In making a rangefinder cam for my Super Speed Graphic to use with this lens, I noticed a focusing issue. Wide open and focused at distances from 4 feet to infinity as seen on the ground glass, sharpest focus is easily seen through a 10X loupe. And it's near perfect for rangefinder coincidence with the cam I made.
I made several focus tests from 4 feet to infinity and each one required refocusing when the lens was stopped down to f/16 or smaller. A 20 x 30 inch landscape print from a 9.4 megapixel (about 750 ppi) scanned image on Ilford FP4+ taken at f/22 looks pretty good for this lens. Here's a 3 x 5 inch crop near the print's lower right hand corner:
I've been told that this lens may have been taken apart then reassembled with the elements in the wrong order or position. I know this lens ain't the sharpest 90mm around, but I don't think it would perform as well as it does if the lens groups/elements were in the wrong place. I think it does pretty good for a $90 investment in a wide angle lens for my 4x5.
Any ideas why this lens' focus shifts when stopped down?
Comments welcomed; I'm still learning about large format stuff.
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