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Overrated? Trioplan 100mm 1:2.8
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PostPosted: Fri Nov 01, 2013 12:25 pm    Post subject: Reply with quote

iangreenhalgh1 wrote:
Are you sure it's over-correction of spherical aberration? The two main weaknesses of the triplet design at large apertures are uncorrected spherical aberration and curvature of field.

http://ocw.mit.edu/courses/mechanical-engineering/2-71-optics-spring-2009/projects/design-of-a-cooke-triplet/MIT2_71S09_sw06.pdf


We need to be careful of the terminology here - uncorrected could refer to both undercorrected and overcorrected. Indeed, most of the triplets may look like they have undercorrected spherical aberrations. That is what makes trioplan different.

Besides, this type of bokeh has nothing to do with triplet lens design per se. As was already mentioned in this thread, other, non-triplet, lenses can show the same effect, like Tamron 70-150/2.8 soft, and the Primotar 135/4. It is also present in Primoplan 58/1.9, but due to considerable astigmatism, the "bubbles" are not "complete".

This is the interesting read about bokeh: http://www.luminous-landscape.com/essays/bokeh.shtml


PostPosted: Sun Nov 03, 2013 1:10 pm    Post subject: Reply with quote

ZoneV wrote:
Alex H wrote:
...
I need to try and do side-by-side comparison between Trioplan and Tamron, even just for myself.


This would be great!


Used two different cameras and shot incamera JPGs with different preset WB (forgot to change), so sorry for the different colors, but it will make it easier to tell the lenses apart.

Left-most – Trioplan, four others to the right - Tamron 70-150 soft.
Both set to F/2.8, 1m focusing distance, Tamron set to approximately 100mm.

Soft settings were changed in Tamron from 0 to 3 (left to right).



PostPosted: Sun Nov 03, 2013 2:05 pm    Post subject: Reply with quote

Thank you very much Alex H!
Great, I suppose most Tamron 70-150 soft images I saw online where made with soft 3 setting, and so thicker bright border circle.
With soft 2 settings the border looks thin like with the Trioplan 100.

Do you know what´s the reason for the bokeh structure - aspheric lens or dust, or something else?
Found nothing about an aspheric element in this lens.


PostPosted: Sun Nov 03, 2013 2:18 pm    Post subject: Reply with quote

ZoneV wrote:
Do you know what´s the reason for the bokeh structure - aspheric lens or dust, or something else?
Found nothing about an aspheric element in this lens.


Probably dust... It is less obvious, but also present in Trioplan shot.


PostPosted: Sun Nov 03, 2013 7:34 pm    Post subject: Reply with quote

Nice work Alex, thanks! Structures visible in bokeh "bubbles" are usually
dirt/dust on lens surfaces - a fine method to test how clean a lens is... Wink


PostPosted: Sun Nov 03, 2013 9:07 pm    Post subject: Reply with quote

kds315* wrote:
Nice work Alex, thanks! Structures visible in bokeh "bubbles" are usually
dirt/dust on lens surfaces - a fine method to test how clean a lens is... Wink


Yeah, one of the few reasons for me to clean inside a lens.


PostPosted: Tue Nov 05, 2013 6:57 am    Post subject: Reply with quote

I actually really like those bubbles. So, is it the dust or the lens design?


PostPosted: Tue Nov 05, 2013 7:43 am    Post subject: Reply with quote

In case you mean the structure in the hole bokeh circle it is most likely dust - but for example some few (not all) Samyang lenses have nearly such a structure likely due to the aspheric lens.

The outer bright ring on the bokeh circle is lens design - one reason why I love the Trioplan 100.


PostPosted: Wed Nov 06, 2013 10:13 pm    Post subject: Reply with quote

Any other lenses that can do soap bubble bokeh or just this one? Aka, what's the exact design of this one called?


PostPosted: Wed Nov 06, 2013 10:21 pm    Post subject: Reply with quote

A "Cooke Triplet" it is... http://en.wikipedia.org/wiki/Cooke_triplet

Last edited by kds315* on Wed Nov 06, 2013 10:32 pm; edited 1 time in total


PostPosted: Wed Nov 06, 2013 10:26 pm    Post subject: Reply with quote

So say, Zeiss Jena Triotar would produce similar images, right?


PostPosted: Wed Nov 06, 2013 10:42 pm    Post subject: Reply with quote

SkvLTD wrote:
So say, Zeiss Jena Triotar would produce similar images, right?


No, common mistake to think all triplet like Trioplan , not at all, all have own finger print may you find them similar may not.
Trioplan 50 and Trioplan 100 has difference too.

In simple point of shoot style , Triotar 135mm way sharper , better lens than Trioplan 100 , better contrast too.


PostPosted: Wed Nov 06, 2013 10:44 pm    Post subject: Reply with quote

I can believe that. Really gotta do more digging around here for some visual gems that fancy my eye.


PostPosted: Wed Nov 06, 2013 11:04 pm    Post subject: Reply with quote

SkvLTD wrote:
I can believe that. Really gotta do more digging around here for some visual gems that fancy my eye.


Look forward your results!


PostPosted: Wed Nov 06, 2013 11:29 pm    Post subject: Reply with quote

Interesting. Doesn't the Tamron, like other lenses with a softness control, add more and more spherical aberration by moving an element? If so, that would point to spherical aberration being the cause of the outline on the bokeh highlights and would suggest that the Trioplan 2.8/100 has those outlines because it has a lot of spherical aberration?


PostPosted: Thu Nov 07, 2013 7:53 am    Post subject: Reply with quote

iangreenhalgh1 wrote:
Interesting. Doesn't the Tamron, like other lenses with a softness control, add more and more spherical aberration by moving an element? If so, that would point to spherical aberration being the cause of the outline on the bokeh highlights and would suggest that the Trioplan 2.8/100 has those outlines because it has a lot of spherical aberration?


You are partly correct, Ian. if You want to understand better, about how it works, I am re-posting the link again: http://www.luminous-landscape.com/essays/bokeh.shtml. It clearly shows how the outline of bokeh highlights appear with soft focus lenses and how it can be present or absent in different parts of images.

It is not only the presence of aberrations, but also the way they were corrected, that matters here. Because in most lens design correction for aberrations are not symmetrical for the areas in front and behind the best focus point. Remember people saying how lenses have smoother out-of-focus areas either in front or behind the focused part?

I do not have time right now to test my other lenses, but here is a simple test, and please ignore the dust here! It is not relevant to the discussion. Same lens here, same Trioplan. Same "point" light source. The shape of OOF highlight when the light source is placed behind and in front of the best focus point. It is obvious, that the Trioplan is corrected for spherical aberrations differently for different parts of the image.



I will do the same test for Tamron later on.


PostPosted: Thu Nov 07, 2013 8:28 am    Post subject: Reply with quote

Very well done Alex!


PostPosted: Thu Nov 07, 2013 9:56 am    Post subject: Reply with quote

Overcorrected spherical abberation gices bubbles in background, and soft bokeh in foreground.
Undercorrected spherical abberation gives soft bokeh in background, and bubble bokeh in foreground.

The Trioplan 100mm f/2.8 seem to have a very strong over corrected spherical abberation. The Diaplan / Pentacon AV 100 the same. The Pentacon AV 80mm/2.8 seem in first tests less strong over corrected spherical abberation.

Spherical abberation in normal helicoid focussed lenses (not IF, no floating elements, not front or backlens focussing) is corrected for one distance, and so front and back bokeh behavior changes with distance.
Knowing this I took a lens with extra macro focussing ring to get the possibility to have a lens with spherical abberation control - like Nikon Defocus Control!
I found the Sigma YS 135mm lens as a good lens for such bokeh control.

In both fore- and background only apodization lenses gives very smooth bokeh.