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Old March 26th, 2004, 09:30 AM   #1
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New guy

I'm brand spankin new to these boards, and followed a trail of breadcrumbs that lead here.

I'm really curious about the Agus35, and Aldu35 models, and when the technology is perfected, or near to perfected as possible I would love to try my hand at developing a system for myself.

Before the new thread is activated, I wonder if the first topic should be a recap of the most important R&D of this new technology, not to mention some screen grabs, Videos and perhaps even a spec list. Which adapter is the better of the two?

First and foremost I'd love to know the pros and cons of using each device.

Second of all, what is it about this add on that actually gives DV camcorders such a shallow depth of field? Why can't we have consumer priced cameras that have this feature built in? (I don't know a lot about cameras yet, so humour me please.)

And lastly, has anyone tried to have their housing and other parts to their Agus, and Aldu's built with a milling machine, my knowledge of Engineering technology is limited, but i remember in highschool how we had a milling machine that would construct parts given the information set up on autocad software. I'm just curious if anyone has gone this route considering you could build the thing with even the smallest detail.

Just curious, anyway, carry on.
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Old March 26th, 2004, 12:44 PM   #2
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Hi Trevor, welcome to the forum.
Although your questions may seem small, they're actually very involved. Fortunately, a large majority of what you brought up has already been discussed in detail... sometimes more than once. Unfortunately, the Agus35 and Aldu35 threads are monsters, as I'm sure you quickly noticed. I'll try my best to point you to some answers/designs and the other folks can ring in and help you out too.

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Before the new thread is activated, I wonder if the first topic should be a recap of the most important R&D of this new technology, not to mention some screen grabs, Videos and perhaps even a spec list.
Chris Hurd created a condensed "important info only" copy of the original "Homemade 35mm Adapter" thread started by Agus Casse (which lead to the Agus35) back in November. This must have taken Chris hours and hours to accomplish and helped newbies get caught up for a while. Unfortunately, since the condensed copy, both the Agus and Aldu threads have grown way beyond control and a condensed version probably isn't possible... even if it was, I doubt Chris would be up for it. Here's a link to the edited copy - http://www.dvinfo.net/conf/showthrea...threadid=18950
Quote:
First and foremost I'd love to know the pros and cons of using each device.
That is up to you. Keep in mind that there is no right or wrong design of either the Agus35 or Aldu35. Basically, everyone has joined forces to come up with a solid, basic idea. Then everyone takes their own approach and designs a personal, unique adapter. You'll just have to do some research and join in on the conversations, then decide which design you prefer and how you want to go about creating it. The basic idea is that the Agus35 has spinning glass which "hides" the grain and creates a more acceptable image, but it also requires moving parts and is substantially bigger. The Aldu35 requires no moving parts, is much smaller, can easily contain a condenser lens layout (disperses the light better), but the grain tends to be more visible (depending on the materials used).
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what is it about this add on that actually gives DV camcorders such a shallow depth of field?
Basically, the 35mm lens shallow depth of field relies mostly on the size of the image recorded through the lens. On a 35mm still camera, the film cell is 34mm wide. The largest prosumer camcorder's ccd is only 1/3" (8.5mm) wide. The mini35, Agus35 and Aldu35 all use ground glass to achieve a "projected" image that the camcorder can then record. Its the same principle as the viewfinder in an SLR camera. The full 35mm image is captured onto the ground glass and depth of field is preserved, so the camcorder just focuses on the ground glass plane and records the projection like its a flat image, like recording a piece of paper.
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Why can't we have consumer priced cameras that have this feature built in?
The adapters are basically providing a means to emulate 35mm shallow depth of field until the technology is good enough to not need these adapters. Although it would be wonderful if the low cost adapters were manufactured and integrated into prosumer camcorders, most people feel that the big companies are more concerned with just getting full 35mm sized ccds and wouldn't care to deal with this temporary solution.
Quote:
has anyone tried to have their housing and other parts to their Agus, and Aldu's built with a milling machine
Yes, Filip Kovcin made an Agus35 out of aluminum (http://www.astercity.net/~tarasuma/agus35.htm) and it turned out great. As far as I know this is the only one created out of metal. Most Agus35s use an empty 50 CD-R spindle (see Chris's edited thread linked above) and Aldu35s use 2" PVC pipe (http://ideaspora.net/aldu35/, http://home.austin.rr.com/aqua99/adapter/) or record straight into an SLR camera (http://www.paddlefilms.com/vm35mmadapt.htm).
Also, check out Olivier Vanaschen's movie "Marla" shot with his homemade 35mm adapter. This thread http://www.dvinfo.net/conf/showthrea...threadid=21567 provides links to the movie as well as still frames and behind the scenes pictures.
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Old March 26th, 2004, 05:20 PM   #3
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Thanks for the reply.

One thing I don't get, and maybe some explanation is in order.

When the 35mm film lens picks up the image and throws it at the spinning CD, or ground glass or whatever it is you want to use. The image is projected on the GG, and gets thrown through a macro magnifying lens and into the Camcorders CCD.

Now how does the image from the film lens go through a rather opaque frosted CD without loosing a great deal of image clarity?

I'm confused with this particular procedure.

Trevor
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Old March 26th, 2004, 07:27 PM   #4
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That is a tough question that you probably won't understand until you play around with a lens and some ground glass, then it will make total sense.
Basically, clarity depends on the ground glass. Finer grain creates a more uniform, white surface, which preserves more detail/clarity from the projected image.
Try not to think of the image as going through the opaque surface so much as it is captured ON the opaque surface. Here's a link that will describe this effect much better than I can http://topcontechnotes.home.att.net/...tem/page3.html. The link is to page 3 of 16 that completely breaks down the SLR camera's imaging design, which is the exact same technology used in these adapters. I recommend reading all of the pages, they'll help you get a much better understanding of the designs.
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Old March 27th, 2004, 12:00 AM   #5
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It definitely loses a substantial amount of clarity. We shot with the DVX w/mini35, and compared those shots to the DVX+anamorphic adapter (no mini35). The anamorphic shots are much clearer.

However, the mini35 shots are substantially more filmlike, even without taking advantage of the shallow DOF (i.e., a wide shot on the mini35 with deep depth of field, looks more filmlike than a wide shot on the DVX without the mini35). Even though the non-mini35 shot was clearer, the mini35 shot looked "better" (i.e., it looked like it came from a 35mm film camera instead of from a video camera).
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Old March 27th, 2004, 01:17 PM   #6
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Here's a link to a site that I found.

I'm not sure if it's a workable solution to film grain on your 35mm adapters, but it's worth a look.

Perhaps someone has already mentioned this.

http://www.bromwellmarketing.com/boards.htm

"Bosscreen offers an alternative to fresnel and ground glass; a sandwich of two pieces of glass fused by a parafin type laminate. It eliminates the grain of ground glass, but retains its sharp in-focus/out-of-focus image snap."

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Old March 27th, 2004, 03:50 PM   #7
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Bosscreen has been mentioned a few times as a potential for better ground glass, but I don't think anyone has actually tried it yet. This topic is fairly popular on the large and medium format camera forums. Apparently a high quality ground glass and Bosscreen each have advantages and disadvantages over the other. So basically its all about personal preference. Either way, its certainly worth a try if you can get ahold of a piece.
The downsides are that Bosscreen tends to be more expensive, larger in size (you would have to have custom made pieces), and usually has a grid embedded into the glass (like crosshairs).

I have read on quite a few medium and large format camera forums that you can accomplish basically the same as Bosscreen with a good ground glass that has been thinly coated with vaseline. The biggest benefit of Bosscreen is the brighter image. Vaseline supposedly provides this advantage but would, in turn, require a condenser to diffuse the hotspot. Of course the downside to vaseline is that it collects dust so easily and will start to turn yellow over time. I plan to experiment with this soon.

Another ground glass replacement that is being tested is holographic diffusers. This was a big topic a couple months ago, but sort of vanished lately, so maybe it didn't work out well.
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Old March 27th, 2004, 05:21 PM   #8
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probably the best approach is to build a boss condenser.
You put the paraffin on the flat side of the lens and cover it with a coated UV filter (coating turned toward the 35mm lens).
I think it should no t be a problem to fuse some paraffin due to the low temperature needed (round 50-60 celsius deg.)
for the thickness, we can probably use some aluminium paper (or other more or less thin material) disposed in the border of the lens.
We should try to find what thickenss is used in a boss screen and what kind of parrafin.(will white candlestick be ok ?)
that would really be a nice piece of art and i think we can expect nice result too.
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Old March 27th, 2004, 10:25 PM   #9
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how come you couldn't just take the design of a normal camera to make the image go through a penta prism to make it rigth side up?

Is there something about the pentaprism that screws up the image transfer into the CCD of the camcorder?
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Old March 28th, 2004, 01:34 AM   #10
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The pentaprism (technically a penta-roof prism... that's very different than a plain pentaprism) from a plain old SLR camera does a great job of orienting the image properly. Unfortunately, the image is so small in there (due to the distance from reflecting all over inside the prism) that you will have to have a pretty darn powerful macro lens to focus on the ground glass. Another setback is that the roof part (the prism is shaped like a house) is hard to get framed properly.
That is a great idea though. Ultimately, if you could figure out how to use a pentaprism, you'd have a really nice adapter.
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Old March 28th, 2004, 05:40 PM   #11
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i made some experiment with boss screen.
it looks easier to deal with wax than with aluminium oxide, especially that you can redo the process as much as you need with the same lens and glass.
first put the UV glass on another glass or ceramic plate.
It would be clever to add under a piece of printed paper (post stamp ?), so you can check the quality of the result. the picture or text must be perfectly visible, while the glass when looked through should look white.
put some easy removable glue (neoprene or contact glue) so there will be no liquid wax going under the glass.
fix all around the UV filter little square of aluminium paper or other thin material (plastic sheet for transparency).
one half is on the UV glass and the rest is fixed on the support.
this will guarantee that the layer of wax is the same thickness on all the surface.
then heat all the stuff in your kitchen or bathroom. You do not neet to cook it , so a good hair dryer should be enough.
apply a minimum of wax on all the UV glass.
I use the white interior of a green candlestick, but we need to probably check with different kind of white wax to find the best one.
Rule is that you alway end up with more wax than needed on the UV glass but that is not a problem. just leave the excess flow out of the glass.
before applying the second glass (or in my case the condenser lens), make sure it is hot enough to prevent the wax solidifying.
If both of your glass are perfectly flat, a gentle pressure should bring the two glass in contact, just separated by the material you put in between and a layer of liquid wax, that is at that stage totally liquid and transparent like water.
take care because the wax is like oil and the lens is floating, so it is difficult to keep it centered. i just brake one by moving all the stuff and the lens slip and explode on the floor.
Probably the secret of a good boss screen is to let the wax solidifying slowly. that is easy with the air dryer.
if you are not happy with the result, just clean everything with hot water .
Probably 1/10 th of milimiter of wax is enough.
I made no test yet, but as far as i see already, there is no grain visible (could be a problem you believe it is needed for the film look).
There was some comment about putting some grease on a GG to make it more transparent. some good test would be to make a boss screen with a GG glass to combine the GG grain+ the boss effect.
other experiment would be to use 2 condensers glued together with wax to eliminate vignetting
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Old March 29th, 2004, 10:36 AM   #12
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Looks like I'm about to embark on this grand adventure.

I've decided to go with an agus model, I like the image quality I've seen with this handy device.

I own a sony TRV-950.

Anyway, before I do so I want to be up to speed with most problems that occur throughout the building and testing process.

1. The GG, whether it be ground glass, ground CD, or the already frosted store bought which comes in a case of 40 fake CD, what type has the best image quality?

2. The type of lens you use? 35mm, 50mm, does it make a big difference? Right now I'm thinking of going with a Canon 50mm.

3. The distance from your Lens to your GG where the image will be in perfect focus is the focal point am I correct? Is there anything I should know before setting up this distance, or is it pretty self explanatory.

4. With the fresnel lens inbetween the film lens and the GG, how far should this be set up in front of the GG, Approx?

5. In reference to a macro lens, some have gone with a +10, others a +7, which has the best results?

6. If I focused the path of the light which is already coming through the film lens by building a tunnel towards the fresnel and GG, will this trap and focus more light? Or is this not needed?

I'm probably missing a hundred more questions, but this will do for now.

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Old March 29th, 2004, 11:46 AM   #13
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1. actual ground glass is by far better optical quality than the plastic cds and especially the frosted ones. Also, the finer you grind the glass (3 micron is the limit before its polished) the brighter and more detailed picture (more hotspot to diffuse).

2. My whole approach to this is to use a mounting ring so I can switch lenses as need be. 50mm lenses are considered the closest to reality, so that's a good one to start with. The one big decision to go with here is what brand lens to use and then stick to it.

3. Each company (Canon, Minolta, Olympus, Nikon, etc.) have their own mount and specific flangeback, or flange-to-film distance. This is the distance between the lens flange and the ground glass and is absolutely necessary to take advantage of the lens's full focus range. For instance, Canon FD lenses require 42mm (check this chart http://lists.cdegroot.com/pipermail/...il/001383.html) but Minolta MD requires 43.5mm. If you settle on one brand and mount it properly, you will be able to change lenses.

4. As close as possible, with the ribbed surface facing away from the ground glass. Keep in mind that the fresnel lens will disperse light very well, while noticibly decreasing detail. That's another one of those no-wrong-answer areas that will be personal preference.

5. That is all going to depend on your adapter. I'm sure there is a formula to calculate this according to source size and distance (if anyone happens to know this formula I could sure use it), but the best way to find out is just to go to a photo shop and test them out. Draw a square on a piece of paper that is 36mm x 24mm and hold it the same distance from your camcorder as the ground glass will be. Then just screw on the different diopters, zoom in until the area is full-frame, and see which strength works best.

6. This is another area to experiment. You want to preserve as much light as possible which the tunnel will help with. but at the same time, you don't want any reflections, so the tunnel would need a very dull interior surface.
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Old March 29th, 2004, 11:34 PM   #14
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Roughly how big of Pentaprism would you need to compensate for the camcorder?

How big is a standard pentaprism? Who makes them?

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Old March 30th, 2004, 02:38 AM   #15
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A few more questions.

Sure a shallow depth of field is great, but what about when you don't want a shallow depth of field? Can you adjust the f stops through the 35mm film lens? Or will it be fixed?

Can interchangable lenses be integrated with the home made kit, as long as they are the same thread and model so they maintain the same focal length?

Thanks again. I'm in the preproduction phase of my agus. I hope to have something to show real soon.

Ciao

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