Roland Zwiers Posted July 19 Share #21  Posted July 19 Advertisement (gone after registration) 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?  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. 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 next slide shows a contemporary recommendation in the British photo-magazine Amateur Photographer. Link to post Share on other sites More sharing options...
Advertisement Posted July 19 Posted July 19 Hi Roland Zwiers, Take a look here What is the LIFA P 100 filter mentioned by Dr. Paul Wolff?. I'm sure you'll find what you were looking for!
Roland Zwiers Posted July 19 Share #22  Posted July 19 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/423117-what-is-the-lifa-p-100-filter-mentioned-by-dr-paul-wolff/?do=findComment&comment=5835752'>More sharing options...
Roland Zwiers Posted July 19 Share #23  Posted July 19 So how do I know that Ernst Leitz was also aware of this route? 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 19 Share #24  Posted July 19 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/423117-what-is-the-lifa-p-100-filter-mentioned-by-dr-paul-wolff/?do=findComment&comment=5835755'>More sharing options...
Roland Zwiers Posted July 19 Share #25  Posted July 19 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/423117-what-is-the-lifa-p-100-filter-mentioned-by-dr-paul-wolff/?do=findComment&comment=5835756'>More sharing options...
Roland Zwiers Posted July 19 Share #26  Posted July 19 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/423117-what-is-the-lifa-p-100-filter-mentioned-by-dr-paul-wolff/?do=findComment&comment=5835758'>More sharing options...
Roland Zwiers Posted July 19 Share #27  Posted July 19 Advertisement (gone after registration) 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/423117-what-is-the-lifa-p-100-filter-mentioned-by-dr-paul-wolff/?do=findComment&comment=5835759'>More sharing options...
Roland Zwiers Posted July 19 Share #28  Posted July 19 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 post-war Leica literature has alternative views, then I would appreciate a transparent and respectful discussion between openminded researchers. Link to post Share on other sites More sharing options...
Roland Zwiers Posted July 19 Share #29  Posted July 19 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. 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. How would he have done this? 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. In 1914 these may very well have been bought from third parties. In the period 1915-1918 Oskar Barnack may also have used the Agfa Fliegerfilm. Max Berek (1948) refers to this. For aerial reconnaissance photography fine grain was important, but equally important was sensitivity to colour. So, if Oskar Barnack could access remnants of the Agfa Fliegerfilm, he would certainly have used these for experimenting with colour-correct results. Good candidates are several pictures that Oskar Barnack took in 1917 in the Black Forest! I hope that the Leitz Archive in Wetzlar will allow me to study these negatives/ pictures in greater detail.  If Oskar Barnack already experimented with colour in 1914, why would he not have given Ernst Leitz II similar films for his June 1914 visit to the USA? This is reatively easy to explain. The increased sensitivity to colour would last only one or two days. This was no option for a journey that would last several weeks. Note that Max Berek (1948) also mentions the poor shelve life of the wartime Fliegerfilm. William, I would very much like to discuss this subject with researchers at the Leitz Archive in Wetzlar. Could you write a letter of recommendation for me? Roland 1 Link to post Share on other sites More sharing options...
beoon Posted July 21 Share #30  Posted July 21 I found in my collection the brochure for the Lifa P100 (dated 1932). For your reference. Alan 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! 2 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/423117-what-is-the-lifa-p-100-filter-mentioned-by-dr-paul-wolff/?do=findComment&comment=5836786'>More sharing options...
beoon Posted July 21 Share #31  Posted July 21 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! 2 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/423117-what-is-the-lifa-p-100-filter-mentioned-by-dr-paul-wolff/?do=findComment&comment=5836787'>More sharing options...
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