CK's Lens Post: Dyotar 180mm f/4.7 Soft Focus Lens

Started Jul 28, 2016 | Discussions
Ching-Kuang Shene
Ching-Kuang Shene Veteran Member • Posts: 6,049
CK's Lens Post: Dyotar 180mm f/4.7 Soft Focus Lens
6

Soft focus lenses were very popular for portrait shots in the late 19th century.  The game was started, perhaps, by Dallmeyer and Taylor, Taylor and Hobson.  Then, in the 20th century, the king was Rodenstock's various Imagon lenses, which were used extensively by Hollywood photographers.  Nowadays, people are chasing after sharpness, and, as a result, soft focus lenses are no more popular.

This post is about a rarely seen soft focus lens: Dyotar 180mm f/4.7.  I don't know who made it and for what cameras.  However, it is very likely a large format lens that can cover 5x4 film.  I have never tried it on my technical 5x7 camera though.

This is a rather simple lens.  It has aperture control without focus mechanism.  Thus, a bellows or something like that would be needed.  This lens can be disassembled into three sections: front lens, rear lens with aperture control mechanism, and a tube that holds the screen mounted to the rear end of the lens.

Dyotar 180mm f/4.7 Soft Focus (Front)

Dyotar 180mm f/4.7 Soft Focus (Rear)

Dyotar 180mm f/4.7 Soft Focus Disassembled

The screen tube screws onto the rear lens section and has a diameter slightly larger than 56mm.  What I did was inserting a 72-58 step-down ring to the rear lens section and screwing the screen tube back.  Note that this 72-58 step-down ring has to be thin enough so that the rear lens section still has enough thread space so that the screen tube can be screwed back.  Now, we have a 72mm thread as shown below:

Adding a 72-58mm step-down ring between the rear lens section and the screen tube gives us a 72mm mounting thread.

But, why is 72-58?  Can we use a smaller step-down ring?  Well, the fact is that we will need several step rings to produce a tube so that the last available thread will be slightly longer than the rear end of the screen tube.  After trying many combinations with my step rings in hand, I decided to use 72-58, 77-72, 72-77, 77-72, 86-77, 77-86, 62-77, 77-62, 55-77, 52-55.  There are 10 step rings in total!  This approach yielded a tube that is slightly longer the screen tube as shown below.  Of course, you could use a different combinations to achieve the same effect.

Add a number of step rings so that we will have a usable thread.

Why did I end with a 52mm?  The main reason is because I need to a Nikon bellows and related accessories.  Nikon made a K2 adapter that has a female 52mm thread and a Nikon F mount.  This is what I want.  I also added a 12mm extension tube so that I could do some close up work.  Finally, this setup is mounted on a Nikon PB-4 bellows and paired with a Nikon D60 DSLR:

Dyotar 180mm f/4.7 Soft Focus lens adapted on a Nikon DSLR

The following shows some images shot with this combo.  I did not record the aperture being used.  For most cases, the used aperture was f/4.7.

More information can be found here.  This is my blog article written in 2009 in Chinese.

Hope you like this post and this lens.

CK

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QuangFoto
QuangFoto Regular Member • Posts: 361
Re: CK's Lens Post: Dyotar 180mm f/4.7 Soft Focus Lens

Interesting.  Thanks for sharing.  Wow, how many blades does the that aperture control have?  It looks like a perfect circle.  And how do you focus if there's no focus control?

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MOD Tom Caldwell Forum Pro • Posts: 39,343
Re: CK's Lens Post: Dyotar 180mm f/4.7 Soft Focus Lens

CK

In my ignorance I had thought that soft-focus was soft across the focused range.  Here you show that a soft-focus lens can be quite sharp in the in-focus range but gives a pleasant soft look out of focus rather than a distinctive bokeh that many lenses produce.  It does look good in my opinion.  If other soft focus lenses can produce similar results then perhaps the continued pursuit of sharp focus and crazy bokeh has left another type of capture unfortunately orphaned.

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Tom Caldwell

ProfHankD
ProfHankD Veteran Member • Posts: 6,818
Wire mesh and other aperture arrays

Tom Caldwell wrote:

In my ignorance I had thought that soft-focus was soft across the focused range.

No; that's never what it meant. Even smearing Vaseline on a lens doesn't quite do that.

Here you show that a soft-focus lens can be quite sharp in the in-focus range but gives a pleasant soft look out of focus rather than a distinctive bokeh that many lenses produce. It does look good in my opinion. If other soft focus lenses can produce similar results then perhaps the continued pursuit of sharp focus and crazy bokeh has left another type of capture unfortunately orphaned.

The screen here is a minor variant on the "sink strainer" filters (such as the Fujinon SF lenses or this ghetto version using an actual sink strainer ). It's not particularly effective in comparison to those,and it's especially odd that the screen doesn't even seem to have the holes with a 1:1 aspect ratio -- so turning it should allow a little control of the bokeh texture it imposes.

Basically, any array of apertures will show as a textural pattern in the bokeh when the light sources are sufficiently out of focus (OOF), but that textural pattern basically adds noise that breaks-up other structures (artifacts) in the bokeh. Less OOF stuff fails to resolve the aperture pattern, so you basically get fairly even bokeh approximating the density distribution of the apertures. For example, it is fairly common to use wire screens as filters for telescope s -- primarily approximating an apodizing filter (think Minolta/Sony STF or Laowa STF) by having a clear center with a few layers of wire mesh with increasing diameter holes cut in the middle. Such filters not only help bokeh, but also can improve the ability to resolve fine details (yes, some soft focus filters effectively increase sharpness).

In general, you can add such structures to most lenses with very similar effects... and you usually don't even have to open the lens and replace the iris to do it, but can stick your filter in front or behind (if things are sized correctly). There are some issues with the optical quality (or lack thereof) when you laser-print filter patterns on overhead transparency material, but that's probably the most flexible way to make arbitrary patterns. Neater than cutting wire mesh, anyway.    I've also made them with a programmable paper cutter or printed them 3D printer, and of course a laser cutter would work well too.

In any case, my Poorly Focused Talk gives a pretty good explanation of how manipulation of the OOF point spread function (OOF PSF) works to modify bokeh.

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jaktini New Member • Posts: 2
Re: Wire mesh and other aperture arrays

Can't you order this wire mesh in disc form so you don't have to cut it yourself?  I just quickly googled "wire mesh discs" and got back a bunch of results - Take a look here - Woven Wire Cloth + Discs

There is no way that this is a do it yourself kind of project - these circles have to be cut perfectly.  There is no way to cut a perfect circle by hand - and if one wire gets loose, this can do major damage to your equipment.

ProfHankD
ProfHankD Veteran Member • Posts: 6,818
Re: Wire mesh and other aperture arrays
1

jaktini wrote:

Can't you order this wire mesh in disc form so you don't have to cut it yourself? I just quickly googled "wire mesh discs" and got back a bunch of results - Take a look here - Woven Wire Cloth + Discs

There is no way that this is a do it yourself kind of project - these circles have to be cut perfectly. There is no way to cut a perfect circle by hand - and if one wire gets loose, this can do major damage to your equipment.

By hand? My apertures are cut by programmable paper cutter or laser engraver, or extruded on a 3D printer. However, I don't do wire meshes....  

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