The Kodak 170 f/6.3 Anastigmat

KODAK’S 170mm (= 7ins) f6.3 Anastigmat lens seems to be a bit of a curiosity. At first I understood it to have been cannibalised from a 1920s or 30s Kodak Autographic 3A folder and pressed into service with my 1964 Crown Graphic. However, today I noticed a faint but definite bloom on the lens as it reflected the afternoon sky.

Lens coatings were not introduced until the late 1930s and this lens certainly seems older than that. Is the bloom the result of some natural oxidation or did someone like the lens so much they had it coated in later life? Or does it just happen to have been made in the two or three year gap between Kodak introducing their first coatings and bringing in their alphabetical lens date-codes?

It is clearly a four-element lens: the back group unscrews easily and quite obviously comprises more than one lens. It is also obvious at that point that there are a couple of lenses in front of the aperture diaphragm.

Shining a pen-light into the back group at a slight angle shows pairs of reflections, indicative of two lenses separated by an air space. The front group has similar reflections. So it seems that this Anastigmat is a four lens design, with the lenses all separated by an air space – a design known as a dialyte.

The pre-war Kodak anastigmats fell into three groups – triplets, Tessars and dialytes, so the result is in line with that, though no official details seem to be available anywhere for the 170/6.3.

Users’ views on dialytes seem to be rather mixed, some report amazing results, others have had versions that disappointed. The f7.7 203mm Kodak Ektar, which is a dialyte, is very well-regarded so hopefully this smaller sister will turn out to be equally good. Everything seems to be fine on the ground glass – but time and use will tell.

The main problem in using it, apart from the lack of filters, is that the Ilex shutter’s measured speeds topped out at about 1/37s (for both 1/50 and 1/100 on the dial). So with 100 ISO film in normal daylight I will already be looking at apertures of between f/22 and f/32. In daylight, ISO 400 will be out of the question.

About ambientimages

Paul Cowan is a former journalist turned full-time photographer.
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3 Responses to The Kodak 170 f/6.3 Anastigmat

  1. Jim Sandling says:

    Recieved the 170mm f/6.3 today..I also have ny curosities about it, however it is a Dialyte, si it will be very sharp,,,but probably low on contrast…should be very good on black & white with appropriate yellow or orange filteration…will probably have to make something up…but this is the first dialyet I believe I’ve see that is a 6.3….most have been 7.7. o. well, the negative will speak fo it…lets’ go shoot…Jim

    • Yup, that’s the proof of the pudding. If you post any shots taken with it onlne, I’d be grateful for a link to them.

      Do you know what size/type of filter to use with it? I haven’t got anything that small.

      • jim sandling says:

        looks like close to 30-31mm, according to my calipars..nothing to post yet, but I’ve been very pleased with a couple of other dialytes I have. I have learned to not discount the possibilities of the old glass…just because it is old, and not coated…on black & white they work very well when effective filtering is used. jim….

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