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More tests with the TTH Cooke Anastigmat
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PostPosted: Thu Sep 20, 2007 4:58 am    Post subject: More tests with the TTH Cooke Anastigmat Reply with quote

Having fixed the lens permanently and made the lens hood, I did some more testing, this time at f/8, first under low contrast conditions and then in sunshine. The lens has some cleaning scratches on the back element near the edges, and this probably causes some extra flare when shooting wide open. Stopped down to f/8, none of this flare is evident anymore. The back element is also very, very slightly damaged at the center, which may or may not have some effect on the IQ, but anyway even with this effect the IQ seems to be very good.

Most of my lenses longer than 105 mm show some red-green CA in OOF areas in the Cathedral shots. This CA is quite negligible with the Cooke at the full f/4.5 aperture and even less at f/8. Here is one of the "standard" shots:



Of course, only quite extreme CA would be visible on this down-sampled copy, but you cannot find much even by closely examining the full-size copy at http://galactinus.net/vilva/retro/cooke3_files/ca8130.jpg .

Here is a very minimally sharpened crop of another photo:



There is no purple fringing on the watch knob, and quite small details on the watch face are clearly discernible.

More photos in sunshine at http://galactinus.net/vilva/retro/eos350d_cooke3.html .

I took a similar series of photos on a cloudy day, shooting at ISO 400 so there is some noise. Here is a crop:



and a down-sampled example:



More cloudy day photos at http://galactinus.net/vilva/retro/eos350d_cooke2.html .

Looking at these photos, I just wonder how much difference any modern lens would make on any decent sized print. Photos taken with the last version of 135 mm Elmarit may have a tad more micro contrast, but there is also slightly more OOF CA and a slightly larger proportion of the photos are a bit out of focus - making small adjustments is much easier with the bellows.

Veijo


PostPosted: Thu Sep 20, 2007 5:15 am    Post subject: Reply with quote

Extraordinary results from such an unlikely source. Thanks


PostPosted: Thu Sep 20, 2007 8:05 am    Post subject: Reply with quote

These results confirm the first impression of great quality.
In fact the Cooke triplet optical scheme is the base from which the Sonnar scheme was developed, and the Sonnar is one of the two schemes (the other is the Gauss) upon which most if not all the medium tele lenses of today are still based.
So, again, the advances in technology during one century may have regarded mostly the materials and the precision of the building and the mechanism, but optically speaking, the foundation of the tele lenses of today lies still in the Cooke triplet.


PostPosted: Thu Sep 20, 2007 8:54 am    Post subject: Reply with quote

katzer wrote:
I think I am asking a question that many other are asking:
Where did you find this lens? (we want to hear the story;))


From "photography:vintage lenses" of the UK eBay, but similar lenses can be extracted from old LF reflex cameras, which often are otherwise useless (except possibly for decorative purposes.) The lens was cheap, but adding the rest of the necessary components (the bellows and two sets of extension tubes, two types of epoxy) raised the total price (incl. P&P) to more than 100 Euros, which is still quite reasonable in view of the results obtained. Of course, the bellows assembly can be used to mount other non-focusing lenses (longer than 100 mm) fixed to their own M42 extension tubes.

Veijo