DIY spinning 35mm adapter discussion
 

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.

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.

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.

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.

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:

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

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.

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!

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!

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.

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!!

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.

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.

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.

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!!??).

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.

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!!??).



If you mount straight to the project box, cut the lens mount hole only just wide enough to allow the lugs on the lens to be able to turn - just. You will find on the spring, three little inward sectors which the lugs of the lens engage with. You will also find on the spring, reliefs cut for the screws to clear through and the lock pin also. In back of the mount there is a channel cut to accommodate this spring. The bulges the lens lugs ride upon rise rearwards.

When you place the spring against the plastic of the box around the hole you have cut, then place the mount over it, you will observe the mount rides about 0.7mm high because the bulges in the spring lift it up. Where these bulges go is where you mill out a clearance with a Dremel or hot soldering iron. If the spring is a bit of a sloppy fit in there that is okay, as long as it is not holding the mount away anu longer and you still have enough meat in the plastic for your screw threads to be cut in or your through-bolts to be supported against rocking and working loose.


Quote:
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?


No. - You are only using the centre [ + ] of the camcorder frame marker view to accurately place the centre of Nikon lens, relative to the camcorder image centre before you install your groundglass. A small pilot hole is about the only way for a mug like me to do this. I do it this way because the camcorders I have dealt with all had their centre of sensor not co-incident with the lens optical centre. You can check for this by fixing your camera on a tripod, zooming in, marking a target at centre on the wall or whatver, then zooming back and checking to see if it is still in centre. Chances are in most instances, the image will walk to the right as you zoom out. If you mount your achromat separate from the camera, don't offset the acrhomat but make sure it is centred to the camcorder optial axis. This is important but a trap for beginners. So you don't zoom back to establish an optical clearance for the hole. There is no point as you are using the groundglass image. If your camcorder zoom-in walks the image, then you need to first check with your achromat installed to the camera and test target drawn on a piece of paper, just how far you have to be zoomed in to obtain your chosen frame size. For home-build purposes to keep things fairly simple, don't aim for more than 28mm frame width on the groundglass at most. Once you have established this frame width and the zoom position needed to achieve it, you can then make up the mount for the camera lens filter thread fitting. To establish the distance from groundglass to camera, the preference varies. P+S seem to have preferred to set the MINI35 up with the camcorder focus towards the infinity end, probably to minimise distortion, however your build accuracy has to be spot-on to do this, well within their engineering abilities as many of them used to build ARRI cameras but not so mine with hacksaw files and breadknife. I set mine up so that focus was closer to about 4M or about 16 feet. This is more central of the available range of focus movment instead of confined towards the infinity end like the MINI35.

It is entirely up to you whether you want to fix your Nikon mount directly to the front of the project box or bring it forward on a tubular extension. Be mindful that your box has to support the odd heavy lens and the furthur outboard of the structure it is on a tube extension, the more leverage the weight of the lens, handling and the occasional thump will have on the front case structure and things may be more easily bent. If you have to add length, then it is best added in the section between the rear of the project box and the camcorder because you can brace to the camera baseplate. It is not always convenient to brace forward under a heavy lens when homebuilding. You may find that you need to re-inforce the front face of your project box. Sometimes after the mold has been released the plastic will try to bow inwards in an attempt to return that which it once was, a blob. If it has done this, the axial alignment of the lens mount will be off angularly. You may need to add a 2mm piece of aluminium to the inner face of the case to force it straight.



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.



For the Nikon lens, distance from flange face of the lens mount to ground surface of groundglass is 46.5mm.

For your 8+ achromat or whichever one you choose, you will need to determine the front-of-camcorder to ground-surface-of-groundglass distance by measuring from a reference point on your camera to the groundglass surface when you have achieved your preferred frame size and zoom position at about 4M or 16 feet focus setting on the camcorder. From front of achromat when mounted to the camera is may be in the ballpark of about 4".

It is desirable to provide backfocus adjustment. You can do it with fixed shims under your nikon lens mount, but it is awkard and consumer level plastic project boxes change shape with time, so the adjusmtnet may not hold. It is easier to move the groundglass by making a wide mount plate for the motor and make the three or four corner fixing points adjustable. My personal preference was to put springs over long studs, then pull the mount plate down against these springs with adjusting nuts. This enables both a linear backfocus movement and angular adjustment to deal with any axial misalignment of the lens mount. There is no x-y adjustment of the camcorder view or angular optical axis correction for the camera unless you design this in with a sliding plate mount and a similar angular adjustment ayatem. It is best to get the front and rear faces dead parallel and the problem goes away leaving you with only centres to get accurate.



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..


If Wayne is quoting you an achromat, it will likely work. Just ask him what power it is. He might even be able tell you the groundglass-to-camcorder distance for that achromat if your camcorder is not the latest and greatest. His current product is for flip adaptors and these require a less powerful achromat.


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.


Don't feel bad, just pay some favour forward some day.

Terry,

as Bob said, if Wayne is quoating you for an Achromat, I'm sure it's one that he's manufactured. If you're unsure, just ask him. What you want to do is make sure you get the Achromat for a non-flipped version of his adapter. That's essentially what you are building.

-M

Hey everyone,

Alright.. alot of information to take in here. Good to know I am talking to people who know what they are doing. That is certainly proven.

I emailed Wayne and asked him what power the achromat is along with the distance from ground glass to camera for that paticular achromat. I hope to hear from him tomorrow. I haven't been able to get back to the camera shop and retrieve the circular spring but hopefully tomorrow.

I found quite a selection of project boxes on ebay but don't really know the dimensions yet since I don't know the dimensions of the GG disk. Do you think Wayne also has a GG disks?

As soon as I get all of the parts I will start trial and erroring all of the information that you have both given me.

My list thus far is - project box (size depending on GG), circular spring for lens mount, tube to fit achromat in (What size?), ground glass disk, CD player motor (nothing over 3Vdc), Toggle switch, wire and battery.

When I fit the achromat to the camera, Do I use a step up ring that attaches to the tube that the achromat goes in?

Again, thank you all!
Terry.

Wayne is an obliging fellow and am sure he will help you out with advice as he started off in these from way back right here on dvinfo.

Being now a manufacturer and vendor, he may now be in the situation of having to pull back personal interaction with home-build enthusiasts otherwise nothing will get done if there are too many requests.

I understand he had a UK supplier of both glass and acrylic disks when he was still in R&D of his first commercial device.

To be fair though, do not get heart-broken if he cannot supply, or declines to supply a disk for your application.

The fact that you have to hack a fitment to your own design carries with it the potential for a dissatisfied customer issue even if all bets are off related to performance and warranties.

CD player motor. These cope with a range of DC voltages. 3v max was my recommendation. There are CD player motors and CD player motors. You may find that DVD transports are being used in CD players.

Some newer motors are brushless DC which require an electronic circuit to drive them. Just soldering on a couple of wires won't get you anywhere with them.

The older "can" style motors are what you want if you are hacking kitchen table style. However, if you are up to designing and building brushless DC motor control circuits, you give yourself a few more options for speed control, maybe even syncing up to camera frame rate to eliminiate any flickering artifacts from pushing the shutter speed and lens aperture envelope.

The wall for adaptors is generally accepted as 1/100th sec shutter and f5.6 but there are a few exceptions with some lenses.

His disks may now be a custom fitting to a special spindle hub to a different motor. You may be able to get his swap-in disk as a part and make your own custom spindle hub to suit your chosen motor.

Regarding the spring, take your mount with you as there are two styles, a four-screw and five-screw. The springs I think are different.

Remember that if you're thinking about getting a GG from Wayne, the GG he uses currently is a much smaller diameter than what Bob or I built. In fact, the RotoRazor as it is branded, is only about 73mm in diameter (2.874"). The cool thing about the RotoRazor is that it comes with a motor installed. Also, they make 3 different flavors of the RotoRazor.

take a look at this comparison chart:

Untitled Document

Depending on which RR you choose, you can use shutter speeds up to 1/500 and up to f22.

I have personally pushed RR2 to f8 which is more than advertised, pointed at a bright blue sky with no grain visible.

I guess you could just purchase a RR and mount that in your project box. The problem is that the optics used with the RR are very custom. The image projected on the GG is smaller than on your typical DIY adapter ( it has to be to fit such a small GG) so your optics need to be pure to achieve good results.

That said, if you can get a hold of the older (and larger) SGPro GG, then it will be more in line with what you're building.

-M

Wayne emailed me back and told me the distance from ground glass to camera should be 100mm.

I'll email Wayne and ask him if he has a SGpro GG.


Off to get the spring part for the mount and a stop at a couple hardware stores to see if they have project boxes!

Now how's that for guesstimate, 4" = about 100mm.


It seems that what you are going to end up with is a Q-ship SGPro?SGBlade hybrid.

My personal preference would be to hold on getting that project box until you have the dimensions of your working components locked down. The box itself is basically to keep the light, rain and your dandruff out and need not be a loadbearing element if you use a carry-though structure to bridge between the Nikon lens and camera.

The AGUS35 version I built used plumber's pipe, mainly because it was handy not for practical reasons except one.

In common with some of the non-flip and fixed groundglass adaptors I have used a tube as a carry-through structure, entire from front to back. This helps to ensure maintenance of the optical axes of the Nikon lens and camcorder plus dioptre on a common axis.

It also eliminates bending loads on the front and rear panels of whatever you enclose the groundglass in, my case being two sewer caps.

Wayne's smaller diameter rotorazor disk, if that is what you are getting, offers you the possibiity of a smaller case and the possibility of passing a support rods structure beneath the case from the camera. This is why I suggest you don't buy in the case until you have the bits and pieces gathered.

A bigger groundglass diameter rules this out because the case gets in the way of either the path of the rods if you offset down or gets blocked by overhanging handles or on-camera mikes if you offset up. Offsetting sideways is not an option as your useable area of the groundglass becomes an upright rectangle.

In my version, the whole structure was too big. Any bridgeing structure to carry rails around to the front was huge, heavy and impractical.

The carry-through tube was slotted so that the disk and motor could enter the tube from below. I glued the whole thing together once I had it worked out and left one pipe cap unglued as a detachable cover.

I also used smaller pipe caps for the Nikon mount to fasten to on front and for the camera on the rear.

Because plastic caps and my holes cut in them are of less precision than a machined tube, I skewed them on the tube for the last bit of axial alignment, taking care to make sure the front face of the lens mount was parallel to the camera mount face.

My case arrangement was a bayonet to the lens hood mount on the camera. The caps were internally tapered which permitted me to do this.

I mounted the achromat to the camera via the filter thread separately and the rest of the adaptor mounted around it onto the lens hood mount. This eliminated loading the threads but did not eliminate loading the case structure of the camera.

I got away with this because my casework and parts were relatively light but the outboard loading caused by a heavy metal lens was always a worry.

Alright so I was able to stop by Chuck's finally to get the rest of the lens mount. He just gave me the rest of the camera and told me to bring it back. I explained to him that everyone is saying that I need also the circular spring that allows the lens to lock into place. He was confused as to what I was talking about. He showed me the camera he got the flange off of and I too am confused. Pictures below.

By the way, Wayne is giving me the Achromat and Ground glass from the SGpro for 45 Euro. Decent?


Hmmm. Its not letting me upload anything..Keeps saying 503 service unavailable. I'll try again soon.

Wierd. Worked instantly.

That is a decent price (although I would think it would be British Pounds Sterling, not Euros) at the current exchage rate for BPS to USD it's about $74 which is a lot less than what the current SGBlade GG is going for.

I'll let Bob answer the questions about the lens mount.

You're right! BPS. In Portugal its Euros and I keep getting the symbols mixed up eventhough they look totally different.

$74 sounds like a great price. Now lets see if I can build the rest for $26!

Terry.


That has me a little bit perplexed. That appears to be an FM2 there in the image, therefore there should have been a spring unless it had already been ratted to fix another camera and the mount put back on.

There should have been a spring which looks like a corrugated big flat washer, about 0.3mm thick, as wide as the hole the mount fits over, with chunks cut out of it to allow it to fit around the pillars in the castwork. The broadness of the spring from outer circumference to inner circumference is only about 5mm - 6mm.

If you look at the 12-30 clock position, you can see one of the clearance cut outs, there should be others at about 5-00 o'clock and at 8-00 o'clock.

It has probably already been stripped. Either that or it fell off when he took the flange off. I'll have to go back in there and see if he has another FM2 that he doesn't mind parting out.

Ok so I think I have the clearance cuts highlighted in the image below, however I think I might have highlighted to much so I took red and highlighted a slot between what appears to be a lip that runs around the edge. Are these what you are talking about?

Terry.


That is pretty much where they are.

The rearwards raised "bow shapes" in the spring are only about 1cm long each and about 2mm broad I think and they stick out into the path where the lens lugs will arrive as you twist the lens into its mount.

There are reliefs cut out of the spring to clear the support pillars where the screws go in and a bit of a zig-zag when the latchpin comes through. The cutouts stop the spring which almost floats in the space from turning when the lens is twisted.

If you look close inside, you may see a 0.3mm shiny flat mark against the clockwise face of one or more of the pillars where the edge has born against the side of the pillar.

As long as your lens focus mechanism is not stiff - most old ones will be because the lube will have dried out - the lens will stay put in the mount, certainly the modern AF lenses will as there is not resistance in the focus movement.

I see the areas where the flat leaf like springs will fit and on mine thats the only place I see where the lens will connect with the spring system. After looking in my D40, I see exactly how these things will connect.

It wouldn't be to hard to make this box out of metal althought that is added weight to the front and I would want to use thin metal. But if I do that I won't have enough depth to drimmel out the slots for the springs, or does it matter if there is no material behind the springs?

I just paied for the Achromat and GG. Should be on its way tomorrow.

Terry.


I think from memory, the thicknes of the flat areas of the spring fit inside the back of the mount ring itself. The reliefs only have to be cut to allow the three "bows" in the spring to not be squashed. The hole behind could probably be wider so they are in the clear.

The problem you will have will be having enough material where those four screws thread in unless you cut the hole as small a diameter as you can and yet still clear the lugs on the back of the lens when it is inserted.

YouTube has gone bellyup as I write this so I can't refer you to the agus35 dismantled clip but I think it is listed back a page or two on this thread. You will see the mount is not let down inside of the plastic at all, just screwed down onto the face.

The mount was screwed down directly into the PVC plastic or the pipe cap I used fro front of case. The wall thickness of the Iplex caps is about 3mm and the plastic is tough. Other plastic caps have a 2mm wall thickess.

You may find that you only need to Dremel out clearances for the spring bows about 1mm deep as the flat portion of the spring will rest up inside the back of the mount ring. The little sharp ridge around the outside of the mount ring will sit high about 0.5mm. That's okay.

Haven't given up Bob, still waiting on the achromat and ground glass. Have yet been able to stop back by the camera store. This Thursday is my birthday so i'll be heading to Fort Lauderdale and Miami beach. By the time I get back i'll have everything and I can get down to business on building this thing.

Thanks again,
Terry.

Alright so I now have in my posession the achromatic glass and the ground glass disk. What I have yet to obtain is the lens mount, which I will hopefully find soon.

Alright so now to set this achromat into place with my lens... What do I use?

For testing to get the proper distances or for your final connection to the camera?


By the way, as far as the lens mount goes, if you don't find one soon, there's always the one from shoot35.

Yea sorry I was kind of vague with that question..

By lens I meant the camera lens, not the 35mm lens. What should be the distance of the achromat from the camera?

Do I find some sort of tube that this large piece of glass will fit into thus attaching it by a step up ring?

Thanks!
Terry.

The achromat should actually screw right into the filter threads of the A1. If it's from an old SGPro than it should be 72mm filter thread which is exactly the size on the A1. So, basically, the achromat should be as close to the A1 lens as possible.

I endorse Marcel's suggestion.

What Wayne sent me was a bare piece of glass. My camera is an HV30 though...therefore I will have to use a step up ring.

What you have is an unmounted achromat, a wrinkle in the process but not an insoluble problem.

To do properly would require mounting in a machined metal or plastic barrel of some kind with 72mm filter thread on the camera end and a suitable internal thread on the other end to mate up with a tube at the adaptor end if that is the way you are going.

A method of mounting a lens in a barrel and to have front internal thread is to have a threaded retainer ring going in from the front and sharing the common thread.

Depending on how much you are willing to spend on this thing you could make a custom tube going from front to back with a clearance slot for a disk and motor. The Nikon mount would go on the front as with extention tube.

The achromat could fit facing forward in the rear of the tube against a machined shoulder and a threaded hollow plug go in from the back as retainer ring with the camera thread machined onto the back of it.

An appliance made of plastic and glue will have to be supported from the camera baseplate with no loads on the camera filter thread at all.

Unless you have the machine shop and skillset to use it, that option is going to be beyond you unless you can go into the photographic equivalent of a wreckers yard and mine through all their bits and pieces.

You could do it on the cheap by using plastic water pipe, glue and a 72mm filter ring. The achromat would be retained in the plastic tube by two rings of smaller diameter tube or thin cuts of the same tube with a piece cut out and squeezed in to fit the inner diameter then glued into place with the lens in between them.

Getting the optical axis correct with the elcheapo method will be extremely difficult but it can be done. Best would be to have the faces of all tubes and rings cut on a lathe or use one to score accurate reference marks for hand cutting and filing.

One of the internal retaining rings should be cut at least 3/4" long so that it tends to fit accurately in the tube without skewing the optical axis sideways. This would be the fixed shoulder in a metal arrangement.

To make the tube fit in the lathe chuck without deforming and falling out would require a tight plug to be made to fit inside the tube to resist the crush of the chuck jaws.

I can't emphasise enough that the achromat optical centre axis must be centred to the camera optical centre axis and that there is no angular deviation of the achromat centre axis. The rest of the appliance can be out and you will still get a workable image.

Wayne may be able to sell you a barrel for the achromat with 72mm filter thread but it may be that the mounting of the achromat was integral with the rear body of the SGPro in which case the only other separate part might be a threaded retention ring.

The lens, if it is made of optical glass will be very brittle, easily chipped and sensitive to sudden temperature changes if they are localised to an area of the lens glass. You will have to be careful when trying it into any mounting system you design until you get it securely mounted.

Any metal barrels or retaining rings should have a fine finish on the contact faces. My personal preference would be to make up thin washers of fine paper or plastic shim material to cushion these surfaces. Retention of the lens in a metal barrel should be lightly snug, sufficient to prevent movement but not tight.

Luckily I have a friend who has a lathe and uses it all the time. All I would have to do is bring him a 72mm UV filter and have him match the threads on the camera side.

In other words I will be screwing something with the function of a washer/retainer in on the internal thread to hold the achromat in place? Thus shimming it tight (but not to tight) in from the other side.

Well noted. I will certaintly pay attention to this. What could I do to ensure that it is truely set at the camera's optical centre axis?



Terry.