[K David]

I've been shooting a Mamiya RB67 with 180mm f4 for portraits lately. I've been looking a the 150 SF for the 67 system. The lens includes (if you're lucky) three discs that look like the one inserted in this lens:



Does anyone know what those discs are called? Are they sold as filter add-ons? If I could just picks some up for my 77mm FA, I would be able to lighten my portrait kit significantly.

[RAART]

They are called "Softness Control Disc" and you should have 3 with Mamiya lens you pictured above.
Here is the excerpt from the manual...

Adjustment of the Soft Focus Effect

The degree of soft focus effect varies depending on whether or not the Softness
Control Discs are used and in accordance with which of the three Discs is used. The
amount of effective softness, however, will also depend on the type of subject,
distance, lighting conditions, the amount of enlargement given the negative, the
concept, personal Iikes, etc.

1. When not using a Softness Control Disc
The soft focus effect varies depending on the aperture used. At full aperture (f/41
the softest effect is obtained. The effect is less at f/5.6 and completely disappears at
f/8 or smaller apertures to produce a normal sharp image.

2. When using a Softness Control Disc
There are three different types of Softness Control Discs, each with a different
diameter hole in the center.

* Always set this lens at full aperture (f/4) when using one of the Softness Control
Discs. The f-value of this lens changes according to the Disc used. When the No. 1
Disc is used the effective lens aperture is approximately f/5; for the No. 2 Disc this
value is approximately f/5.6; and for the No. 3 Disc it is approximately f/6.3.

How to attach the Softness Control Discs

1. Remove the front lens barrel by rotating it counterclockwise.
2 . Slip the disc to be used over the rear end of the front lens barrel.
3. Put the front lens barrel back into place and tighten by rotating it clockwise.

Depth-of-field

The depth-of-field and the degree of softness can be easily checked by stopping
lens down to the preset aperture by operating the depth-of-field preview lever

[K David]

Those are perfect links. That gives me a great idea. I'm going to pick up a piece of black cardstock from the local dollar store, break a few plastic 49mm UV filters, and cut a set of these out with a compass and razor. Thank you, DC!

---------- Post added 05-05-15 at 11:42 PM ----------

RAART, I had trouble finding the 150mm manual on line. I'm definitely going to try and make a control disc. I think that's got some potential. I may also just print out photos of them, put an unused, but good, UV filter on one of them, and draw in the filter with a sharpie. I'm going to try making one first, though.

I can't believe there's none of these coming out of China. seems lik this would be a pretty simple milling job.

[RAART]

Here you go... Link to PDF Manual

and the picture from ebay

Attached Images

 

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Last edited by RAART; 05-06-2015 at 12:06 AM.

[IgorZ]

Those are perfect links. That gives me a great idea. I'm going to pick up a piece of black cardstock from the local dollar store, break a few plastic 49mm UV filters, and cut a set of these out with a compass and razor. Thank you, DC!

---------- Post added 05-05-15 at 11:42 PM ----------

RAART, I had trouble finding the 150mm manual on line. I'm definitely going to try and make a control disc. I think that's got some potential. I may also just print out photos of them, put an unused, but good, UV filter on one of them, and draw in the filter with a sharpie. I'm going to try making one first, though.

I can't believe there's none of these coming out of China. seems lik this would be a pretty simple milling job.

Hello David,

Did you end up making these disks? I am thinking of getting a 150mm soft focus lens for RB67, and the one I am bidding on does not have those disks... Would like to try to make them, since they seem to be difficult to find...

[K David]

Did you end up making these disks?

Not yet. The time since I had this idea has been filled with planning and executing an inter-state move and a number of other smaller items that have pushed basically all of my DIY projects to the back burner.