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MacKay · 04-03-2010, 06:40 PM

hello all

when using my F280T with a wireless trigger i get pictures that are underexposed. when just using the built in flash the pictures turn out great. what would be my problem? My camera is a K200D if that helps any. I know that the flash is TTL only would that be the problem?

thanks

bdery · 04-03-2010, 06:45 PM

Do you use the flash in TTL mode or auto mode? If in auto mode, are you using the green (low power) or the red (high power) mode? Have you set the camera according to the exposure recommendation at the back of the flash?

Otherwise, you could just just use the flash in full power manual and it should work flawlessly.

MacKay · 04-03-2010, 07:02 PM

I tried auto, manual and the grean and red. the results are the same i have the ISO on 100. with the F280 off and just the camera flash on everything is dead on. that is the part I find wierd. the same if i just use the F280 on the camera instead of using the wireless trigger everything is great after a bit o tweaking on the camera.

Wheatfield · 04-03-2010, 07:24 PM

I'm betting that there is a significant delay happening. Can you see catchlights or any other indication that the flash is firing at the right time?
Try dropping your shutter speed to around 1/60 and see what happens.

MacKay · 04-03-2010, 07:35 PM

Originally posted by Wheatfield

I'm betting that there is a significant delay happening. Can you see catchlights or any other indication that the flash is firing at the right time?
Try dropping your shutter speed to around 1/60 and see what happens.

I just tried that it it has the same effect I even tried it at 1/40. It looks like it is going off at the same time. maybe i will post some pics tomorrow one with the AF280 and wireless trigger and one with just the built in flash

SOldBear · 04-03-2010, 08:53 PM

Originally posted by MacKay

It looks like it is going off at the same time...

To be sure, take a photo in front of a large mirror. Make sure the image of the AF280T in the mirror is visible in the photo.

You can tell whether the AF280T is firing during actual exposure.

MacKay · 04-16-2010, 05:30 PM

OK so i took 2 pics. the difference between the exposures. I am assuming i am doing something wrong can anyone enlighten me. thanks

Picture 1 is with the AF280T the wireless trigger and the built in camera flash the external flash is sitting on the lefthand side right past the cds pointing inward
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Name: with external.jpg
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picture 2 is with just the internal flash
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SOldBear · 04-16-2010, 05:49 PM

Mackay,

Did you take a test photo with all flash units visible in front of a mirror as recommended in my previous post?

You can NOT trigger an optical slave with the built-in flash.

The built-in flash fires two strobes: a pre-flash strobe and a main flash.

The pre-flash strobe, for light metering, happens before the mirror raises. The mirror has to be in the "down" position because the light sensors are in the prism. The light entering the lens needs the mirror bending the light to hit the light sensors.

The main strobe is to illuminate the scene during metering.

The problem is that the optical slave is triggered by the pre-flash strobe, firing the external flash before the exposure. Thus the external flash does not fire (not enough time to charge up) during the exposure.

The pre-flash strobe and the main strobe, in normal case, are only about 1/50 second apart. Most people can not tell that there are two strobes.

To verify this, set your camera to 2 second delay mode. After hitting the shutter release, you will see in sequence: the pre-flash strobe (and the external flash firing), the mirror raising, 2 second delay, the shutter opening (and the main strobe from the built-in flash).

The only case in which the built-in flash fires ONE strobe at full power is when you have a manual lens (non A) attached to the camera body.

See this thread for similar problem (a bit more complicated, but the cause is the same). My post is on page 2.

MacKay · 04-16-2010, 06:48 PM

solddear, i just read that other post and I think it help explains some stuff. does the pre-flash strobe always fire? i am assuming it does. thanks for all the great info, i am really new to using external flashes. so the only way around this is to use an external flash mounted and then another external flash with trigger, i have a metz 48 aswell

rgibbons · 04-16-2010, 06:52 PM

Do you have Red-eye reduction turned on for the in-camera flash?

Russ G.

MacKay · 04-17-2010, 03:16 AM

red-eye reduction is not turned on

Mike Cash · 04-17-2010, 06:52 PM

Are you using wireless (radio) triggers? Or an optical slave? What mode are you shooting in?

04-03-2010, 06:40 PM	#1
MacKay Inactive Account Join Date: Jan 2010 Location: Fredericton Posts: 68	AF280T+ wireless trigger= underexposed hello all when using my F280T with a wireless trigger i get pictures that are underexposed. when just using the built in flash the pictures turn out great. what would be my problem? My camera is a K200D if that helps any. I know that the flash is TTL only would that be the problem? thanks

04-16-2010, 05:30 PM	#7
MacKay Inactive Account Join Date: Jan 2010 Location: Fredericton Posts: 68 Original Poster	OK so i took 2 pics. the difference between the exposures. I am assuming i am doing something wrong can anyone enlighten me. thanks Picture 1 is with the AF280T the wireless trigger and the built in camera flash the external flash is sitting on the lefthand side right past the cds pointing inward picture 2 is with just the internal flash

04-16-2010, 05:49 PM	#8
SOldBear Veteran Member Join Date: Feb 2009 Location: Alameda, CA Posts: 3,206	Mackay, Did you take a test photo with all flash units visible in front of a mirror as recommended in my previous post? You can NOT trigger an optical slave with the built-in flash. The built-in flash fires two strobes: a pre-flash strobe and a main flash. The pre-flash strobe, for light metering, happens before the mirror raises. The mirror has to be in the "down" position because the light sensors are in the prism. The light entering the lens needs the mirror bending the light to hit the light sensors. The main strobe is to illuminate the scene during metering. The problem is that the optical slave is triggered by the pre-flash strobe, firing the external flash before the exposure. Thus the external flash does not fire (not enough time to charge up) during the exposure. The pre-flash strobe and the main strobe, in normal case, are only about 1/50 second apart. Most people can not tell that there are two strobes. To verify this, set your camera to 2 second delay mode. After hitting the shutter release, you will see in sequence: the pre-flash strobe (and the external flash firing), the mirror raising, 2 second delay, the shutter opening (and the main strobe from the built-in flash). The only case in which the built-in flash fires ONE strobe at full power is when you have a manual lens (non A) attached to the camera body. See this thread for similar problem (a bit more complicated, but the cause is the same). My post is on page 2. Last edited by SOldBear; 04-16-2010 at 05:57 PM.

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04-03-2010, 06:45 PM	#2
bdery Pentaxian Join Date: Mar 2008 Location: Quebec city, Canada Photos: Gallery Posts: 9,363	Do you use the flash in TTL mode or auto mode? If in auto mode, are you using the green (low power) or the red (high power) mode? Have you set the camera according to the exposure recommendation at the back of the flash? Otherwise, you could just just use the flash in full power manual and it should work flawlessly.

04-03-2010, 07:02 PM	#3
MacKay Inactive Account Join Date: Jan 2010 Location: Fredericton Posts: 68 Original Poster	I tried auto, manual and the grean and red. the results are the same i have the ISO on 100. with the F280 off and just the camera flash on everything is dead on. that is the part I find wierd. the same if i just use the F280 on the camera instead of using the wireless trigger everything is great after a bit o tweaking on the camera.

04-03-2010, 07:24 PM	#4
Wheatfield Moderator Join Date: Apr 2008 Location: The wheatfields of Canada Posts: 15,991	I'm betting that there is a significant delay happening. Can you see catchlights or any other indication that the flash is firing at the right time? Try dropping your shutter speed to around 1/60 and see what happens.

04-03-2010, 07:35 PM	#5
MacKay Inactive Account Join Date: Jan 2010 Location: Fredericton Posts: 68 Original Poster	Originally posted by Wheatfield I'm betting that there is a significant delay happening. Can you see catchlights or any other indication that the flash is firing at the right time? Try dropping your shutter speed to around 1/60 and see what happens. I just tried that it it has the same effect I even tried it at 1/40. It looks like it is going off at the same time. maybe i will post some pics tomorrow one with the AF280 and wireless trigger and one with just the built in flash

04-03-2010, 08:53 PM	#6
SOldBear Veteran Member Join Date: Feb 2009 Location: Alameda, CA Posts: 3,206	Originally posted by MacKay It looks like it is going off at the same time... To be sure, take a photo in front of a large mirror. Make sure the image of the AF280T in the mirror is visible in the photo. You can tell whether the AF280T is firing during actual exposure.

04-16-2010, 06:48 PM	#9
MacKay Inactive Account Join Date: Jan 2010 Location: Fredericton Posts: 68 Original Poster	solddear, i just read that other post and I think it help explains some stuff. does the pre-flash strobe always fire? i am assuming it does. thanks for all the great info, i am really new to using external flashes. so the only way around this is to use an external flash mounted and then another external flash with trigger, i have a metz 48 aswell

04-16-2010, 06:52 PM	#10
rgibbons New Member Join Date: Nov 2008 Location: Los Altos CA Posts: 23	Do you have Red-eye reduction turned on for the in-camera flash? Russ G.

04-17-2010, 03:16 AM	#11
MacKay Inactive Account Join Date: Jan 2010 Location: Fredericton Posts: 68 Original Poster	red-eye reduction is not turned on

04-17-2010, 06:52 PM	#12
Mike Cash Veteran Member Join Date: Jan 2007 Location: Japan Photos: Gallery Posts: 6,950	Are you using wireless (radio) triggers? Or an optical slave? What mode are you shooting in?

AF280T+ wireless trigger= underexposed

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