Re: 4x5 field camera considerations - Reply

["Willem-Jan Markerink" <w.j.markerink@xxxxx>]

On 16 Dec 96 at 6:59, Murray White wrote:

> >With 35mm camera's the golden rule is to close aperture 2-3 stops
> >from the highest opening (best performance of the lens), 
>
>         Willem- this seems a bit confusing. What is highest opening? Is it
> not preferable to speak in terms of widest and smallest aperature. Does
> highest mean smallest opening, largest # ie f22 or because you use the term
> close aperature, do you mean highest to mean widest, ie f2?

Sorry, I ment largest aperture....;-))
(ie low F-number)

>         If highest and smallest are equal then you are not closing the
> aperature but rather opening it. If highest is widest aperature, then the
> faster the lens is, the wider the optimum aperature would be. ie a f 1.8
> lens stopped down 2 stops f 5.6 (approx) yet the minimum aperature will
> probably be f16. 

Nah, most lenses go down to at least f22 or f32.

>         Perhaps I am incorrect but I believe the optimum aperature is 1 stop
> open from the minimum aperature of the lens. This will work with all formats
> I believe. You large format users could correct me on this.

Sorry, never heard of that rule....8-))
The 2-3 stops closing from largest aperture almost always results an
aperture in the middle of the range, which almost never equals just
1 stop opening from smallest aperture (high F-number).

I'll just have to buy a true APO lens to overcome my focus 
problem....unless Canon introduces a CF-option to get IR-focus 
correction within AF, a la Konica Hexar. 
I have vented this opinion many times to Canon rep's high 
up....who knows what future will bring for us IR-nuts....;-))

 
--
Bye,

       _/      _/       _/_/_/_/_/       _/_/_/_/_/
     _/  _/  _/               _/       _/  _/  _/
     _/  _/ illem    _/     _/ an    _/  _/  _/ arkerink
                     _/_/_/  



      The desire to understand 
is sometimes far less intelligent than
     the inability to understand


<w.j.markerink@xxxxx>
[note: 'a-one' & 'en-el'!]

------------------------------

Topic No. 10