P-TTL preflash

yeedub · 03-07-2009, 03:14 PM

I have a Sigma EF-530DG Super flash with my K20D, and also used it with my K10D. I have never seen a preflash come from the flash unit even though I have it set to P-TTL mode. The only time that I have seen a preflash was when I had my camera set on the IR remote mode to take a self portrait picture.

I'm not complaining though, I am really pleased with my flash and find that the flash exposures are accurate nearly a 100% of the time.

mattdm · 03-07-2009, 04:07 PM

The preflash is really, really fast. It's very hard to perceive separately from the real flash. Probably when you did the IR remote, you used the 2-second timer, right? Then it preflashes at the beginning and then takes the picture two seconds later, making it very clear.

yeedub · 03-07-2009, 05:35 PM

Oh, alright that makes sense now. Thanks! Is Pentax the only flash that uses the preflash method?

Arpe · 03-08-2009, 04:26 PM

No, they all do now.

Matt says the preflash is hard to perceive, it may just be me, but I can definitely see it, and certain people definitely have time to start blinking before the second flash fires. Maybe they could lessen the delay between them to try and overcome this.

**sinus007** · 03-08-2009, 05:18 PM

Hi,
I don't know about other cameras, I have k200d, but I can see the preflash when I use 2sec timer: the pre-flash goes off when I press shutter release, the main flash goes off 2 sec later. When shooting normally, I can't see the gap between the two.
This is true for 2 flashes I have 360 and Metz 48.

Gooneybird · 03-08-2009, 06:29 PM

Taking a slightly different viewpoint - my problem with the pre-flash on my K10D is that I cannot turn it off at my choosing. There are times I use an external slave flash with an optical trigger, and the pre-flash (from the onboard camera's flash) always triggers the slave before the shutter is opened. My contacts with Pentax confirm there is no option available to turn it off, so I bought a hot shoe adapter and a hot shoe flash unit to mount on the camera. This does NOT put out a pre-flash, and the slave flash works fine. Of course, the pre-flash has some useful benefits at times also, but not in my example.

**DAZ** · 03-08-2009, 07:13 PM

I have read that manual aperture lenses will not work with P-TTL so the camera defaults to a single full power flash. So a workaround (if you have a lens that is manual or you can take off of A) is to use the lens to forces the camera to manual (non P-TTL) mode to trigger the slaves. Not perfect and you still have some problem but they to can be worked out.

DAZ

Timd · 03-09-2009, 04:23 AM

Originally posted by sinus007

Hi,
I don't know about other cameras, I have k200d, but I can see the preflash when I use 2sec timer: the pre-flash goes off when I press shutter release, the main flash goes off 2 sec later. When shooting normally, I can't see the gap between the two.
This is true for 2 flashes I have 360 and Metz 48.

When using the on board flash on my K200d, I can see the preflash in the viewfinder. It must be the pre-flash as the mirror should be up when the flash goes up. Hence if you see the flash through the viewfinder, it must be the pre-flash....

Tim

Deni · 03-09-2009, 07:14 AM

When using an optical slave set the on board flash compensation to -2ev, this way it will be very weak. It works for me at least.

03-07-2009, 03:14 PM	#1
yeedub Forum Member Join Date: Jan 2008 Location: Vancouver BC Canada Posts: 78	P-TTL preflash I have a Sigma EF-530DG Super flash with my K20D, and also used it with my K10D. I have never seen a preflash come from the flash unit even though I have it set to P-TTL mode. The only time that I have seen a preflash was when I had my camera set on the IR remote mode to take a self portrait picture. I'm not complaining though, I am really pleased with my flash and find that the flash exposures are accurate nearly a 100% of the time.

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03-07-2009, 04:07 PM	#2
mattdm Veteran Member Join Date: Feb 2007 Location: Boston, MA Photos: Gallery Posts: 2,948	The preflash is really, really fast. It's very hard to perceive separately from the real flash. Probably when you did the IR remote, you used the 2-second timer, right? Then it preflashes at the beginning and then takes the picture two seconds later, making it very clear.

03-07-2009, 05:35 PM	#3
yeedub Forum Member Join Date: Jan 2008 Location: Vancouver BC Canada Posts: 78 Original Poster	Oh, alright that makes sense now. Thanks! Is Pentax the only flash that uses the preflash method?

03-08-2009, 04:26 PM	#4
Arpe Pentaxian Join Date: Sep 2006 Location: New Zealand Photos: Gallery \| Albums Posts: 4,452	No, they all do now. Matt says the preflash is hard to perceive, it may just be me, but I can definitely see it, and certain people definitely have time to start blinking before the second flash fires. Maybe they could lessen the delay between them to try and overcome this.

03-08-2009, 05:18 PM	#5
sinus007 Site Supporter Join Date: Jul 2008 Location: Cleveland, OH, USA Photos: Gallery Posts: 292	Hi, I don't know about other cameras, I have k200d, but I can see the preflash when I use 2sec timer: the pre-flash goes off when I press shutter release, the main flash goes off 2 sec later. When shooting normally, I can't see the gap between the two. This is true for 2 flashes I have 360 and Metz 48.

03-08-2009, 06:29 PM	#6
Gooneybird Forum Member Join Date: Aug 2008 Location: Florence, SC Photos: Gallery Posts: 75	Taking a slightly different viewpoint - my problem with the pre-flash on my K10D is that I cannot turn it off at my choosing. There are times I use an external slave flash with an optical trigger, and the pre-flash (from the onboard camera's flash) always triggers the slave before the shutter is opened. My contacts with Pentax confirm there is no option available to turn it off, so I bought a hot shoe adapter and a hot shoe flash unit to mount on the camera. This does NOT put out a pre-flash, and the slave flash works fine. Of course, the pre-flash has some useful benefits at times also, but not in my example.

03-08-2009, 07:13 PM	#7
DAZ Loyal Site Supporter Join Date: Sep 2006 Location: Everett, WA USA Photos: Gallery Posts: 744	I have read that manual aperture lenses will not work with P-TTL so the camera defaults to a single full power flash. So a workaround (if you have a lens that is manual or you can take off of A) is to use the lens to forces the camera to manual (non P-TTL) mode to trigger the slaves. Not perfect and you still have some problem but they to can be worked out. DAZ

03-09-2009, 04:23 AM	#8
Timd Senior Member Join Date: Dec 2008 Location: Cape Town, SA Posts: 262	Originally posted by sinus007 Hi, I don't know about other cameras, I have k200d, but I can see the preflash when I use 2sec timer: the pre-flash goes off when I press shutter release, the main flash goes off 2 sec later. When shooting normally, I can't see the gap between the two. This is true for 2 flashes I have 360 and Metz 48. When using the on board flash on my K200d, I can see the preflash in the viewfinder. It must be the pre-flash as the mirror should be up when the flash goes up. Hence if you see the flash through the viewfinder, it must be the pre-flash.... Tim

03-09-2009, 07:14 AM	#9
Deni Veteran Member Join Date: May 2007 Location: Tirana, Albania, South Europe, Planet Earth Photos: Gallery \| Albums Posts: 621	When using an optical slave set the on board flash compensation to -2ev, this way it will be very weak. It works for me at least.

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