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Old January 26th, 2005, 05:17 PM   #1
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What am I doing wrong?!?!?

Ok, I have a Tele 2.0X zoom lens (for my Mini DV camera) at the end of a tube (only about 3 inch tube) - I put the GG (frosted CD) at the other end and then my DV camcorder near the Frosted CD on the other end. I look through my view finder and only see really blurry frosted glass (static CD). I cannot make out anything on the other side of the frosted CD!?!
Is the CD too frosted? Is there such a thing? I am really bewildered about this and I have tried my best to research this and get caught up on all the threads - what the devil am I doing wrong? It seems alot of other people are having success, but this simple task, I cannot figure out !!!

Help me please!!!
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Old January 26th, 2005, 05:51 PM   #2
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I think the lens you use is not right. You have to use a 35mm lens, so that would be from a movie camera or a photographic camera. That lens (on the same distance to the GG as the film would be) has to be focused and project a sharp image on the GG.
You should also see it sharp without the DV camera.

I think your tele zoom lens has no focal point, at least not the same as a 35mm.
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Old January 26th, 2005, 06:58 PM   #3
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The lens is a KENKO Digital Wide .5 and a KENKO digital Tele 2.0X - but that doesn't seem to be the problem. If I put my video camera close to the frost CD - there is no way that you can see through it!! I don't know what others are using, but even without any equipment, trying to look through this CD is impossible, so I am not sure how it can be reflected back or reversed when the image won' t be clear from the other side! Again, maybe I am missing something major and I cannot believe it would be this difficult considering most of the other people on the list are crying out Eureeka! every five posts or so...

I must be doing somehting wrong, either with the frosted glass or otherwise, still not sure which, but I want to figure it out soon!!!
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Old January 26th, 2005, 07:17 PM   #4
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I think the problem is like I said, because your lens in a conversion lens, so it depends on the lens it is mounted on.
Maybe you are missing the ground principal of the whole thing.

If you have a normal photo camera (with standard 35mm film), set the shutter to B (so if you press the shutter it will stay open until you release the button)

Now open the camera and hold the GG on the place where the film should be and press the shutter. You should see the image you'd be photographing on the GG.
If not, try tracing paper. I use this anyway until I make a better GG.
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Old January 26th, 2005, 07:20 PM   #5
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No I don't have a normal photocamera. I guess right now I believe you when you say that, I really don't have any other information why it won't work. I have tried this with my KIRON MACRO 35mm lens 80-200mm f/4 MACRO 1:4 but that doesn't seem to work either - is it the distance from the GG that I am getting wrong? I know that the image should appear on the GG, but I can't seem to get that .

Also what is the difference between a 35mm lens and a conversion lens?
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Old January 26th, 2005, 07:22 PM   #6
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Can you post a pic of your lens?

Try changing the distance between the ground glass and the lens. If it isn't perfect you won't get an image.
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Old January 26th, 2005, 07:34 PM   #7
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35mm stands for the film, not for the lens. Cinema film is recorded on 35mm, but because most photographic cameras also use 35mm film, those (much cheaper) lenses can be used for the adapter we are making.
A conversion lens is one that is placed in front of another lens, so it's not designed to get an image on its own. It needs the other lenses to get an effective focal point I think, but I'm not an expert on this.
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Old January 26th, 2005, 08:04 PM   #8
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Ocar,

You are right. I tried out a lens from and old 8mm camera that I took apart ages ago - put it in front of the GG and voila, an image! What a relief that is. My problem is that using my Mini DV camera, when I zoom in too far, it gets very blurry, but if I zoom out on the GG, it is too small to be useable. s this why a macro lens is needed?
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Old January 26th, 2005, 08:16 PM   #9
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So I need to figure out how to zoom in close enough to see what is through the 8mm lens (which is really small to begin with). Should I put the KIRON macro in front of the GG?
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Old January 26th, 2005, 08:41 PM   #10
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Mandy,

The macro would go between the DV camera and the ground glass. Also, to keep from getting barrel distortion, you should place the ground glass a bit away from the DV Camera / macro and then zoom in and focus on it. Recording at the telephoto end ensures a 'flatter' image, so you should have less of the barrel distortion.
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Old January 26th, 2005, 09:38 PM   #11
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Ok, because I don't have two sets of 35mm lens, I tried out the MACRO at the ACTION end - and yes it worked. Problem is, as I am sure others know, that I cannot perform a rack focus because just getting anything in focus is a chore. Once I have something in focus (thank goddness I have a manual focus ring -even though it is electronic), it looks good with the barrel distortion non-with-standing.

Ok, a couple of questions :

1) My DV camera is very close to the GG - what is the correct distance or is it all up to experimentation?

2) I am stacking Binocular lens in front of my DV camera to simulate a macro lens until I get one - is this acceptable?

Thanks for all your help guys!
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Old January 27th, 2005, 06:30 AM   #12
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If your image is not about 35mm wide you have to get another lens, because the reason why you'd make the whole thing is to get the depth of field of a 35mm film.
If you use a smaller one, like an 8mm, the DOF will be bigger, probably something like the DV itself.
A lens from a photo camera (one that you can screw off) could be found second hand very cheep. Also, once you focus the DV camera on the GG, the rest of the focusing will be done with the 35mm one.

So, if you have the right lens, you probably don't need a macro lens.
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Old January 27th, 2005, 07:12 AM   #13
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Frank.

The Kiron lens Mandy is talking about is a SLR lens with "macro" funtion, not in itself a "macro" lens in the sense many here use to describe an accessory or attachable close-up lens whicb is used to enable the camcorder to be placed closer to the gg in order for the usable groundglass image to be tightly framed and sharp focus to be achieved on the groundglass.


Mandy's tasks are :-

1. Enable the camcorder to focus close and sharp on a rectangle 24mm wide by 18mm high. This target can be a hand drawing on paper, postage stamp, pentium computer label. Until the video camera can do that, all the rest is forgetable.

Things which can make that happen are :-

a. Video camera can do it itself. = No.

REMEDY: Close-up lens on front of video camera, probably of 5+ to 7+ magnification power.

b. Find back-focus point of the Kiron lens which is the SLR lens in this case.

REMEDY: Simplest method but requires two people.
Find a room with a small daylight window. Take the Kiron lens. Hold it near the wall opposite the open window. Get the second person to be ready with a rule to measure. Bring the back of the Kiron lens closer to the wall until an image can be seen on the wall. When this image is sharpest, get the second person to measure the gap between the wall and the rear face of the three things which stick out around the back of the lens which hold it onto the camera it normally fits to. For most lenses this distance is usually about 46mm or thereabouts. The wall in this case is where the groundglass would be in an Agus.

c. Find or make a good groundglass. The finish on it should be fine like the satin finish inside a pearl household incandescant light globe. Any coarser than that and the groundglass is going to be no good.

Until these basic principles are self-demonstrated by the builder and understood, there can be no furthur progress.


Mandy.

The video camera does not look through a groundglass directly at the subject through the SLR lens, but looks from behind, at an image drawn on the groundglass (projected) by the SLR lens.

In an Agus/Aldu/Mini35, there are two focussing things going on.

That Kiron lens must draw (project) a sharp image on the groundglass.

The video camera must be able to see that image clearly from behind and the image must fill the frame, top to bottom and from left to right without the corners getting cut off or being darker.

Go to www.dvinfo.net/media/hart and look about halfway down the file list for the images :-

Agus1.JPG, Agus2.JPG and Agus3.JPG. These demonstrate the "looking out the window measuring against the wall" principle except that the SLR lens is an X-Fujinon f1.8 50mm which is quite adequate and usually quite cheap secondhand. The wall in this case has been replaced by a groundglass disk.
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Old January 27th, 2005, 08:32 AM   #14
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I have posted two pics of my results :

http://dvstuff.250free.com

Again, I focused in on the 'image' and then started filming. But as I stated, I cannot 'rack-focus' for the life of me because when I get one object in focus, racking seems to take everything out of focus - BUT I can move the macro lens forwards and backwards to give me the same effect (but I realize this isn't what I want in a closed housing for the machine. So my quest is to figure out how to fix this!

Here is my setup :

ACTION << KIRON MACRO <<GG << DV Camera

And, the set up is about 6-7 inches long now - I am guessing too long. Not sure how to rectify this. Any ideas?

AND how does one discover whether a magnet will work in reversing the image? Does this work with all cameras that have a flip LCD screen?

Again, thank you very much for all the input.
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Old January 28th, 2005, 12:51 AM   #15
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The term "rack focus" has its wordstuff origins in one method of achieving focus, originally with a simple prime lens by use of a "rack and pinion gearset" with the pinion gear driven by a handwheel or knob.

Modern SLR lenses achive focal movement by use of a barrel ring or entire moving barrel section on the lens body itself. To replicate the traditional "rack" focus method with its more convenient, rapid and controllable handwheel movement, some barrel control lenses are modified by added gears or friction devices to be focussed by a handwheel or knob.

As long as the subject is within the focus range of your Kiron lens, the barrel ring or moving barrel mechanism is sufficient. Modifying these lenses for traditional "rack focus" style actuation is a dark art I have neither the knowing of nor intent to explore.

For your Kiron lens to work correctly through its entire zoom range, you cannot use the older "rack focus" system of moving the entire lens, as it is a complex zoom lens with a precise focussing mechanism built into it, not a simple prime lens.

The rear face of the lens mount must be fixed in the correct distance from the focal plane, the gg disk if you want all the functions on this lens to work as designed. There is nothing to stop you from moving the entire lens with a rack mechanism if you wish, but there is little point to it as the lens overall will provide inferior performance under these conditions.
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