Basic colour principles

The properties of colour filters have been known since at least 1855, when James Clerk Maxwell submitted a paper to the Royal Society in Edinburgh, in which he explained the possibility of producing full-colour images by taking three black-and-white photographs of a subject, each through a different coloured filter, and combining the images.  In 1861 this was demonstrated by Thomas Sutton, working with Maxwell, who took separate black and white photographs through red, green and blue filters.  At the time of writing, more information on this can be seen on the website of the Clerk Maxwell foundation, here.  The negatives thus created were copied in order to produce three separate positive black and white images on glass – the original version of reversal slides for projection.

Using filters in Colour Photography

It is obviously possible to use colour filters in colour photography, to achieve a particular “artistic” effect.  The result is an essentially monochrome image in varying shades of the colour of the filter, especially in the case of darker filters, such as dark reds.  However, most of the time obviously-coloured filters are not used for colour photography, in which the following types of filters are common:

• Ultra-violet (abbreviated “UV”).  These filters are purported to reduce the effect of atmospheric haze, although most of the time they are principally used to protect the front element of the lens from damage.
• Polarizing filters.  These filters reduce the light in one axis.  They therefore need to be in rotating mounts and it is necessary to look through the filter while rotating it, in order to see how the effect changes at different angles in relation to the sun.  The best way to do this is to use an SLR camera, which will view the subject through the lens, and therefore also through the filter.  Polarizing filters substantially reduce reflections.  Images in East German publications frequently show them being used to take photographs, from the street, of shop-window displays, without reflections of the street scene being visible in the glass of the window.  However, polarizing filters can also reduce reflections from other sources, such as shiny leaves on plants, resulting in more saturated colours.
• Neutral density filters (often abbreviated to “ND”).  These grey filters reduce the light entering the lens, enabling wider apertures or slower shutter speeds to be used when desired.  In recent years they have become very popular in pictures that include moving water (rivers, the sea, ...), to enable such a slow speed to be used that the water becomes more or less blurred.  For such photographs, a tripod is obviously essential.  In the absence of an ND filter, a polarizing filter can achieve largely the same effect.
  
• Various colour-correction filters that have a very pale density.  They are designed to compensate for an undesirable colour shift, as may be caused by some slide films or close to sunrise or sunset, when the ambient colour may be “warmer” (redder) than normal.  They are available in various intensities and their use is essentially limited to photography on reversal (slide) film, since with colour negative material, any slight colour shift or colour cast will (or should!) be eliminated during the printing process.  The digital equivalent is the “White balance” setting on some digital cameras.
  
• In 1978 the French photographer Jean Coquin developed graduated filters.  These filters were not round but square or rectangular.  They typically had a dark colour (often grey, but not necessarily so) that faded to totally transparent at the other end of the filter.  They were eventually marketed under the anglicised name “Cokin”.  They can be ideal in landscape (and seascape) photography, to darken the sky and so bring out sky detail, without under-exposing the lower part of the image.

Naturally, all these types of filters can also be used in black and white photography (although colour-correction filters are unlikely to result in a visible difference in the picture). Other filters that can be used both in back & white and colour photography include: Close up filters.  An example of such filters can be seen here and here. Cross and “starburst” filters.  These can add sparkle to images that include reflections of the sun or that have multiple light sources (such as street lights), where rays of light extend from the light source in four, six, or more directions. Multiple-image filters.  These can reproduce sections of an image miltiple times.  This generally works best on a dark background. Soft-focus filters, which are sometimes used for portrait photography. To the right we see an example of the use of a multi-image filter on a Pentacon Six, taken by Dr W Gerhard Heyde and reproduced in the third edition of his book “Pentaconsix Praxis” (p. 124), published in 1980 by VEB Fotokinoverlag, which on the title page indicated its location as being no longer Halle but now Leipzig.  The photograph is in fact of the logo for the Leipzig trade fair, which is known in German as the “Leipziger Messe”.  According to Wikipedia (here), the double M logo was designed in 1917 by Erich Gruner.  The Leipziger Messe was used for commercial fairs in many sectors of trade and commerce, and generally both in the Spring and in the Autumn during a large part of the 20th century it hosted a photographic fair, where new products were often announced or launched.

[multiimg.jpg]

Filter factors

If a filter is holding back some of the light in the scene, obviously less light will reach the film.  With a particularly dense or dark filter, under-exposure will result (the image will be too dark).  It is easy to compensate for this, and filters should be supplied with a filter factor or exposure factor.   This will typically be along the lines of “2×”, which means “double the exposure indicated by the hand-held meter or other exposure guide”.  This is easily achieved by opening up the lens by one stop (for instance, from f/11 to f/8) or doubling the exposure time (for instance, by using 1/125 sec instead of 1/250 sec).  Likewise, a filter that had an exposure factor of 4× would require the lens aperture to be opened by two stops (since each stop will double the light intensity entering through the previous, smaller aperture setting), or using a shutter speed “two down” from the unfiltered speed (for instance, in the above example, by using 1/60 sec instead of 1/250 sec).

Again, a table in Dr Heyde’s book “Pentaconsix Praxis” may help to clarify the options.  It, too, is to be found on page 98 of the first and second editions and on page 80 of the third edition.

However, photographers who use the TTL metering prism on the Pentacon Six are spared all these calculations, since the meter will measure accurately the amount of light actually coming into the camera via the lens and the filter.

Filters for Pentacon Six lenses

Naturally, filters from any manufacturer can be used with any camera, provided that there is a convenient way of fitting them to the lens.  In the 1930s and 1940s, many filters were in “push on” mounts.  That is to say, they gripped the front of the lens rather in the way that most lens caps did until very recently.  However, already in the 1930s many photographic lenses had a female thread at the front, so that filters could be screwed in, and by the 1950s this became the most popular way of attaching filters to a lens.  In order to do this, it was necessary to know the diameter of the filter thread on the lens and the pitch, i.e. the distance between each turn of the thread.

Carl Zeiss Jena succeeded in limiting the filter mounts on lenses for the Pentacon Six to one of three sizes:

• 58mm with pitch 0.75.  This was used for the 80mm Tessar and the 80mm Biometar standard lenses.
• 67mm with pitch 0.75.  This was used for the 120mm Biometar lens.
• 86mm with pitch 1.  This was used for the 50mm and 65mm Flektogon wideangle lenses and the 180mm and 300mm Sonnar telephoto lenses.

Standardising on filter sizes was popular with photographers, since it meant that filters that they bought could be used on several different lenses, thus reducing financial outlay.

I am aware of four East German manufacturers of filters for Pentacon Six lenses:

• Panchromar (see the changes to the manufacturer’s name below)
  
• VEB Jenaer Glaswerk Schott & Genosse
• Hugo Arnz Optische Werkstätte, Jena
  
• Carl Zeiss Jena

We note that three of these manufacturers were in Jena, the main centre for lens making in Germany and the location of the original Carl Zeiss headquarters, while the other one was in a suburb of Dresden, the centre of excellence in camera design and manufacture.  Here I give some brief information on filters from these four manufacturers.  All the filters from these manufacturers that I have seen were also front-threaded, so that a lens shade (hood), or even another filter, could be added.  This also makes it possible to store filters by screwing them together and adding a screw-on back cap and a screw-in front cap, for protection.

Panchromar filters were apparently originally manufactured by the firm of Lehmann & Balzer.  They manufactured a wide range of 58mm  filters suitable for the 80mm Tessar and Biometar lenses, as well as 67mm filters suitable for the 120mm Biometar and 86mm filters for the four Zeiss lenses that required this size, which were probably the only lenses being made at that time in East Germany that took 86mm filters. The flyer illustrated to the right was found in inside the book “Pentacon Praxis” by Kurt Hartmann, which was published by VEB Fotokinoverlag Halle  (3rd edition, 1961).  The Pentacon camera referred to in the title of the book was the post-war 35mm Contax camera that was designed and manufactured in Dresden.  Unlike the pre-war version, this was a single-lens reflex camera with a built-in pentaprism.  This camera was initially referred to as the “Contax S” (although no cameras bore the “S” on the name plate).  That camera is described here.  Subsequent versions included the Contax D and E (see here).  Subsequently, following numerous legal challenges by the new Contax firm in West Germany, the manufacturers coined a new name for their Pentaprism Contax, and renamed the camera “Pentacon”  (see here). The text of this flyer states: “Panchromar Light filters Colour filters Ancilliary lenses Soft-Focus filters Lens hoods (shades) for the PRAKTICA LEHMANN & BALZER – Lommatzsch / Dresden District Firm with Government shares”		[planflyer_a.jpg]
The reverse side of the same flyer details the products available (translation from the German by the author of this website): Panchromar Light filters for Black & White Photography light yellow middle yellow yellow-green green orange light red dark red Infrared Infrablack blue ultra-violet I ultra-violet II* light neutral grey* middle neutral grey* dark neutral grey* * also for colour photography Panchromar Colour Filters for Colour Photography to correct blue or red colour casts and enable use of daylight film in artificial light and artificial light film in daylight. To correct blue casts RC 1.5 RC3 RC 6 RC 13 To correct red casts BC 1.5 BC 3 BC 6 BC 12 (The numbers after the letters indicate the conversion strength in Decamireds.) Panchromar-Ancilliary lenses for 5 cm lenses Close-up lens I   0.5 dioptre  (focussing down to 40 cm possible) Close-up lens II  1.0 dioptre  (focussing down to 34 cm possible) Close-up lens III 2.0 dioptre  (focussing down to 25 cm possible) Panchromar Soft-Focus filters for 5 cm lenses Soft-focus I   Light softening Soft-focus II Stronger, more obvious softening All light filters and colour filters are made from Jena optical dyed-in-the-mass glass (solid glass filters).  The glass is resistent to the sun’s rays and safe for use in the Tropics.  Request leaflets and operating instructions. Even though some filters are specified for 50mm lenses (for a 35mm camera), we must bear in mind that this flyer was probably produced in 1961.  We know that Panchromar filters in other sizes were subsequently manufactured.		[panflyer_b.jpg]

Some Panchromar filters still come with the instruction sheet that was probably originally enclosed with all their filters.  This is shown to the right.  Those who wish to study it in detail will get to a higher resolution copy by clicking on the side of the sheet that interests them. It would appear that by the time that this leaflet was produced (for inclusion with a filter for a Pentacon Six lens), one of the constant GDR government reorganisations and expropriations of private companies had resulted in the firm being renamed “VEB GLASTECHNIK LOMMATZSCH”.  We remind readers that “VEB” stands for “Volks Eigener Betrieb” (usually written “Volkseigener Betrieb”), which means, literally, “People’s Own Works”, a euphemism for State-owned, since they were subject to the control of the East German government and the communist party (which was known in the GDR as the “SED”). [58mmPan_bxs_01.jpg] Boxes of a selection of 58mm Panchromar filters suitable for the 80mm Tessar and  Biometar lenses (and other lenses that take 58mm filters, such as the Carl Zeiss Jena 55mm f/1.4 two-pin Pancolar lens designed for the Pentacon Super 35mm camera, which was manufactured between 1968 and 1972).

[panchroBA01s.jpg]

[panchroBA02s.jpg]

[58mmPan_fils.jpg]

On the left, view of the filters that came in these boxes.  It seems strange that with two of these filters, the front retaining ring is bright chrome, instead of being anodized black to prevent any possible risk of reflections.  There are reasons to believe that this particular set of filters was manufactured between about 1960 and 1962, and shortages of all sorts of materials were so severe under the communist system that old components could not be thrown away but had to be used.  It seems that with with the UV filter on the left and the orange filter on the right, we are witnessing one of the transitions in which old stock was used in the manufacture of newer products. The photograph on the right shows that the filter was supplied in a plastic hinged case, within its carboard box, with the instruction sheet that is reproduced above.

[58Pan_box_case.jpg]

[58mmPan_bxs_02.jpg]

The text on the top flap of these boxes helps with the dating of the manufacture of these filters.  Some of the boxes have “Made in Germany” while others have “Made in GDR”.  We have seen (here) that they key date for the commencement of the use of “GDR” and “DDR” in East Germany, instead of simply “Germany” was the building of the Berlin Wall, which started on 13th August 1961.  Again, old stock, even if it was just cardboard boxes, could not be thrown away, so some of these boxes have the old designation, even though all of these filters were probably manufactured at about the same time. The plastic filter case illustrated below came in a post-1961 box labelled “Made in GDR”, yet it has the old designation “Germany” – another example of old stock being used instead of being discarded. [58Pan_case.jpg]

We will conclude this section on Panchromar filters with one last picture, this time, of the box in which an 86mm Panchromar filter was supplied.  We can see that this is a UV filter, and the box states “Verlängerung: praktisch keine” – “Exposure extension: virtually none”. What surprises us is the nature of the box: the cover from a box for a smaller filter has been roughly cut out and pasted slightly off-centre on this blank cardboard box.  We do not wish to be unfairly critical of the hard-working people who lived in Eastern Germany: they did their best with what they had, but frequently suffered from shortages of the most basic things.  This box is illustrative of that sad state of affairs.

[86mmPan_box.jpg]

These filters were supplied in smart, wooden boxes.  The ones shown here were painted grey, although other boxes have been seen that are blue in colour (see here). Below we see a selection of these filters: [schott05.jpg]

[schott10.jpg]

This filter is labelled “Skylight”, which is a common name for the R1.5 filter that reduces blueness in the image through slight warming.  It is still popular and would probably be especially helpful for slides (reversal film) shot with Ektachrome film, which can tend towards blue.  We note that the little label included in the box says “o. Verl.”, short for “ohne Verlängerung”, which means “without lengthening [of exposure]”.  The box to its right has been placed upside down, to reveal the text of the label on its base.  We can see that it is a UV filter, and the designation “M86 × 1-W” shows the filter diameter and pitch, while the “W” after this presumably stands for “Weitwinkel”, which means “Wide-angle” – an indication that the front thread is wider, with a diameter of 95mm, to avoid vignetting when used on a wide-angle lens (essentially the two medium format Flektogons). [schott06.jpg]

With these two filters we see that a ticket and a label were included.  The rectangular ticket has the manufacturer’s name and certain other information.  See close-ups of both sides of the this ticket below.  The round label contains information specific to the filter in question.  The one on the left has a reference number followed by “gelb, mittel ca. 3×”, which means “mid yellow, [exposure factor] approx 3×”.  The one on the right again gives the manufacturer’s reference number, this time followed by “rot, hell ca. 3–5×”, which means “light red, [exposure factor approx 3–5×”.  This does remind us that when using such filters, it is advisable to carry out tests at different exposures in order to see the effect of using the filter, or to bracket one’s exposures (take a series of pictures on the metered value and either side of it). [schott07.jpg]

[schott_ticket_07.jpg]

The front of the ticket states “VEB Jenaer Glaswerk Schott & Gen., Jena   Betriebsteil Fotofilter   Jenaer Glas”, followed by a company logo.  The meaning of the text is “State-owned Schott & Co. Jena, Jena Glassworks.  Business section: photo filters, Jena Glass”. The back of the ticket gives the manufacturers reference number, the exposure factor and the colour, followed by “86 mm EW”, which gives us the rear thread diameter.  It is presumed that “EW” refers to "wide-angle", perhaps “Extrem Weitwinkel”, which means “extreme wide-angle”. Schott was and is a world-leading manufacturer of glass and glass products.  The Wikipedia article referred to above states that “During Germany's division, there were two independent companies: the VEB Jenaer Glaswerk at the historic site, which would later be integrated into the combine VEB Carl Zeiss Jena, and the glassworks in Mainz that traded under the name Jenaer Glaswerk Schott & Gen. After the close cooperation of the two glassworks in the first years following World War II had been cancelled by the GDR in 1953, a dispute arose over the use of company names and its logo, a square with a circle and the words Jena Glass with a superscript "er,". The two parties finally reached an agreement in 1981, which allowed the West German company to use the name "Schott" and the square with a circle, while the East German company was permitted to use the term "Jenaer Glass." After the fall of the inner German border in 1989, the company based in Mainz acquired the East German company in Jena.”

In the first three images here, a red Schott 86mm filter with 95mm front thread is mounted on a Carl Zeiss Jena 300mm f/4 Sonnar telephoto lens with the Pentacon Six mount.  Here we see the lens’s standard lens hood mounted directly onto the filter. [schott01.jpg]

This side view permits the shape of the filter mount to be appreciated more easily, also showing how the lens hood, which has a rear screw thread of 95mm, is screwed into it. [schott02.jpg]

By removing the lens hood for this picture, we are able to see the shape of the filter mount more clearly. [schott03.jpg]

Here is the lens hood as supplied with the 300mm Sonnar.  The thread on the shade itself is 95mm, and it is supplied with the adapter ring that can be seen here already mounted on the lens hood.  The ring states its front and rear thread dimensions. [86mm95adpt.jpg]

This manufacturer of photographic filters advertised in the book “Exakta Kleinbild-Fotografie” by Werner Wurst, published by VEB Fotokinoverlag Halle  (6th edition, 1961). The image shows an “old-fashioned” clip-on (not screw-in) filter that also is not front-threaded to receive a lens hood or other filter.  It shows a hinged plastic box for the filter, and an outer cardboard box. The text states: “A Sign for Quality All light filters for black & white and colour film, A-Z Colortester, Polarisationfilters, Ancilliary lenses and Soft-Focus filters” There is no indication of filter sizes, and Arnz may have concentrated principally on filters for lenses for 35mm cameras, which mostly had a smaller diameter.  However, in his “Praktisix Buch” (Fotokinoverlag, 1964), Dr W Gerhard Heyde recommends the “Colortester” from Arnz, Jena (p. 196), and some Arnz filters in sizes suitable for Pentacon Six lenses are still occasionally to be found. [arnzfils.jpg]    In the photograph on the left here, we can see two Arnz filters suitable for Pentacon Six lenses. The one on the left is a 67mm UV filter, suitable for the 120mm Biometar lens. The one on the right is a 86mm polarizing filter, suitable for any of the four Carl Zeiss Pentacon Six lens that take filters of this size.  It is in a rotating mount. Both filters are front-threaded, to receive further filters or a lens hood (although the use of more than one filter on wide-angle lenses is not generally advisable, as it can result in vignetting).  Note that the front thread of the polarizing filter is also 86mm, unlike the 86mm filters from Jenaer Glaswerk Schott und Genosse that are described above. Both filters are supplied in a very smart wooden box.  Neither filter bears any lettering, although the polarizing filter does have an index dot to aid in orientating it correctly. Writing in April 2023, Michael G from Germany writes, “I could confirm, that UV (Nr.100) also exists in M86/M95 version, just bought it on Ebay.” To the right we show a photograph of that filter, received from Michael.  Clicking on the image opens a larger copy of it.  “Ohne Verlängerung” on the label means “without lengthening [exposure]”, which is of course unnecessary with a UV filter.

The hinged plastic box in this illustration is similar to the one in which some Panchromar filters were supplied. [arnz.jpg] [Arnz_100_86_95s.jpg]

A polarizing filter in a rotating mount was manufactured by Carl Zeiss Jena for the standard Biometar lens (and also in a 49mm mount for lenses used on the 35mm Praktica cameras).  The 58mm version that is illustrated here was supplied in a beautifully-stitched custom leather case. The straight white lines on the front edge of the filter were designed to make it easier for the photographer to align the filter correctly, even without needing to look through the camera viewfinder.  Thus, the photographer could rotate the filter in front of his/her eye and note from the white lines the angle that gave the best effect, before screwing the filter onto the lens.  The knurled edges make rotating the filter easier, once it is mounted on the lens.

[czpolfiltr.jpg]