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I am new to 4x5, I am looking at a caltar 90mm 1:6.8 ll-n. I will be shooting so me architectural work and will make full use of the movements. So, is there anyo ne who has a feel for my potential need of a cf? Also maybe you have a reccomend ation for some rich literature covering all these alien issues I've bought into. Thanks
A 90mm is not that wide of a lens for 4X5. I do not believe a center filter is needed. Test the lens and if you feel one is needed then buy the filter. Jeff
I am not sure the f/6.8 version of this lens needs a center weighted filter (cwf ) as the image circle isn't as large as the i.c. for the f/4.5 version. I use us e a Heliopan C.W.F. with my 90mm f/4.5 Caltar Iunder 2 cirmumstances: 1.) Using extr emes of rise/fall or shift or both and 2.) Using it on the 6x17cm ( 2.25 x 6.75 inch) V-pan camera. i use the Heliopan (the o.45ND version) rather than th e Calumet or Rodenstock filter as the quality is just as high and the cost is significantly lower.
This lens has light falloff typical of wide angles. The coverage is about 2/3 stop down at the top of the frame (2 in. from center), about 1 stop down at the side (2.5 in. from center) and about 1 1/3 stop down in the corners. The center filter is designed to reduce the light on the optical axis to give even illumination across the entire frame. This is important in some applications (architectural, for one). Again, this is typical of wide angles, not just the Caltar. The wider, the worse it is. Try a few shots and see if its a problem for you, and then decide. If you get serious with architectural photography, you are going to get very intimate with wide angle lenses!