Taylor Hobson Cooke Anastigmat 12.5cm f2.5: Shorter Extension

e6filmuser

This time, I used only the A7R full frame so there is no crop factor to complicate aperture/DOF. I found a way of temporarily mounting the lens ca 10mm closer to the sensor than in the previous experiment, 35mm rather than 45mm. This would get the lens closer to its design registration distance, which I believe to be a bit shorter than for NEX lenses. This gave a FOV ca 10mm wide (previously 8mm).

Unlike the previous session, I had bright sunlight to help with framing and focusing. I wanted to use f11 but this gave no images with useful DOF. So I took some at f16. Even with this, the shots of the pink, candyfloss-like Arcyria were mostly OOF.

This image is of a rather concave surface with crowded Trichia spore sacs on it. Those nearest the lens have matured, split open and expanded, showing fine detail. I took two non-consecutive shots which make a reasonable crosseye stereo pair (slightly cropped at right side).

For those who would say "why bother to do this with an old, legacy film lens" I say "why not?". I suspect it is a 16mm film lens.

Harold

e6filmuser

As has been pointed out to me elsewhere, I have muddled the focal length with that of another macro lens. This one is 12.5mm not 12.5cm.

Harold

puzzledpaul

e6filmuser wrote: »

For those who would say "why bother to do this with an old, legacy film lens" I say "why not?".

Well, I for one wouldn't say 'why bother ... ' in such circumstances.
The journey is often just as interesting - if not more so - than reaching the destination imo.

In the days when I used to do more macro, such experimenting was quite a frequent occurrence ...

pp

e6filmuser

puzzledpaul wrote: »

In the days when I used to do more macro, such experimenting was quite a frequent occurrence ...

Here is a setup I used quite successfully, before I could afford the lenses I use now:

Kiron 28-70mm Zoom reversed:

On 110mm extension at f11 (nominal) and at focal length 70mm, it gave a field of view 3mm wide at 28mm and 10mm wide at 70mm focal lengths. The working distances under this configuration were 45mm at 28mm and 65mm at 70mm. If I remember correctly, the two focal lengths had the same focus.

Harold

GOLDENORFE

any noticable differences in distorsion/softening compared to other lens ?

e6filmuser

Phil,

(I don't see how to quote in the new format).

I have not yet given the lens much to do. At the higher magnification, I thought it might be a bit soft. The slightly lower magnification is more encouraging. I need to do some direct comparisons with my HM 40.

The subject matter does not offer much scope for checking distortion .

So far, it looks like a worthwhile lens to carry for the A7R when I am on a trip specialising in using ultra wide angle and wide angle lenses, the reason for purchase of the camera. I could then shoot any unmissable macros.

As value for money, not my first concern, at < £6 it has to be a winner. (Add £25 or so for adapters).

Harold

e6filmuser

Some thoughts on the lens:

I was, so far as I can establish, one of a line of lenses for the top quality 16mm cine cameras of the day. It was based on a Cooke Triplet design, to be found in other lenses. There was no focusing, this relying on hyperfocal distance, such that the choice of aperture was the only option. Any lens designed for such use, in my opinion, would be optimised for medium to small apertures. Hyperfocal focusing is not relevent to macro. The lens would not have been intended for close work, let alone macro, but this does not mean it will not perform well.

A general point about small lenses is that making them to high specification is much more affordable than the ones with large elements.

Harold