REGARDING THE DIFFRACTION PROBLEMS AT SMALL FSTOPS : From what I have read and found via experience to be pretty true, is that diffraction limit of a good designed lens is roughtly 1600/f-stop. this means that at F-16 with a really good lens, you can still resolve up to approx 100 lines/mm which is definately very sharp, even is small formats like 35mm film or Pentax DSLRs. Even F22 could go about 70 lpmm and F32 50 lpmm which is not great but not completely horrible either. jco
-----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of DagT Sent: Tuesday, March 11, 2008 6:59 PM To: Pentax-Discuss Mail List Subject: Re: GREAT "general purpose" Zoom for the Pentax DSLRS? Well, nothing is very sharp with f:22 and K10D as diffraction is dominant, but most things are sharp at f:11. My problems wtih the lens were at f:4-f:8. Apart from that I agree that the mechanics of the A24-50 is very good and that it is smaller than DA*16-50. DagT Den 11. mars. 2008 kl. 18.55 skrev J. C. O'Connell: > that's good to know but are you talking much sharper > at F11-F22? I cant see how there would be a big > difference in that range, the A24-50 is really good > in that range on digital size sensor. The A24-50 is > also much smaller and lighter tha the 16-50 > isnt it? That matters to me when the camera is hanging > on my neck for long periods... > jco > > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf > Of DagT > Sent: Tuesday, March 11, 2008 12:21 PM > To: Pentax-Discuss Mail List > Subject: Re: GREAT "general purpose" Zoom for the Pentax DSLRS? > > > I tried the A version on K10D this summer. I´ve had it since the mid > 80s and it has been great with film, but compared to my primes in that > range it wasn´t not sharp enough for my use on K10D. My DA*16-50 is > much better. > > DagT > > Den 11. mars. 2008 kl. 04.22 skrev J. C. O'Connell: > >> Did you have the A version or the F version? I have had both and my A >> version is better than the F which I sold. Dont forget, I am talking >> about >> near >> range >> usage and at small fstops like 11-22 because the flash is powerful >> enough >> to allow those stops even at iso 200. I have no idea if its any good >> at >> infinity >> or anywhere near wide open, but if used like I am using it, its damn >> nice, >> not too expensive, and good build quality too.( I ususally dont like >> most >> A lenses in terms of build, but this one aint bad.) >> jco >> >> -----Original Message----- >> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf >> Of Adam >> Maas >> Sent: Monday, March 10, 2008 10:56 PM >> To: Pentax-Discuss Mail List >> Subject: Re: GREAT "general purpose" Zoom for the Pentax DSLRS? >> >> >> Tried one out at one point. It was alright, but not any better than >> the >> 18-55 DA in its range, larger, heavier, harder to manual focus due >> to lack >> of contrast wide open at 24mm. Wasn't much impressed with it on >> digital. Of >> course, I may have had a bad sample. >> >> -Adam >> >> On 3/10/08, Walter Hamler <[EMAIL PROTECTED]> wrote: >>> Never seen that particular lens. I had a 35~105 years ago that I >>> really liked except it was pretty heavy. My biggest problem is at >>> my >>> age the AF is almost a requirement anymore :-) >>> >>> Walt >>> >>> >>> On 3/10/08, J. C. O'Connell <[EMAIL PROTECTED]> wrote: >>>> I have been using for about a month now the SMC PENTAX-A 24-50/4.0 >>>> Zoom almost exclusively ( mostly product photos for ebay on > >>> tabletop ) on my *istDS DSLR. Its a two ring zoom so you never > >>> get >>> any annoying "zoom creep" and it holds focus perfectly > when >>> zooming. The F4 speed is a little slow but the lens is so > >>> contrasty >>> that its easy to focus at 50mm ( I use a split image > screen - >>> third >>> party model - in my *istDS ). Anyway, after you > figure in the >>> 1.5X >>> lens factor you are left with a 35mm SLR > equiv of 36mm to 75mm >>> which is a very versatile "super normal" > lens. This model is >>> extremely contrasty, great color saturation, > and freedom from >>> flaring. It works beautifully for tabletop > product photography. I >>> have never needed wider or longer, as it > has a pretty decent >>> magnification at 50mm and min focus. The constant > aperture (F4 >>> thru >>> the zoom range) is great when using manual full > power flash >>> like I >>> like to do. > >>>> Anyway, if you do a lot of ebay or similar product photography for >>>> web, >>>> I recommend this lens very highly. Much more versitile than a >>>> prime or macro 50mm with the 24m capability. >>>> >>>> I must add I have never used the stock 18-55mm that was sold >>>> with the camera, but I doubt it can match this lens, let alone >>>> beat it. Maybe it can? Anyone ever compared the two in the 24-50mm >>>> range? >>>> >>>> jco >>>> >>>> > > -- > PDML Pentax-Discuss Mail List > PDML@pdml.net > http://pdml.net/mailman/listinfo/pdml_pdml.net > to UNSUBSCRIBE from the PDML, please visit the link directly above and > follow the directions. > > > -- > PDML Pentax-Discuss Mail List > PDML@pdml.net > http://pdml.net/mailman/listinfo/pdml_pdml.net > to UNSUBSCRIBE from the PDML, please visit the link directly above > and follow the directions. -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions. -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
