DIY soft focus lens

[mikkokam]

I'm a great fan of the glowing results created by Vilva, Arkku and others by using a Kodak Vest Pocket meniscus lens with digital cameras.

Monocle lenses seemed to be another hack that produces glow (of different kind) - that I wanted to test for portraits. After some Google-time I found advice for building monocle lenses from Helios-44. But I like the Helios much too much to hack it. So, I selected the worst lens I had, a Pentacon 50/1.8 that had been battered badly at some point.

I disassembled the lens with tools and some violence (one of the elements seemed to be glued, so I broke it). The backmost element produced best result reversed. The front element gave a too long focal length and also gave an even softer image in the center. With the backmost element, the lens can focus from 0.6 m to beyond infinity, the frontmost required extension rings.

The results seem quite OK. The center is a bit sharper, sides dreamy. There is glow. Stopping down the lens adjusts the effect.

Need to test it for portraits still.

Result from 1st test shots:


More pictures at Flickr: http://www.flickr.com/mikkokam



Anyone else built monocles? What lenses did you use and did you leave the front or the back element in?


Mikko

[luisalegria]

The simplest to build would be to use a +10 closeup lens on extension rings or bellows. I have also tried +1, +2, and +3 closeup lenses stacked.

The results are soft indeed.

Alternately, you can try one of the 3x teleconverters with any SLR 50-55mm lens wide-open.

[FernandoB12]

Yes Luis,

There are a sample of Takumar 50mm 1.4 plus Soligor MC Tele converter 3X.



The same flower without the tele converter.

[Screamin Scott]

I've always used women's hose stretched over the front of the lens (white or black)

[Seele]

Luisalegria,

If you have some close-up supplementary lenses, you can build a version of the Puyo & Pulligny "Symmetrical Anachromatic" lens; the method is well-known but I'd just be as well repeat it here.

Get a pair of identical close-up supplementary lenses, and mount them back-to-back (concave sides facing each other), the distance between them at one-sixth of their common focal length. Example: a +2 supplementary lens has its focal length at 1/2m, so the distance between them would be 1/18m, or 8.3cm; a central stop can also be added if so wish. This whole lens unit is then moved in relation to the camera for focussing.

There is no real need to make the lens too elaborate; cardboard tubes would be quite sufficient for getting a taste of it.

[martinsmith99]

[mikkokam]

[mikkokam]

[FernandoB12]

Hi Mikko,

Thank you. The Takumar 50mm 1.4 at the moment my best lens, so it was easy to got good results.....
You got very good results with your DIY lens. Congratulations.

[martinsmith99]

I've just ordered a few closeup lenses to experiment with, and a stepup ring to mount on my bellows.

If anyone has any info on construction of such a beast I'd like to hear.

[Minolfan]

My soft focus solution is a Rokkor 50/1.2 with generic MC/MinAf converter. I hoped something else of the converter, but as softfocus help it works well.

[edumad]

I've got a Super-Paragon 135mm that is soft focus, not intentionally I think

[martinsmith99]

After doing a bit of digging around I see that I need 2 closeup filters of the same type. I need a length of pvc tube to connect them and the length of the tube will be the focal length of the lens. I'll make some carboard disks of various sizes to act as an iris.

Questions for those that are in the know.....

What difference with +1, +2, +4 dioptres make?

With the lens on bellows, what focal length do I require to obtain infinity focus?

[Seele]

Martin,

The focal length of this doublet assembly should be somewhat less than the combined focal lengths, but the distance between the lenses should also be a factor as well. Using different close-up supplementary lenses would just alter the focal length of the combined lens, hence my suggestion of using cardboard tubes first to get the measurements right before committing to more costly materials.

However, in the past I had done some custom projects and found that home-made cardboard tubes are totally satisfactory. First use a cylindrical object as a former, if too slim, wrap paper very tightly around it to make up the correct inner diameter, then wrap it tightly in cling film which prevents the tube in construction to stick to it.

You can use brown paper for the lamination, if you wish you can use woodworking glue, but if you want it even stronger, use a powder form resin mixed in water for boat-building, sold under the name "Cascamite" or similar; when dried, it becomes solid and will not be affected by moisture.

Two tubes can then be made to telescope within each other, the larger one attached to the end of a T-mount, if you so wish, and the other can just be grabbed at the front edge for trombone-action focussing. The inside can be lined with stick-on velvet, and the outside covered in black Con-Tact paper for a smart refined appearance.

If you wish to install a central stop, the lens can be broken into two pieces and washer stops dropped in.

There is some leeway regarding the separation between the two lenses, the minimum distance is one-sixth of their common focal length, and this can be increased somewhat; experiment to see the effects if you can.

Several years ago at another forum I described this home-made lens and it generated a bit of discussions at yet another forum:

http://www.largeformatphotography.info/forum/archive/index.php/t-19092.html

Here is a real one on eBay:

http://cgi.ebay.fr/LENS-ANACHROMATIC-OF-Mr-the-Ct-PUYO-SOFT-FOCUS-RARE_W0QQitemZ120420591328QQcmdZViewItemQQptZFilm_Cameras?hash=item1c09a066e0&_trksid=p4634.c0.m14&_trkparms=%7C301%3A1%7C293%3A1%7C294%3A30

... and it has a non-adjustable central stop which stops it down only slightly.

[mikkokam]

[Helios]

Grease on uv filter ....

[orly_andico]

I'd like to point out that two symmetrical achromats back-to-back is a standard Anastigmat formula. You don't even need to buy close-up diopters, places like www.surplusshed.com sell a lot of cemented achromats for their eyepiece kits.

For example their "26mm Super Plossl kit" has two, identical cemented achromats which is just handy for these types of experiments.

http://www.surplusshed.com/pages/item/l1714.html

and for only $6.50 ! sure beats scrounging ebay for diopters..

[greg]

That is a very neat place, actually only a few hours drive away. I may have to take a look.

[martinsmith99]

The formula isn't making much sense to me. I'll just play it by ear and see what I get.

Unfortunately that shop is in the US so it's still cheaper to get the closeup lenses. I just don't know which ones should work best. I'm after a FL of 50-90mm I guess. So should I get weak +1s or strong +10s?

[LucisPictor]

You can try different means of deteriorating lens performance and increase optical aberrations. Some of these methods might bring the effect you want.
The key is to achive a good edge sharpness and still have the glow. That's the tricky part.

[Seele]

orly_andico,

While there are "Double Anastigmats" consisting of a pair of identical achromats, such as Dagor, Double Protar, Turner Reich, Collinear etc, having a pair of achromats arranged symmetrically does not automatically correct for astigmatism in addition to the other optical defects. The Rapid Rectilinear and the identical Aplanat from 1866 certainly did not, and even with the availability of optical glass from Jena, Schroder stumbled when designing the Concentric for Ross by correcting astigmatism but left spherical aberrations uncorrected.

Martin,

As a lens' focal length is the inverse of its diotric power, it means a +2 has focal length of 500mm, +3 has its at 333mm, and so on. With a pair of +3 lenses the focal length would be around 150mm if my calcuations are not too far off, and a pair of +4 should give about 135mm.

[martinsmith99]

[alex]

[martinsmith99]