[rollei_list] Re: Rollei B&W filters blog
- From: Laurence Segil <ljsegil@xxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx
- Date: Mon, 1 Aug 2011 12:44:50 -0500
Thanks Carlos!
Larry
On Mon, Aug 1, 2011 at 9:08 AM, CarlosMFreaza <cmfreaza@xxxxxxxxx> wrote:
> 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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