Thursday, 25 December 2014

Dufaycolor

Dufaycolor transparency, 1937
In my posts about making colour images from monochromatic separation negatives, I wrote about one early technological approach to capture colour in photography. Although advanced cameras were produced which could simultaneously expose three plates, the ability to capture a colour image in a single exposure was a highly desirable goal, and one which produced a number of different processes at the end of the 19th and the early 20th century. One of these was Dufaycolor, and the images illustrating this post come from my partner's family when I was given the opportunity to digitize the original photographs.

The Dufaycolor process was introduced as cine-film in 1932, followed by rollfilm for still cameras in 1935 when Ilford acquired an interest in the company. The Dufaycolor system was based on an earlier plate process, Louis Dufay's Dioptichrome plate from 1909, itself preceded by Diopticolore. This was one of many additive colour screen processes that were developed from the end of the 19th century, partly enabled by increases in spectral sensitivity which allowed photographic emulsions to capture a wider range of visible light. These colour processes all worked in essentially the same way: a photographic emulsion is exposed through a screen comprised of minute colour filters (using either a separate screen plate or as an integral plate containing both filter screen and emulsion), and then reversal processed to produce transparencies. The best known of these processes is the Lumière Autochrome, which used a mosaic of dyed potato starch grains coloured red-orange, green and violet. The grains had a tendency to form irregular clumps which gives Autochromes a Pontillist appearance. Most of the other screen processes used mechanically ruled lines, however, either in parallel (as were many of the early and crude attempts) or with the lines crossing at perpendicular angles, which is the case with the Dufaycolor system, where the screen or réseau comprises red lines interspersed with rows of green and blue rectangles. These lines, at 500 to the inch, are fine enough not to be visible by the naked eye, but would be evident when used for cine-film and projected, although many examples of Dufaycolor cine film I've found online are not of sufficient quality to resolve this detail. Dufaycolor, as the last additive screen-film process to appear on the market was durable and popular enough to survive into the late 1950s, although it was unable to compete with the technologically superior subtractive colour Kodachrome and Agfacolor, which essentially set the template for all future colour photographic processes.

Dufaycolor transparency c.1937
Using extension tubes gave enough magnification to create the image below, a detail of the dog which clearly shows the ruled screen. As the transparency above is about 6.5cm tall, the enlarged detail is roughly 5mm square, which demonstrates how fine the lines of the réseau are. This is around double the resolution of earlier screen processes, such as Joly plates, the first to be produced commercially, and the Dioptichrome plates that Dufaycolor itself had evolved from, and also finer than standard commercial printing today. Incidentally, when a point source of light is viewed through a Dufaycolor transparency, the réseau diffuses the light into a series of banded highlights, which may be one way of identifying the process in the absence of other information.

Macrophotograph of Dufaycolor image showing detail of the réseau
The transparencies had been kept in an original envelope. Although the reversal processing needed could have been accomplished by any competent lab or amateur, Dufaycolor films had a dedicated 'processing station' (it's unclear whether this service was included, "process paid", as part of the cost of the film), with the address on the envelope, although the envelope itself shows no evidence of how it had been returned to the customer, either being posted directly, or from a local lab.

Dufaycolor envelope
Dufaycolor transparency in mount
The transparencies were originally supplied in mounts; in the image above, the mount provides a degree of cropping to make the horizon more level, while silvering around the edge of the frame is quite evident, which appears as dark brownish marks on the transparency below. As the photographic emulsion is exposed through the film base and the réseau, the correct orientation is to view the transparency from the emulsion side. The image at the top of this post shows that the exposed emulsion surfaces have suffered more from silvering: it is apparent that the clearer portion of the photograph is due to another picture lying on top at an angle, perhaps for a number of years.

Dufaycolor transparency, 1937
The Dufaycolor transparencies proved to be too dense to scan, so instead I photographed them on a light box. There were two different sizes of transparency, 6x9cm and 6.5x11cm, which relate to 120 and 116 medium format rollfilms. The images all show a lack of sharpness  to a varying degree, which may be from focus problems, or film flatness. The film was rated 10 ISO, and, judging by the tilting horizon lines in many shots, these were all taken hand held, which would have meant slow shutter speeds and relatively wide aperture (by comparison, at the date these photographs were taken, Ilford had introduced the first HP film, at 160 ISO, and Selochrome was rated 100). Dufaycolor was faster than Autochrome, a version of which had been released in rollfilm format, but colour filters always reduce the amount of light reaching the emulsion (according to Colour Photography: The first hundred years 1840-1940, Dufaycolor had a transmission rate of 21%, compared to Autochrome's 7.5%, which meant that 92.5% of the light entering the camera when exposing an Autochrome plate was absorbed by the filter layer before reaching the photographic emulsion). Some of these screen processes struck a compromise between colour saturation and the speed of film or plate: the less intense the colours in the filter screen, the more light would be available to reach the emulsion.

Dufaycolor envelope (back)
Many of the images are underexposed and not very sharp - the back of the envelope has a series of abbreviations (rather in the manner of the stickers that used to come back with photos from Boots and other D&P establishments): on the image of the mounted transparency above, 'S.X.' is marked in the top right hand corner. Although the transparencies had been kept in one envelope, as there are two different sizes, and the Dufaycolor rollfilm came in rolls of six frames, the fifteen photographs must be from at least three rolls of film. Intriguingly, the shot below shows two cameras being held, one appears to be a box camera in a case, the other a folding camera - the white highlight being the brilliant finder rather than the lens. It is just conceivable that both cameras in the picture were also loaded with Dufaycolor and that all the transparencies in the envelope were shot simultaneously, on two occasions, one with all the family in Cornwall where they stayed in New Polzeath in summer 1937, the other possibly by the Thames, where the family had a house near Henley, which appears in some of the other photographs.

Dufaycolor transparency c.1937
In photographing the transparencies, I attempted to keep the colours as close to the original values from camera to screen, while bringing out more detail from the underexposed shots. The colours do have a distinct look quite unlike modern films, due to the dyes used in the process, but these colours have proved very durable.

Dufaycolor transparency 1937
Dufaycolor transparency c.1937
Dufaycolor transparency c.1937
Dufaycolor transparency c.1937

Sources/further reading:
Colour Photography: The first hundred years 1840-1940, Brian Coe, 1978
Dufaycolor on Photomemorabilia
Dufay entry on Camera-wiki 
Early colour photography PDF from the National Media Museum

Monday, 8 December 2014

127 Day - Winter 2014

Studio window, Baby Ikonta with Ilford Selochrome
One aspect of taking photographs on certain annual recurring days, such as the '127 Days', is that repetition can become an archive when photographing the same scenes as time (and the seasons) passes, such as the shot of Dagenham Brook below, which I had shot in July; in December last year, I took a walk along the same route I'd taken the year before. For yesterday's 127 Day I had one roll of Ilford Selochrome with a develop before date of January 1970 which I hadn't shot on this year's 127 Day in July. I also shot two rolls of Kodak Verichrome Pan in 828 format with a develop before date of August 1974 which I'd rolled with 127 backing paper, and similarly, a roll of 35mm Rollei ATO 2.1 Supergraphic. All films were shot with my Zeiss Ikon Ikonta 520/18 - otherwise known as the 'Baby Ikonta'. I shot half the roll of Selochrome around the house, which allowed me to make a couple of diptychs shooting through windows, and, although the skies briefly cleared, by the time I went out to take some more photographs, it was a typically grey December afternoon (the weather being one reason I tend not to shoot on 27th January, the other 1/27 in the calendar when written in the form used commonly in the US).

Dagenham Brook, Kodak Verichrome Pan
Both rolls of Verichrome Pan exhibited very pronounced texturing from the backing paper. The Ilford Selochrome also showed a trace of this effect, but having retained more sensitivity, with a denser negative this was much less apparent and only really showed up in shots which were underexposed. The lighting conditions weren't sympathetic to shooting the Verichrome Pan film with a slower rating than 50 EI which may have helped. The film also had a very strong curl which caused problems with film flatness: it seems this was enough to force back the camera's pressure plate in a number of shots.

Kodak Verichrome Pan, showing a lack of film flatness
The poor lighting conditions were less than ideal for using Rollei ATO 2.1, which has a nominal rating of 25 ISO, but performs better at lower exposure indexes, and, unlike July this year, I did not have a tripod with me for longer exposures (most of the shots illustrating this post were at fairly wide apertures and at shutter speeds of either 1/50th or 1/25th). The image below was the best shot from the roll of ATO; I attempted some shots at 1/10th, but the Baby Ikonta's shutter was beginning to stick at that speed.

Leyton Sign, Rollei ATO 2.1
All films were stand developed in Ilfotec LC29 for one hour, at 1:100, except for the ATO 2.1, for which I used a dilution of 1:200. As I was developing the first couple of rolls of film, the clouds began to break up again in time for the sun to set and I shot the second roll of Verichrome Pan.

Winter Afternoon, Kodak Verichrome Pan
Sunset, Kodak Verichrome Pan

Tuesday, 2 December 2014

Old Lenses

"Now, of course, the most important parts of cameras are lenses."
"Ooh no, you can't say that, old boy, you can't say that."
"Why not?"
"That's not grammatical. You should say lends. Lends. I lends, he lends, or he borrows, or he scrounges, that's you. You can't say lendses." 
"Yes you can, you don't understand me, the lens, the lens is in front of the camera and it is through this that the light gets to the plate or film."
"Sounds like a little dental outfit, doesn't it?"

Clapham & Dwyer, 'On Photography'

Not to be confused with Susan Sontag, the above exchange from a 1930s 78rpm record of a variety act works better aloud than being read on the screen, and, in titling this post 'Old Lenses', for some reason, I thought of them. In the post I wrote about the MPP Micro-Technical camera, I didn't put enough emphasis on one attraction of large format cameras: the ability to use a very great variety of lenses. As long as the lens can actually be mounted on the camera, which in practice means fitting to a lens board, the only considerations as to suitability are, firstly, bellows draw, whether the bellows can be extended (or retracted) enough to focus the lens and, secondly, the image circle the lens projects, whether this is wide enough to cover the film format and if it is large enough to also allow movements (a chief attraction in most large format camera designs itself).

When I bought my MPP Micro-Technical Mk VI camera, it came with a 150mm Schneider Kreuznach f4.5 Xenar lens. On the 4x5 inch format, a 'normal' angle of view, based on the diagonal measurement of the image sizes would be 150mm. However, the angle of view for a normal lens is not directly comparable with a 50mm lens on a 35mm camera (for example), as 4x5 has different, squarer, frame proportions and the 150mm lens sometimes felt a little wide for many shots (I also bought a wide angle 90mm Schneider Kreuznach Angulon lens, although I've rarely used it). Although I've been shooting large format for around four years, it does feel like I still have much to learn (more so than with other formats), and still making mistakes. Considering the options for longer focal length lenses, these can be very expensive, and while it would be ideal to use the best equipment available, an initial outlay of hundred of pounds in lenses that might not be used very often, although an investment, may not be the best way to start shooting large format. Close to the Xenar's 150mm focal length, I found a very cheap (under £40) f5.3 Zeiss Tessar 16.5cm lens in a dial-set Compur shutter, which I've used for many of the large format glass plate night shots (I've written elsewhere about my preference for dial-set shutters over the rim-set versions).

Carl Zeiss Tessar 16.5cm f5.3 lens
There isn't much to add about the Tessar lens here, except perhaps that it may be slightly lower in contrast to the Xenar due to being a pre-war uncoated lens. This may work better for situations such as in the image above, shot with Kodagraph Ortho Negative film, a high-contrast repro film (the Xenar, not a recent lens by any means, is a Tessar-type design, but my lens, from the 1950s, is at least coated, and perhaps better suited to colour work than an uncoated lens). Given the age of the Tessar lens (the serial numbers on the lens and shutter date it to 1926) and the focal length, it possibly came from a camera such as the Ica Lloyd or Nixe, a camera using 'postcard' format 122 rollfilm with an optional plate back.

Bausch & Lomb Rapid Rectilinear lens in Kodak Ball Bearing shutter
Kodak's 122 format was made for their No 3A Folding Pocket Kodak. The 122 rollfilm gave negatives of 3¼×5½ inches (8.25x14cm), a sufficient size when most photographic prints were made by contact printing. The No 3A Folding Pocket Kodak was provided with a number of lens/shutter combinations: I had one with a Bausch & Lomb Rapid Rectilinear lens in a Kodak Ball Bearing shutter, and had intended to convert the camera for (cropped) panoramic shots on medium format film. However, having languished in a drawer for a number of years, I decide to mount the lens and try it with the MPP camera. The Rapid Rectilinear lens design dates back to 1866; this one has a patent date of 'Jan 18 1910' on the shutter. The lens itself doesn't provide very much information: there's no serial number and no indication of focal length. The apertures are marked in U.S. stops: 4, 8, 16, 32, 64, 128. These equate to the standard f-stop system of f8, f11, and so on; the U.S. stop of 16 is the same as f16, which is useful to work out how the two systems match up (although U.S. stands for Universal System, it was not widely adopted, and went out of use around 1920). The ball bearing shutter has speeds of 1/25th, 1/50th, 1/100th and T and B settings. I tested the shutter speeds by making an audio recording and found that all speeds were the same, around 1/40th. Mounted on the MPP camera, the focal length of the lens appears to be around 180mm, although this would probably have been expressed in inches originally. As the Rapid Rectilinear lens is made from two sets of cemented symmetrical elements, I'd read somewhere that it should be convertible: both front and rear sets of lens elements are sufficiently well corrected to form an image alone, and this aspect of the lens I wanted to try for myself.

Bausch & Lomb Rapid Rectilinear lens with yellow filter
Bausch & Lomb Rapid Rectilinear lens - rear lens elements only
When shooting with the Rapid Rectilinear, there were a number of calculations to work out the exposures required. To begin with, I used an exposure index of 250 with the Fomapan 400 film and factored in a deep yellow filter for the first of the two images above; the US stops had to be converted; and with only the rear elements in the lower image, I also had to calculate the bellows factor, which I've written about in my last post on Distars and Proxars.

I also shot the same scene with the Xenar lens for comparison: the Xenar clearly is much better for edge to edge sharpness, and it is in the out of focus areas where the difference between the two lenses is clearest: the Rapid Rectilinear's characteristics are most noticeable in the long grass in the foreground. In both shots it's possible to discern the astigmatism in these out-of-focus parts, which the Rapid Rectilinear is not corrected for, especially in the second photograph, which was shot with just the rear lens elements at the widest aperture, which would have been equivalent to f16 at a focal length of around 360mm. This was also shot without the deep yellow filter, which reduces the contrast further. However, the Rapid Rectilinear is still good stopped down and large format is very forgiving at a relatively small scale of reproduction; in a large print it may be a different matter.

Left: Xenar; right: Rapid Rectilinear (rear elements only)
The images below, starting with a photograph using the 16.5cm Tessar, were all shot at smaller apertures. These were also shot on Fomapan 400, this time rated 320. I also used the deep yellow filter on the shot without the front lens elements, as the shutter's screw mount protrudes enough for the push-fit filter. With the ball bearing shutter only firing at around 1/40th, by necessity the exposure with just the rear elements of the Rapid Rectilinear was two seconds on the 'T' setting, allowing me to stop the aperture down to the equivalent of f64. As the clouds were moving away from the lens, rather than across the field of view, the length of exposure did not result in blurred clouds, but movement shows up in some of the trees.

Carl Zeiss Tessar 16.5cm lens with yellow filter
Bausch & Lomb Rapid Rectilinear lens with yellow filter
Bausch & Lomb Rapid Rectilinear lens - rear lens elements only with yellow filter
As the results show, these lenses do have their own character and quirks, and although many better lenses have been designed since the Rapid Rectilinear (and, indeed, the Tessar), and the results will not be as good, older lenses represent a possibility, if also a compromise, of cheaply expanding a range of focal lengths available (especially with convertible lenses) for view and large format cameras. 

Sources/further reading:
Through A Vintage Lens on the Rapid Rectilinear
Rapid Rectilinear on Camera-Wiki

Wednesday, 19 November 2014

Distars and Proxars

Ica Trona with Distar supplementary lens
Having achieved some good results recently with the Ica Trona, use of the camera's full 9x12cm frame size is limited by the number of plateholders with films sheathes I possess, and also limited to the few films manufactured in the 9x12cm size. Using a rollfilm back with the camera is convenient and means being able to shoot with any medium format film available. However, this leads to cropping the image, or, to put it another way, using the rollfilm back provides an image with a narrower angle of view. For most of the cameras I habitually use, I'm almost always happy shooting everything with the 'normal' focal length lens for the format and most of my cameras have fixed, non-interchangeable lenses. For cameras of a similar age or design to the Ica Trona, if the photographer wanted to use different focal length lenses, there were three approaches to achieve this: more expensive cameras did have interchangeable lenses, often with a bayonet mount, like the Voigtländer Bergheil (although this did require each lens to also have its own shutter); certain lenses were designed to be convertible or combinable, where front and rear lens elements were each sufficiently well corrected to be used individually either behind or in front of the shutter; and there were also supplementary lenses, to be used like filters, which change the focal length of the lens they are attached to. The Ica Trona has a Tessar lens, the design of which does not lend itself to being used as a convertible lens. When writing the blog post for the Trona, the Zeiss catalogues on Camera Eccentric were an invaluable resource; the 1933 catalogue includes a detailed section on Zeiss's supplementary lenses. Zeiss introduced the Distar first (seen in the 1927 catalogue, page 18), which increases the focal length of a lens; this was then added to by the Proxar, decreasing the focal length. The Proxar proved to be the more useful of the two, and was produced to fit many cameras for a number of decades. Other manufacturers also produced supplementary lenses.

Zeiss Proxar supplementary lens with case
The Distars and Proxars were initially made as push-fit accessories to fit onto a camera lens in the same manner as a filter, in a variety of sizes and different powers of magnification. Both have gold lettering inscribed around the mounts and the pre-war Proxars are brown, perhaps to be easily identifiable at a glance. On the Camera Eccentric website, the reproduced Zeiss lens catalogue from 1933 has both Distars and Proxars listed with a full description and tables for use (the 1929 catalogue also lists both, but the 1933 one has better illustrated examples). To quote from the catalogue:
The Distars are single lens components of small diverging power [...]. When placed in front of the camera lens they increase its focal length with corresponding increase of the camera extension. They thus add to the scope of camera lenses, especially those of an unsymmetrical type, since these, from their very nature, are only adapted for use on cameras with single extension in that their components are not corrected independently for use as long-focus lenses. In conjunction with the Tessars the Distars form wide-range sets of convertible lenses.
[...]
PROXARS are lenses of small converging power [...]. When attached in front of the camera lens, they produce an effect opposite to that of the Distars in that they shorten the focal length. Thus, Tessar F/4.5, f=13.5cm has its focal length reduced to about 13cm, 12.5cm, 12cm, or 11.5cm according to the converging effect of the Proxar selected. The range of uses of the Tessar is thereby widely extended in a twofold direction, viz:

For obtaining large figures of near objects [i.e. close focus images]
[...]
For taking wide-angle photographs at greater distances
Use of the Distar depends on the camera having sufficient bellows extension to achieve infinity focus, the greater the power of the Distar, the longer this distance needs to be, while the Proxars, to focus on infinity, need less bellows extension than the lens would normally require. This last fact is the reason for the Proxar's greater usefulness: on rigid-body cameras, it is usually impossible to reduce the lens-to-film plane distance, meaning that a Proxar could not be used for wide angle photographs ("at greater distances") as the lens would not focus on infinity, but it would still work as a close-up accessory, which Proxars were sold as, post war, no longer brown, as either push-fit accessories or with screw threads for mounting.


Ica Trona 210 with Proxar supplementary lens
I recently bought one of each: a Distar 3/III and a Proxar 2/III. According to the table in the Zeiss 1933 catalogue, the Distar 3 increases the equivalent focal length of the 13.5cm Tessar lens to 22.5cm, needing a bellows extension of 23cm to focus on infinity; the Proxar 2 reduces the equivalent focal length of the lens to 11cm, with infinity focus at 10.5cm. Reiterating what I've written earlier in this post, one reason I wanted the Proxar was to be able to use the rollfilm back with a 'normal' angle of view: a standard lens for the 6x9cm frame size is 105mm, so 11cm is very close.

The first set of test photographs I made with the Proxar were all out of focus, initially confusing as I'd used the ground glass screen to focus the images. When I shot a second set of test images, I realised where the problem arose: once the image was focussed, I discovered the tendency of the lens to slide forward on its runners when removing the back and replacing it with a plateholder, especially when pointing the camera downwards. On the Trona, the lens is designed to be pulled forwards to the infinity stop at 13.5cm, the focus knob is then used for closer focus and partly as a result of use, the lens moves with relative ease to the infinity stop itself (there is some friction, but perhaps the additional weight of the Proxar helps overcome the inertia). The Distar attachment provided different concerns: what's known as bellows effect, not mentioned in the Zeiss catalogue, which, for purposes of exposure and using the ground glass screen, results in a dimmer image. As the bellows are extended, moving the lens further away from the film plane, the relationship between aperture size and lens to film plane distance are changed significantly. To simplify the numbers for the purposes of giving an example, an aperture of f4 on a lens of 100mm focal length has a diameter of 25mm. If that lens is extended to a distance of 200mm from the film plane, that 25mm diameter of the f4 aperture is now one-eighth rather than one quarter, giving an effective aperture of f8, two stops difference in terms of exposure. Returning to the Distar 3 on my Tessar lens, as the focal length wasn't doubled, being nearer to an increase of half the focal length, for ease of calculation, I increased exposure by one stop (the same effect in reverse would be the case with the Proxar at infinity focus, but a decrease in focal length from 13.5cm to 11cm is not as dramatic, and although logically the image should be brighter, it is not different enough to compensate for in exposure).

The images below were all shot hand held: although for testing the qualities of the Distar and Proxar themselves it would have been better to use a tripod, I wanted to use the supplementary lenses in conditions that I have been using the Ica Trona camera. I push processed the 9x12cm Fomapan 100 to 200 in order to provide an extra stop in exposure, to use a smaller aperture at a faster shutter speed. The images are arranged from shortest focal length to longest.

Ica Trona 210 with Proxar supplementary lens, Fomapan 100 rated 200 EI
Ica Trona 210, Fomapan 100 rated 200 EI
Ica Trona 210 with Distar supplementary lens, Fomapan 100 rated 200 EI
When shooting the tests, I focused with the ground glass screen, then used the wire frame finder (the 'Iconometer') for framing once the screen had been replaced with a plateholder. The wire frame finder continues to give a fairly accurate framing as the angle of view changes relative to how near or far the finder is to the eye piece (this is also true with the front rise and cross movements). The top image of the three, taken with the Proxar shows some vignetting and also has a shadow at the left had edge due to the bellows on my camera being slightly deformed. In addition, the bellows on my Trona do not have the clips that many double extension folding plate cameras often possess to gather the bellows when the lens is closer to the film plane, i.e. at or near to infinity focus.

I also shot a sequence of images with the rollfilm back. Using Rollei RPX 400, I gained an extra stop in exposure from the push-processed Fomapan 100 sheet film. On the frames with and without the Proxar, I stopped the lens down further; with the increased focal length using the Distar, I chose a faster shutter speed to guard against camera shake. These provide a better example of the change in angle of view than the sheet film shots above as the framing is more consistent across all three photographs.

Ica Trona 210 with Proxar supplementary lens, Rollei RPX 400 in rollfilm back
Ica Trona 210, Rollei RPX 400 in rollfilm back
Ica Trona 210 with Distar supplementary lens, Rollei RPX 400 in rollfilm back
For comparison with the images from the rollfilm back, I also shot the same scene with the Zodel Baldalux: the 6x9cm frame size is the same and the focal length with the Proxar and the rollfilm back is close to the 105mm lens on the Baldalux - the reason for my interest in the supplementary lenses. Using the Proxar as a close up attachment rather than for wide angle, with the double extension bellows on the Trona, it is possible to focus very close to a subject. Bellows effect also applies, as with the Distar, and I also found focus difficult: even with the lens fully opened the image on the ground glass was still dim, and depth of field was extremely shallow. The photograph below was stopped down to f25 and by necessity, this was shot with a tripod (exposure was around 30 seconds). Although the shallow depth of field limits the use of such extreme close up photography, the scale of the mouse on the negative is actually larger than life size.

Ica Trona 210 with Proxar supplementary lens, Rollei RPX 400 in rollfilm back
The 1933 Zeiss catalogue contains an illustration (p30) showing six different views achievable from the same standpoint with a 15cm Tessar and Distars and Proxars of different powers with the caption, "Convert your ZEISS TESSAR at small cost into an objective of wide utility." Most of the remarks about the use of Distars and Proxars in the Zeiss catalogues relate directly to their use with the Tessar lens. The other designs listed under 'Universal Lenses' are Dagors and Protars, the first being symmetrical and the second composed of components of different focal lengths, but both can be used as convertible lenses. The introduction of the Distars and Proxars was intended to add this flexibility to the Tessar;
The Tessar is [...] pre-eminently the lens for hand cameras with single extension. In the course of recent years it has more and more taken the place of symmetrical and semi-symmetrical lenses in cameras with double extension, thanks to the introduction of our Distars and Proxars. These are single attachable front lenses whose curvatures are so computed as to increase or decrease the focal length of the objective within certain limits. They form, therefore, with the Tessar a very comprehensive convertible set, so that it can be used on hand cameras with single extension, and to a still greater extent on cameras with double extension, with a new range of applications. 
Zeiss lens catalogue, 1933

Ica Trona 210 with Proxar supplementary lens, Rollei RPX 400 in rollfilm back

Sources/further reading:
Zeiss Lenses Catalogue 1933
Supplementary lenses on Early Photography

Wednesday, 12 November 2014

Adox Silvermax 100/21

Adox Silvermax - left: old style labels/right: current label style
Earlier this year, out of curiosity, I bought, and shot, a roll of Adox Silvermax 21. Silvermax is relatively new film, introduced two years ago. That first roll had a label that was inkjet printed, suggestive of a small production run. It was not DX coded and the name Silvermax 21 referred to the film speed expressed in the DIN scale rather than ISO; more recently, the last couple of rolls I've bought were Silvermax 100, still with printed labels and without DX coding, but no longer printed by inkjet. It is currently available in 35mm and also Super 8 as Adox Pan-X Reverso. According to the data sheet, Silvermax is a mix of traditional cubic and t-grain crystals, in a single layer emulsion with enhanced silver content, hence the name.

Adox Silvermax latitude test contact sheet
The roll I'd shot earlier this year had been without any prior testing of the film, but I decided to return to it. As in some of the other film tests posted on this blog, I shot a roll (with an Olympus OM10) at a variety of exposure indexes to test the film's latitude. The contact sheet of this test is above. The first and second rows of six frames are rated, left to right, 12, 25, 50, 100, 200, 400. The third row was all shot at the box speed of 100 ISO. Incidentally, these negatives appeared low in contrast, and at first glance perhaps indicating underexposure, although these scanned well.The negatives also have a half-frame numbering system: rather than the more normal set of numbers in the film rebate of 1, 1A, 2, 2A and so on, there are two numbers per frame in a continuous series. I developed the film in RO9 One Shot (Rodinal) diluted 1:25 for 8 minutes at 20ºC. The contact print was made on Ilford Multigrade RC IV without a Multigrade filter.

Adox Silvermax at box speed developed in RO9 One Shot 1:25
I shot two series of images for the latitude test: one of a low contrast subject and one of high contrast, to compare how the film would perform under both conditions. The low contrast subject above was easy to scan without too much adjustment across the whole range of exposures, which would most likely hold true for darkroom printing. The negatives resulting from the high contrast subject were more indicative of the film's capabilities.

Adox Silvermax at EI 12 (three stops overexposed)
Adox Silvermax at EI 400 (two stops underexposed)
The two images above are exposures separated by six whole stops. The highlights in the image shot at 12 are not noticeably blocked out, while the shadows in the lower image, although thin, and the tonal range is more compressed, hold detail. In the first row of photographs shown on the contact sheet above, as a lower contrast subject, the difference between each is less. I pulled detail back from both extreme ends of the negatives in the scanning - the film has a clear base, which is designed to aid reversal processing, explicitly mentioned by Adox, but perhaps also to help scanning when developed as negatives. Adox claim 14 zones when developed with their own propriety Silvermax developer; it would appear that Rodinal or RO9 achieves something similar. On the data sheet for Silvermax, the curve's shoulder has a slow roll over, which, if I am interpreting it correctly, shows that, in the upper range, density builds more slowly as exposure increases, meaning that the highlights resist blocking out. Given the appearance of excellent latitude from the first test, exposing the film at a variety of ratings and changing the development time to suit should provide even better results. As a relatively new film, there is not a great deal of information on push or pull processing; indeed there are not development times for a wide amount of film developers, although for unlisted developers, Adox recommend using times for (the old version of) Agfa APX 100. From the first test roll that I shot, the film does appear to have relatively prominent grain for its speed, which shows in areas of continuous tone, such as skies like the image below, this may in part be due to the developer used (I haven't used the Silvermax developer for comparison) but also scanning rather than printing can exaggerate the appearance of grain.

Adox Silvermax at box speed, developed in RO9 One Shot 1:25
Although recommendations for push and pull processing are few, on the Massive Dev Chart, there is an entry for rating the film at 80 and semi-stand developing in Rodinal diluted 1:50 for 14 minutes with agitation every three minutes which I wanted to try. The negatives appeared lower in contrast than the roll shot and developed for the latitude test, which was partly the subject matter, but the results had a very pleasant tonality and scanned well. However, rating the film one-third of a stop less and compensating for this a little in the developing is hardly likely to show much of a difference to the standard time and dilution for Rodinal; it may have been a better comparison to shoot at box speed and try Rodinal at 1:50 to see any discernible difference to the dilution of 1:25.

Adox Silvermax at 80EI semi-stand developed in RO9 One Shot 1:50
As I have been using Ilfotec LC29 for developing at home, I also wanted to use this with Adox Silvermax and compare it to Rodinal/R09, although the data sheet for the film does not list the developer. For the first roll developed with Ilfotec LC29, I used one hour's stand development with a dilution of 1:100, as a fairly reliable method when faced with unknown variables.

Adox Silvermax at box speed, stand developed in Ilfotec LC29 1:100
Adox Silvermax at box speed, stand developed in Ilfotec LC29 1:100
Adox Silvermax at box speed, stand developed in Ilfotec LC29 1:100
Finally I also tried a one stop push, rating the film at 200. To develop this test, I looked at development times for the old version of Agfa APX 100 in Ilfotec LC29, and extrapolated for one stop of push processing, extending development time from 9 to 14 minutes at 20ºC in Ilfotec LC29, diluted 1:29. As the latitude test suggested, Silvermax coped perfectly well with a small amount of push processing.

Adox Silvermax rated 200, developed in Ilfotec LC29 1:29, 14m at 20ºC
Adox Silvermax rated 200, developed in Ilfotec LC29, 14m at 20ºC
Of the different development routines, Ilfotec LC29 appeared to provide better results in comparison to Silvermax in Rodinal, and on the limited tests I've done, I preferred the look when stand developed. The film test on the Massive Dev Chart shows Silvermax in Adox's Silvermax developer giving a little smoother grain appearance, a better proof may be in darkroom printing, the images in this post are all scanned from the negatives.

Adox Silvermax at box speed, Kodak Retina IIa, developed in RO9 One Shot 1:25
Adox Silvermax at box speed, Olympus OM10, developed in RO9 One Shot 1:25
Adox Silvermax at box speed, Olympus OM10, stand developed in Ilfotec LC29 1:100
Adox Silvermax at EI 200, Olympus OM10, developed in Ilfotec LC29 1:29 for 14 minutes