DIY spinning 35mm adapter discussion

[Terry Lee]

Hello everyone,

My eyes are starting to cross from reading countless forum posts about 35mm adapters. I want to build one. Not because its cheap but because we are building everything from scratch. I've come across some people who have built a spinning 35mm adapter. The footage that they have posted looks WAY better than anything i've seen from a viberating adapter. However, I take it that there are only certain lenses (mid-format) that can be used? I have no clue. That fact came up to be common sense among people partaking in the threads. one thread below.

Mid-Format DOF Adapter - DVXuser.com -- The online community for filmmaking

Anywho. I'd like to get information on building one.

[Bob Hart]

Brian Valente who posts here - his company, Redrock still sells a DIU kit last I knew.

You are not stuck with medium format.

Basic rules.

Nikon lens > 46mm > groundglass finished with 5 micron aluminium oxide > approx 150mm to close-up lens, typically a 7+ achromatic dioptre >> camcorder will get you a quite acceptable image from an approx 24mm wide image projected onto the groundglass.

Search Agus Casse and you will find the longest thread in the entire universe on the subject here at dvinfo.

[Marcel D. Van Someren]

Originally Posted by Terry Lee

... However, I take it that there are only certain lenses (mid-format) that can be used? I have no clue. That fact came up to be common sense among people partaking in the threads. one thread below.

Mid-Format DOF Adapter - DVXuser.com -- The online community for filmmaking

Anywho. I'd like to get information on building one.

Terry,

I'm the person who built the mid-format adapter in the thread your referenced. The fact that it was mid-format was a choice and not a necessity. The idea of using a mid-format lens over a 35mm lens was that it would project a larger image on the (larger) Ground Glass so, theoretically, the image would be a higher resolution and you wouldn't have to zoom in onto GG as far so light loss would be better as well.

My purpose for building it was:

1) To learn as much about adapters as I could
2) To decide if shooting with an adapter would produce the results I was looking for and if it was worth the extra effort required when shooting with an adapter.
3) just to see if I could do it :)


In the end, I decided I liked the look that an adapter provided and was something I wanted. The problem I had was that the mid-format adapter that I built was just too bulky, and since it was mostly plastic and glass, the build quality probably wouldn't withstand daily use. I tried reducing it in size, but I still wasn't happy with the build quality. Eventually, I ended up getting the SGBlade 35mm adapter- primarily because of it's compactness and build quality. The fact that it also had interchangable GG was a plus as well. A far as I know, it's the only spinning adapter that has that feature.

I still have my mid-format adapter and keep it as a back-up.

I highly recommend that people who are so inclined, build an adapter even if they will eventually purchase a commercially available adapter. The education you will receive is invaluable.

[Terry Lee]

Marcel,

You were the person I'd hope to get to talk to about this. Fantastic job by the way. I have had a real problem with 35mm adapters because of the barrel distortion and vignette but the footage I watched with your DIY adapter was much better. I suspect due to the size of the mid-format lens. I think your theory proved true.

The bulkyness for me isn't an issue. The more compact version I don't think is much bigger than the Redrock M2. Looks about the same actually (even the handel :)

The problem for me is I don't know how to build a spinning one. I've only seen the plans for the viberating adapters. You are the only one i've seen who has a pretty good handle on building the spinning version.

[Marcel D. Van Someren]

Hi Terry,

Actually, the real expert on DIY Spinning adapters is Ted Ramasola who is a member of this forum and DVXUsers forum as well. He has built both mid-format and 35mm adapters that look similar in shape to mine, but his build quality is much better and metal construction. He has shot travel commercials with his adapters and much more. Take a look at how his footage looks: Ted Ramasola On ExposureRoom

He was very helpful when I was building my adapter. His recommendation of which achromat to use made all the difference.

That said, I can answer any questions about how I built my adapter.

I posted a simple diagram here:

http://www.dvinfo.net/conf/alternati...m-adapter.html

And here's what it looks like on the inside:

[Terry Lee]

Marcel,

Thank you for your help. I do have a few questions

Are the mid-format lenses alot bigger? What decresses light loss in your adapter? That I have a real concern with when it comes to 35mm adapters. There is such a length that the light has to travel that there is significan't light loss.

I suppose that it makes a difference how far things are from each other? particularly the length of the gound glass from the condensor. What exactly does the condensor do by the way and why is it optional?

I will probably be working with Nikor 50mm lenses simply because I have a couple. Would the only modification to the diagram you have given be a nikon extension tube?

One other thing, The box. Did you fabricate it?

Thanks alot for your help!!

Terry

[Marcel D. Van Someren]

Hi Terry,

The mid-format lenses are slightly larger than the 35mm lenses. Their FOV is also different. For example, a Mamiya 80mm lens mid-format lens has approximately the same FOV as a 50mm 35mm lens.

Light loss is always a consideration with any adapter. That's why it's important to choose a lens that is fast. For example, a 50mm f1.2 or f1.4 is a better choice than an f1.8

Next the quality of and the number of elements in your adapter also affect light loss. Generally speaking, the more elements you have, the more the light loss.

The GG plays a big part in the light loss but also in the bokeh rendition. A finely ground, GG will allow more light through but the bokeh will tend to be hazy. A coarser ground, GG will let less light through, but the bokeh will look nicer.

The placement of each element in relation to each other is very important. For example, if the GG is not the right distance from the 35mm lens, you won't be able to focus at the lens' infinity setting, and/or the distance measurements will be off. The diagram I posted has rough measurements that I used. It took many hours of fine tuning before I got it right. Your measurements will likely be different to some degree.

A good way to start is to go outdoors where there is plenty of light and there are objects more than 30 feet away but you are in the shade...take your Nikkor 50mm lens, set it to infinity and wide open. Aim it towards one of the objects that is more than 30 feet away. Now take your ground glass and and hold it behind the lens. Now start to move it away from the lens until the image projected on the GG glass is in focus. Now you know what distance your GG must be from the lens.

I used the condenser to help eliminate the hot spot I noticed when it was a bright image and I panned the camera. In my case it worked best between the mid-format lens and the GG glass. other designs place the condenser between the GG and the achromat. You'll need to experiment to see which works best for you or if you even need one.

As far as the extension tube goes, the reason I used one was because I couldn't find a mid-format lens mount. For a 35mm adapter, you can easily find a lens mount, so don't even use an extension tube. It will affect the distance measurements between the components but I think the results will be better.

The box I used was just a plastic project box I found at an electronic's store. If you can get a metal box, you'd be better off. Of course it will be a little harder to work with.

[Terry Lee]

Marcel,

Very good explination, thank you!

Yes, the lenses I have are a 50mm 1:2 and a 28mm 1:2.8

Very good method on determing the distance of the elements. I suppose i'll have to bring a table outside to sit a ruler on so I can measure the distance. Where would you suggest I get a panel of ground glass? I'll have to learn how to cut glass to. Was it that hard? I'd hate to end up breaking the ground glass I just bought :( Also how do you determine the diamater of the ground glass disk? Would that depend on the size of the box I obtain?

I have been searching awhile for the right lens mount but I can't even find one on ebay. I'll check with this vintage camera place in town and see if they have one. I do have the right lens though, 50mm nikon nikkor 1:2, right? About the fastest you can get?

The box I think I can have built out of metal. I have a fabricator who is building my crane, track and dolly.


Again, Thank you for your help. Soon I will be on my way to building this thing!

[Marcel D. Van Someren]

The lenses you have are good for an adapter.

I understand your concern about breaking the glass. I had the same. That's why I watched some tutorials on yourtube, bought the right tools and practiced on a few pieces of regular glass (from picture frames) before I cut the ground glass. Once you get the hang of it, it's pretty simple. Remember, you don't have to use glass. you can use other materials. There was a guy on ebay last month selling ground glass disks, but he doesn't have a listing currently. You can also purchase a GG disk from redrockmicro. I believe Ted Ramasola ended up buying one of their GG disks for his DIY adapter. They also sell lens mounts and so does shoot35.

Happy building!

[Bob Hart]

I understand in relation to condensor lenses that the gold standard more or less is to place two condensors in the path with flat sides towards the groundglass. One condensor between Nikon lens and groundglass and the other between groundglass and achromat. The condensors shoud apparently be as close as practically possible to the groundglass.

A two-condensor setup is used in the fixed groundglass Movietube. The condensors which have flat or "plano" faces on one side, actually form part of the groundglass itself in that they have a wax layer between them in the Movietube.

It is more common to find only one used and most often used between the groundglass and achromat.

A correction to my earlier post.

The flange to focal plane distance of the Nikon F-mount style lens is 46.5mm not the 46mm I quoted.

It seems more common for the groundglass surface to be on the rear face of the groundglass ( on the camera side ). Therefore the dimension from flange of Nikon lens to rear of groundglass will be 46.5mm. If you shove condensors in the optical path, then the flange to focal plane (groundglass) distance and/or the groundglass to camcorder distance will change slightly.

[Terry Lee]

Since I will be building this thing I am going to post a photo update of my progress. There, Marcel and anyone knowledgable can discuss what I am doing wrong or doing right.

I think I will end up getting the ground glass from Redrock just so I know that I have the right stuff and don't lose money on breaking the thing :) Watch me still break it, haha.

Alright so today I stopped by Chuck Rubin's, a vintage camera store in Louisville and got a Nikon 50mm lens mount. Chuck is an awesome guy. If ever you find yourself in Louisville stop by. I asked him what I owed him and he discussed it with another guy working there and they agreed that I only owed them a bag of oranges. HAHA! First it was a water mellon but then they remembered they had one so a bag of oranges it was :D!

Anyway, I now have a lens mount which I have posted a photo of. After looking at the ones that Shoot35 are selling I notice that they have a bit of an extension and a base plate that fits onto the box I suppose.

So here is my first question. How long to make the extension from the lens mount, which is virtualy flat, to the box that houses the spinning ground glass?

Second question, How do you fasten the ground glass disc to the CD player motor? Well properly so It doesn't fly off..

Third question, The acromat. I asked Chuck about it, which is a man surrounded by millions of camera parts, and he was sort of confused on what I needed. He told me to ask what lens the people I was talking to got it out of and he may have one. I checked on Redrock and they have an 8x 55mm achromatic lens for $95 bucks (Redrock 8x 55mm achromatic lens)

Final question for this round, The toggle switch. Will any do or is there something certain i'm looking for here.


Thank you for your time!!

[Bob Hart]

Terry.


If you are using the genuine Nikon mount which is a good thing to do, you need the circular spring which goes behind it, otherwise your lenses are going to rattle and spin when you pull focus.

You can get away with just using the spring alone for keeping the lens firm but best if you can also rig a locking pin and release. I didn't bother because it is a bitch to engineer. Needle rollers out of automotive drive shafts make handy pins.

Unless you are also using a piece of extention tube on the front, you will also need to Dremel out clearances in the case for the raised portions of the spring to locate in without the case pulling down tight on them and flattening them out in which event they won't work.

The spring has to be free, not crushed. In cutting the clearances you need to take care to leave raised sections where the screws thread in otherwise you may never get them to stay tight as they are very short. You could use longer screws and go right through the case into nuts or another ring with threaded holes in it.

The locking pin hole goes at the three o'clock position on the right at viewed from the front.

Disk to motor? Ask Brian here or the Redrock people. They made the disk so I don't know if it has the standard 15mm centre for the CD spindle. Many home builds use a CD spindle hub. The spindle motors have a very long shaft, which may not fit in available sapce. I used a shorter shaft motor from the CD load mechanism or tracking mechanism. Older CD players used three similar motors, two short-shaft and one long-shaft. I took the spindle hub off a longshaft motor and fitted it onto the short shaft.

Whe pulling the spindle off a long-shaft motor, don't haul it off by prising the rim. It will break. Use paired stacks of screwdrivers to lever from behind between the shank of the spindle and front of motor.

I used water-cheanable bathroom sealer to glue the disk onto the spindle, a thin layer on the contact face and some more added over the front of the hole to lock it on.

I ran the motor straight away before the glue set so that the disk would run true and pull a little bit of the glue under where it lifts just a little. Brian's kit may have a better solution which you should use. You can use the original CR magnetic and spring loaded pressure plate but I found it a bit tricky to set up.

Don't use any other type of glue. The bathroom sealer sets firm but pliant like putty and can be pulled off without damaging the plane surface of the spindle face if you get it wrong and have to reset the disk. Any other sort of glue will chemically damage the face or you will trying to chisel it off and it will be useless thereafter.

Don't use more than 3Vdc to power your spindle motor. Faster is not always better. I actually use 1.5v to keep the noise down but I used a fullsized 5" disk.

I used a toggle switch which some people also call a Nagra switch. These are good, simple and robust but inclined to catch on things and get switched on.

You will need to use a small drill to gouge out a locating hole for the tang on the inner washer to lock into the inner face of the case, otherwise the switch will loosen and turn in its hole or turn and break your wires off when you tighten the collar nut when installing it.

Put it in a sheltered place, usually on back of the box somewhere. Others use the Letus style push-button switches with LED light in them to let you they are switched on.


http://www.youtube.com/watch?v=CnweOEEqlRY

This clip is of a home build but not the project box version Brian designed. The project boxes are better as the alignments are easier to achieve.

Fit up the camera and achromat first because you need the camera to be working so that you can get the Nikon mount lens hole perfectly centred if you are mounting direct to the case. You do this by drilling a 2mm or 1/16" pilot hole for the centre of the hole you are going to cut for the Nikon mount, zoom in the the camera to about 80% which should be ballpark.

You then file out the pilot hole wider in one direction until you get it optically centred for the camera view, then ream this centre out for a hole-saw centre or use it for a centre hole for a dividers or compass if you are makring the outline of the larger hole for cutting out by other means.

If you build to the Redrock plan accurately you do need to do this.

[Marcel D. Van Someren]

Originally Posted by Bob Hart

Fit up the camera and achromat first because you need the camera to be working so that you can get the Nikon mount lens hole perfectly centred if you are mounting direct to the case. You do this by drilling a 2mm or 1/16" pilot hole for the centre of the hole you are going to cut for the Nikon mount, zoom in the the camera to about 80% which should be ballpark.

You then file out the pilot hole wider in one direction until you get it optically centred for the camera view, then ream this centre out for a hole-saw centre or use it for a centre hole for a dividers or compass if you are makring the outline of the larger hole for cutting out by other means.

If you build to the Redrock plan accurately you do need to do this.

Wow, Bob! I just used a ruler and math to figure out where to place the holes. LOL

Seriously, though, that was the first time I saw that video of your adapter. I think would get arrested walking around in southern california with that rig. It looks like a machine gun! However, it certainly looks like a solid design.

Did I notice a DIY flip module? Are those prisms from binoculars?

Terry,

Ted suggested that the best achromat for DIY use is the one that was used for the SGPro. I tried a few lesser expensive achromats but the one he suggested worked the best for me. Shoot35 no longer makes the SGPro. However, you might try emailing Wayne at info@sgpro.co.uk and see if perhaps they still have one laying around that they could sell you.

[Bob Hart]

I failed maths from Grade 5 onwards, so there's your answer.

There is another driver for this however. Depending on the material used, diligence of molders in cleaning the machinery conditions of storage packing and transport, there can be a bit of variation with plastic boxes if the material goes slightly out of shape.

Additionally, the corners are not always sharp but have a round edge to them. UNless you are vigilent to use a straight edge and setsquare to check the box and to measure from across the round corners your pilot hole centre can be a bit off.

0.5mm doesn't matter much in our world but across a 24mm wide image 18mm high it can mean quite a bit.

That is a prism pair you can see, larger than binocular prisms, much smaller than the Letus.

[Terry Lee]

Hey Bob, nice adapter. Yes, it certainly looks like a tommy gun haha. Was it all built with PVC?

I knew I was missing something when I got that lens mount.. It looked alittle bare.. I will go back in there and try to get the circular sping you are talking about. Do you think it will be hard to get that spring mechinism to to function the same way? I understand what you are saying about not smashing the spring flat to the body of the box when I screw the mount on. So what I will have to do if I understand this correctly is build an extension that I can mount the lens mount and circular spring to so that it raises it away from the box. Like how Shoot35 are selling them (which btw are almost $100!!??).

You then file out the pilot hole wider in one direction until you get it optically centred for the camera view, then ream this centre out for a hole-saw centre or use it for a centre hole for a dividers or compass if you are makring the outline of the larger hole for cutting out by other means.

Ok so in other words, zoom in about 80% then boar out the center untill all of it is out of sight. Correct?

To get the distance from the lens to the GG, like Marcel said, go out side with the lens, hold it to the sunlight and back the GG up until the image is focused on it. There is how far apart I want the two.

Marcel - I emailed Wayne, he said he has A Achromat for 20 Euro... A achromat means just some random achromat doesn't it.. not the same from the SGpro..

I think i'm starting to understand this now..

Honestly, i feel bad I made you guys sit there and type all that stuff out. I honestly appreciate you explaining all this.