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Playing with bubbles Agfa Solinar 3.5/75
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PostPosted: Sat Oct 21, 2017 1:33 pm    Post subject: Playing with bubbles Agfa Solinar 3.5/75 Reply with quote
Lazy Saturday and experimenting to get some higlight bubbles effect. Installed quick and dirty this lens from dead Isolette III to NX10. Focusing primarily by moving the tube.

Interestingly you can change the properties of the lens by turning the original focus ring.

here the bubbles are in front of the focus
#1


turn the ring and the bubbles are behind the focus Very Happy
#2


the lens setup
#3


PostPosted: Sun Oct 22, 2017 4:23 am    Post subject: Reply with quote
That's certainly interesting. I prefer the 2nd image.


PostPosted: Sun Oct 22, 2017 9:43 am    Post subject: Re: Playing with bubbles Agfa Solinar 3.5/75 Reply with quote
kansalliskalaCafe wrote:
Lazy Saturday and experimenting to get some higlight bubbles effect. Installed quick and dirty this lens from dead Isolette III to NX10. Focusing primarily by moving the tube.

Interestingly you can change the properties of the lens by turning the original focus ring.

here the bubbles are in front of the focus
#1


turn the ring and the bubbles are behind the focus Very Happy
#2


the lens setup
#3

The Solinar is a Tessar clone with 4 elements in 3 groups. In order to reduce to production costs of cameras, manufacturers of that time imagined to focus the lens not by moving it back and forth as a whole (unit focusing), but by moving only the front element or group thus increasing or decreasing the distance between it and the rest of the lens (front cell focusing). The effect of moving only the front cell is modifying the focal length of the lens, just like our modern internal focus (IF) lenses. The downside of front cell focusing was that the lens could only be perfectly corrected of the spherical aberration for a specific distance and not over the whole range.

Usually, the lenses were computed to have their optimal correction at around 2 or 3 meters, i.e. the usual distance for portrait work. When focusing closer, spherical aberration would be undercorrected, leading to pictures like your second one (with an overall soft focus effect), while focusing further away will overcorrect spherical aberration, leading to pictures like your first one (with the plane of focus appearing sharper, which is in fact good for landscape work).

You can think of these old front cell focusing lenses as variable bokeh/soft focus lenses. A few years ago, Veijo Vilva published some interesting experiments with a front cell focusing Radionar triplet: http://galactinus.net/vilva/retro/radionar_uf.html

Cheers!

Abbazz

Last edited by Abbazz on Sun Oct 22, 2017 6:59 pm; edited 1 time in total


PostPosted: Sun Oct 22, 2017 1:16 pm    Post subject: Reply with quote
Thanks for info!

So if I want best image quality, I should set the distance sdale at about 2-3 meters?


PostPosted: Sun Oct 22, 2017 7:36 pm    Post subject: Reply with quote
kansalliskalaCafe wrote:
Thanks for info!

So if I want best image quality, I should set the distance sdale at about 2-3 meters?

That's right, you should get the best correction by doing so.

But undercorrection of the spherical aberration can lead to pleasant results (in my book) by producing images with fine definition and diffused highlights, just like most soft focus lenses do. In this case, the background bokeh is very smooth, with nice soft edged diffusion disks around out of focus highlights.

On the other hand, overcorrection of of the spherical aberration can give the impression of a sharper look (by enhancing edges), at the expense of a busy looking background bokeh with lots of brightlines around the out of focus highlights.

There is a nice explanation with graphics there: http://bokehtests.com/styled/index.html#spherical_aberration

Cheers!

Abbazz


PostPosted: Mon Oct 23, 2017 7:59 pm    Post subject: Reply with quote
Which reminds me of Sigma YS System Focusing (sometimes named differently) leses that have additional front helicoid. They try to market this feature as macro but users were probably very disappointed if real macro results were expected. Clearly a soft-focus feature. http://forum.mflenses.com/sigma-ys-system-focusing-lenses-t38337,highlight,%2Bsigma.html


PostPosted: Tue Oct 24, 2017 11:26 am    Post subject: Reply with quote
Pancolart wrote:
Which reminds me of Sigma YS System Focusing (sometimes named differently) leses that have additional front helicoid. They try to market this feature as macro but users were probably very disappointed if real macro results were expected. Clearly a soft-focus feature. http://forum.mflenses.com/sigma-ys-system-focusing-lenses-t38337,highlight,%2Bsigma.html

Or the famous Sears 135mm and its numerous avatars: https://www.pentaxforums.com/userreviews/sears-135mm-f-2-8-macro-zone.html

Cheers!

Abbazz
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