Focotar 4.5/50 diagram ?

[a.noctilux]

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Hello everyone,

I do have "googled" to find this out, but have found nothing.

I am wondering about the lens diagram of Focotar construction: triplet or double-gauss.

 

Arnaud

[aesop]

Hello everyone,

I do have "googled" to find this out, but have found nothing.

I am wondering about the lens diagram of Focotar construction: triplet or double-gauss.

 

Arnaud

 

 

...Arnaud, I have no diagrams and am not entirely sure which version of the Focotar 50/4.5 you are referring to, but here is some information culled from one Ferrel Anderson of the Leica Users Group (dated 7 December 1998). I have tried to summarise below:

 

The first Focotar listed below has the lens specification written on the face of the front flange, whereas the latter two Focotars have their specification written on the side of the lens barrel:

 

- 50/4.5 Focotar, catalogue #16781R, manufactured between 1953-70, is a five element triplet optical design.

- 50/4.5 Focotar, catalogue #17581A, manufactured between 1970-74 by Schneider, is a five element Gauss design, with three elements before the diaphragm. It has larger diameter front and rear elements than the 16781R and 17582 designs.

- 50/4.5 Focotar-2, catalogue #17582, manufactured between 1974-82, is a six element Gauss design with three elements before and three elements after the diaphragm.

 

*Source: Leica Users Group, 7 December 1998.

 

Incidentally, I am aware that there was also a 50/4.5 "Focotar-3", but I am led to understand that this was essentially a 17582 with an f-stop window (and, yes, I have seen an image of it). To the best of my knowledge, it was never available commercially.

 

Hope this helps.

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[Bateleur]

Interesting, was the Focotar-2 a Schneider co-operation too?

 

Regards

Charles

[telewatt]

Interesting, was the Focotar-2 a Schneider co-operation too?

 

Regards

Charles

 

No, I guess not. The (Schneider) Focotar 1970-1974 had a Schneider serial number. The Focotar-2 had a Leitz number ...

 

regards,

Jan

[tobey bilek]

The I version was optimized for 5x7 and 8x10 is a stretch for it.

 

The Schneider is easily recognized by the large front element and makes 16z20 with ease from a good negative in a glass top or full glass carrier. Works from 5.6 to 11 or 16

 

The Focotar 2 has a little more contrast, local contrast and pop, but gives up the nice flat field of Schneider to get it. You need to stop to 8 to negate the out of focus corners due to lack of a flat field.

 

Version 1 has nowhere near a flat field, but printed curved field mounted slides quite nicely. This thing was an embarrassment to Leica when larger prints were being made, so they worked with Schneider to get something decent.

 

Just so you know before you go shopping.

 

The 40 mm 2.8 is really nice on the V35 diffusion, terrible on any condenser I have. Wide angle Schneider 45 mm 2.8 is the same. Do not think about putting a WA lens on a condenser.

[aesop]

 

...<snip>The Focotar 2 has a little more contrast, local contrast and pop, but gives up the nice flat field of Schneider to get it. You need to stop to 8 to negate the out of focus corners due to lack of a flat field.

 

 

...tobey bilek, I was under the distinct impression that stopping down ~2 stops from maximum aperture produced the optimum results in most enlarging lenses. Re: your specific "f8" comment, would you normally print at f4.5 or f5.6?

[tobey bilek]

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No, but a non flat field is a defect. The Schneider does not require this cover up. I can put the Peak long mirror grain magnifier into the very corners and it is almost perfect at 4.5 and 16x. A 16x20 print would not use that slightly imperfect area.

 

It is up to you if you want to have to stop down or not with the Schneider. You do get a bit more "clarity" with the Focotar 2

[eilert anders]

Nice to see that I am still quoted and appreciated!

 

I have the diagrams for all three versions of the 50mm Focotars, for the 60mm Focotar and for the 100mm f4.5 and f5.6 Focotar II lenses.  I will find them and post.

 

I don't share the view that the earlier Focotars suffered from field curvature.  I have also examined projected images with the Peak grain magnifier, and did not detect any curvature, and most importantly, I have printed with the first Focotar on a Focomat 1C up to 16 x 20 with no problems (I am currently conducting tests of the three 50mm Focotar lens designs, and will post the results).  I was not looking for field curvature, only resolution across the whole field, which was spectacular, but I will check again.  In comparing the Focotars against Schneider and Nikor EL lenses, the resolution of all is without reproach, but the Focotars suffered from no flare or lateral chromatic fringes like the other brand lenses, which resulted in higher contrast.  To be fair, I think the modern enlarging lenses are designed for diffusion light heads and so would have difficulty in dealing with the concentrated and focused light generated with condenser light systems.  I did test an early 50mm f2.8 Nikon EL enlarging lens, and it showed similar results to the Focotars.  The modern version of this lens, with the large back element, did suffer from flare on the Focomat 1c on which I tested all of these lenses.  The Focomat 1C has a single condenser  with a opal light bulb in a diffusion chamber - kind of a hybrid when compared to the Focomat IIC which has a double condenser system.

 

I must note that Ctien in his book "Post Exposure" did not include any 50mm Focotars on his list of the best enlarger lenses then  available.  I contacted him by email about this, and he stated that his primary criteria in choosing lenses to test was light fall-off, which he said the Focotars did not meet.  I replied that this was an incorrect criteria since this "problem" was accounted for in the Focomat enlargers with a compensating condenser/lighting system.  His reply was that this is "unfortunate".  His criteria is correct if one is planning on using a lens for any system.  I should test this out by using one of the lenses he chose to see if it produces a hot spot on a Focomat 1C enlarger!  He did test and include the 100mm f5.6 Focotar II up to a 6X7 format.  I suspect that if he tested this lens up to 6X9 format, it too might not have met his criteria since the optical design seems to be very similar to the 50mm f4.5 Focotar II lens.

 

Ferrel Anderson

[M.Hilo]

Like Ferrel in the previous post, I have printed (and still do) with all versions of the Focotar, except for the much older 5cm version. Using Valoy II, Focomat 1c and  2c, from the late seventies. I have many larger prints, 40X50 and 50X60cm, from all these years and they never have any problems. As a rule I stop down twice, unless a negative is so dense that I need to open up. In general I have the feeling the later two Focotars are better in that (printing 1 stop closed or even full open). For sure the Focotar-2 100mm is very good at that. The 60mm Focotar of the 2c is often written off as inferior and it always makes me laugh. The same goes for the Elmar 100mm.

 

Ferrel, what I am curious about is your remark about the 1c and its "diffusion chamber". Maybe it is language, but I have never thought the 1c has anything diffusion about it. Then, even while I love the 1c, I do think its light system is not easy to get right in terms of even illumination and fall-off. I find the small Valoy II better at this, also at these larger sizes I mentioned. And if I have a 135mm negative that really needs total even illumination, then I use the Focomat 2c.

 

Michael

Edited June 29, 2017 by M.Hilo

[tsleica]

Focotar 2 is best wide open or at 5.6...anything further down degrades resolution..

In my tests..it has a nice flat field too at 5.6..the corners are very sharp...

I own the Focotar 2 100 mm too..but never got to use it much as I never got the 2c..

[Guest]

I think the Ic is actually semi-diffused. A true condenser would involve a point-ish light source where the light emitting part (wolfram filament, p-n junction, whatever) is as close to a point as possible and as best in the focal point of the condenser lenses as possible. The Focomat Ic/IIc are something in between, I think. First there's the opal lamp, which diffuses the light. Then there's the added reflection further diffusing the light. It's more akin to a ulbrichts-sphere combined with a condenser exit.. yet not quite that since the position of the opal bulb matters (the V35 utilising an practical version of the archetypical UB-spehre). Of course, that's splitting hairs. One could easily argue that it is a semi-condensor. Or a special version of a diffuser or condenser enlarger. In practical terms: the Ic/IIc design leans towards the side of a condenser, the V35 design leans towards the side of a diffuser.

 

cp. http://www.durst-pro-usa.com/world_images/specular_light.htm

 

 

As for the Focotar-1. Someone stated, as if were a universal fact, that a non-flat field at full aperture is a defect. I contest this statement. It would only be a defect if it would be a unintended side-effect and causing a sub spec performance. Or if it would have been advertised as flat field and is not. I don't know if this is true as I don't know the original Leitz specifications. Its of course not impossible, but I hardly believe a company, at that time, would have sold a defect item in such large quantities (the latest VW Diesel scandal notwithstanding . Also one needs to take into account the whole system. The 50mm Focotar was probably designed for the Focomat/Valoy enlargers. They utilise a negative carrier in which the negative may slightly warp when it warms up a lot, kind of a framed slide (it may not, but since there's no double-glass carrier, it could be a possibility). So a non-flat field might actually be designed on purpose to counteract that effect. Though I do not know, just a possibility that can't be ignored outright without actual knowledge what the desingers where thinking. There are compromises in any design of any apparatus. For example, the degradation caused by diffraction. Discernible at f11 and clearly visible f16 upwards. Compromise? Defect? I'd say compromise. A unilateral view would conclude this to be a defect and in consequence must must follow the removal of aperture f11+. I'd prefer having the option going there with compromise.

 

 

As for practical performance I came to the same conclusion as Ferrell and M.Hilo. Those are great lenses and the image quality is excellent (though anyone with a sane mind might consider that opinion void as my printing skills and experience my no means rival those of the two gents).

Edited July 6, 2017 by Guest

[Tomasz Jarnicki]

On 6/26/2017 at 7:58 AM, eilert anders said:

Hello Ferrel its possible to see diagrams al veriosn of Focotar ? Many Thanks

I have the diagrams for all three versions of the 50mm Focotars, for the 60mm Focotar and for the 100mm f4.5 and f5.6 Focotar II lenses.  I will find them and post.

[sandro]

Do Focotars 4.5/50 mm have serial numbers? where are they to be found?

Lex

[M.Hilo]

2 hours ago, sandro said:

Do Focotars 4.5/50 mm have serial numbers? where are they to be found?

Lex

Yes Lex, they do: they're situated on a black ring at the rear of the lens. You miss them easily. I have used a loupe sometimes.

On this site, go to Wiki (English) and on the right part of the first page you find Darkroom and Enlargers and Film processing which leads you to serial numbers and years of manufacture. You can find the year your lens was made.

If you don't find the number, I can send a picture . . .

Edited June 12, 2021 by M.Hilo

[sandro]

Thanks, I just found it. I did indeed need a loupe and an extra light and then found it.

Lex

[a.noctilux]

This old thread needs some upgrade.

One of the rare published diagram of five lenses in four groups.

I found some more infos in LEICA FOTOGRAFIE n°3 / 1971, page 119

 

the Focotar 4.5/50 is suitable for close-up and macro 1:2 to 1:5 using in reversed ( sorry in french )

 

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I have the two types of 4.5/50 Focotar which I use happily for 'scan' my negatives and slides.

Having compared them, they are hardly distinguishable from each other.

 

I have one with special numbering at rear : 11 605 545 ( Schneider Gauss as post #2 ? )

and another one normal black on black engraving as 2368614 maybe this one is triplet (5 lenses ! ) from 1969 if we read Wiki's article here

Edited July 4, 2021 by a.noctilux

[Michael Geschlecht]

Hello Arnaud,

Thank you for the added information. Optical design of enlarger lenses is not always easily obtainable.

A point of clarification: The lens in your Post #16, just above, is a modified triplet somewhat similar to, but different from in design, a 50mm f2.5 Hektor. The Hektor designs in various lenses of various focal lengths are variations of this type of modified triplet.

A 50mm f2 Summicron-R, second version, is more typical of a double Gauss design, as it might be found in a Leitz/Leica lens.

Best Regards,

Michael

[M.Hilo]

Arnaud,

Re your question-mark, yes that serial number is typically Schneider. I just checked mine: 11 891 332

Michael

[Tach]

Thanks for the interesting discussion and the link - I have just checked my Focotar 2 (2 851 765) - seems it was in the last hundred being produced.

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[M.Hilo]

26 minutes ago, Tach said:

Thanks for the interesting discussion and the link - I have just checked my Focotar 2 (2 851 765) - seems it was in the last hundred being produced.

That's special. I have seen many Focotar-2 50mm lenses but always from quite early years. It crossed my mind that perhaps there were few produced at the end.