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TTL Flash Control by Sony Rx100-III

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I use Sony Rx100-III inside an Ikelite housing hooked up to two Sea&Sea strobes (Ys-D1 and Ys-D2) via fibers.

 

The camera is set to Manual, with the internal strobe raised, since that's seems the only possible way to use the Rx100-III with external strobes.

 

At TTL setting on the strobes, the camera is supposed to control the amount of light emitted from the strobes, using its light metering sensors.

 

Can somebody please explain how does the camera do that?

Since there is no other connection between the camera and the strobes other then the fiber, i guess it is done thru it. Is it by controlling the actual amount of light emitted by the internal flash and running thru the fiber? That does not sound right, since the Ikelite fiber jacks are partially obstructed by the white piece of plastic which is supposed to prevent the light from the internal strobe from reaching the subject...

 

If the camera does not control the strobes, what is the point of using TTL at all? How is it different from Manual?

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The flash gives out a different amount of light depending on the fstop. U can try it without the Strobe and housing. Try extreme end of the f stop and see the differences.

 

I would stick to manual mode for both camera and strobe. The ttl is not too accurate, and it will usually be too bright. Then u have to push down the light on the strobe. Then what's that different from using manual in the first place.

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Thx Hellhole!

 

That actually explains a lot...

The TTL is really way too bright.

Moreover - i was stupid enough to try and compensate by setting smaller aperture and faster shutter. Obviously that did not work too well since then the camera pushed even more light fighting my compensation.

Its really strange, since Sony takes so much pride in their TTL mode, which is not very useful.

Will use Manual in the future.

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I use Sony Rx100-III inside an Ikelite housing hooked up to two Sea&Sea strobes (Ys-D1 and Ys-D2) via fibers.

 

The camera is set to Manual, with the internal strobe raised, since that's seems the only possible way to use the Rx100-III with external strobes.

 

At TTL setting on the strobes, the camera is supposed to control the amount of light emitted from the strobes, using its light metering sensors.

 

Can somebody please explain how does the camera do that?

Since there is no other connection between the camera and the strobes other then the fiber, i guess it is done thru it. Is it by controlling the actual amount of light emitted by the internal flash and running thru the fiber? That does not sound right, since the Ikelite fiber jacks are partially obstructed by the white piece of plastic which is supposed to prevent the light from the internal strobe from reaching the subject...

 

If the camera does not control the strobes, what is the point of using TTL at all? How is it different from Manual?

The strobes are controlled by the duration of the on board flash. The strobes turn on when light is detected in the fibre optic cable and turn off when the light stops.

 

More light required means the on-board flash and hence the strobes stay on longer.

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Thx Hellhole!

 

That actually explains a lot...

The TTL is really way too bright.

Moreover - i was stupid enough to try and compensate by setting smaller aperture and faster shutter. Obviously that did not work too well since then the camera pushed even more light fighting my compensation.

Its really strange, since Sony takes so much pride in their TTL mode, which is not very useful.

Will use Manual in the future.

Well.. At least it has that option...

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Is it correct to say that manual cranking up the external strobe guide number, physically increases the flashed light intensity, whereas using TTL camera control rules the time of the flash duration, keeping its intensity as per the manual setting?

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Is it correct to say that manual cranking up the external strobe guide number, physically increases the flashed light intensity, whereas using TTL camera control rules the time of the flash duration, keeping its intensity as per the manual setting?

The "intensity" can not be changed,only the duration. The flash tube only has 1 brightness.

 

Higher manual power setting means the strobe stays on longer at the same brightness.

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I have a Sony NEX-5N and single Inon Z-240 strobe connected by fiber optics. Most of the time I have the camera in manual and use the sTTL mode on the strobe. For shots where the strobe is the main source of light I do not get a lot of over-exposures unless there is a lot of white in the picture. I do get over-exposures frequently when shooting over white sand, etc. where the ambient light is high since I am slow at increasing the shutter speed to values where the strobe won't sink. Previously, I used a Nikon 105 strobe with an adapter and electrical connection. This gave me a lot of over-exposures because the Nikon 105 is quite slow at shutting off compared to the Z-240 so couldn't mimic the camera output very well.

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Hi Rwe,

By "shutter speed values where strobe won't sink" you mean that the shutter closes before the strobe flash is over, "thus missing" part of the emitted light?

Is there a way of knowing what is this speed for a particular guide number setting of the strobe?

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Hi Rwe,

By "shutter speed values where strobe won't sink" you mean that the shutter closes before the strobe flash is over, "thus missing" part of the emitted light?

Is there a way of knowing what is this speed for a particular guide number setting of the strobe?

The sync problem is because the strobe is too fast, not too slow.

http://www.scantips.com/speed2.html this link is an interesting read and will give you some idea how fast scuba strobes (speedlights) really are.

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Hi Giffink,

Thank you very much for the link. It impresses me each time from a new how people invest of their time and knowledge to create these posts for the benefit of all.

I have also found a link to the subject of High Speed Flash Sync in one of your previous posts - also very educational.

Thx!

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I have been spent lot of time to measure the flash power with special Light meter what i have made and I use Photo transistor for the measure.

I have attached some photos and you can understand the different between flashes.SB600 and SB700 nikon flashes were the test flashes.

You can see the flash time.

SB600 was 0.151 mSec

SB700 was 0.131mSec

 

1/16 manual mode.

853080.jpg

853081.jpg

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Hi Giffink,

Thank you very much for the link. It impresses me each time from a new how people invest of their time and knowledge to create these posts for the benefit of all.

I have also found a link to the subject of High Speed Flash Sync in one of your previous posts - also very educational.

Thx!

Thanks. I try to learn and share facts that I know or have discovered.

 

You may also be interested in my ongoing serial blog on scubaboard? http://www.scubaboard.com/community/threads/my-strobe-controller-blog.516524/

It is a personal ongoing project. I have learned many things. Not sure how useful they are...

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I have been spent lot of time to measure the flash power with special Light meter what i have made and I use Photo transistor for the measure.

I have attached some photos and you can understand the different between flashes.SB600 and SB700 nikon flashes were the test flashes.

You can see the flash time.

SB600 was 0.151 mSec

SB700 was 0.131mSec

 

1/16 manual mode.

853080.jpg

853081.jpg

What power level? The posts I discovered revealed that power level had a very severe impact on the curve. Low settings interrupted the strobe before it reached maximum output. High settings generally had a long decay.

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Is your camera's flash set to manual or TTL?

 

If set to TTL, the external strobes will mimic the output of the internal flash. If the internal flash is set to manual, the flashes will simply mimic whatever manual setting you the applied....

 

Adam

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Actually.. Just set up your gear. Put something in front of it. Set manual.. 1/250 iso100 Put to f8 or something. Set to ttl. Take a picture. Then set another f stop.

 

Then make the choice if ttl is accurate or not. I blieve it is not... Even the d1 manual say u make adjustments after u see the picture...

 

Go manual... Adjust your own light output u want from the strobe

Edited by hellhole

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