Re: Horseman SW 612 & also 47mmXL

["Mitchell P. Warner" <indepth@xxxxxxxxxxxxxxxx>]

Don, 

	Good chance the stacked filters ARE causing the problem. You can check by
pointing the camera at  bright sky or a well lit wall and look thru from
each of the corners to the opposite corner. make sure the lens is perfectly
centered.  Look with lens open and stopped down.  If there is a vignette
you should be able to see it.  Then put the polarizer on and look. then the
center filter (alone) and look, then the combo.  Also.  I'm no techi' on
this but: The polarizer will not have an even effect over the whole width
of the lenses horizontal angle of view.  You can see this easily on a 35mm
with a standard lens and polaizer.  Look 90 degrees from the sun and rotate
the polarizer for maximum effect.  Then, while looking, turn slowly thorugh
90 degrees, either way.  The change in the polarizers effect on sky,
clouds, water will be obvious.  Your 47mm Apo-Grandagon has a horizontal
view of 110 degrees.  The difference of the angle between the center point
of the lens, when at maximum polarization, and the edge of the lens
horizontal view is so great (55 degrees) that the amount of polarization is
changed, possibly resulting in the light fall-off you see.  
Shooting at small f-stops will NOT lessen the polarizer fall-off effect. It
is the result of the angle of the sun relative to the plane of
polarization.  I have the same problem with a 72mmXL on a 5x7 format.  I
cannot use the polarizer without fall-off.  Using just the center filter
gives a much better image.  I suggest using a graduated ND filter such as
Lee or Cokin, to darken your sky.  Get the P size filter from Cokin, or the
4x4 from Lee, they work well. 
mpw



At 01:13 PM 6/23/99 -0500, you wrote:
>Ellis, yes.  I first mounted a 67mm Polarizing filter with a thin rim
>and over that the Heliopan 67 to 86mm Center filter.  Is the polarizer
>filter cutting some image off?
>Don
>=====================================================
>
>>>> Ellis Vener <evphoto@xxxxxxxxxx> 06/23 10:48 AM >>>
>Don:
>Wow! Something was definitely wrong with your camera. I have used the 47XL
>on my 4x5 Arca Swiss F-line camera and had full coverage (plus shift) on
>4x5 transparency. Did you use use a filter of some sort (either with or
>without the Center filter) on the lens?
>
>Ellis Vener
>
>DON WHIPPLE wrote:
>
>> I have a similar problem with the 4x5 Cambo Wide 47XL.
>> It is advertized by Calumet as a 4x5 with 15mm shifts.
>> I use a Horseman 612 back on it and a Helipan center filter.
>> Even shooting at f/32 the lens will not cover the 612 format
>> without shifting.  It barely covers 6x9.
>>
>> Don Whipple, AIA  <dwhipple@xxxxxxxxx>
>> ==============================================
>>
>> >>> Joel Seaman <jseaman@xxxxxxxxxxx> 06/23 5:00 AM >>>
>> Has anyone had experience with a Horseman SW612?  I have one with a
>> 45MM Apo-Grandagon lens that produces images with substantial light fall
>> off.
>> These images occur despite the use of the ridiculously priced and
>> overrated Rodenstock center filter!!!  The light fall off is not
>> consistently strong and seems to vary, perhaps in relatiion to the angle
>> of the camera relative to the sun. Any
>> experiences would be appreciated.  The Rodenstock filter has the added
>> benefit of producing "outstanding" examples of flare if the rays of the
>> sun even feign towards the camera .
>>
>> Joel
>
>
>
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