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09-16-2009, 01:02 PM   #1
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K-7 and wireless pTTL restrictions (and praise!)

I'm only going to link to this shot because it's heavily post processed and may be a hair on the risque side. I took this shot for an entry on the DPS forum's weekly assignment on the topic of the "Seven Deadly Sins".

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I've been using my AlienBees cybersyncs for about a year now, but a couple weeks ago I had some trouble with them and figured I needed a new battery in the transmitter. That completely slipped my mind until last night, late, when I went to set up my lights and I realized I was going to have to use the optical slave mode on the Met 48-AF and command it from my on camera flash. I'd never done that before, because when I bought the cybersyncs I was shooting a k-110d which couldn't drive the flash, and when I upgraded I never had any particular desire to learn.

It was pretty straightforward to set up, and when I got done, I realized I was pretty amazed by the results. Usually, it takes me quite a bit of tinkering with my lights on full manual to get the exposure I'm looking for if I don't do the math in my head with the guide number, but the wireless pTTL and the K-7's exposure control just... WORKED. Every shot was exposed just how I pictured it, with no tinkering, even though I had a blue gel over my onboard flash, and a red gel over the metz, in a tiny white shower stall, with the off camera flash bounced off the side, with all kinds of mirrors and reflective surfaces around. I didn't really notice how smoothly it went at the time, but looking over the results I was pretty blown away with how well it prevented anything from blowing out, how well it white balanced in weird lighting, and just how solidly it performed.

All that said, I didn't feel like digging out my manual last night, but does anyone know why it can't command the flash with a fully manual lens on the camera? I fell back to the FA-35mm, which was fine, but I had wanted the slightly wider view of my old Sears 28mm f/2.8. Is there a way to command the flash with an M series type lens?

09-16-2009, 02:34 PM   #2
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it won't command with a fully manual lens on the camera because P-TTL is only an option with A series or higher lenses.
09-16-2009, 02:44 PM   #3
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Yes, the camera needs to know what lens is on the body to control exposures and M.K and M42 lenses have no electrical contacts to transmit this. Knowing focal length isn't enough.

I've had to do the same a couple of times and surprised how nicely it works. Twice I left my bag of cords home on a remote shoot and had to resort to this setup. It's great to know we have a workable backup if the wireless transmitter system we have has an issue.
09-17-2009, 12:00 AM   #4
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Yup, I really like the K-7's flash system....nothing just WORKS, every time.

p-TTL is tied to the electronic exposure it won't work on a non-A fully manual lens.

Last edited by kittykat46; 09-17-2009 at 12:09 AM.
09-17-2009, 07:15 AM   #5
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Actually, you can make PTTL work with manual lenses...

You'll have to do three things:
- short all the contacts (including the recessed data pin, and it's not easy!)
- use a manual aperture lens (m42), or the partway mounted trick for P-K lenses (don't turn the lens fully into the mount so the aperture lever is not engaged - you can drill a second locking hole just for this!).
- ensure the selected aperture on the body is the smallest available (f/1.0 if all contacts are shortened), no matter what is the actual aperture currently set on the lens...

The body will believe that a manual f/1.0 A lens is on the mount... P-TTL will be enabled.
09-17-2009, 01:16 PM   #6
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WAY too much DIY for me to get P-TTL to work with manual. Instructions with words like "short the contacts" and "drill" give me nightmares when it comes to a $1299.99 camera!

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