

By the way, Agus... what sort of processing are you doing on that footage? It looks very dark, what are the settings you're using? And maybe it's just me, but I'm seeing a little vignetting on the edges... did you not zoom in like you said you were before? All in all though, that looks really good.
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Old December 1st, 2003, 04:13 PM   #56
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I was also just thinking that in a later version of "Angus35" it would be possible with maybe the use of mirrors to vertically flip the image before it got recorded onto the camera to take away from the hassle.
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Old December 1st, 2003, 04:58 PM   #57
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Jon Yurek,
Thank you. That answers my question. I guess the angle of the light changes when it hits the frosted glass.

Agus,
I do understand how it works. I have been looking into this for almost 2 years. I have not tried it yet because I lost everything to a fire some months ago before I could start. I never said that you could get away without the frosted glass only asking if you had tried and what you got. Jon's answer explains why that wouldn't work. You have the DOF and no grain but it also looks dark especially around the edges. Sorry if I got off topic but thought this thread might lead someone on another quest like earlier threads led you to this one.

Noah Posnick,
Stay tuned I am sure you will see other versions.
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Old December 1st, 2003, 05:07 PM   #58
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why are you still calling me angus ? it is Agus.. from Agustin , .. hehehe

Yeah. my comercial version will use a pentaprism to correct the image. but that will take long until it will be avaible, now you can try up the free version :)

About the vigenting Jon, in some scenes i use it as visual effect, :-) i dont see it very dark, could it be that maybe your screen brightness is too low ? (i have to admit, that while i was shooting, the adaptor move a little to the right, check the other side there is no vigneting, after a stupid kid came running and made my camera fall !!!!, that also scracted and bump my 50mm lens... damn, but i can ensure you that there is no vigneting when it is centered, i just didnt noticed.)


I tried to copy a mini35 demo video, which use motocross racers, this is not motocross actually, but you will get the idea, i use Magic bullet, and look suite, and RE smoothkit (to take out the staicases from the interlacing... my cheap TRV18 needs some help always)...

Chek the part where the guy fall, you will see that the other bikes coming in front are really blurred, and also the behind the crash the same happens, your attetion will be only with him, that is the real DOF meaning.
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Old December 1st, 2003, 07:02 PM   #59
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Hey Agus,

I have a few questions (trying to build my own now! And I have a Sony TRV17! :-)

1. How exactly did you affix the end of the motor to the spinning CD? It seems difficult to center/stick to the CD... what did you use to do this?

2. What toy did you get the motor out of? Was it a dreamcast controller, coz if so, I have one of those lying around myself :-)

thanks!! I will take pictures of my Agus35 as well once I get it going...

paulb
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Old December 1st, 2003, 07:11 PM   #60
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hehehe you got the my little sister camera of my own.. the TRV18 and 17 are almost the same...

ok.. dont laugh, but i took a lego toy, and remove one pice that was the wheel, put it into another bigger lego piece (they are great, cause they are 100% centered) , and then make the cd to fit to that piece...

the toy was a Xmas ball that start throwing some fake snow... from there i took the switch and the batery holder as well.

let me post some pictures of it, so you can understand it more.
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