Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
02-03-2016, 08:03 AM   #91
Veteran Member
awaldram's Avatar

Join Date: May 2008
Location: Hampshire
Photos: Gallery
Posts: 720
QuoteOriginally posted by ScooterMaxi Jim Quote
I'd have to disagree with you, starbase. My upgrade path was *istD (followed by two midgrade Canons), K20D, K-01/K-30, K-3. Along the Pentax side of it, each body improved upon the latter significantly. Largest gap probably was from the K20D to the K-30. I could shoot college indoor sports with a f/5.6 (screwdrive) zoom with the K-30 and have a 30% keeper rate; it went up to about 70% with the K-3. Prior to that, keeper rate was so low I was far better off shooting MF.

Some of the SDM lenses are remarkably slow focusing, and that would include the 16-50. Not that the lens would be used much for action, but my understanding is that even kids playing move too fast for its focusing.

It seems that lens technology is the biggest obstacle, but the better body AF capabilities have somewhat closed the gap with the leaders. Someone with engineering expertise might want to chime in regarding the limitations of the Pentax mechanical mount design.
Mmmm more old wives tale than fact, lens design (turns end-end) effect speed and accuracy inversely rather than the technology driving it.

Unless you can get enough torque to steplessly drive the optica then you will be limited by gearing and glass weight, Only technology that comes close currently in mainstream use is ring Piezo motors but it possible the dc linear motor as patented by Pentax may be faster.


But torque effects tracking capability (ability to controls AF speed and direction quickly) rather than end to end speed and here piezo motors are significantly superior than in body motors.

Such, something like the slow end-end Sigma HSM is clearly superior than the fast Sigma ex DG 70-200


and even the long throw 50-135 is no slouch


and the da*16-50 is a better proposition than the wizzy 28-70



Last edited by awaldram; 02-03-2016 at 08:10 AM.
02-03-2016, 02:08 PM   #92
Pentaxian




Join Date: Jul 2009
Location: Tromsų, Norway
Photos: Albums
Posts: 955
QuoteOriginally posted by awaldram Quote
Unless you can get enough torque to steplessly drive the optica then you will be limited by gearing and glass weight, Only technology that comes close currently in mainstream use is ring Piezo motors but it possible the dc linear motor as patented by Pentax may be faster.
I just read Sony FE 35/1,4 has a non rotating mechanism and motor to focus the lens elements. That eliminates the power and energy going into a rotating motion. Its just pure push-pull linear motion.

LensRentals.com - Sony FE 35mm f/1.4 ZA Lens Teardown
02-03-2016, 02:40 PM   #93
Pentaxian
D1N0's Avatar

Join Date: May 2012
Location: ---
Photos: Gallery
Posts: 4,349
QuoteOriginally posted by awaldram Quote

and the da*16-50 is a better proposition than the wizzy 28-70
Pentax 28-70 Screw - YouTube
The FA 28-70 F4 is a budget lens. Very plasticy and as big ast the DA 18-55
02-03-2016, 07:50 PM   #94
New Member




Join Date: Jun 2010
Posts: 24
So I'm not sure if I understood this correctly, but from the very little information we have, it seems to be that this patent is about using an IR sensor to combat misfocus due to IR on the AF sensor. A possible way in which it could work, I speculate, is as follows. Please tell me where I am going wrong:
  • AF sensor sees both IR and visible light, and can therefore get stuck on finding maximum focus in infrared, which is typically slightly shifted from visible light due to dispersion.
  • In the patent, the camera has both an IR sensor and an AE sensor. From these two sensors the camera can estimate the ratio between IR and visible light. depending on the exact nature of the sensors used, it could do so specifically at the location of selected focus points.
  • IR always has a longer wavelength than visible light, therefore the best focus on IR light is always either before or behind the visible focus. Because the camera knows how much IR light there is compared to visible light from the AE and IR sensors, it can estimate which part of the focus curve to ignore, reducing the chance of achieving maximum focus in IR, and increasing the chance to achieve perfect focus on visible light.
If it works like that, the camera actually does not need much information about the lens for this to work accurately, only if the lens causes IR radiation to focus in front or behind of visible light. To speculate even further: if the IR sensor has some resolution, it might be able to figure that out from the IR sensor as well, such that no lens information is needed for this to increase AF precision.

Does this story sound plausible to anyone else? Or am I completely missing the mark?

02-04-2016, 03:46 AM   #95
Veteran Member
awaldram's Avatar

Join Date: May 2008
Location: Hampshire
Photos: Gallery
Posts: 720
QuoteOriginally posted by D1N0 Quote
The FA 28-70 F4 is a budget lens. Very plasticy and as big ast the DA 18-55
I think you missed the point of my post .

Its about Af technology vs af end-end speed vs AF tracking capability .. Nothing to do with lens IQ or target market. (though the 28-70 is the 16-45 of its day both are crxp build quality)

---------- Post added 04-02-16 at 10:46 AM ----------

QuoteOriginally posted by Simen1 Quote
I just read Sony FE 35/1,4 has a non rotating mechanism and motor to focus the lens elements. That eliminates the power and energy going into a rotating motion. Its just pure push-pull linear motion.

LensRentals.com - Sony FE 35mm f/1.4 ZA Lens Teardown
Now that has some serious potential..

Was just looking at the 70-200 DFA vids it looks like it may have a linear DC motor inside (I could hear no gearing during the af run) If so this would be new for Pentax and might be why it got pulled for further work.
02-04-2016, 07:28 AM   #96
JPT
Pentaxian




Join Date: Jan 2012
Location: Tokyo
Photos: Gallery
Posts: 1,252
Original Poster
They're at it again. A method to avoid flicker in live view.

https://translate.google.com/translate?hl=en&sl=ja&u=http://egami.blog.so-ne...04&prev=search

Not really related to autofocus, but equally not worth starting another thread over.
02-04-2016, 08:54 AM - 1 Like   #97
Pentaxian




Join Date: Apr 2007
Location: Romania
Posts: 9,336
Nice to see they're so busy.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
accuracy, af, body, camera, canon, d700, fa 28-70 f4, focus, images, improvement, ir, k10d, lens, lenses, light, low-light, nikon, patent, pentax, pentax news, pentax rumors, people, post, ricoh, sensor, star, telephoto
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Ricoh Patent: Improved DSLR AF system JPT Pentax DSLR Discussion 18 12-14-2015 04:20 PM
Ricoh smartphone docking camera patent D1N0 Pentax News and Rumors 17 11-18-2015 07:58 PM
Ricoh lens patent and new q sensor? Belnan Pentax News and Rumors 28 11-15-2014 06:45 AM
Ricoh patent for 24/2 APS-C lens robbiec Pentax News and Rumors 3 03-19-2014 09:40 AM
Does sigma HSM lens improve AF accuracy on the k5? telly0050 Pentax K-5 10 09-19-2012 08:19 AM



All times are GMT -7. The time now is 09:16 AM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top