Archived posting to the Leica Users Group, 2007/04/01
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Hi Didier, It is probable that there is not only the focus shift with aperture at work here but also sample variation. A friend of mine who was a renowned Sports pro, now retired, was allowed to hand choose his lenses by the importer. He would shoot with 25 or so and select the best for himself. The others were distributed to dealers(!). The differences between the best and worst of a batch of nominally identical lenses was considerable. I will leave the manufacturer out of it (it was not Leica) Frank On 1 Apr, 2007, at 21:44, Didier Ludwig wrote: > Jeffery > > It's the digital rangefinder cameras that allow to check the > focusing accuracy much better and quicker than with film > cameras. But the problem is old. I guess every RF lens always > had it's own tolerance and focusing behaviour. > > Past january I had received an email from a Robert White > employee who told me about the focus accuracy tests they > had made with some Epson R-D1. This test concerned focusing > an object at 1m distance with open apertures, but I'm quite > shure it would look similar with varied distances and aperture. > Let me quote him: > >> ...we also tested 6 different lenses in our shop, these lenses >> were a mixture >> of new and old and from several manufacturers. We were truly >> amazed by >> the different results. A number of well known manufacturers lenses >> faired >> poorly with regards to this problem. > > Didier > > > > >>> I suppose that I should set up some sort of contraption to find >>> the "soft >>> spots" on all of my lenses. It would have been a prohibitive pain >>> in the ass >>> without the M8. But the test I ran on the Nikkor tells me that if >>> I took a >>> portrait of someone at 5' and at f/5.6, her eyes would be out of >>> focus. >>> >>> For now, I think I need to decide which one of my 28's, 35's, and >>> 50's will >>> reside most of the time on my M8 and test them. >>> >>> Jeffery Smith >>> New Orleans, LA > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information