I dont agree - focal lengths should be geometrically evenly spaced and your chart shows an exponential curve and it should be a linear curve ( A line actually, no curve ). I say the gap/difference between 14mm and 20mm is very large and even on your curve, you can see its a big ol' leap from one to the other. A 14mm lens covers approx 64% more area than a 20mm lens, or conversely, a 20mm lens only covers 61% of the area of a 14mm lens. This is a fairly large difference visually, and would be marginal to me on the wide end because you cant afford to be doing any cropping on the wide end when the 20mm is just a little too long for the job.
Regarding prime lens spacing or steps, what works best is a gemetric progression of the focal lengths, like 10mm, 20mm, 40mm, 80mm, 160mm, etc. and how close you want to space them up to you but the progression constant should be the same number as you go up the scale in focal length. What I have settled on over the years and I find works well for me is a constant of approx 1.2X from prime lens to lens. This works well because each lens change gives you square root of 2 difference in coverage area, and every two lens changes gives you a twice the difference in coverage area. For a more limited number of lenses, 1.4X can be used with each lens change resulting in twice the area of coverage but the difference is quite large and when the longer lens just misses, you end up having to do a lot of cropping which is bad on 35mm/APS digital. jco -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Godfrey DiGiorgi Sent: Sunday, March 04, 2007 2:27 PM To: Pentax-Discuss Mail List Subject: Re: beauty shot: Pentax K10D On Mar 4, 2007, at 9:50 AM, Jack Davis wrote: > Have one..love it! <LOL> > I was putting you on as a way of salving my stinging jealously. I figured as much. ;-) As you can see from this graph http://homepage.mac.com/godders/FoVs-Pentax-DSLR.jpg the spacings are wide but nicely distributed. Just how I like them. I much more commonly want something between 21-35 mm than between 14-21 mm. That's where the FA20-35 comes in handy. G -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
