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Digital SLR and P-TTL flash guide


MattMatic

Link Posted 03/07/2009 - 21:45
That was quick work Don
http://www.mattmatic.co.uk
(For gallery, tips and links)

Don

Link Posted 04/07/2009 - 02:22
you wanna know the sick part?
took less time to read it than to print it...
I read it once and it''l take hold for life...
Fired many shots. Didn't kill anything.

Sitav

Link Posted 30/07/2009 - 10:16
ewen_r wrote:
I have noticed that my GX20 (K20d equivalent) massively under-exposes PTTL flash shots when I have a split-image focussing screen fitted.

Haven't found any elegant solution to this other than to replace the focussing screen with the default one.

Wondering if any Pentax users have seen this too?

I've had this trouble with my K10, I put the new screen in this morning and wondered why everything was under-exposed, I've put the original screen back in and it's back to exposing correctly.
I've only just bought the flash (Metz 58 ) so haven't really looked into a solution yet, I guess it could be compensated for manually but that somewhat negates buying a dedicated flash doesn't it.
Simon

K10D
www.photonetics.co.uk

MattMatic

Link Posted 30/07/2009 - 11:57
Simon,
All metering for P-TTL, as well as for non-flash metering, is performed through electronics housed in the top of the pentaprism. The same 16-segment meter sensor is used to evaluate the preflash as is used for normal exposure (though it appears that for flash exposure the whole frame is used, irrespective of the metering mode you select ). Consequently, anything that affects the mirror or focus screen can potentially affect exposure.

If you use the flash on "A", or "M" mode then there's no such problem
Matt
http://www.mattmatic.co.uk
(For gallery, tips and links)

Hiljon

Link Posted 31/07/2009 - 00:58
Thank you so much for this. I have really waiting for this. it is much appreciated. Thank you

rakn

Link Posted 01/08/2009 - 16:24
Hi Matt,

That was an excellent guide !

Two things that may be worth mentioning in the next Flash Guide version is that the lightning icon in the viewfinder can disappear right after exposure for more than one reason. If the camera did not get as much flash light as it wanted (as stated in the guide), or if the flash gun needs a second or two (or three...) to recharge from the batteries. It took some time for me to sort that out... I got perfect pictures but the icon disappeared all the time. And it's hard to tell the reason, a bit confusing I think.
Also the unexpected behaviour of K10D/K20D to use some average flashlight measuring mode in P-TTL instead of the user choosen mode.

If I set the flash compensation to +1 and wireless mode (fn button) and "use built-in flash as master in wireless mode" (custom menu) in my K10D, will I get +1 for both the built-in flash and the wireless one ?

Thanks
Ragnar
K10d, AF-540fgz, some Pentax Tamron & Sigma lenses 20-200 mm, Manfrotto tripod.

Don

Link Posted 01/08/2009 - 16:45
If you ever add a chapter on advanced multi flash p-ttl set ups let us know... ps it has been a couple weeks now and Gerri is improving! I still go with everything on manual...
Fired many shots. Didn't kill anything.
Last Edited by Don on 01/08/2009 - 16:46

MattMatic

Link Posted 05/08/2009 - 05:44
Ragnar,
As far as I am aware, the compensation for slave units is only set on the flash itself. The flash compensation on the camera applies to the pop-up alone (or the flash unit on the hotshoe).

But there are other factors too... Pentax term this "contrast control" flash, IIRC.

TBH, I'll have to try it out. When I use multi-flash it's in a studio-type environment and I have everything on manual Drop me a PM in two or three weeks to remind me if I haven't updated this thread!

@Don: glad it's helped. I'll see what I can do about extra chapters

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

ChrisA

Link Posted 05/08/2009 - 08:11
MattMatic wrote:
Ragnar,
As far as I am aware, the compensation for slave units is only set on the flash itself. The flash compensation on the camera applies to the pop-up alone (or the flash unit on the hotshoe).

Based on the test I ran and described last year, I believe this is incorrect.
.
Pentax K-3, DA18-135, DA35 F2.4, DA17-70, DA55-300, FA28-200, A50 F1.7, A100 F4 Macro, A400 F5.6, Sigma 10-20 EXDC, 50-500 F4.5-6.3 APO DG OS Samsung flash SEF-54PZF(x2)
.

rakn

Link Posted 05/08/2009 - 08:53
From your test Chris, it looks to me that
- in controller mode the remote flash is affected
- in master mode both flashes are affected
Thanks for sorting this out.
K10d, AF-540fgz, some Pentax Tamron & Sigma lenses 20-200 mm, Manfrotto tripod.

MattMatic

Link Posted 05/08/2009 - 09:25
Well in that case... the Fn control must be an overall adjustment, while the compensation on the slave itself is an adjustment relative to that slave (perhaps )

As I say, when I get a chance I'll give it a whirl with two remote flashes and see what happens

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

stevejcoe

Link Posted 05/08/2009 - 09:43
MattMatic wrote:
Well in that case... the Fn control must be an overall adjustment, while the compensation on the slave itself is an adjustment relative to that slave (perhaps )

As I say, when I get a chance I'll give it a whirl with two remote flashes and see what happens

Matt

Matt my experience is in line with your comment.

Steve
Last Edited by stevejcoe on 05/08/2009 - 09:44

Bluemerlin

Link Posted 06/08/2009 - 19:30
Thanks for this I was going through hell trying to guess how to do it.
View My Flickr Photostream
Pentax K20D + BG2- Pentax DA 18-55MM AL

MattMatic

Link Posted 22/08/2009 - 17:45
Had a quick play on holiday with a single AF540...

It works like this:
* The flash exposure compensation on the camera body sets the overall flash compensation (a base-point if you like)

* The exposure compensation on the slave flash works from the base point that was set on the body.

Consequently, you can set the relative exposure balance of multiple remote flashes using the dial on each slave. You may want a master at +0, with a fill in at -2. Then you can adjust the relative exposure of the all the remotes from the body - adjusting up and down as needed.

Hope that makes sense (and agrees with what you find in practice!)
Matt
http://www.mattmatic.co.uk
(For gallery, tips and links)
Last Edited by MattMatic on 22/08/2009 - 17:45

Thordell

Link Posted 14/10/2009 - 20:12
Just what I needed at this moment, E-book ordered and keenly awaited. Thanks MattMatic.
Jackie H
K7, K20D, istDS, Optio SV, ME
Most used glass
50mm f1.4, 60-250mm, 28-80mm,
Sigma 105mm 2.8 Macro & Bertha 50-500
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