K100d flash / AF-assist operation?


ZaphodB

Link Posted 24/06/2007 - 22:49
Hi, I recently posted in the Flash section of the forum that the AF Assist lamp on my new Sigma flash was not working (on a K100d). I've since noticed that the AF assist function of the K100d's pop-up flash also does not work in any mode except "Auto Pict". Now I never use Auto Pict, ever, so this isn't much use to me. I also know that the AF assist previously worked in Av mode. Does anyone have any experience of the AF Assist not working when it clearly should (I tried using it in a completely dark room where autofocus was clearly impossible)?

Edit: I just realised the obvious answer. A fairly disconcerting thought. The AF assist on the K100d used to work in all modes. I attached a Sigma on which the AF assist did not work, and now the AF assist on the K100d doesn't work... could the Sigma have messed up the K100d's flash? It's certainly possible for overly powerful flashes to completely fry the flash circuitry, so is it possible that a lesser fault could cause only partial damage?

If so this is fairly annoying since I will have to return the faulty Sigma and have the K100d fixed, and both were from different shops.

Thanks in advance for any thoughts.

George Lazarette

Link Posted 25/06/2007 - 00:51
I think it is unlikely that the Sigma has damaged the Pentax. Flashguns haven't used high voltages for years.

G
Keywords: Charming, polite, and generally agreeable.

ZaphodB

Link Posted 25/06/2007 - 01:01
OK it may not have been a high voltage, but if the Sigma did not cause the problem then it seems a very strange (and even more unlikely) coincidence that this problem would only develop during and after using the Sigma...

Surely either the Sigma caused the problem or the K100d caused the problem, one way or another something went wrong with that combination which has now altered the functionality of the camera.

George Lazarette

Link Posted 25/06/2007 - 08:02
ZaphodB wrote:
OK it may not have been a high voltage, but if the Sigma did not cause the problem then it seems a very strange (and even more unlikely) coincidence that this problem would only develop during and after using the Sigma...

Surely either the Sigma caused the problem or the K100d caused the problem, one way or another something went wrong with that combination which has now altered the functionality of the camera.

Or you are doing something wrong. These are complicated bits of kit, and it is all too easy to overlook or misunderstand something written in Japlish.

As you say, it's rather a coincidence that two things have gone wrong at once, but I should be surprised if the Sigma has caused a problem with the camera. If the flashgun were a twisted, smouldering, piece of molten plastic then perhaps the capacitor got shorted and destroyed everything, but the fact that in every other way everything seems to work suggests to me that the voltage is under control.

G
Keywords: Charming, polite, and generally agreeable.

ZaphodB

Link Posted 25/06/2007 - 10:40
Edit: I was wrong

stevejcoe

Link Posted 25/06/2007 - 11:15
First let me say that I have no experience of this camera or problem, but have you considered that somehow the cameras 'firmware' might have become corrupted. The fact that the AF assist works in auto pic mode would seem to indicate that the circuitry is still functional.

MattMatic

Link Posted 25/06/2007 - 11:27
I do seem to remember that focus assist does not work in AF.C mode, but only AF.S

Probably the Auto Picture mode only uses AF.S so that would explain why it works.

George is right... there are things hidden away in the "English" translation of the Japanese manual that catch the unwary!!
Page 125 of the K100D manual - it doesn't actually say that focus assist doesn't work in AF.C. You can only imply it because it says it works in AF.S mode

Matt
http://www.mattmatic.co.uk
(For gallery, tips and links)

ZaphodB

Link Posted 25/06/2007 - 11:43
You are right - the AF Assist only works in AF-S. I nearly always use AF-C and it didn't occur to me that I might have used AF-S on the occasions when I used the AF Assist lamp. Problem solved. Thanks for the help everyone, and George, sorry I doubted you

MattMatic

Link Posted 25/06/2007 - 11:55
Glad to help
Matt
http://www.mattmatic.co.uk
(For gallery, tips and links)
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