Don, Have been casually following this thread and finally have a question. Your last post included the comment;"a good bit of motion blur" even though all 22 frames were apparently shot "wide open". (f/2). Poor lighting and dull subject? Under the circumstances, it would seem difficult to assign blame to lens. I own an M 50 f/1.4 (also an A f/2 that came with a Super Program a few years ago)) and I'll try some shots at f/1.4. I'll use a heavy tripod, mlu and self timer. They'll be on film, so will take a little longer.
Jack --- Don Sanderson <[EMAIL PROTECTED]> wrote: > Thanks Godfrey, for going to all that work. > I think I've just reached the point that either the > A50, or my attitude, > needs an overhaul. > I am 100% certain that there is nothing wrong with > the lens. > Either my eyes, camera, attitude, or a combination > of them is > my problem. > I have had good shots with this lens on the D, but > they're > more the exception than the rule. > I went out after a rainstorm this morning with the D > wearing an > older (all metal) M50/2 I had just cleaned. > 22 shots, all wide open, and not a single seriously > mis-focused > one. (Good bit of motion blur though!) ;-( > Granted the smaller stop is a big help, but it's > just strange that > I can't do this with the brighter lens. > Oh well, ya gotta use what works. ;-) > > Thanks again for the tests. > > Don > > > -----Original Message----- > > From: Godfrey DiGiorgi [mailto:[EMAIL PROTECTED] > > Sent: Sunday, September 04, 2005 4:28 PM > > To: pentax-discuss@pdml.net > > Subject: Re: A50/1.4 versus M50/1.4, Comment > Please > > > > > > Don, > > > > Your tests with the 50mm lenses made me interested > to do a little > > testing, since I have F50/1.7, A50/1.4, A50/1.7, > and A50/2 lenses at > > present. I also have a K50/1.4 lens belonging to > another PDMLer which > > needed a quick test because the box it was shipped > in was so crushed > > in shipment to me (I'm handing this lens off to > yet another PDMLer.. > > yeah, complicated). > > > > I set up the tripod and DS body on my porch, used > a set of U-Haul > > moving boxes (for their printed matter) at about > 10' distance as a > > focusing target. My F50/1.7 has been the only > "problematic" Pentax > > lens on AF I've got ... it is the only one that > regularly doesn't > > focus smoothly and quickly ... so I started with > that. I set aperture > > wide open, set exposure via Av for the F and A > series lenses, set the > > same exposure manually for the K, and made two > exposures each: one > > focused manually by eye, one focused manually with > the 2x magnifier. > > I made an additional exposure with the F50 using > AF. I wasn't looking > > at OOF rendering or other characteristics in this > test, just near- > > center resolution/contrast and my ability to focus > the lenses > > accurately. > > > > The results: > > - For all lenses, a noticeable change in focus was > seen with the 2x > > magnifier when making a focus ring change of less > than 10 degrees. > > The F50 ring has the shortest turn and is the most > sensitive to > > change. The focus indicator light is illuminated > through 10-15 > > degrees turn of the focus ring with all of these > lenses, so for f/1.7 > > and f/1.4 lenses, it simply cannot be trusted at > wide open aperture. > > > > - F50/1.7 focused very poorly on AF with this > target. Out of 5 tries > > (set focus on my hand at 20 inches, let refocus on > the target), four > > were badly defocused, the fifth was passable only. > Focused manually, > > it produced the sharpest and clearest image. > > > > - Differences between the A50/1.4 and K50/1.4 are > small but > > noticeable. The A50 is sharper and more contrasty > wide open, lead to > > greater focusing accuracy with either eye or > magnifier. Both require > > some delicacy and patience in setting critical > focus... even a tiny > > movement of the focus ring can throw them off the > best setting. > > > > - The A50/1.7 was almost the same as the F50, > although *slightly* > > less contrasty. Perhaps they improved the lens > coatings between the A > > and F versions at tiny bit? The difference is > within my average focus > > error, it seems. The A50/2 was also surprising > close to the A50/1.7 > > on center too, although corners and edges fell off > more. > > > > - The use of the 2x magnifier helps, but it still > requires patience > > and care to set accurate focus with such a large > lens opening at this > > distance. Three out of the five sets showed no > significant difference > > in focusing by eye, vs with the magnifier, one was > better and one > > slightly worse. That says to me that it helps but > only to a limited > > degree, at least on this kind of target. > > > > I would certainly not refer to any of these lenses > as "unusable" at > > wide open aperture, however. More difficult to > focus, yes; not as > > desirable on certain types of subject matter, > maybe. But all of them > > turned a creditable quality image for wide open > work, as long as you > > make an effort to focus them accurately. > > > > > http://homepage.mac.com/godders/50mm-focus-snips.jpg > > > > Godfrey > > > > > > On Sep 3, 2005, at 3:13 PM, Don Sanderson wrote: > > > > > Thanks Rob, that's about what I found on these > when on the ist-D. > > > It's nice to have the bright finder but if it > won't focus for me > > > anyway it's no advantage. > > > The thing is I never had a problem wide open > with the M on film. > > > The _good_ thing is the FA50/1.7 seems to really > shine when used > > > on the digital. > > > Live and learn. I happy now and I'm sure someone > will enjoy the A. > > > > > > Don > > > > > > > > > > > >> -----Original Message----- > > >> From: Robert Whitehouse > [mailto:[EMAIL PROTECTED] > > >> Sent: Saturday, September 03, 2005 4:52 PM > > >> To: pentax-discuss@pdml.net > > >> Subject: RE: A50/1.4 versus M50/1.4, Comment > Please > > >> > > >> > > >> Don, > > >> > > >> I also own an "M" 50/1.4 and an "A" 50/1.4. > > >> > > >> I found that they are both just about un-usable > at f1.4 and I > > >> wouldn't try > > >> unless I am desperate. > > >> > > >> However, by the time you get to f2.8 they are > both fine and at > > >> f4.0 they are > > >> the sharpest lenses that I have - I know that I > can get great > > >> results with > > >> portraits at f4.0 to f5.6 on both film and > digital. > > >> > > >> Rob W > > >> > > >> > > >> > > >> -----Original Message----- > > >> From: Don Sanderson > [mailto:[EMAIL PROTECTED] > > >> Sent: 03 September 2005 02:44 > > >> To: PDML > > >> Subject: A50/1.4 versus M50/1.4, Comment Please > === message truncated === __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com
