Controlling OM1 flash intensity from dial

[Litos]

Perhaps some of the OM1 here know how to solve this:

 

I am trying to control flash intensity of an RC controlled strobe (AOI Q1RC) from the camera dials. I want this because, while shooting super-macro, moving the flash control knob makes me loose the critter in frame.

 

I have the flash set to RC and manual, so I can enter the flash intensity on the super control panel... but this uses the screen so I loose the ability of keeping my target in the screen.

 

While I can add flash exposure compensation to a dial, this does not work for manual mode, and I have not found any way of controlling the flash manual power using the dial. Is there any way of doing this?

 

I don't want using TTL: it is too slow because of the several flashes and disturbs many creatures.

 

I will be also be delighted if other OM1 users may provide useful hints about camera control configs for underwater use. In my case I use in the AOI housing:

-fun 1/2 for changing between cross and single point CAF. I am not using tracking since I felt it to be very erratic.

-AEL for bird detection (works quite well for fishes)

-ISO for x2 magnify

-rear dial for Fstop (here I would like to control  the flash power)

-front dial for shutter speed (I would place here Fstop)

-arrow pad for adjusting focus area and composition 

-así of course back button focus

 

I mostly shot 1/250 and F6.3 to F11 with ISO200. I am still to research if using faster shutter speed and FP flash sync has any advantage.

 

Any help will be welcome!

 

[Chris Ross]

If you are shooting super macro having the flash on manual should work well without much need of adjustment.  Your distance to the subject is more or less constant so the flash power will remain constant. 

 

I found on my camera with exposure mode manual using an olympus flash in the hotshoe that I could assign flash exposure compensation to a dial (OM-1 Mk1) with the flash turned on and it would allow me to vary it.  BUT - it only actually worked to change flash exposure in TTL it had no impact if the flash was in manual, be it RC manual or regular manual.  Presumably OM thinks if you are in manual you want fixed flash output

 

By the way if you are using RC this sends out flash control signals prior to the main flash in manual mode if you are varying manual power from the camera, this is how it varies the flash power from the camera. 

 

I'm not sure what you are doing with TTL, it should only have a single pre-flash and be effectively instantaneous, though RC mode TTL might be a little slower perhaps?, I've never really used RC mode much.  I also don't have your trigger and it may slow things up a little and behave differently to a regular flash.  I assume you have already disabled red-eye reduction as it will cause significant delay.

 

Looking through what I can see on my camera, you can do two things.  First go to full manual and change flash exposure on the flash.  Second use TTL and see if you can find out why it is slow - with an olympus flash in the hotshoe I can't detect any lag or detect a pre-flash.  To use full manual set the flash power before you move in to your subject on a part of the reef at the high magnification you want to use.  Then approach and frame up your subject.  If you are the same distance then you should be very close on exposure as long as the flash is positioned such that it is not shaded by parts of the reef.  If the subject is slightly over exposed stop down a touch more.  I find I rarely adjust flash power if I'm shooting the same size subjects.

 

On your settings - I tend to shoot f10-11 most of the time as it means I'm not fiddling with flash power too much and I generally want the depth of field.  The only reason to try high speed sync to get beyond 1/250 is to get your background water darker.  If you use HSS then you start to significantly lose flash power.

[Litos]

On 1/29/2025 at 1:24 AM, Chris Ross said:

I found on my camera with exposure mode manual using an olympus flash in the hotshoe that I could assign flash exposure compensation to a dial (OM-1 Mk1) with the flash turned on and it would allow me to vary it.  BUT - it only actually worked to change flash exposure in TTL it had no impact if the flash was in manual, be it RC manual or regular manual.  Presumably OM thinks if you are in manual you want fixed flash output

 

This is exactly what I experienced: if the mode is not on TTL, the flash compensation is not used.

 

On 1/29/2025 at 1:24 AM, Chris Ross said:

I'm not sure what you are doing with TTL, it should only have a single pre-flash and be effectively instantaneous, though RC mode TTL might be a little slower perhaps?, I've never really used RC mode much.  I also don't have your trigger and it may slow things up a little and behave differently to a regular flash.  I assume you have already disabled red-eye reduction as it will cause significant delay.

 

Red eye was disabled as far as I know, but I will double check. I got the impression that the pre-flash was scaring some of the targets. When having some time in the lab, I will try to measure withthe oscilloscope what RC TTL, RC manual, FP RC TTL and FP RC manual are doing. I just need some spare time...

 

On 1/29/2025 at 1:24 AM, Chris Ross said:

Iooking through what I can see on my camera, you can do two things.  First go to full manual and change flash exposure on the flash.

 

this is mostly what I am doing... but wanted to move the controls from the strobe to the camera for not having to mode the camera and improving ergonomics.

 

On 1/29/2025 at 1:24 AM, Chris Ross said:

The only reason to try high speed sync to get beyond 1/250 is to get your background water darker.  If you use HSS then you start to significantly lose flash power.

 

That was my idea.

 

Thanks for the very detauiled answer!

 

 

 

[Chris Ross]

3 hours ago, Litos said:

Red eye was disabled as far as I know, but I will double check. I got the impression that the pre-flash was scaring some of the targets. When having some time in the lab, I will try to measure withthe oscilloscope what RC TTL, RC manual, FP RC TTL and FP RC manual are doing. I just need some spare time...

 

I have seen insects on land that can depart between pre and main flash, they are mostly small flies, very fast to react, I would think water would slow most things down enough for most subjects.  The time between pre and main flash is generally pretty small.  Having said that With a bit of thought and practice I would think you should be able to get manual to work for you first time.