OLY 5050 housing / strobes

[lindner514]

Hi,

I just got my c5050 and DS-125. I'm confused about the slave setting. The DS-125 is supposidly preflash compatible...so should I even care about the slave setting. If so, what effect do the slave intensity settings have.

What about the flash intensity settings ... and just how does the DS-125 know how bright its supposed to flash based on what the camera is thinking and how good should I expect that to work.

Thanks,

 

[dora]

My name is Dora an I'm from Spain, a friend of mine is diving in PALAU, she has a Olympus C5050 and has been a problem with his PT 015 housing, I'm trying to send her a new one but no one give me any guarantee about the delay, she will return next 14th so it will be suitable to have the device at least next Monday.

Could anybody give an address, or telephone for buying it in Australia or Japan, maybe they could guarantee me the deliverance date.

Thanks in advance

;-0

 

[ReyeR]

dora, check your PM. BTW what problem is she facing with the PT-015? Can you share with us?

I just got my c5050 and DS-125. I'm confused about the slave setting. The DS-125 is supposidly preflash compatible...so should I even care about the slave setting. If so, what effect do the slave intensity settings have.
What about the flash intensity settings ... and just how does the DS-125 know how bright its supposed to flash based on what the camera is thinking and how good should I expect that to work.

lindner514, what housing and which Ikelite slave sensor (TTL or manual) do you have?

 

[lindner514]

PT-015 and the TTL Sensor

 

[ReyeR]

lindner514,

I just got my c5050 and DS-125. I'm confused about the slave setting. The DS-125 is supposidly preflash compatible...so should I even care about the slave setting.

You don't have to worry about the slave flash settings if you're not going to use the DS125 manually ie by selecting a manual strobe output setting (full, 1/2, 1/4 and 1/8) to light the subject you are photographing. If you are then leave the setting on 1. This will be enough to trigger the DS125 and at the same time recycle the camera's flash very fast and you'll be ready to take the next shot quicker. On a minor point it will also save battery life.

If so, what effect do the slave intensity settings have.

Only to get smaller output settings than 1/8 on the DS125, but I won't get into that here...

and just how does the DS-125 know how bright its supposed to flash based on what the camera is thinking

This is known as TTL or 'Through The Lens'.
The flash settings on your camera: flash on (thunderbolt sign in P and A; slow in S and M) and flash mode 'Int + Ext'. The setting on the DS125: switch to TTL.
In this method you let the camera decide how long it needs to fire the camera's flash to get what it thinks is the 'correct' exposure. It does this by firing a pre-flash first and then uses it to calculate the duration of the main flash that follows a few milliseconds later. What the TTL slave sensor does is it 'mimmicks' this sequence in sync with the camera's flash - so it 'tells' the DS125 to fire a pre-flash and then a main flash as well. It 'watches' the main flash sequence of the camera and quenches the DS125 when the C5050 quenches its flash. If you've block the camera's flash by putting something on the housing (and you should to prevent backscatter) then the camera doesn't know (or care) if the light coming back from the scene is from the camera's flash or the external strobe. It simply quenches its flash according to what it thinks is the correct exposure based on the pre-flash calculation.

and how good should I expect that to work

TTL works well but has it's limitations. It won't work if the foreground you're trying to light does not fill enough of your frame for your camera to determine the correct exposure. It also won't work if the foreground (or large parts of it) are particularly absorbant or reflective. In these cases the camera will get 'fooled' and you will get under or over exposure, depending on the case. The best thing to do is take the picture and check it in the viewfinder.

What about the flash intensity settings

You can use the flash intensity settings to manually fine tune your TTL exposure - whether it's a consistant over or under exposure or in situations where the camera is getting 'fooled'. (+)settings will 'force' it to throw more light on the scene. Use this to compensate when the camera is underexposing the picture in TTL. (-)settings will do the opposite.

 

[lindner514]

Thanks alot

Is this statement correct...

In TTL mode, with the c5050's "FLASH" set to "Int-Ext" and the "FLASH MODE" set to say "SLOW 1", the c5050 calculates the duration of the internal flash it will need based on information obtained during the preflash.
The "FLASH [+/-]" would not a part of this calculation nor would the difference between the intrinsic brightness of the internal flash vs that of the external strobe.
If the "FLASH [+/-]" is set to some EV value, then the c5050's internal flash will fire for its calculated duration plus or minus whatever duration the EV value represents.
The actual brighness of the internal flash is unaltered.

If it is ...

Now with the "FLASH" set to "SLAVE" is the preflash disabled ... thought I read that somewhere on the Olympus site ... may be wrong.
Do the "SLAVE settings [1-10]" also adjust the duration of the internal flash, but in this case, with no preflash to calculate the duration, you're on your own.
The external strobe would fire for the same duration of the internal flash based on the "SLAVE settings [1-10]" and you get to compensate by setting the external strobe somewhere between 1/8 and FULL.
Also, would the "FLASH [+/-]" also help you in this case to compensate the duration of the internal flash.

 

[ReyeR]

Sounds correct except this doesn't make any sense:

The "FLASH [+/-]" would not a part of this calculation nor would the difference between the intrinsic brightness of the internal flash vs that of the external strobe.

Yes, with the flash set to 'slave' pre-flash is disabled.

Do the "SLAVE settings [1-10]" also adjust the duration of the internal flash, but in this case, with no preflash to calculate the duration, you're on your own.

True the settings 1-10 adjusts the duration but I don't think it was designed to be used as a form of illumination. It was designed to trigger non-preflash and non-Olympus TTL compatible flashes. So yes you are correct in saying that 'you're on your own'.

The external strobe would fire for the same duration of the internal flash based on the "SLAVE settings [1-10]" and you get to compensate by setting the external strobe somewhere between 1/8 and FULL.

Simply put, when you switch the external strobe (the DS125 in this case) to a manual output setting, eg 1/2, it doesn't care how long the camera's slave flash fires. The DS125 will fire for the duration that the 1/2 setting corresponds to. It only uses the slave flash to trigger (start) this event. In this case, since slave setting 1 is enough to trigger this event, it would make sense to leave it at the lowest setting to get minimum camera recycle time and also save batteries. Should you need to re-locate the DS125 and sensor further away from the camera then you can 'pump up' the level of the slave flash so there is 'enough light' to set off the DS125.
Spin off: Because the DS125 has the lowest setting of 1/8 it is often too bright when lighting subjects close to the camera. In this case, and purely as a work around, you can use these levels of 1-10 to get lower than 1/8 output from the DS125. To do this you need to switch the DS125 to TTL and select different levels of the slave flash. In this case, because the strobe is in TTL mode, it will 'mimmick' the duration of the slave flash, and because most of these durations are small, some of the levels will get the DS125 to give outputs lower than 1/8. You wouldn't have to do this if you had the manual slave sensor instead of the TTL.

Also, would the "FLASH [+/-]" also help you in this case to compensate the duration of the internal flash.

I don't think it'll make a difference in slave flash mode.
_

 

[lindner514]

Hi,
I talked to an Olympus Tech ... he said that the SLAVE settings [1-10] as well as the FLASH INTENSITY [+/-] adjust the intensity of the main strobe and not the duration...do you think this is correct...the reason I ask is because, at first, he was reciting from the reference manual (which I have under control) and as I pressed him for more, I had the feeling he may have been speculating. If it is correct, then FLASH INTENSITY [+/-] is essentially useless with the DS-125/TTL Sensor rig, and, in fact, may even adversely affect the calculated duration depending on how the software weights the [+/-] setting against the aperture, shutter speed, ISO and exposure [+/-] settings.

He also said there was a difference between the FLASH MODEs "flash-on" and "SLOW 1". He said something about different sensors...but wasn't clear. What do you think the difference is ... and why do you think "flash-on" is not available in (M)anual mode. It seems to me that "flash-on" is just a "SLOW 1" subject to a faster shutter speed.

 

[digitaldiver]

My understanding of strobes is that duration IS intensity. That is, the flash only gets so bright, no matter what, but the longer that brightness is maintained the more light is delivered. The person who explained this to me should know, he makes his living building strobes.

 

[lindner514]

An issue of semantics...wouldn't a brighter strobe will deliver more light (explosure) for a given duration than a dimmer strobe. In this sense, I was thinking of intensity as the actual brightness of the strobe...I may need an adjustment here so that we all understand each other.