Focus Light

Hi all. I am new to this forum although I have taken great pleasure in acquiring a lot of knowledge from reading the various threads here.

First, let me set out my rig. I use the Canon G9 in the Ike housing, twin YS110a and I have been happy with the results of the DS TTL features when shooting macro. I have just recently added a Fantasea 360 LED focus light but have yet to get that wet.

I wish to draw on the experience of those of you out there who use focus lights and TTL. Assuming that the focus light is on, would the camera be able to accurately set out the TTL parameters. I would imagine that the TTL would be compromised as the camera would actually beleive that there is more light than there actually is and as such all the photos would be underexposed. Am I right?

If so the focus light can only be used in manual mode?

I am embarking on a dive trip in early August and I rather not find out the hard way.

I would be grateful if anyone out there who has had this experience can drop me a reply. Many thanks.

Your particular focus light shuts off briefly (2 seconds, I think) when the strobes light-up - which would mean that it wouldn't be on when it counts. Even if it didn't cut out, it would then be on the whole time and therefore contribute to exposure and metering.

So ... I don't think it should be an issue for you and you should be able to use your focus light with TTL strobe control.

Thanks Jeremy for taking the time to reply. Usually metering is done with the focus light on and if so, with the focus light on, won't the camera think there is more light than there actually is and thus shut off the flash that much quicker?

You are absolutely right that the focus light will shut down for two seconds when the strobe goes off. But won't the metering be affected before the flash?

Thanks

Hi Guys,

I'm probably over thinking this issue, but if the camera takes a light reading while the focus light is on and then programs the strobes for a certain flash duration, for the taken reading, wouldn't the resultant flash cycle be too weak if the focus light turns off during the strobe cycle and this lighting is no longer available for the equation?

I've often pondered this question. . . . and many others.

Bruce...

The camera meter does not measure the light for TTL before exposure, only during it's duration. It might, maybe have an effect with slow shutter speeds, but for all practical purposes, it doesn't. The strobes are so much more powerful they wash it out.

Jack

Thanks for that reply, Jack. Given your extensive experience in this area, I am heartened to know that I can proceed to use the strobe whilst using TTL metering.

Thanks for that reply, Jack. Given your extensive experience in this area, I am heartened to know that I can proceed to use the strobe whilst using TTL metering.

It ain't like I owned the very first SLR to do TTL flash control or anything ... like 25+ years ago ...

Seriously ... enjoy the trip and be sure to come back and share your images!

Dude, no disrespect intended, but you know, Jack Connick's and Optical's credentials are obvious, whereas I did'nt know yours. Wow, 25years?

Thanks though. That's two views that give me some inkling of what to do.

Thanks, I will be enjoying the trip. Its been three months since I last inhaled compressed air and I am missing it already. I will post some of the pics when I get back (if they don't embarrass me)

Ahh Jeremy, I used a Speed Graphic when you were in diapers!!!

Just to finish the subject, Arunk. What you're missing is that TTL isn't really metered, it's separate function of the camera that shuts off the light from the strobe. It doesn't adjust the aperture/shutter speed/ISO.

Jack

PS, do a few dives with the 360 Light. I sold a bunch of them and then had several fail. I complained to Fantasea, they re-tested and pulled them from the market for the time being. The problem was with the switch failing after a few dives. If you bought it from me, I can replace it with a NanoFocus or upgrade it to a Big Blue. Otherwise contact Fantasea customer support if you have problems. The majority sold have had no issues, but it seemed like a repeatable failure. I understand they are working on finding a different manufacturer for them.

Thanks again Jack. On the issue of the Fantasea LED 360, I will keep my fingers crossed. I have a good relationship with the store I bought it from (heaven knows I give them enough business) and should be able to sort out any warranty issues.

I've used the FantaSea nano focus light for about 18 months now. I find it very useful, except that the switch mechanism is a bit temperamental: I've had to (gently!!) tweak the contacts to keep it going. I have a second unit with a red filter (the stick-on from an Inon strobe) that I use at night, tho' it really only works with my 60mm micro lens: I need the white light to allow my 105mm micro to work in AF.

Tim

Ahh Jeremy, I used a Speed Graphic when you were in diapers!!!

Did they have TTL flash powder back then?

Did they have TTL flash powder back then?

Cold man, real cold.

Did they have TTL flash powder back then?

Nah, we used TTL flash bulbs. Small, Medium and Holy Cow!

Jack