G'day Godfery, I don't work for NASA or JPL, so I don't think Pentax would send me 20 samples of each of the lenses I'm interested in. <g>
I've never tested any of my lenses. I use it and if I like the results I use it some more. But... These informal tests are the only thing I have to go on when I'm looking at buying a lens. 1) I can't afford to just buy it and hope it's OK. 2) I can't just walk into a camera store here and pick one up and try it. All of my Pentax glass had to be ordered in special. Besides if you read 20, informal lens tests and 15 report it's a good or bad, then I think it's gives some indication of it's performance. Dave S On Apr 6, 2005 10:56 AM, Godfrey DiGiorgi <[EMAIL PROTECTED]> wrote: > On Apr 5, 2005, at 7:16 PM, Rob Studdert wrote: > > > On 5 Apr 2005 at 19:07, Godfrey DiGiorgi wrote: > > > >> I learn by using my own lens, thank you. There's been nothing in this > >> thread to learn from. 40-odd messages worrying about a lens that is > >> well known to be a good performer, if not as good as the finest prime, > >> is just stupid. > > > > Ahh, it seems you may have missed the point again. Not all of us have > > to funds, > > facilities, opportunities to get hands on certain lenses, however if > > compared > > to a lens we do know then we have a reference. > > Relying upon a casual test as definitive is to me foolish, regardless > of how well your 'trusted reference lens' performs in this situation. > > When I worked for NASA/JPL and was helping to select lenses for a data > acquisition project, we'd have manufacturers send us 20 examples of > their best primes in the focal lengths required. I put them on the > light table and did resolution chart tests, and all the ones that > didn't hit the top numbers within 1 sigma were returned. There were > usually three of them that hit within 1 sigma of the same quality in > any batch of 20; that's normal variation. This goes for any brand of > mass-produced lenses. > > Godfrey > > > > And for the record I've owned > > many Pentax lenses in multiples over the years (for instance I only > > have 3 x > > A50/1.2 at the moment) and there is very little variation between > > samples in > > their primes. So using Pentax primes as reference is a pretty reliable > > way of > > long distance lens comparison. You are indeed fortunate if you can > > afford to > > buy and then test a lens. > > > > Big nose, > > > > > > Rob Studdert > > HURSTVILLE AUSTRALIA > > Tel +61-2-9554-4110 > > UTC(GMT) +10 Hours > > [EMAIL PROTECTED] > > http://members.ozemail.com.au/~distudio/publications/ > > Pentax user since 1986, PDMLer since 1998 > > > >
