Problem with lens mount adapter (mamiya/B4) at DVinfo.net

David C Wright · January 5th, 2009, 04:03 PM

I just bought a lens adapter that should enable me to use Mamiya 645 stills lenses on a B4 mount. I shoot wildlife films and often need long telephotos, so this would be very useful. I have tried a 100mm,200mm,300mm & 500mm lens each with a progressively worse problem. None will allow me to reach a far infinity focus (a distance of approximatlry 1/2 mile or more). I am guessing the mount is just a fraction too deep. I am using a Panasonic HDX900 camera. Does anyone have any suggestions other than returning the adapter? Thanks

David
www.lunaseafilms.com

Enrico Gombala · January 13th, 2009, 11:44 AM

David, I have the same issue with Panasonic AG-HPX500 camcorder, Mamiya 120mm Macro lens and Mike Tapa M645 to B4 Adaptor. Lens cannot be focused into infinity and when shooting against sun it makes also terrible reflection. Shots are unusable.

Unfortunately, this Adaptor with camcorder body doesnť meet flange focus distance of Mamiya lenses. Now it lays on my shelf...

Enrico Gombala
info@natura-tv.cz

Colin Mounier · January 19th, 2009, 08:27 AM

Hi David, your mount is just a fraction too LONG, the lens need to come closer to the camera. I do not know the mamiya/B4, but i had to fixe a Nikon/C mount.
My mount has 2 parts:a Nikon lock system fixed (4 screws) to a C mount threaded bowl.
I parted the mount and took off few 1/100 milimeters on the flat surface in between the 2 apparats. The bowl part was in bronze, a soft metal..
You need a flat surface, a confortable position and a sheet of fine grain emery paper; you rub the surface gently and as evenly as possible turning the piece 1/4 turn every few strokes.
Take your time, as you do not know how much metal you have to take away, re built the mount try your lens (the longest) and again ..
What wrong can you do? 1) mess every thing, if you use a file, yes.
2) be slightly more "in" on one side, you will be: your hand works not to the micron! But remember even the longest lens to the infinity has a lot of DOF and on closer shots it will not be visible exept on test chart.
3) take too much metal: the lens will focus beyond infinity. Most of modern lenses have that pecularity, its help to focus in humid air.. And test your lens, do a new mark for infinity if you need to.
An other solution is to find a shop, or a friend with a shop.. Best regards.

Robert Lane · January 30th, 2009, 07:58 PM

If you really want the best quality for a B4 lens adapter look no further than here:

Letus Corporation

They've just released two versions of the relay/backfocus mount allowing full use of any B4 mount with their lens adapters.

January 5th, 2009, 04:03 PM	#1
David C Wright Regular Crew Join Date: Mar 2005 Location: Appleton, ME Posts: 160	Problem with lens mount adapter (mamiya/B4) I just bought a lens adapter that should enable me to use Mamiya 645 stills lenses on a B4 mount. I shoot wildlife films and often need long telephotos, so this would be very useful. I have tried a 100mm,200mm,300mm & 500mm lens each with a progressively worse problem. None will allow me to reach a far infinity focus (a distance of approximatlry 1/2 mile or more). I am guessing the mount is just a fraction too deep. I am using a Panasonic HDX900 camera. Does anyone have any suggestions other than returning the adapter? Thanks David www.lunaseafilms.com

January 13th, 2009, 11:44 AM	#2
Enrico Gombala Tourist Join Date: Apr 2007 Location: Ostrava, Czech republic Posts: 1	Enrico Gombala David, I have the same issue with Panasonic AG-HPX500 camcorder, Mamiya 120mm Macro lens and Mike Tapa M645 to B4 Adaptor. Lens cannot be focused into infinity and when shooting against sun it makes also terrible reflection. Shots are unusable. Unfortunately, this Adaptor with camcorder body doesnť meet flange focus distance of Mamiya lenses. Now it lays on my shelf... Enrico Gombala info@natura-tv.cz

January 19th, 2009, 08:27 AM	#3
Colin Mounier New Boot Join Date: Dec 2006 Location: Istanbul- Turkey Posts: 6	mount adapter Hi David, your mount is just a fraction too LONG, the lens need to come closer to the camera. I do not know the mamiya/B4, but i had to fixe a Nikon/C mount. My mount has 2 parts:a Nikon lock system fixed (4 screws) to a C mount threaded bowl. I parted the mount and took off few 1/100 milimeters on the flat surface in between the 2 apparats. The bowl part was in bronze, a soft metal.. You need a flat surface, a confortable position and a sheet of fine grain emery paper; you rub the surface gently and as evenly as possible turning the piece 1/4 turn every few strokes. Take your time, as you do not know how much metal you have to take away, re built the mount try your lens (the longest) and again .. What wrong can you do? 1) mess every thing, if you use a file, yes. 2) be slightly more "in" on one side, you will be: your hand works not to the micron! But remember even the longest lens to the infinity has a lot of DOF and on closer shots it will not be visible exept on test chart. 3) take too much metal: the lens will focus beyond infinity. Most of modern lenses have that pecularity, its help to focus in humid air.. And test your lens, do a new mark for infinity if you need to. An other solution is to find a shop, or a friend with a shop.. Best regards.

January 30th, 2009, 07:58 PM	#4
Robert Lane Go Go Godzilla Join Date: Nov 2004 Location: Scottsdale, AZ USA Posts: 2,788 Images: 15	If you really want the best quality for a B4 lens adapter look no further than here: Letus Corporation They've just released two versions of the relay/backfocus mount allowing full use of any B4 mount with their lens adapters.