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TTL Strobe Use - Advice Needed


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#1 nitrox38

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Posted 11 November 2011 - 04:38 AM

Apart from the usual holiday snaps, using point &click compact cameras, I have little experience of photography. I have recentlybeen playing around with a Nikon D5000, housed in a Nimar housing using a NimarPrimo TTL strobe.

After using the camera without a light source, it soon became evident the needfor a strobe. As the Nimar Primo offered TTL capability, it seemed like a goodchoice at the time. However, after numerous practice sessions, both in theswimming pool & in open water, I'm growing incredibly frustrated with theresults.

No matter what I do, I can't seem to get the correct exposure using the flash.I get better results by turning the flash off and putting the camera intoautomatic mode. I have tried numerous settings, shooting in both Aperture &Full Manual modes, adjusting both shutter and aperture settings. The camera isset to use Flash using TTL, but I'm not sure if I'm missing another setting orjust using the strobe incorrectly.

Am I right in thinking that TTL flash, should monitor the surrounding light anddeliver a flash sufficient to light the scene. It seems no matter what I do thepictures are well over exposed. I have tried different strobe positions &varied the distance from the subject. I have even set the strobe to manual mode,through the cameras settings and taken the same picture on full power, then on1/32 power, again the same results appear.

Does this sound like an issue with the strobe, or could I be missing something.

Any advice would be fantastic, it might stop me from going mad.



#2 tdpriest

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Posted 11 November 2011 - 07:00 AM

What lens do you use? Overexposure of nearby subjects is common in TTL photography with wide-angle lenses as the sensor is folled by the dark background.

Can you post an image that shows the problem?

Unfortunately, I can't find out how the Nimar strobe achieves TTL.

Tim

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#3 bvanant

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Posted 11 November 2011 - 09:47 AM

Apart from the usual holiday snaps, using point &click compact cameras, I have little experience of photography. I have recentlybeen playing around with a Nikon D5000, housed in a Nimar housing using a NimarPrimo TTL strobe.

After using the camera without a light source, it soon became evident the needfor a strobe. As the Nimar Primo offered TTL capability, it seemed like a goodchoice at the time. However, after numerous practice sessions, both in theswimming pool & in open water, I'm growing incredibly frustrated with theresults.

No matter what I do, I can't seem to get the correct exposure using the flash.I get better results by turning the flash off and putting the camera intoautomatic mode. I have tried numerous settings, shooting in both Aperture &Full Manual modes, adjusting both shutter and aperture settings. The camera isset to use Flash using TTL, but I'm not sure if I'm missing another setting orjust using the strobe incorrectly.

Am I right in thinking that TTL flash, should monitor the surrounding light anddeliver a flash sufficient to light the scene. It seems no matter what I do thepictures are well over exposed. I have tried different strobe positions &varied the distance from the subject. I have even set the strobe to manual mode,through the cameras settings and taken the same picture on full power, then on1/32 power, again the same results appear.

Does this sound like an issue with the strobe, or could I be missing something.

Any advice would be fantastic, it might stop me from going mad.

In general, TTL for electrical sync works by sending out a pre-flash to the scene then measuring the corresponding light coming back then setting the flash power to compensate. I am confused by "turning off the flash". I am assuming you have the hotshoe plugged in so the internal flash can not work. You are using the NIMAR cable, right?

Bill

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#4 DrMark

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Posted 14 November 2011 - 06:43 AM

I have been shooting with TTL and getting good results (sorry to the original poster, I don't know what I am doing differently, so I can't offer help). However, it is looking like I'm going to have to go to manual strobe control for my next camera (I have Ikelite strobes, and Ikelite isn't making housings for any of the current appealing cameras).

So, to make this post relevant to the original topic, can anybody provide pointers to resources on how to best manually set strobes for underwater use?

Thanks in advance,

--Mark

#5 tc_rain

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Posted 17 November 2011 - 07:07 PM

In general, TTL for electrical sync works by sending out a pre-flash to the scene then measuring the corresponding light coming back then setting the flash power to compensate. I am confused by "turning off the flash". I am assuming you have the hotshoe plugged in so the internal flash can not work. You are using the NIMAR cable, right?

Bill



I am trying to understand the TTL system too. If your strobe has a 2 or 3 second recycle time does it have to completey recharge from the pre-flash?

#6 bvanant

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Posted 18 November 2011 - 02:02 PM

I am trying to understand the TTL system too. If your strobe has a 2 or 3 second recycle time does it have to completey recharge from the pre-flash?

Typically not, the pre-flash is very very low power.
Bill

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#7 ATJ

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Posted 18 November 2011 - 03:13 PM

Most importantly, what shutter speed and aperture are you using on the camera?

The shutter speed is important as if you set it to fast it won't synchronise with the flash and you'll either get a dark image or a partially chopped image.

If you set the aperture of the camera too small, the flash won't be bright enough to light the seen.

For starters, set the shutter speed to 1/60s and the aperture to f/8, then try taking a shot of something close, e.g. a cup or something around that size lying around the house.