Hi Chuck,
I should like to correct your statement about my Ross lens, though your
approach would appear to be correct. My lens has a maximum apperture of
f/16, 1/2-inch dia for an 8-in FL. This permits the use of the wheel-type
Waterhouse stop mechanism, with openings corresponding to f/16 through f/64.
It seems there was some sort of aperture-mechanism patent at that time that
led to the continuation of the Waterhouse stop approach.
The next generation of lens was probably classed as the "rapid rectilinear",
and, with apertures up to f/6.8, the openings were too large to be used with
a wheel. Somehow the patent squabble was overcome, and the modern internal
iris mechanism was used.
Jim Nichols
Tullahoma, TN USA
----- Original Message -----
From: "Chuck Norcutt" <chucknorcutt@xxxxxxxxxxxxxxxx>
To: "Olympus Camera Discussion" <olympus@xxxxxxxxxxxxxxxxx>
Sent: Monday, January 03, 2011 6:42 PM
Subject: Re: [OM] IMG: My Ross Lens Project
> From this <http://en.wikipedia.org/wiki/Ross_%28optics%29> it appears
> that Ross was fairly well along in lens design for the time. I suspect
> that the good performance shown by Jim's lens is due to long focal
> length (200mm), moderate max aperture (f/8) and especially much smaller
> image format than the lens was designed for. I tried looking up the
> history of apochromats but couldn't find when the first was designed.
> Actually, the trick was not the design effort but having glass of
> suitable index of refraction.
>
> Chuck Norcutt
>
>
> On 1/3/2011 2:48 PM, Jim Nichols wrote:
>> Jan,
>>
>> In reviewing all of the images, I found one that I liked in color. It is
>> linked below:
>> http://gallery.leica-users.org/v/OldNick/Mocking+Bird.jpg.html
>>
>> I have not searched it critically, but the colors and bokeh look pretty
>> good
>> for a 19th Century design.
>>
>> Jim Nichols
>> Tullahoma, TN USA
>> ----- Original Message -----
>> From: "Jan Steinman"<Jan@xxxxxxxxxxxxxx>
>> To:<olympus@xxxxxxxxxxxxxxxxx>
>> Sent: Monday, January 03, 2011 12:44 PM
>> Subject: Re: [OM] IMG: My Ross Lens Project
>>
>>
>>>> From: "Jim Nichols"<jhnichols@xxxxxxxxxxxxx>
>>>>
>>>> The best example is shown below, showing battle flags at a local
>>>> Confederate Cemetery. This was made at ISO 200, 1/400 at f/16, RAW,
>>>> converted to B&W using a PhotoPlugins converter.
>>>> http://gallery.leica-users.org/v/OldNick/Flags+BW.jpg.html
>>>
>>> That looks promising, but I'm wondering about colour, and why you chose
>>> to
>>> convert to B&W.
>>>
>>> Old lenses that predate colour film (certainly 1890) are generally not
>>> corrected for colour.
>>>
>>> On the colour images, do you see any evidence of fringing or CA? It
>>> would
>>> probably be most prevalent in the corners, where spectral dispersion
>>> would
>>> be expected to be greatest.
>>>
>>> ----------------
>>> Every now and then go away, have a little relaxation, for when you come
>>> back to your work your judgment will be surer. Go some distance away
>>> because then the work appears smaller and more of it can be taken in at
>>> a
>>> glance and a lack of harmony and proportion is more readily seen. --
>>> Leonardo da Vinci
>>> :::: Jan Steinman, EcoReality Co-op ::::
>>>
>>> --
>>> _________________________________________________________________
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>>>
>>>
>>
>>
> --
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>
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