Here are some test photographs taken with the combination of the Opticron Classic IF2 fieldscope and the Nikon Coolpix 4500.The lampost you are viewing is the farthest away, 2nd from the right in the first photograph. The focal lengths of the individual photos are from the first lamp photograph on the left. Conditions overcast,Photographs not enhanced. Size of eyepiece 20WW
7.85mm, 10.7mm, 13.8mm, 18.2mm, 23.1mm, 26.4mm, 29.9mm, and 32.0mm.
You will see that vignetting disappears at the focal length of 18.2mm but the vignetting in the three photos before it are to my mind of an acceptable level and could be cropped and still have a reasonable sized photograph



 

   7.85mm             10.7mm

  
13.8mm          18.2mm

  
23.1mm             26.4mm

  
29.9mm                32.0mm
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