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12-14-2009, 11:37 AM   #1
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P-TTL w/ manual lenses?

Hi,

Can a P-TTL flash still work with all the functionality if you are using a manual lens without an "A" setting? I Use some M42 lenses & shoot mostly in "M" mode. Will I get any benefit with say a Metz 58 AF-1 and these lenses?

Thanks!

George

12-14-2009, 12:10 PM   #2
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You really need an A lens for all the automatic functions to work, especially P-TTL. Then again, you may not always need the full set of features. If your lighting is not changing that quickly, you can get by using the flash's sensor or even manual mode, and adjust aperture and shutter speed yourself. My flash makes it fairly easy to adjust power manually. With some test shots I can dial it in pretty quick.
12-14-2009, 12:46 PM   #3
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Just put a little bit of foil over the aperture ring contact part between the lens and the camera body. Have not tried it yet:

https://www.pentaxforums.com/forums/pentax-dslr-discussion/80525-any-way-redu...re-lenses.html
12-14-2009, 01:07 PM   #4
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P-TTL will work with a Manual lens if the camera thinks it is an "A" type lens.

The camera will think the lens is an A type if you short circuit the A pin on the camera mount. I did it by removing the camera's mounting ring, covering the A pin with foil, and replacing the mounting ring (this is easy and low risk):


Others stick a small ball of foil over the pin, while others have deposited a small ball of solder on the pin.

Dave

12-14-2009, 01:09 PM   #5
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Eruditass, thanks for the link. All of that modding looks interesting but I'm kind of nervous to do any of that to my K20!

Has anyone out there tried these mods?

Thanks!

George
12-14-2009, 01:15 PM   #6
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QuoteOriginally posted by Eruditass Quote
Just put a little bit of foil over the aperture ring contact part between the lens and the camera body. Have not tried it yet:

https://www.pentaxforums.com/forums/pentax-dslr-discussion/80525-any-way-redu...re-lenses.html
You'll know that you are successful when F-- is replaced by F1.2 or some other numbers in the viewfinder.

I recommend turning the viewfinder f-stop as low as it'll go, then presetting the actual aperture using the lens' ring. When this is done, the camera will not try to close the aperture and will give the correct exposure.

If the lens you are using doesn't let you manually stop it down with the aperture ring (ie. a K mount lens), don't turn the lens all the way when you mount it. If this makes you nervous, you can drill a small indent in the lens' base to engage the locking pin.

Dave

PS removing and replacing the camera's mounting ring is pretty much idiot proof (at least for the K100D).

Last edited by newarts; 12-14-2009 at 01:22 PM.
12-14-2009, 01:28 PM   #7
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QuoteOriginally posted by newarts Quote

...PS removing and replacing the camera's mounting ring is pretty much idiot proof (at least for the K100D).
Dave,
Are you sure that this hack works on the K20D? I know that it does not work on my K10D.

Steve
12-14-2009, 01:35 PM   #8
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QuoteOriginally posted by stevebrot Quote
Dave,
Are you sure that this hack works on the K20D? I know that it does not work on my K10D.
It has to work as there is no other way for the A pin to work. The A pin is either an open or a closed, nothing more.

Thank you
Russell

12-14-2009, 02:09 PM   #9
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QuoteOriginally posted by stevebrot Quote
Dave,
Are you sure that this hack works on the K20D? I know that it does not work on my K10D.

Steve
Steve,

I've tried shorting out the A pin with a ball of foil. It is hard to do because the pin is recessed, plus the stupid foil ball shifts out of place easily when mounting the lens.

You'll know you are successful when the F-- indicator gets numbers; it may be the case that the "data" pin (farthest from the A pin) must also be shorted & this may not happen if the lens has a black base.

I recommend shorting all the pins with a sheet of foil on top of a ball of foil over the recessed A pin. If this works then the foil over the A pin under the mount trick will also work.

There is no risk to the camera in shorting all these pins. The camera is designed for that scenario because one of the defined A lenses shorts all the pins.

Dave
12-14-2009, 03:09 PM   #10
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QuoteOriginally posted by gsrokmix Quote
Eruditass, thanks for the link. All of that modding looks interesting but I'm kind of nervous to do any of that to my K20!

Has anyone out there tried these mods?

Thanks!

George
I believe you can just put a ball of foil with a little tape over it instead of unscrewing the mount.
12-14-2009, 04:17 PM   #11
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I didn't make it clear that the foil under the mount method of making all lenses A lenses is intended to be semi-permanent. It is easily reversible if you want, but I've never found a reason to reverse it.

Dave
10-04-2010, 10:45 PM   #12
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QuoteOriginally posted by newarts Quote
I didn't make it clear that the foil under the mount method of making all lenses A lenses is intended to be semi-permanent. It is easily reversible if you want, but I've never found a reason to reverse it.

Dave
After some testing, only shorting the A pin does not work with P-TTL. It gives Av/Tv, focus trap, etc. but the flash always fires at full power.

If I short the data pin with the A pin, P-TTL works and everything is great except my AF lenses are detected as MF, which sucks!

In short, if your lens shorts the rest of the pins with its base (any K-mount lens) all you need to do is short the A pin. If you are using a M42 lens, you need to make sure the base pins are shorted.

Last edited by Eruditass; 10-24-2010 at 04:34 PM.
04-17-2012, 02:25 AM   #13
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Hello,

Old thread I know but relevant to me, any input would be appreciated =)

I'm after a method to get less than 100% default output on a pttl connected 360 set to trailing curtain sync using M42. From what I gather, non-a lenses and PTTL don't play nicely; although I can get my 360 to pop at the end of the exposure, it only seems to pop at full power. The problem is Itypically take 500 shots for a focus stack and I can't have my flash flake out halfway through the run because it's used up its battery juice. So I need the trailing flash but only using a portion of its power to preserve that battery life. If I read this thread correctly, by shortening all those pins, I should at least be able to use either the PTTL controls of the flash itself (+-EV), or oncam settings to tone down its trailing pop, is that right? (for me the trailing pop is just a signal rather than useful lighting as I've got a firefly on its way that'll trigger 2 540s for me on manual settings)

Am I also correct that the other alternative to achieve a weaker default flash output would be to perform minor surgery on the unit, add a pot and circuit, and use this as an analog variable power mod? Has anyone tried this with a 360?

Many thanks for your time
04-17-2012, 04:33 AM   #14
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Hello,

Would I be right in thinking there maybe a 3rd option, purchase of a Metz 48 or 58, which can do a trailing sync output on non-a using a manual power setting? Ie I'd use this but on 1/64, thus preserving battery life?

Thank you very much
04-17-2012, 10:20 AM   #15
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Just wanted to thank Robin for testing this for me

QuoteQuote:
Wow, yeah this works. With the 58 AF-1 on M mode, you can indeed turn on REAR sync. And then dial in whatever power you need. I have tested this with a manual lens and the camera in M mode. I set things up for a 4 second exposure. The flash definitely goes off at THE END of the four seconds.
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