Re: 4x5 field camera considerations - Reply

[Murray White <murphy@xxxxxxxxxxxxx>]

At 07:36 PM 12/14/96 +0000, Willem-Jan Markerink wrote:
>On 14 Dec 96 at 15:32, francisco sandoval wrote:
>
>> What difference will it make if you take your picture to the higher
>> F-stop that your lens allows you, so you will get higher details, is
>> that correct or not, am I wrong?????? 
>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?
        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. 
        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.
suggest *not* to stop 
>down too far, since diffraction ('bending' of light around the 
>aperture blades) is twice as bad with IR than with visible light, and 
>diffraction is one of the 'errors' that increase with small 
>apertures. 

        Which is why generally one does not work at optimum DOF but 1 more
stop below this which is why f8 with 35mm and medium format might then be
considered to be "optimum f stop". Then again for those that want isolation
and out of focus backgrounds, f8 is hardly optimum.:)
Murray White APPO MPA
murphy@xxxxxxxxxxxxx
wedding photographer/knife collector
LEAD ME NOT INTO TEMPTATION, I CAN FIND IT MYSELF.


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Topic No. 9