[rollei_list] Re: Rollei B&W filters blog
- From: CarlosMFreaza <cmfreaza@xxxxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx
- Date: Mon, 1 Aug 2011 11:08:58 -0300
The Rollei Infrarot filter with optical compensation was only made for
the TLR from 1951 to 1981 (BI; from 1952 for BIII and from 1956 for
BII ). A IR filter with optical compensation does not make sense for a
SLR since, as you wrote, it's impossible to focus and to compose with
an IR filter, they are called "black" filters. Rollei TLR cameras
lenses never had HFT or multi-coating during the F&H and Rollei
Werke/F&H era regular production, the number and size of the lenses
elements did not justify this expensive process (at the beginning
specially); when the Rollei IR filter with optical compensation was
designed, Rollei TLR lenses already had the single layer coating.
I really think HFT lens multicoating can not affect the Rollei IR
optical compensation since regular MC processes are made to cancel
reflections from the main visible spectrum rays (400-700nm being about
550nm the main wavelenght chosen for single and multi layer lens
coating), at least they are not made for the infrared, beyond regular
wavelengths; if a lens has a coating and optical correction for IR
rays made from special material, it wouldn't be an issue for the
filter since they are in the same wavelength, but it would be
redundant. The way to know for sure if the HFT multicoating could
affect the Rollei TLR IR filter with optical compensation performance
would be to use it in a 2.8F Platin or newer TLR models with HFT MC, I
never read about a problem with the Rollei TLR IR filter and lens
multicoating and I'm pretty sure it couldn't happen.
The SL 66 camera has means to compensate the IR photography focus
shift in the focusing knob, it requires to focus wothout the IR filter
of course. The more significant lenses manufacturers produced and
produce expensive lenses for SLR cameras with optical correction for
five or six light wavelengths including IR, f.e. the Carl Zeiss
Sonnar 5.6/250 Superachromat for Rollei SL 66 and Hasselblad, I recall
a Nikon lens too, these lenses can be focus for IR directly without
focus shift compensation.-
Carlos
2011/8/1 Laurence Segil <ljsegil@xxxxxxx>:
> How well do the lenses with HFT coating pass IR wavelength light? Does the
> multicoating filter out the longer wavelengths? I am thinking here of the
> newer SL66 lenses in particular. Would the modern Rollei infrarot filter
> also serve for IR focus correction on the SL66? It seems to me that if it
> does so on a TLR, then the same ought to be true on the SLR if focus is
> achieved prior to placement of the filter. I have not found it possible to
> view any image on the ground glass of the SL66 (a Maxwell screen on my
> camera) with the IR filter in place, it is simply too dark to compose or
> focus (or even imagine what the lens might be pointed at). All of the
> collective expertise of the forum is appreciated.
> Best,
> Larry
>
> On Mon, Aug 1, 2011 at 12:44 AM, hari ho <hariho@xxxxxxxxxxxxxxx> wrote:
>>
>> Thanks Carlos.
>>
>> Hari
>>
>>
>>
>>
>> On 30/07/2011, at 7:21 PM, CarlosMFreaza wrote:
>>
>>> 2011/7/30 hari ho <hariho@xxxxxxxxxxxxxxx>:
>>>>
>>>> .... How can I tell if my Infrarot filter is post-1951? The markings on
>>>> the front says
>>>> "FRANKE & HEIDECKE GERMANY Rollei - Infrarot" in black with the
>>>> Rollei
>>>> 'R' logo in red.
>>>
>>> According W D Emanuel book on the Rolleiflex, if your filter has the
>>> "R", it is provided with the IR optical compensation. The red for the
>>> "R" could indicate your filter is from the earlier '50s.
>>> Carlos
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