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02-07-2011, 04:26 AM   #1
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P-TTL and A-series lenses on 645D?

Does anyone here have experience with P-TTL flashes (the 360, 540 or the ring flash) on manual focus lenses for the 645D?

I'd be very grateful for any observations you can share.

02-09-2011, 10:16 PM   #2
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I have the AF 540 FGZ flash. The book says that it can be used on the 645, 645N and 645N II. I would expect that the 645D would also be supported. The book says that the 645 N II (the latest 645) - the 645D should have similar specs, and might even support P-TTL, although TTL is as good IMHO)

P-TTL Mode is not available.

TTL Mode:
  • Leading Curtain sync
  • Trailing Curtain sync
  • Slow-speed sync
  • Auto switch to X xync speed when flash is charged
  • Flash ready display in finder
  • Auto Check display
  • AF spot beam

Auto mode:
  • Leading curtain sync
  • Slow speed sync
  • Auto switching to X-sync speed when flash is charged
  • Flash ready display in finder
  • Slave flash

Manual flash is the same as Auto, but also can activate the AF spot beam, and activate the spot beam without flash.

I hope this is a help.
02-10-2011, 06:38 AM   #3
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QuoteOriginally posted by Canada_Rockies Quote
P-TTL Mode is not available.
Thanks for taking the time to collate that info, Canada_Rockies. My worries was along the lines of what happened to flash compatibility in K-mount with the introduction of the K-series DSLRs. I specifically bought the AF-160FC ring flash for use with the A*200/4 macro, only to find that TTL metering works great on *istD but not on K-7.

Pentax could very well have chosen to drop TTL support from 645D the same way. However I got the opportunity to borrow a 645FA 120/4 macro to compare with my old 645A 120/4 since I posted the question. What I find is that exposure is correct with 645D + AF-160FC.

See attached image of a piece of non-reflective cotton fabric, taken at ISO 100 and a working distance of 22 cm. The histograms are screendumps from LightRoom. At this range, the flash output is too strong until f/8, matching the specs cited at Pentax USA's website as "range: 0.18-2m at f/8 and ISO 100".

What the image does not show, however, is a difference in Auto white balance selection. With the FA, the camera selected the same WB for all shots (5450K). With the A, the WB varied among shots with up to 700 K, in the range of 5450-6150 K.
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02-10-2011, 11:43 AM   #4
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You're welcome to the info. I received an infinite amount of help from others when I joined this forum having purchased a K10d, and knowing nothing about the quirks of the digital world. The P-TTL/no TTL came in with my K10d, as far as I know. That made me replace my perfectly good AF 500 FTZ because it was only usable in Manual mode on the K10. I now have the AF 540 FGZ, and it works in P-TTL, Auto and Manual just fine. Pretty pricey swap just because Pentax changed the specs. I cannot complain about Pentax too much, though. The lenses still work fine in manual exposure, even the screw mount versions, and the green button is almost as good as auto exposure. Compare that to Canon's history, or Minolta/Maxxum. Nikon has been a little better, but only on their high price cameras where they allow limited functionality with older mounts.

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