With the new 90-180 zoom being able to stop down to f/45, this gives us the ability to have the DOF we have always wanted when we attach a 2x converter. But the question is, do we really want to do this? If we use the diffraction formula 1390/f#, we find that the maximum lp/mm will only be 15. The actual lp/mm will be less due to the use of the converter, so f/90 for 6x7 film size is not so good. I guess that's why Pentax goes no smaller than f/45 on their lenses.

-- Steve Rasmussen (srasmuss@flash.net), March 14, 2002

Answers

Mark, I don't own it yet so I can't say. My post was more about the possibilities of the 90-180 or maybe its lack of them. Am still waiting for Delta to get a quantity of this zoom in.

-- Steve Rasmussen (srasmuss@flash.net), March 15, 2002.

Steve: Do you find that your new 90/180 lens is in the same league as the test proven 55/100 zoom in terms of overall performance? Flare, edge to edge, distortion, pin cushion, contrast,color rendition,etc I'll bet it's close. mark smith

-- mark smith (msmith@fayar.net), March 15, 2002.

Yes, it offers the DOF some of us want. But -IMHO, of course- the longer the lens the less I am concerned with depth of field. I am trying to envision myself using standard slower speed film and that zoom @ 150-180mm with TC & f90 and it seems pretty unlikely that I would. I would still -yes, an old complaint- like to see an f32 on the 75mm (the 75mm shift has it, but not the 4.5 or 2.8). Also, the first macro, the 135mm, probably should have gone beyond 32, and the new macro definitely should have; these lenses in particular lend themselves to uses where edge lpm is not always the biggest concern.

-- Carl Tower (cjtowerman@yahoo.com), March 17, 2002.