Roland Zwiers Posted July 20 Author Share #821 Posted July 20 Advertisement (gone after registration) New optical glass and colour-corrected lenses In the 1890s the new optical glass from Schott Jena allowed for the production of ever better lenses for microscopes. This also applied to the correction of lenses for the various colours of the spectrum. Lens types became achromatic, pantachromatic, apochromatic and so on. Of course, the higher the order of correction, the more expensive the lens. The next slides are from a Leitz publication (Wetzlar and New York) from 1894. Link to post Share on other sites More sharing options...
Advertisement Posted July 20 Posted July 20 Hi Roland Zwiers, Take a look here 100 years Null-Serie. I'm sure you'll find what you were looking for!
Roland Zwiers Posted July 20 Author Share #822 Posted July 20 Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/378437-100-years-null-serie/?do=findComment&comment=5836218'>More sharing options...
Roland Zwiers Posted July 20 Author Share #823 Posted July 20 Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/378437-100-years-null-serie/?do=findComment&comment=5836220'>More sharing options...
Roland Zwiers Posted July 20 Author Share #824 Posted July 20 The colours that our eyes can see For our discussion it is important to focus on the intensity curve of the eye. One can see that the colour yellow (between the lines D and E) is the brightest colour by far. Unfortunately, the traditional colour-blind plates and films were predominantly sensitive to the colours ultra-violet, violet and blue. This problem, and how to deal with this, was widely discussed in pre-1918 photo-literature. Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/378437-100-years-null-serie/?do=findComment&comment=5836222'>More sharing options...
Roland Zwiers Posted July 20 Author Share #825 Posted July 20 The colours of colour-blind film A prominent author in the 1900s and 1910s was the German researcher Freiherr (Baron) von Hübl. He compared the intensity curve of the eye (Roman I) with the colour-sensitivity of an ordinary colour-blind dry plate (Roman II). One can see that there is very little overlap. Ordinary plates were even sensitive for ultra-violet, a colour that our eyes do not record. Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/378437-100-years-null-serie/?do=findComment&comment=5836223'>More sharing options...
Roland Zwiers Posted July 20 Author Share #826 Posted July 20 Two complementary approaches for arriving at colour-correct results The approach of Von Hübl had two complementary parts. First, he created a whole library of photographic dyes for making the emulsion sensitive to specific colours. But even with a suitable dye, say Eosin, the colours blue and violet would still be dominant. So the complementary approach was to design filters that would suppress the dominance of blue without sacrificing the colours that had to be enhanced. In this way he created a special Eosin-filter to complement an eosin-bathed plate or film. In his handbook of 1910, he even gave instructions to amateurs how to make these correction filters at home. But amateurs could also buy these filters from what would become the Lifa filter factory in Augsburg. The advertisement below shows that the factory of K. Sill in Augsburg took up the production of “Von Hübl” yellow filters. This factory was taken over by Alois Schäfer and subsequently renamed as Lifa-Lichtfilterfabrik. Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! It is interesting to observe that Dr Paul Wolff specifies his use of Lifa filters in his 1934 book “Meine Erfahrungen mit der Leica”. Wagner has brought this up in a recent thread on this Forum. Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! It is interesting to observe that Dr Paul Wolff specifies his use of Lifa filters in his 1934 book “Meine Erfahrungen mit der Leica”. Wagner has brought this up in a recent thread on this Forum. ' data-webShareUrl='https://www.l-camera-forum.com/topic/378437-100-years-null-serie/?do=findComment&comment=5836225'>More sharing options...
Roland Zwiers Posted July 20 Author Share #827 Posted July 20 Advertisement (gone after registration) Highly corrected lenses for micro-photography Now Leitz and Zeiss made microscopes with highly corrected lenses. Lenses corrected for all colours of the spectrum. Wouldn’t it be nice if they could demonstrate the quality of their microscopes with goodlooking pictures? This brings us to the chapter of micro-photography and even micro-cinematography. But what use would these highly corrected lenses have if the plates and films were still colour blind? Moreover, in micro-photography it was often important to show contrast between the colours yellow, green, orange, red and blue. How to do this with ordinary colour-blind material? Link to post Share on other sites More sharing options...
Roland Zwiers Posted July 20 Author Share #828 Posted July 20 Micro-photography with good-quality orthochromatic plates One approach used by Leitz was to use the best orthochromatic plates on the market, like the famous Perutz Perorto plate. In combination with a yellow filter (or a light source emitting yellow light) this dry plate had an almost ideal colour-correction, but was still insensitive to the colour red. Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/378437-100-years-null-serie/?do=findComment&comment=5836229'>More sharing options...
Roland Zwiers Posted July 20 Author Share #829 Posted July 20 The picture in the previous slide shows the cover of a box with Perorto plates. Note he the green seal, in German: Grünsiegel. In 1925 Perutz finally managed to combine this high-quality emulsion with 35mm film. So this Perutz Grüsiegel film was available for a Leica review of May 1925. For a while this Perutz Leica film became the most popular Leica film. Perutz would even name it: ‘the Perutz Leica film’ so as to distinguish it from the later Perutz Leica Spezial film (also known as Perutz Spezial Fliegerfilm). Link to post Share on other sites More sharing options...
Roland Zwiers Posted July 20 Author Share #830 Posted July 20 Micro-photography with Eosin-bathed plates In case the colour red was important, then it was necessary to bathe a colour-blind plate in a solution like Eosin. This procedure was also recommended in photo-magazines for amateur use. The image below shows a contemporary recommendation in the British photo-magazine Amateur Photographer. Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/378437-100-years-null-serie/?do=findComment&comment=5836233'>More sharing options...
Roland Zwiers Posted July 20 Author Share #831 Posted July 20 Leitz used orthochromatic plates and Eosin-bathed plates for micro-photography So how do I know that Ernst Leitz was also aware of these routes? In the next slides I will show 12 micro-photographic examples published by Ernst Leitz New York in the year 1911.One can see that Leitz both used the highly orthochromatic Perutz Perorto plate and an ordinary plate bathed in an eosin solution (‘Eosin-bathed plate’). Note the frequent use of a yellow filter (in the terminology of the day: ‘yellow screen’). This was the standard for obtaining colour-correct results. It was also possible to forego colour-correctness and to aim at the best colour-contrast. This explains the use of green and blue filters (so as to brighten green and blue as compared to other colours). Note the use of the 1:4,5 f=42mm Micro-Summar; Oskar Barnack would use this lens on his Ur-Leica. Note the use of Liliput arc lamps. In the photographic literature of the day ‘Liliput’ frequently referred to miniature cameras as well. Link to post Share on other sites More sharing options...
Roland Zwiers Posted July 20 Author Share #832 Posted July 20 Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/378437-100-years-null-serie/?do=findComment&comment=5836235'>More sharing options...
Roland Zwiers Posted July 20 Author Share #833 Posted July 20 Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/378437-100-years-null-serie/?do=findComment&comment=5836236'>More sharing options...
Roland Zwiers Posted July 20 Author Share #834 Posted July 20 Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/378437-100-years-null-serie/?do=findComment&comment=5836237'>More sharing options...
Roland Zwiers Posted July 20 Author Share #835 Posted July 20 Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/378437-100-years-null-serie/?do=findComment&comment=5836238'>More sharing options...
Roland Zwiers Posted July 20 Author Share #836 Posted July 20 All in all, in 1914 Ernst Leitz II needed to have intimate knowledge of the colour-sensitivity of plates and films for the production and commercialisation of his microscopes. This also follows from contemporary Leitz publications. Against this background it is in order to explain my working hypothesis again. It is a working hypothesis, since I cannot interview Ernst Leitz II or Oskar Barnack anymore. After more than 100 years it is impossible to state anything with 100 percent certainty. But the working hypothesis is based on pre-1918 photo literature. If other researchers have alternative views, then I would appreciate a transparent and respectful discussion. Link to post Share on other sites More sharing options...
Roland Zwiers Posted July 20 Author Share #837 Posted July 20 In 1914 Ernst Leitz II used colour-blind film In my working hypothesis in June 1914 Ernst Leitz II used colour-blind film for his visit to the USA. This was the ordinary 35mm cine negative film that was produced by the likes of Kodak (USA), Agfa (Germany), Austin Edwards (UK) and Lumière (France). Since he used colour-blind film a yellow filter would have had no purpose whatsoever! There was no yellow sensitivity that had to be emphasised by suppressing the over-sensitivity to blue. A yellow filter would merely have reduced the overall sensitivity of the film. In the next slide I present a selection of the pictures by Ernst Leitz II. I owe these pictures to Ulf Richter (2009) 1 Link to post Share on other sites More sharing options...
Roland Zwiers Posted July 20 Author Share #838 Posted July 20 Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/378437-100-years-null-serie/?do=findComment&comment=5836241'>More sharing options...
Roland Zwiers Posted July 20 Author Share #839 Posted July 20 In 1914 Oskar Barnack already experimented with colour On the other hand, in 1914 Oskar Barnack was free to experiment with making colour-blind films sensitive to the colours green, yellow, orange and even red. The next slide shows Zeppelin pictures that can be dated March-April 1914. These pictures are also included in Ulf Richter (2009). Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/378437-100-years-null-serie/?do=findComment&comment=5836242'>More sharing options...
Roland Zwiers Posted July 20 Author Share #840 Posted July 20 How would Oskar Barnack have arrived at colour-correct results at a time that regular cine negative films were still colour blind? In my working hypothesis he used the same bathing technique as was employed at Leitz for micro-photography. How could one otherwise explain the good colour balance in many of his pictures from 1914-1915? Note that enhanced sensitivity to yellow was not sufficient; without a yellow filter the colour blue would still dominate the results. So somehow Oskar Barnack must have experimented with yellow filters as well. He may have produced a yellow filter himself, following the recommendations of Freiherr Von Hübl. He may have placed the yellow filter in front of, or behind the lens. In 1914 he may very well have bought yellow filters and/or filter holders from third parties. Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/378437-100-years-null-serie/?do=findComment&comment=5836243'>More sharing options...
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