DIY adapters for RB645 and 35mm lenses

[Ted Ramasola]

Once I hit the focus on the GG using the zoom on the fujinon i usually tape it down since its hard to get the focus especially outside the TV safe area.

I also added 10mm worth of filter rings between the GG and achromat to allow me to zoom in a little bit while keeping the achromat snug against the fujinon front element.

The zoom adjustment really cant go far from the ideal target of edge to edge focus. A little deviation and the sides or the center go off focus.

Its really like walking on a tightrope.

[Ted Ramasola]

I plan to make a "mamiya 645 lens-to-nikon mount" so i can flexibly use the mini35 i made to accept the mid format lenses, this way i will carry one adapter housing but "flexible' to use 2 lens types, i assume i'll just 16.8mm in distance from the rim of the nikon mount to comply with the 63.3mm flange depth.

Is this feasible?

[Bob Hart]

Ted.

That is precisely what P+S do with their Mini35 and Pro35. They use a bridgepiece between a universal mount and whatever mount the user chooses which is fitted to the bridgepiece which is a custom added distance for each mount type toi make up the correct flange to focal plane distance.

It just happens that the universal mount is PF profile but in its universal role, the flange of the universal mount is much closer to the focal plane than the PL lens mount's 50mm or thereabouts. (not sure of exact distance).

It therefore gets a bit confusing because a PL mount lens will go straight on to the universal mount but the backfocus is then way off. The PL mount therefore is actually a PL mount at both ends which adds space to make the flange to focal plane distance correct for PL mount lenses.

So for your purposes, to keep it simple, the universal mount can be the Nikon mount and the Mamiya mount with its longer flange to focal plane distance would be a bridgepiece with Mamiya mount on front and a Nikon rear lens end on back. You would also be able to make a Nikon to PL Mount bridgepiece which would be a handy option.

There is a remote chance the edges of the fitting which goes inside the Nikon mount may obscure the corners of the larger format image but I don't think so.

The word "universal" that I use is my own. P+S may use another definition.

[Ted Ramasola]

I finished the 645-to-35 mount for the mamiya 645 lenses.
Respecting proper 645 flange distance i can now attach the 645 lenses to the fixed nikon mount lens adapter.

The mount has a locking pin to prevent the lens from falling.

Though the 35 adapter cant produce the same image size as my dedicated 645 adapter, which gives a 42mm x 24mm image on the GG, the 35 adapter can still give a bigger image on the gg when using mid format lenses.

Im attaching photos below and a chart showing the difference in gg image size.

I was motivated to do this because i felt i had to utilize the large image of mid format while still allowing me the flexibility of diff 35mm lenses, without carrying 2 different adapters.

[Bob Hart]

I imagine you should be able to harvest better centre-area definition when using your widest medium format lens compared to the 35mm stills lens for the same field-of-view.

What quality of edge sharpness from the medium format lenses are you getting with your hybrid setup?

[Agatha Graselia]

kind Ted Ramasola,
I'm a student, and learning for video. from my relative, i can get several mamiya 645 lens, such as 85mm/f2.8. and wish i can attach these lens to my Sony V1.
how can i get the information for DIY ?
thanks in advance,
gracias,

agatha

[Ted Ramasola]

Agatha,

Theres a ton of information in this forum on DIY adapters, this is where i got my information.

Decide on these things about your adapter. Static, Spinning or Vibrating.

I made two kinds of adapters, the first is purely for the mid format, the 2nd was meant for the 35mm lens but evolved to this 'hybrid' that will allow the use of mid format lenses.

As to making a diy lens adapter you must decide which format you will be using and for what needs. It would require certain skills at machine shop tools and some electrical soldering as well.

The initial prototype i made is still posted here,

http://www.tedramasola.9k.com/photo.html

the close up lens indicated in the photo has since been replaced by a higher quality 10+ achromatic diopter from cinevate.

In my adapter there is a 5.9 volt motor thats holds and spins a custom cut "ground glass" from a frosted plastic material.

Try to decide on the housing or casing that you can find locally then determine how you will mount this in front of your V1. In my prototype i used fixed aluminum mounts. The ideal are rods which is flexible to different adjustments and other cameras.

The mid format lenses has a longer flange distance which will have you ending up with a longer adapter than a one using 35mm lenses. Try to decide if you can handle this added length to your set up.

Ted

[Agatha Graselia]

Thanks Ted,
I will search the forum for DIY for this subject.

I see your setup on http://www.tedramasola.9k.com/photo.html
and will try to collect the spareparts.

How to buy (of make) "nikon mount to mamiya lens adapter ??
Cannot find it in internet...

Regards,

Agatha

[Ted Ramasola]

Agatha,

The mamiya-to-nikon mount is something that i made retrofitting a rear lens cap, adding reinforcement and a pin lock, attaching a canibbalized nikon lens rear mount. Consideration is made to carefully compute the dimensions of this mount to accurately get the flange distance of the mamiya lens via this mount/converter/adapter to the ground glass.

Ted

[Ted Ramasola]

Bob,

when using mid format lens of the same fov as with 35mm lenses AND maintaining the adapter position, there is 'not much' noticable difference in center sharpness.

BUT edge sharpness is 'better' with the mid formats.

The mamiya mid format lenses produce deeper colors and contrast compared with the nikon and sigma 35 mm.

When the adapter is repositioned for mid format lens use only, the edge to edge sharpness is 'much better' as compared to 35mm lens use position.
Overall resolution is improved.

Ted

[Agatha Graselia]

Kind Sir Teddy,

I have with me now 2 Mamiya lenses, 45mm and 85mm, and V1 with several raynox :) for V1 and several lens Nikon 80-200, 50mm f1.4, 18-200VR.
And i'm eager to make DIY like yours, and i had push my brother to help me on machining the tools (if needed)

I went through internet today and found these links :
http://www.adorama.com/PRODOFA.html?...pter&item_no=2

Pro Optic 645 DOF adapter, Front lens cover, Rear lens cap, Mamiya 645 lens mount

and also link to the promoter of the product ( kind mr.vargas)
http://www.freewebs.com/wvargas/70mmadapterphotos.htm

and

http://www.fotodiox.com/shop/product...oducts_id=4187

Mamiya lens to nikon mount. (hope the have vice versa)


I know this is DIY forum, but based on your experience, is it better to try the short cut to above pro-optic 645 ???

Thanks for your suggestion,

Agatha

[Bob Hart]

Agatha.

If your friend is not able to make a new complete Nikon to Mamiya adaptor or fashion one out of salvage parts from dimensions provided by Ted, you may find that Les Bosher (in the UK) and other machinists who make lens adaptors already do one.

A "Mamiya-only" groundglass relay device (these also are called adaptors) would be simpler to make than a multi-purpose adaptor which is Ted's most recent evolution. However, if you intend to go the multi-purpose route, Ted's solution should be fine for you.

Your friend will need to take care when making the holes in the casework for the lens mounts and spacers etc.. Step-up rings and threaded spacers are good in that they remain centred but the holes on each side of the box must be accurately centred to parts of a millimetre.

For "normal" and telephoto lenses, this may not be so much of an issue however with rectilinear wide lenses, the diagonal distortion pattern in motion imaging becomes very apparent if it is assymetric due to mismatched centres.

Another small wrinkle is that with some video camcorders, the lens optical centre and centre of sensor do not match. The Sony DSR PD150-PD170/VX2000-VX2100 have this trait and I have been told but cannot verify that the Canon GL1 also does. I don't know if the V1 is offset. Unless you actually test by zooming in on the centre of a test chart, centering the image then zooming back to see if the centre of the chart remains in the image centre, you would likely never know.

This offset if it occurs causes a few small problems in setting centres up if the achromatic dioptre is not to be directly attached to the camera. If you use the camera image of the groundglass image or the image of the front lens mount with the groundglass not fitted, to establish the dioptre image centre by eyematching, although the actual image is correctly centred relative to the lens on front of the adaptor, the achromatic dioptre centre axis and the camcorder optical centre axis become misaligned.

Image sharpness may be inferior and some chromatic abberation may also occur.

To be safe, for the centres, use accurate measuring and marking out onto the job and avoid eyematching through the viewfinder and preferably use Ted's, also the most common method of maintaining optical centre accuracy by using step-up rings threaded into the filter mount of the camcorder to mount the achromatic dioptre if it does not already screw straight in.

Avoid using the threaded filter mount for mechanical support of the groundglass relay device alone but add support with a bridgeplate from the camera tripod mount or bridgeplate and rods. Sooner or later you will add the accessory rods for followfocus and mattebox so may as well integrate it from the beginning.

Some plastic project boxes you might decide to use, may be comprised of a formula which causes latent stresses to reside in the material. When you cut large holes in it, the material may warp and bow inwards. Die-cast metal boxes may also do this.

You may find it necessary to lay up a plate or plywood re-inforcement inside the case to brace the material back to a flat plane. If warping occurs, the lens centres will likely remain accurate however the optical centre axes will become skewed which will throw the projected groundglass image offcentre.

If your friend has a vernier caliper for measuring, to check for parallelism, ignore the faces of the plastic box and measure with the depth-gauge from the front face of the lens mount itself, through the box to the front rim of the achromatic dioptre on front of the camcorder with the camcorder mounted and all bracing or bridgeplates installed.

A more accurate method might be to lay straight edges across both the front of lens mount and rear rim of the achromatic dioptre or step-up ring attached to the case and measure the gap between the straight-edges well outboard of the optical centre axes. This does not enable a final test with camcorder installed but the difference will be negligable.

You could chase the image by eyematching and moving the camcorder end of things about but then the likelyhood is that you will experience an assymetric edge softness.

Finally. The simpler groundglass relay devices or adaptors do not flip the image but present it to the camera upside down. This means you have to flip the image upright afterwards in the editing computer. Some camcorders like the JVC GY-HD250 flip the image upright electronically.

The V1 does not do this. Cineform software if used for capture conversion of footage from .m2t to .avi has a preset which will do this automatically for you. The upside-down image in the viewfinder remains a pest to work with and you may need to add a small LCD monitor which has a built-in flip function or mount it upside-down.

[Bob Hart]

QUOTE:

"It therefore gets a bit confusing because a PL mount lens will go straight on to the universal mount but the backfocus is then way off. The PL mount therefore is actually a PL mount at both ends which adds space to make the flange to focal plane distance correct for PL mount lenses."

END OF QUOTE.


I have been the inadventant purveyor of slight misinformation.

The quote above is from a previous post in this thread above.

My recollection of an event was slightly incorrect. The profile of the PL Mount and the P+S Technik mount is very similar but not identical as I state above.

It is possible to have fitted the PL Mount for a PL lens, then during hasty lens swaps, to have fastened the Nikon or Canon and possibly other other mounts onto the already installed PL Mount in error.

During the event, it was discovered with some concern that the Nikon mount lens simply would not focus after the PL Mount lens was used, - great bokeh though. The PL Mount had become in effect a macro tube. On closer inspection, the fitment is discovered to be not a match but the lens mount will remain re-assuringly firm and does not drop out.

So. Apologies for another firing-from-the-hip error. So soon after another, it looks like it has become habitual.

[Bob Hart]

Agatha.

The fotodiox product would work on Ted's adaptor. You would still need to engineer the added piece which goes in between the camcorder and the groundglass relay device when the Mamiya lenses are used.

[Agatha Graselia]

Dear Bob,

After read more carefully the process and precision needed for this DIY, i think I cannot find enough resources to do the job. Maybe if later i have a boy friend, i will look someone good in machine-drilling... :)

Anyway, even as simple as : http://www.mediachance.com/dvdlab/dof/index3.htm
I doubt I can make it myself....

So , if i can find this fotodiox, what will be the ready solution for me?
I possible I still want to use these Mamiya 45mm and 80mm lenses along with several nikon mount we have (50mm/1.8, 80-200/f2.8, 18-200/f3.5-5.6)

Letus ?? Brevis.... or PRODOFA (whom claim as the only mamiya lens adapter)..

Thanks in advance... again apologize since this is DIY forum.

Regards