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Focus light - What's needed?


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#1 MitHere

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Posted 15 March 2010 - 10:44 PM

Hi guys,

Buying an Inon S2000 for my Canon G11. To get great photos with exposure etc correct, do I need a hardcore focus light or will a nice LED torch handheld be good enough?
Cheers
Adam
UW - Canon Powershot G11 with Inon D4 baseplate, arms, Inon LE240, dual Inon S2000s, Inon lens caddy, dual Inon stackable macros, Dyron 67mm adaptor and Dyron 0.3x WA lens.
Topside - Camera with Lensmate 72mm adaptor and holder, 72mm Kenko Pro1D circular polariser and Velbon Sherpa 435R.

#2 akalars

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Posted 16 March 2010 - 04:43 AM

I have been using a few different techniques for getting focus. I often carry a focus light mounted to my camera to shine a light where I want to get focus. I have also used my main tourch a halcyon 21w canister light to get focus, and then move the light cone out of the image before taking the image. If I forget to move the cone out of the image it will be overexposed in the area covered my the canister light, or underexposed everywhere else.
Lately however I have been experimenting with out focus light. Instead enabling the camera to fire the flash to help get focus. Since I'm using optical connection to my two inon z240 they also light up, an the entire underwater scene lights up. A few times yesterday I was unable to get focus this way. I then used the primary light technique to get focus, but the images always returned way to dark. So if the strobes are not able to light up the scene enough to get focus, they will not be able to light up the scene enough for a good image either. I'm able on my camera to use this teqnique even if the flash is not to be fired when the image is taken, so it seems reliable enough. Though I have only tested it on a couple of dive in Mexico.

#3 jmauricio

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Posted 16 March 2010 - 06:40 AM

Hi guys,

Buying an Inon S2000 for my Canon G11. To get great photos with exposure etc correct, do I need a hardcore focus light or will a nice LED torch handheld be good enough?
Cheers
Adam


There are some fairly inexpensive focus lights ("fisheye mini led" to name one) that lets you use the light to focus and then automatically switch off when it senses the strobe light. this way the focus light does not impact your final image.

#4 N2Bradley

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Posted 16 March 2010 - 09:24 AM

There are some fairly inexpensive focus lights ("fisheye mini led" to name one) that lets you use the light to focus and then automatically switch off when it senses the strobe light. this way the focus light does not impact your final image.


Hi Wetpixel members, replying to this post to both introduce myself (I've been out there lurking for a while) and to get input as I had newbie questions on this subject as well. In regards to focus lights like the type quoted above: how does the photographer compensate to ensure correct exposure? Won't the camera be metering on an area that is artifically lit by the focus light?

#5 CompuDude

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Posted 16 March 2010 - 09:38 AM

Hi Wetpixel members, replying to this post to both introduce myself (I've been out there lurking for a while) and to get input as I had newbie questions on this subject as well. In regards to focus lights like the type quoted above: how does the photographer compensate to ensure correct exposure? Won't the camera be metering on an area that is artifically lit by the focus light?

A good focus light has extremely low output compared to the strobe and offers enough light for the camera to "see" the subject and get a focus lock (hence the name) but not enough light to affect the exposure of the overall image.

Some cut out (like the Fantasea Nano/Fisheye Mini LED described above) and others simply offer a very wide and even beam spread so the small amount of light evenly covers the image area, so again, no hot spots show up in the final image.

#6 MitHere

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Posted 16 March 2010 - 06:46 PM

Hi Wetpixel members, replying to this post to both introduce myself (I've been out there lurking for a while) and to get input as I had newbie questions on this subject as well. In regards to focus lights like the type quoted above: how does the photographer compensate to ensure correct exposure? Won't the camera be metering on an area that is artifically lit by the focus light?


This is the one question that no-one has answered for me yet. Haha
Like Bradley said, it must meter on the focus lit area - The camera doesn't "know" there's a strobe!
Wait, actually I think Bradley (This is for TTL strobes) - You set the camera's flash on and the power etc, then the camera compensates for that with exposure etc and the TTL strobe fires according to the intensity of the flash!
Am I right with this fellas?
UW - Canon Powershot G11 with Inon D4 baseplate, arms, Inon LE240, dual Inon S2000s, Inon lens caddy, dual Inon stackable macros, Dyron 67mm adaptor and Dyron 0.3x WA lens.
Topside - Camera with Lensmate 72mm adaptor and holder, 72mm Kenko Pro1D circular polariser and Velbon Sherpa 435R.

#7 jmauricio

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Posted 19 March 2010 - 08:49 AM

This is the one question that no-one has answered for me yet. Haha
Like Bradley said, it must meter on the focus lit area - The camera doesn't "know" there's a strobe!
Wait, actually I think Bradley (This is for TTL strobes) - You set the camera's flash on and the power etc, then the camera compensates for that with exposure etc and the TTL strobe fires according to the intensity of the flash!
Am I right with this fellas?


if you are shooting on manual control, metering doesn't matter.

#8 derway

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Posted 20 March 2010 - 08:44 AM

I second the fisheye mini led light. Tiny, light weight, does the job. Uses aaa cells, so get rechargeables.

It does shut off, when it sees a flash, so it does not show up in the photos.

When I was using an ike PCa, for focus light, it would sometimes make a noticeable hot spot in the photograph, when the subject was close enough.

I've been using the fisheye mini led for years, in 'A' mode mostly, and and never noticed any problems with the metering being thrown off.

http://reefphoto.com...6aa4314f190ecd8
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#9 echeng

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Posted 20 March 2010 - 09:29 AM

Personally, I am not a fan of lights that turn off when they see a flash. In any situation where you'd need a focus light, you're going to primarily lighting your scene by strobes, which are so much more powerful than a focus light that there is almost no chance that your little light's beam is going to be visible (with some exceptions, as Don mentions). And when that light turns off, if you don't have a secondary light source, you're left in the dark, which gives the critter you're tracking a chance to move away without you noticing.

My focus light doubles as a dive light and is dimmable. It also has a removable red filter so I can get close to many underwater critters that can't see or don't react to red light. I like flood (wide) focus lights, but they do attract more worms...
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#10 Panda

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Posted 20 March 2010 - 02:18 PM

I've used a Nano Fix and Fantasea 360 both of which worked beautifully for a while then died.
No obvious flooding but rust showing around the LEDs. In my circle of divers the same has happened to 5 other Nanos and 1 other Fantasea 360 (which I now believe has been discontinued)
I am very unimpressed with the durability of these products.

I have reverted to using a small Princeton TEC 1 LED torch found underwater years ago.

Edited by Panda, 20 March 2010 - 02:28 PM.

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#11 derway

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Posted 21 March 2010 - 08:37 AM

Personally, I am not a fan of lights that turn off when they see a flash. In any situation where you'd need a focus light, you're going to primarily lighting your scene by strobes, which are so much more powerful than a focus light that there is almost no chance that your little light's beam is going to be visible (with some exceptions, as Don mentions). And when that light turns off, if you don't have a secondary light source, you're left in the dark, which gives the critter you're tracking a chance to move away without you noticing.


Err, the lights only turn off for a fraction of a second, when they see the flash. You'd never notice it by eye.

Remember that the flash exposure is always independent of the ambient exposure, and given a long enough exposure, even the dim focus light can effect the overall image.
Don Erway
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#12 Nicool

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Posted 04 June 2010 - 04:15 AM

Err, the lights only turn off for a fraction of a second, when they see the flash. You'd never notice it by eye.

Remember that the flash exposure is always independent of the ambient exposure, and given a long enough exposure, even the dim focus light can effect the overall image.


Hi Don,

Do you know how long does your Mini Fisheye stays turned off? I've had a look to the Big Blue focus light (FF 1x5), but it stays off for 3 seconds, which seems too much to me.

#13 derway

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Posted 05 June 2010 - 04:37 PM

Hi Don,

Do you know how long does your Mini Fisheye stays turned off? I've had a look to the Big Blue focus light (FF 1x5), but it stays off for 3 seconds, which seems too much to me.


Mine stays off just about exactly 1 second.
Don Erway
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#14 chadbeck

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Posted 06 June 2010 - 05:17 PM

Hi Don,

Do you know how long does your Mini Fisheye stays turned off? I've had a look to the Big Blue focus light (FF 1x5), but it stays off for 3 seconds, which seems too much to me.



I have the Big blue and it is something to get used to that is for sure. I also have the Mini Fisheye which comes back on faster. But it really isn't a big difference. I prefer the big blue with the exception of the size.

#15 wpottinger

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Posted 06 June 2010 - 08:55 PM

A good focus light has extremely low output compared to the strobe and offers enough light for the camera to "see" the subject and get a focus lock (hence the name) but not enough light to affect the exposure of the overall image.

Some cut out (like the Fantasea Nano/Fisheye Mini LED described above) and others simply offer a very wide and even beam spread so the small amount of light evenly covers the image area, so again, no hot spots show up in the final image.


Here's Tim Priest's helpful reply to a related post of mine I hope others find interesting (I trust the moderators will alert me if there is a preferred way to cross-reference related posts):
http://wetpixel.com/...mp;#entry252395

Bill

#16 Undertow

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Posted 15 June 2010 - 02:37 PM

i agree with eric. i don't like a light that turns of. beyond what eric said, it also means more electronics creating greater risk of failure and higher expense.

the only time i've ever had a slight hotspot in a photo was inside a cavern, shooting the entrance light rays at f/2.8, 1/30th & 400iso and using a 10W HID canister on tight spot. not an issue to me.

#17 scubae

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Posted 11 July 2010 - 01:50 PM

Err, the lights only turn off for a fraction of a second, when they see the flash. You'd never notice it by eye.

Remember that the flash exposure is always independent of the ambient exposure, and given a long enough exposure, even the dim focus light can effect the overall image.


After reading the info on the Mini LED it looks like the "shut off" function is based on preflash only. I would take this to mean that if your system does not preflash then your light is shutting off when your stobe light reaches your focus light. That would be roughly the same time it reaches your camera's sensor.
Have you tried the light with and without the shut off setting? I wonder if there is any difference?
Or does your system preflash?

#18 Deep6

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Posted 11 July 2010 - 05:55 PM

There is a simular discussion on aiming lights that morphed into focus lights in Lights Tech. cat.
Aiming Lights
I did the drift over 6-7 K ft. drop off night dive out of Kona 10 days ago using the LED 44 as a aiming light. Not really strong enough for the translucent subjects. I am thinking about doing still/video in the same camera, so I am interested high lums and color balance with varable output.
Bob
P.S. I did 2 dives with the LED 360 before it flooded. the LED 44 is a replacement (it has two dive so far).

Edited by Deep6, 11 July 2010 - 05:57 PM.

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#19 Austincb

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Posted 12 July 2010 - 12:05 PM

wow this is all so confusing for a newbie.
Christi
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