Armin,
Like the Apo-Ronars that you mention the G-Clarons are optimised to work at 1:1. The 150mm at 1:1 has an image circle of 385mm making it suitable for 10x8 whilst at Infinity the image circle is 189mm and only suitable for 4x5. Schneider's description is as follows:
"For a tabletop or macro shot, the G-Claron offers apochromatic correction, is flat field in design, and features a 64? field angle.
"6-Element, 4-Group
"Design optimised for close working distance.
"Apochromatic Flat Field Lens."
I hope that this is of some help ... WG
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