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New Project: Home made "real" soft focus lens??
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PostPosted: Wed Sep 19, 2007 6:02 pm    Post subject: New Project: Home made "real" soft focus lens?? Reply with quote

I am planning to put some time of lens opening/breaking to making soft focus lens.
Yes, there are some old (vest pocket kodak) VPK Meniscus Achromat Lenses, whcih can be used as soft focus lens. I have just made the assembly of lens with broken 135mm f2.8 lens.
(taking a 2-element, single group lens out of VPK front assembly and fixed the lens only to the back element position.. I got the M42 mount lens as well as a real, huge hood)

Now, my next target is to convert some lens to soft focus lens with putting a metallic ring in-between the lens element for optical aberration.

I am thinking on these lines,

1) Planning to use Enlarger lens Graphic Raptar Wollensak 161mm f/4.5. Why???:
- Comparatively fast lens for focal length.
- Not a bad focal length for portrait purposes, although, I would have love something around 100-135mm.
- Huge lens and very simple design. Can be easily open. There is lot of space between front elements and back elements (was key requirement for me).
- Sharp wide open.
- Shallow DoF (nice for portrait purposes).
- Have mounted the lens on broken Nikon lens, so I have this lens with Nikon mount.

2) Planning to get either thin metal sheet or plastic sheet.
- Cut to the size of internal diameter of lens assembly. Th aim is to put this piece of sheet in between the front and back element of lens.
- Drill/Get a bigger hole at the center of this sheet, so that the central part of frame will be sharp (max) or say with minimal optical aberration.
- Drill the smaller holes, all round the side of central big one. The radius ratio between these 2 holes may be of 1:4. These holes will create the softness along the corners of the frame, as well as some hallo effect at the center.
- Place this sheet in between the 2 lens elements.

Now, My questions to forum members,

1) Has any one did this before.
2) What else can be done to get the high quality soft lens.

And why I am doing this,

There are lot of soft lenses available. But all are optimized for full frame, medium format and larger format. Using any of these on crop camera will be killing the real effect. The high optical aberration impact area will not be part of crop camera frame.

It will take a week or 2, to complete this... will keep the people updated...


PostPosted: Thu Sep 20, 2007 2:28 am    Post subject: Reply with quote

Adding an obstruction to a sharp lens doesn't do much if anything to increase softness. The kind of multi-aperture plates you describe are used to decrease the softness of an originally very soft lens in a controlled way. Moving the back element of a triplet may do the trick, but you never know before trying whether the effect is large enough on a crop camera to be worthwhile. An achromatic diopter (anything between +7 and +10) would be the easiest way if you don't want a lot of chromatic aberration - but it's like using a longer meniscus. You could also experiment with the elements from your disassembled lenses, e.g. try adding a concave element in front of a working short lens - with any luck you might find a working combination.

Veijo


PostPosted: Thu Sep 20, 2007 12:17 pm    Post subject: Reply with quote

I guess you already know the Sima SF Lens :

http://www.pbase.com/dang/image/72842790


PostPosted: Thu Sep 20, 2007 2:53 pm    Post subject: Reply with quote

Flor27 wrote:
I guess you already know the Sima SF Lens :

http://www.pbase.com/dang/image/72842790


Yes.. I though about this.. But eventually took the meniscus lens path (learned from Veijo here) (I have fixed the lens in broken 135mm f2.8 lens assembly.
Some results are,
Just a snapshot of family friend... original and other is B&W converted..





You can browse all the pics in this Flickr set,

http://www.flickr.com/photos/asbalyan/sets/72157601602439258/


PostPosted: Thu Sep 20, 2007 5:18 pm    Post subject: Reply with quote

You could experiment with the meniscus, you can get a slow, adjustable soft focus lens. The plate with the holes can be put in front of the meniscus. A central hole with a diameter of roughly half that of the lens will give you something like f/11 for the basic sharpness. Then add smaller holes around it. Or make a star-shaped aperture or anything. Everything is easy as you don't have to do anything to the lens.

Veijo