Pre-Flash and TTL

Hi there,

Hope one day I understand my strobes and camera better, but I have been thinking why on Sea&Sea YS-D3 strobes ( and I believe on other models and other manufacturers) have a pre-flash setting and a separate TTL setting? Why would pre-flash be needed if not for the TTL mode?

Thanks a lot.

The pre-flash setting is for using manual flash on a camera that does not have a manual flash option - a great many compacts and mirrorless cameras don't have an option for manual flash so the strobe is setup so it can ignore the pre-flash and only trigger on the main flash.   You need a separate setting to trigger from a camera with manual flash option as if it is turned to the pre-flash setiing it sees the flash, assumes it is a pre flash and waits for the main flash which never arrives.

So it is not that pre-flash is needed it is to ignore the pre-flash and not trigger if you want to use the external strobe on manual.

5 hours ago, ChrisRoss said:

The pre-flash setting is for using manual flash on a camera that does not have a manual flash option - a great many compacts and mirrorless cameras don't have an option for manual flash so the strobe is setup so it can ignore the pre-flash and only trigger on the main flash.   You need a separate setting to trigger from a camera with manual flash option as if it is turned to the pre-flash setiing it sees the flash, assumes it is a pre flash and waits for the main flash which never arrives.

So it is not that pre-flash is needed it is to ignore the pre-flash and not trigger if you want to use the external strobe on manual.

It took me numerous re-readings of this before I began to understand but it makes sense, thank you. My camera does not have a pop-up flush so the housing had to be equipped with a manual optical trigger. It works sporadically if the strobe is set on single flush but consistently with the pre-flash setting on strobe.

3 minutes ago, Silvana said:

It took me numerous re-readings of this before I began to understand but it makes sense, thank you. My camera does not have a pop-up flush so the housing had to be equipped with a manual optical trigger. It works sporadically if the strobe is set on single flush but consistently with the pre-flash setting on strobe.

That sounds odd, but if it works - it works.  Strobe manuals are notorious for being poorly written and we often field questions because of that.

10 hours ago, ChrisRoss said:

That sounds odd, but if it works - it works.  Strobe manuals are notorious for being poorly written and we often field questions because of that.

It is odd and even that now it works, it bothers me that I don't know why I wonder if they installed the TTL trigger instead of the manual one for the housing.

It will help to understand the situation to know which make and model of camera, trigger, strobe and housing you are using.

28 minutes ago, Kraken de Mabini said:

It will help to understand the situation to know which make and model of camera, trigger, strobe and housing you are using.

Happy to share:

 - Camera: Nikon D850

 - Housing: Isotta with manual optical trigger

 - Strobes: Sea &Sea YS-D3

Thank you!

The Isotta housing has a complicated trigger, at least the trigger in my Isotta D500 is quite complicated, with a built in microcomputer.  Isotta sells the Manual LED trigger and the TT Manual LED trigger  Maybe the preflash is built into the trigger and can somehow be controlled. 
I just looked in the web and see no mention of Isotta user manuals, so allow me to suggest you contact Isotta to see if they have a Manual for it, or better still if they will post the Manual with Instructions on their website. They have been most pleasant when I have dealt with them. 
Please keep us posted of your progress.  

It could also be the camera - depending on how the trigger is designed, if the camera thinks there is a flash attached it may give a pre-flash and the trigger will copy.  It is sometimes difficult to work out what is going on as the camera doesn't know anything about the external strobes and the strobes don't know what the camera is going to do on each shot.  So you have to change the settings to tell the strobe what to expect.  Are there any settings on the trigger?

One may locate the source of the preflash by checking the camera, housing and strobe, one by one, as follows:

To check if the D850 camera is set to preflash, check its Menu settings: Custom Settings Menu > e Bracketing Flash > e5) Modelling flash set to OFF.

If the camera does not preflash,  check the housing's trigger by looking directly at one of its LEDs to see if it preflashes.
If it does, play with any switches it may have, one by one, to see if this turns Off the preflash

If the strobe still preflashes, read its Manual, and adjust its controls to eliminate the preflash. 

2 hours ago, Kraken de Mabini said:

The Isotta housing has a complicated trigger, at least the trigger in my Isotta D500 is quite complicated, with a built in microcomputer.  Isotta sells the Manual LED trigger and the TT Manual LED trigger  Maybe the preflash is built into the trigger and can somehow be controlled. 
I just looked in the web and see no mention of Isotta user manuals, so allow me to suggest you contact Isotta to see if they have a Manual for it, or better still if they will post the Manual with Instructions on their website. They have been most pleasant when I have dealt with them. 
Please keep us posted of your progress.  

 

Thank you for the reply. Below is the link for the Isotta housing manual, I read it few times. I have also been in dialog with Backscatter, their distributor in the US. I have contacted Isotta before on another issue and unfortunately I did not get an answer, but I will try again.

https://www.isotecnic.it/images/pdf/istruzioni/instructions-d850-isotta.pdf

1 hour ago, Kraken de Mabini said:

One may locate the source of the preflash by checking the camera, housing and strobe, one by one, as follows:

To check if the D850 camera is set to preflash, check its Menu settings: Custom Settings Menu > e Bracketing Flash > e5) Modelling flash set to OFF.

If the camera does not preflash,  check the housing's trigger by looking directly at one of its LEDs to see if it preflashes.
If it does, play with any switches it may have, one by one, to see if this turns Off the preflash

If the strobe still preflashes, read its Manual, and adjust its controls to eliminate the preflash. 

Thanks for the list and being methodical!

- camera: Modelling flash set it OFF

 - housing trigger: no preflash, one single bright red light

 - strobe: i don't see it pre-flashing (is per-flashign really visible with naked eye?), but note that the strobe mode setting that the system worked well consistently is the one with pre-flash (first one on the option list below). Backscatter advised me to put in the"without pre-flash mode", which I did but was getting a lot of black screens.

Thanks.

2 hours ago, ChrisRoss said:

It could also be the camera - depending on how the trigger is designed, if the camera thinks there is a flash attached it may give a pre-flash and the trigger will copy.  It is sometimes difficult to work out what is going on as the camera doesn't know anything about the external strobes and the strobes don't know what the camera is going to do on each shot.  So you have to change the settings to tell the strobe what to expect.  Are there any settings on the trigger?

Imagine my disappointment switching from Sony RX100 (compact) to DSLR and spending a boat of $$$, only to have the system not working. I troubleshooted together with Isotta rep for about a week, and after about 3 very frustrating dives, it started to work consistently but not in the way I was told to, it is simply because I tried with strobes in pre-flash and noticed that it worked every time .

The trigger has a on/off button and then a set of 4 pins for each side of the housing. The pins look like attached and Isotta's rep advice was to switch them as shown on the bottom row (Manual). This in itself has been confusing to me as the instructions in Isotta's manual for switching this way is for electric cords and if you have a TTL trigger, which I don't (optical cords, manual trigger). Unless they put TTL trigger instead of manual by mistake.

Thanks.

instructions-d850-isotta 22.pdf

My suggestion is to first check all the batteries, including the Isotta trigger coin batteries,  to make sure they are fully charged,

Next, set the camera to 1/250 sec, f 10, ISO 100 or 200.  Put the camera in the housing, leave the back off, and take 2-3 shots while watching the housing's LED.  It should give a single flash with each shot, with no preflash. 

Now add the strobe and take 2-3 shots 10 20 seconds apart to not overheat the strobe, same goal, a strobe flash with no preflash for every shutter actuation. 

Last, set the strobe to the single black flash mode and take a few shots.  Each photo should now be well lit.  (Careful not to over heat the strobe).

I suggest you shoot everything in Manual, it is much easier.  None of my buddies, nor I, uses TTL.
Hope all now works well, please let us know.

(The Isotta interior switch is an ON OFF switch to save battery power when not it use.)

About the two sets of 4 "pins", they are slide switches for electric sync cords which you are not using, so you can safely ignore them.    

6 hours ago, Silvana said:

Imagine my disappointment switching from Sony RX100 (compact) to DSLR and spending a boat of $$$, only to have the system not working. I troubleshooted together with Isotta rep for about a week, and after about 3 very frustrating dives, it started to work consistently but not in the way I was told to, it is simply because I tried with strobes in pre-flash and noticed that it worked every time .

The trigger has a on/off button and then a set of 4 pins for each side of the housing. The pins look like attached and Isotta's rep advice was to switch them as shown on the bottom row (Manual). This in itself has been confusing to me as the instructions in Isotta's manual for switching this way is for electric cords and if you have a TTL trigger, which I don't (optical cords, manual trigger). Unless they put TTL trigger instead of manual by mistake.

Thanks.

instructions-d850-isotta 22.pdf 154.69 kB · 1 download

Page 20 of the manual says the flash works in manual mode with the S&S dial in pre-flash position if you reset the custom mode of the S&S flash - maybe your flash has been reset to do this?  quote:

"In this way the strobe is set to work in Manual mode, even if with the trigger in TTL, but it is necessary to put the Mode selector on the first position []."

9 hours ago, ChrisRoss said:

Page 20 of the manual says the flash works in manual mode with the S&S dial in pre-flash position if you reset the custom mode of the S&S flash - maybe your flash has been reset to do this?  quote:

"In this way the strobe is set to work in Manual mode, even if with the trigger in TTL, but it is necessary to put the Mode selector on the first position []."

Chris yes, I was thinking of the same, however it refers to making the TTL trigger to work in manual. I have a manual trigger. Anyway, that sentence indeed would explain why it works now, if I can only identify that I have a TTL trigger and not a manual one.

On 11/3/2021 at 8:27 AM, Silvana said:

Chris yes, I was thinking of the same, however it refers to making the TTL trigger to work in manual. I have a manual trigger. Anyway, that sentence indeed would explain why it works now, if I can only identify that I have a TTL trigger and not a manual one.

Happy to report that the mystery of the century has been resolved! Isotta helped me with instructions to check the type of trigger I have. Turns out, Backscatter installed a TTL trigger, while I asked for a manual trigger and trying to make it work with this assumption. The checking of the trigger type is rather simple: with the camera in the housing and the trigger ON, check the back display on the camera by pressing the "info" button. For my camera, bottom left corner says TTL. When turning the trigger OFF, that writing disappears.

With that resolved, following the Isotta's instructions from the manual for TTL trigger made sense and explained why it works for me in the "pre-flash" mode of the strobes instead of "without pre-flash".

Thanks everyone!

Another piece of good Isotta customer service!

I just asked Isotta about a technical issue and received an immediate and clear reply from Elisa Isotta, a pleasure to deal with. 
And congratulations to Silvana for solving a sticky puzzle !