DV35G - A 35mm-Adapter

Hi Folks,
First of all, let me say, my english is not very good. But because of some contacts, I promised to put in an english section on the DV35G. Please excuse, if this section is not as detailed as the german section. But I hope to put together all important facts on my topic ;-) For the curious: My adapter is a static groundglass adapter.

Status:
Okay, now it is completed, but not in the way I expectet it ... At this time I used it to make a very short movie (you can download it since april 2006 in the menu Projekte -> Mit Bande). The construction was very prototype-like at this time, but it worked a bit :-))


I decided, to close the construction at this time, because I had new ideas, and I decided to name the fourthcoming development 35F ... there is a new menu on the left side, but I don't know when I will add a english page. But the DV35G is frozen and completed now.

Background
I decided to start filmmaking, when all the neccessary tools where available to do it complete in the digital domain. Digital cameras(dv), lossless transfer to the computer (Firewire), digital editing (premiere) and digital distribution with dvd-r writers. And I want to be a kind of filmmaker who wants to create shortmovies and suspense but never wanted to do a wedding video. So the first thing I did was a wedding video ;-)
But when I looked out in the internet for other amateuer filmmakers, I recognized, that they are talking about something called the filmlook. The more I looked at it, the more I knew, that this is my look. And the more I read, I recognized, that Depth of Field is one of the very important keys to the filmlook. So I decided to build myself an 35mm Adapter. First of all I got an impression of the principle of any adapter.


I had very vague information on selfbuild existing adapters. The first one I saw, was the DV35K of Matthias Fleischer, a german director of photographie. He had an Panasonic MX 300 behind a Nikon F3 with a sportfinder.


Because he was filming through the finder, his material was on the dv-tape upright and true to side. The rail made the construction rough enough for  real production time. He filmed a movie, that was shown on festivals and was broadcasted twice in the german tv. That made me really think, that this kind of adapter was really working!
Because I never saw the construction before, when I concepted mine, I was always thinking that he constructed it the way I showed in the upper picture of the principle, and not using the finder. So when I was starting to plan my adapter I started with this and created a static groundglass adapter (because I never read about the Agus35 or the DoF Machine before).

Planing
The first problem I recognized on existing selfbuild adapters, was the grain and the hotspot of the groundglass. Hmm. I had to solve this problem. So I looked out for information on groundglasses, how they are made, what is offered commercially and so on. And I found some articles on a groundglass that was used for grabbing super8 movies to video. It's called the Glasscreen (in germany). In comparison with regular groundglasses the press said, it has no hotspot and no visible grain. This groundglass is made out of two perfect glasspanes with a thin layer of paraffin between them. I decided to use this Glasscreen in my adapter. And thats where the name is borrowed, the G in DV35G stands for Glasscreen.
The next problem was, that I hadn't any clue on reflex cameras. So I fetched some information on the net. And I decided to use a Minolta SR-T 101 for my adapter. This is a camera from around 1969 (as old as myself ;-). It is a full mechanic SLR with a mirror-pre-opening. This feature is one of the keyfeatures in my adapter. It had also a button to display the lens aperture in the finder, but this feature turned out to be obsolete in the end. I was planing to place the glasscreen exactly in the film-level of the camera. For sharpness I wanted to use the opticals of the finder of the camera, but for filming I had to let the light through the mirror. So the pre-opening  was very important. And I bought a Minolta SR-T 101 with a 55mm lens at eBay for around $20.
When it arrived, I decided to make a test.

Improvisation 1
Okay, I had no groundglass at this time, but I wanted to have a proof of concept ;-) So i taped some sandwich paper to the SLR and put the DV-Cam behind. To darken the way of light, I used a catfood-can with black paper in it;-)) The construction looked like this:


And here is the result:


(Pictures are from DV. Transfered to the computer and a screenshot was taken in Premiere. The screenshot was saved as JPEG in best quality. If you click on the thump, you will see a picture that should look like the DV original. All screenshots on this page are made like this)
Okay. It's grainy.  What do you think? It's sandwich paper ! At picture 1 you see only the paper and its grain ;-)  At picture 2 I opened the pre-opening and you see a fir, that is not so attracted by the grain ;-)) At picture 3 I shot on a chair. The chair is not dirty. The dirt comes from the grain of the paper. Okay, that is lousy, but it is a proof of concept, an so I ordered the Glasscreen.
Btw. the Glasscreen was available for around $29. I don't have any idea if such a screen is available in the US or somewhere else in the world. In germany you could contact the distributor at www.video-optik.de. But it needs time to get that screen, because they are handmade. It is also known as Bosscreen, but Bosscreens are not available at the time I write this (afaik).
Okay, the glasscreen arrived and I decided to do a second run. During the delivery I looked out for a way to make my adapter a bit more resistant against dust. So I decided to create closed system in the end, and wanted to use a bellow with a thread that matches the thread of the DV-Camera.

Improvisation 2
I taped the glasscreen in the SLR and taped a bellow between the SLR and the DV-Camera. I mounted them on two tripods. The result looked like this:


There is an additional finder, because with the bellow, you can't look through the normal finder. With 30 minutes of work I got the first great picture of this adapter.


Yeah, that was great. Because it was getting dark outside, I decided to do a second run on the next day, and try out all of my lenses I bought for the Minolta (everyone was between $5 and $20, one of the reasons I decided to use the Minolta ... the cheap lenses at eBay). And here is the result of the next day shooting:

focal length 35 mm	focal length 55 mm	focal length 135 mm
focal length 300 mm	zoom 70 mm	zoom 85 mm
zoom 110 mm	zoom 150 mm	zoom 210 mmm

Yes, that's it. That was everything I expected. The lint in the upper left corner is from the bellow, and I recognized it after the complete thing was taped. So I let it in. Some sharpness errors are due to the 2mm glasscreen that is not in the correct level of the film of the SLR, and the distance I took the shoots. But I was really satisfied. The Cam was placed 2,6 meters in front of the lion. I just replaced the lenses. From this point, I knew that I will build my adapter this way ;-)

Problems
Okay, there are some problems that I had, and they are known from other sites. The picture is not upright and not true to side. It appears that way in the finder of the DV-Cam and it is also this way on the tape. First I decided to ignore that, because when I use the mirror mode of the camera, everything was allright (except me, standing in 90 degrees to the cam). And in Premiere this would be easy to change and rotate. But later on, I thought it would be better to have the pictures correct on the tape.
That is where I am now with my adapter. It is constructed just to have the Glasscreen inside, a dust-safe bellow and mount for the DV-Cam (made of a pol-filter glued to the wooden pane), but it does not handle the side problems. The actual version of my adapter looks like this (I cutted off the sides of the SLR):


Next section is covering a rail-construction (or support rods ... leightweight supports ... and many more names) ... but please excuse me ... it all depends on an error in my construction, where I thougt, that I will need an additional mirror to have the picture correct on the tape. If you scroll downwards, you will see, that this 90 degree construction is not necassary.

So I need a rail, that will carry the SLR and the DV-Cam to place them on only one tripod, and I need a solution for the upright and true to side problem. The rail and the problem are going hand in hand. To solve the upright problem, I just have to mount the camera upsidedown on the rail. To solve the true to side problem, I have too place a mirror between the groundglass and the DV-Cam. This will lead to the following rail-construction:


The red arrows are showing the way of the light. The grey thing is the rail. It has two knurled screws to mount the SLR and the DV-Cam. Under it, it has a thread for the tripod. If the Cams are mounted, it will look like this:


Where you see the red arrows and the mirror, there will be a blackbox. To connect the DV-Cam I will continue to use the bellow. On the right side you see a box. that is used as a weight to balance the rail on the tripod. Instead of a metal weight, I just decided to place a 7" TFT there (I just bought one with a 2400x480 16:9 Panasonic panel for around  $170).With this rail, and the modified backing of the camera with a mirror in it, I would be able to record correct to the tape. With the mentioned TFT I can use the 16:9 mode of my DV-Cam perfectly and I can estimate the sharpness perfectly.
I found a locksmith, that will build the rail, because I did everything until here for myself, but the rail seems to need some precision ;-) I don't know how much he will take for the rail, but after some chats, I think it will be low-priced ;-)

Okay .. 28.08.2004 ... I have an update ... as I said, I needed a mirrorbox behind the camera to fix the true-sided problem. Today I finished the mirrorbox. It is  absolute okay. I build a box with a 45 degrees mirror in it. The mirror is reflecting on the surface, so the lightrays are not broken by glass in front of it. I just made a box instead a backing for the camera. I used an eraser to press the mirror in the box against the glued mounts. Here I have four keypictures that show, how I build that mirrorbox:

You need six wood panes to make a box ;-)	I used flagstone crosses to create the mount for the mirror on the bottom. On the top I used a wooden  bar.
Here you see the eraser that will press the mirror against the mounts in the box, when the backpane is screwed on.	And that ist the final mirrorbox. the mirror inside has 45 degrees.

I hope you can see, how that mirrorbox is build. If not, there are some more pictures in the german section 'entstehungsgeschichte'.

But as I said above ... the mirrorbox is not neccassary! I learned that when I made a short movie in 2006 with it. I replaced the mirror-box, by the backplane without the mirror!!!

In winter 2005 ... up to february 2006 I was making a shortmovie for a competition. I decided to use the not finished adapter. when I made first tests, I recognized, that the picture was wrong-sided on the tape.


So the mirrorbox was a wrong solution. In fact the rotation of the cam for 180 degrees IS a 2 time mirroring of the picture. That is mathematically correct!  So I replaced the mirrorbox with the old backplane for the adapter.
And then I did some prototyping with some screws an a wood plate.


This was the final prototype of the DV35G Adapter. I made the short movie with it. Here are some stills from it (captured from the DV Stream as BMP in Premiere, and then converted to JEPG in max quality with Photoshop).


The quality is mainly poor because of the onechip dv-cam. I am shure, because the noise is dynamic and not static in the DV stream.

In the future ... I will design the 35F ... that means it will have a flexible rods support system .. it will be flexible for more DV-Cams ... it will be quick mounted via magnetic attachment  and it will be able to run static, rotating and oszillating groundglasses :-)))
stay tuned ... :-))

 I hope this site was helpfull if you plan to build an adapter yourself. Take a look at the german submenus for the DV35G. Maybe you don't understand the german language there, but there are some more pictures, that could be helpfull ;-))