Will phase focusing go the way of the dinosaur?
in [Digital Cameras]
|
Prev: Historical Center at night
Next: Forget Dpreview's B.S., "diplomatic language" NEX 16mm lens is not good
From: James Nagler on 7 Jun 2010 04:49 On 07 Jun 2010 06:30:16 GMT, rfischer(a)sonic.net (Ray Fischer) wrote: >James Nagler <jnagler(a)spamproofed.net> wrote: >> rfischer(a)sonic.net (Ray Fischer) wrote: >>>RichA <rander3127(a)gmail.com> wrote: >>>>Forget for the moment the benefits of going away from phase focusing, >>>>such as much lower cost going to contrast focusing. Phase's main >>>>important claim to fame is speed. But that is diminishing, or >>>>contrast is improving. The main problem with phase focusing is the >>>>constant problems with back or front focusing with various lenses, >>>>doesn't matter what brand of camera. This is a pain, one that >>>>contrast focusing apparently does not have or if it does, the >>>>incidence is very small. Most decent DSLR's now come with >>>>compensation features for this, but who wants to have to go though the >>>>elimination process for each lens they own and how often has this >>>>compensation not even been enough, or consistent? >>> >>>And how many contrast-detection focusing systems can track moving >>>objects at 10 frames per second? >> >>If I need 10 frames per second then I put my camera in 30 or 60 frames per >>second video mode. Contrast focusing seems to track moving subjects just >>fine in video mode. > >And after all, focusing doesn't have to be as accurate with a 2MP camera. > Where on earth did you get that stupid and ignorant idea? Inventing things as you go along again just because you think it sounds plausible in that pea-brain of yours? (Just more misguided and misinformed DSLR-Troll's inane justifications no doubt.) I have a 2.1MP Fuji Finepix from long ago. It has some of the sharpest and clearest images I've ever seen from any camera. Resolving all details to individual pixels in every shot. 8x10 prints from it are the norm. It has to focus just as accurately on that very small sensor as it does on newer and larger ones with more pixels. It has a pixel density of 9.0-MP/cm^2. That's almost twice the pixel density (smaller photosites) than a Canon EOS 550D with 5.4-MP/cm^2 density. So what you are saying is: the focusing for a Canon EOS 550D, an 18MP, $1000 camera (today's price, body only), must be less accurate than that of a 2.1 MP, $149 (10 year old price), P&S camera because 550D's photosites are almost twice as large.
From: James Nagler on 7 Jun 2010 05:00 On Mon, 7 Jun 2010 08:09:12 +0100, "David J Taylor" <david-taylor(a)blueyonder.co.uk.invalid> wrote: >"RichA" <rander3127(a)gmail.com> wrote in message >news:edf0060b-5c66-46b6-a6d7-73c66719150c(a)g19g2000yqc.googlegroups.com... >> Forget for the moment the benefits of going away from phase focusing, >> such as much lower cost going to contrast focusing. Phase's main >> important claim to fame is speed. But that is diminishing, or >> contrast is improving. The main problem with phase focusing is the >> constant problems with back or front focusing with various lenses, >> doesn't matter what brand of camera. This is a pain, one that >> contrast focusing apparently does not have or if it does, the >> incidence is very small. Most decent DSLR's now come with >> compensation features for this, but who wants to have to go though the >> elimination process for each lens they own and how often has this >> compensation not even been enough, or consistent? > >You appear to forget that phase-focusing provides an instantaneous and >continuous measurement not only of the direction of the focus error, but >its magnitude as well, so that the camera knows which direction to move >the lens, and by exactly how much to move it. One lens move. Focus done. > >Contrast focus, by comparison, takes time to evaluate how much in focus an >image is, moves the lens in an arbitrary direction, evaluates the focus >once again, has a 50% chance of finding the focus is worse so has to move >the lens in the other direction, has to evaluate the focus again, move the >lens, etc. etc., until the focus is worse again, so it's moved past the >point of best focus, and finally has to move the lens back to /about/ the >correct focus. You appear to forget that some contrast focusing cameras are just as fast as phase focusing cameras today. Your desperate diatribe to justify phase-focusing sounds good in theory but doesn't hold up to reality. Catch up with this decade.
From: SMS on 7 Jun 2010 07:16 On 06/06/10 1:04 PM, RichA wrote: > Forget for the moment the benefits of going away from phase focusing, > such as much lower cost going to contrast focusing. Phase's main > important claim to fame is speed. But that is diminishing, or > contrast is improving. Still a long way off in terms of speed. Compare a D-SLR in contrast-detect AF mode (live view on) with phase detect AF (live view off). If you need fast AF and/or a high frame rate then you can't get by with contrast-detect. The real question is if there will be any more P&S cameras that include contrast detect AF. I only know of one (a Ricoh model) that ever existed. The main problem with phase focusing is the > constant problems with back or front focusing with various lenses, > doesn't matter what brand of camera. Not really. Both Canon and Nikon have minimized this problem through firmware tweaks (at least with their own lenses, maybe it exists to a larger degree with third party lenses). Some people still complain about the Nikon AF system, whose slowness caused so many professional journalists to move to Canon (film D-SLRs) back in the 1990's and never go back (that and the fluorite lenses) but in D-SLRs Nikon has caught up, and in some cases surpassed Canon in AF performance.
From: whisky-dave on 7 Jun 2010 08:28 "GMAN" <Winniethepooh(a)100acrewoods.org> wrote in message news:feVOn.196202$ot7.172634(a)en-nntp-16.dc1.easynews.com... > In article > <7055b134-9c54-4649-b6d4-cb3b3edf4826(a)q36g2000prg.googlegroups.com>, > Twibil <nowayjose6(a)gmail.com> wrote: >>On Jun 6, 1:04=A0pm, RichA <rander3...(a)gmail.com> wrote: >> >>"Will phase focusing go the way of the dinosaur?" >> >>You mean "will phase focusing eventually evolve into birds and remain >>very much on the scene for the forseeable future?" >> >>Seems unlikely. > There wasn't any T Rex's left after the great extinction to evolve into > the > chicken!!! So how did KFC evolve from KFT.Rex ?
From: Stuffed Crust on 7 Jun 2010 09:38
In rec.photo.digital.slr-systems James Nagler <jnagler(a)spamproofed.net> wrote: >>>If I need 10 frames per second then I put my camera in 30 or 60 frames per >>>second video mode. Contrast focusing seems to track moving subjects just >>>fine in video mode. >> >>And after all, focusing doesn't have to be as accurate with a 2MP camera. > > Where on earth did you get that stupid and ignorant idea? Inventing things > as you go along again just because you think it sounds plausible in that > pea-brain of yours? (Just more misguided and misinformed DSLR-Troll's inane > justifications no doubt.) Full HD video is 1920x1080, which equates to 2.4MP, considerably less than the 12MP or whatever that the camera does in still mode. - Solomon -- Solomon Peachy pizza at shaftnet dot org Melbourne, FL ^^ (mail/jabber/gtalk) ^^ Quidquid latine dictum sit, altum viditur. |