Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
08-11-2010, 02:52 PM   #16
Site Supporter
boriscleto's Avatar

Join Date: Dec 2009
Location: Liverpool, NY
Photos: Gallery
Posts: 12,869
This site has a good rundown of P-TTL flashes.

The Definitive Guide - Pentax P-TTL Flash Comparison

As well as more info about P-TTL

Further P-TTL Information - Pentax P-TTL Flash Comparison

08-11-2010, 04:00 PM   #17
Site Supporter
ChipB's Avatar

Join Date: Nov 2007
Location: Austin, TX area
Photos: Gallery | Albums
Posts: 1,641
QuoteOriginally posted by jonhock Quote
eccs19 & Chip B,
Do you guys set it in "auto" mode and if so do you use the green auto or the red auto?
Interesting, I just picked up the flash and it was set to "TTL Auto"?? Not sure why - I simply pick red or green depending on distance and f-stop (DOF) wanted.
08-11-2010, 05:34 PM   #18
Veteran Member
RioRico's Avatar

Join Date: Jun 2008
Location: Limbo, California
Posts: 11,264
QuoteOriginally posted by Lowell Goudge Quote
QuoteOriginally posted by Christopher M.W.T Quote
Is there any actual theoretical technical advantage of P-TTL over TTL?
The technical advantage comes with fill flash.
...
With P-TTL the cameras metering can evaluate the mix of natural light and flash from the pre flash and calculate the correct duration which should lead to correct exposure
Maybe it helps with fill, but it sucks with non-A-type lenses. All my previous TTL flash usage depended on it being actually TTL, Through-The-Lens, with the camera measuring the light that actually reaches the frame. P-TTL constantly over-exposes with non-A-type lenses, rendering the vast majority of my glass useless with flash. I see this as a MAJOR shortcoming of my K20D. My 1976 Argus-Chinon CR-3E SLR reads directly off the film; why can't newer cams read the sensor and adjust accordingly? This is one reason I hardly ever use my not-inexpensive AF360 flash. Good thing I prefer ambient light.
08-11-2010, 06:25 PM   #19
Veteran Member
mattdm's Avatar

Join Date: Feb 2007
Location: Boston, MA
Photos: Gallery
Posts: 2,964
QuoteOriginally posted by RioRico Quote
Maybe it helps with fill, but it sucks with non-A-type lenses. All my previous TTL flash usage depended on it being actually TTL, Through-The-Lens, with the camera measuring the light that actually reaches the frame. P-TTL constantly over-exposes with non-A-type lenses, rendering the vast majority of my glass useless with flash..
It's not that it's over-exposing because it's getting things wrong. It's over-exposing because it's just firing at full power because the camera sees that it can't set the lens aperture and then goes all dumb in response.

QuoteOriginally posted by RioRico Quote
I see this as a MAJOR shortcoming of my K20D. My 1976 Argus-Chinon CR-3E SLR reads directly off the film; why can't newer cams read the sensor and adjust accordingly? This is one reason I hardly ever use my not-inexpensive AF360 flash. Good thing I prefer ambient light.
Allegedly, the difference in reflectance of film and a digital sensor makes it problematic. Not sure I buy this, but that's the official line from pretty much all of the camera brands.

08-11-2010, 08:31 PM   #20
Site Supporter
jonhock's Avatar

Join Date: Oct 2009
Location: NorthEast Pennsylvania, USA
Photos: Gallery | Albums
Posts: 377
Original Poster
Alrighty then,

Thank you eccs19, I know that B&H has a Transend 4gb class 10 for $14.97 but now I believe I'll look around at the class 4sss and 6sss in an 8gb card.:ugh:
Green mode sounds good. Is that close to the green button?
I see a couple k10/20D users here. Have any of you had any experience with third-party battery grips?
You guys are helping me quite a bit, and I DO appreciate the input!

Last edited by jonhock; 08-11-2010 at 09:06 PM. Reason: another question please....
08-12-2010, 03:47 AM   #21
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,400
QuoteOriginally posted by RioRico Quote
Maybe it helps with fill, but it sucks with non-A-type lenses. All my previous TTL flash usage depended on it being actually TTL, Through-The-Lens, with the camera measuring the light that actually reaches the frame. P-TTL constantly over-exposes with non-A-type lenses, rendering the vast majority of my glass useless with flash. I see this as a MAJOR shortcoming of my K20D. My 1976 Argus-Chinon CR-3E SLR reads directly off the film; why can't newer cams read the sensor and adjust accordingly? This is one reason I hardly ever use my not-inexpensive AF360 flash. Good thing I prefer ambient light.
QuoteOriginally posted by mattdm Quote
It's not that it's over-exposing because it's getting things wrong. It's over-exposing because it's just firing at full power because the camera sees that it can't set the lens aperture and then goes all dumb in response.
exactly right, p-ttl needs to know the maximum aperture so that it can evaluate the flash intensity of the preflash when it meters wide open, so if there are no aperture contacts,it goes into manual mode. mowt _pttl flashes have no other option but full power
QuoteQuote:

Allegedly, the difference in reflectance of film and a digital sensor makes it problematic. Not sure I buy this, but that's the official line from pretty much all of the camera brands.
I don't buy it at all, the real issue is the additional sensor and input channel cost money.

TTL works as it should on my *istD, and the difference in reflectance is something the camera can calibrate out and not all films are the same so ttl would be more variable on film than with digital, since once calibrated you never change the sensor do you.
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!
camera, p-ttl, pentax, pentax help, photography, ttl
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Difference between TTL and P-TTL flash. rod_grant Pentax DSLR Discussion 35 12-25-2012 06:42 AM
P-TTL vs Canon E-TTL Taikonaut Troubleshooting and Beginner Help 2 04-22-2009 07:28 PM
P-TTL _AND_ C-TTL flashes? Zewrak Flashes, Lighting, and Studio 9 07-31-2008 03:36 AM
P-TTL VS TTL.... what is the difference to the average user? slip Pentax DSLR Discussion 16 01-17-2007 12:22 PM



All times are GMT -7. The time now is 07:41 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