Re: [Leica] Re: 35/1.4 ASPH vs Noct

["Henning J. Wulff" <henningw@archiphoto.com>]

At 1:10 AM -0800 3/20/00, The Beals wrote:
>Horst,
>   With all returned respect, Mr. Gilcrest's logic seems to be supported by
>basic photographic principles.  Look at an EV chart and tell me how a
>Noctilux at 1.0 with a 1/50 shutter speed is any faster than a 35mm Summilux
>at 1.4 with a shutter of 1/30.  Don't they both register an EV of 6, with
>film speed being constant?  Shutter speed and sharpness are affected by
>focal length.  The combination of focal length and outfit weight also affect
>EV's.  Longer focal lengths exaggerate subtle camera movement, particularly
>as shutter speeds decrease in handheld situations.  This generally mandates
>higher shutter speeds for longer focal lengths and allows slower speeds for
>shorter focal lengths.  Weight of the outfit can fatigue the photographer,
>further increasing the likelihood of camera movement.  (The Gilcrest article
>compared a 35mm Summilux-M to a Noctilux.  I don't know how much of a
>difference exists between the 35/1.4 ASPH and the Noct).  Finally, field of
>view, not accounting for perspective of course, can be compensated by moving
>closer to the subject (which we should be doing more of anyway, right?).
>   I don't think the original posting of this thread can be easily brushed
>aside by "don't compare different focal lengths".  I introduced Dick
>Gilcrest's article as support for the original poster's question.

Your reasoning doesn't work.

If one moves closer to compensate for the wider field of view, and the
magnification of the subject becomes the same again, the same shutter speed
limitation rules again. This means that if you use 1/30sec with the
Noctilux, you would also need 1.30sec with the Summilux at the same
magnification. The reduction in useable shutter speeds only works if you
take advantage of the lower magnification of the shorter focal length lens.

Ignoring the mass of the camera/lens combo, the camera will be subjected to
the same angular movement that is the cause of (stationary) image blur
during slow shutter speed shots no matter the focal length. To what degree
that blur is recorded on film depends on  the magnification, which
increases with focal length and decreasing camera to subject distance. If
you offset the focal length difference by moving closer, thus maintaining
magnification, you will also have the same image blur.

   *            Henning J. Wulff
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