Practice with strobes

Hi WP people,

Having recently acquired a new camera and (so far!) a single strobe I was wondering if anyone has any advice about setting about practicing taking pictures above water. I'm not expecting anyone to coach me... Or spend too much time writing a response.  I'd settle for a link to an article or thread that covers this.  

Is it even worth doing?

SZ

Yep, it is worth trying:

Have a start with this:

https://www.backscatter.com/reviews/post/How-To-Underwater-Strobe-Flash-Placement

Also, Alex Mustard's book, "Underwater Photography Masterclass" and Martin Edge's "The Underwater Photographer" are well worth  a read. Both available at Amazon.

Thanks Tim 

I have Alex's book.  I'll take a look at the other.  

And thanks for the link!  

Paul

No probs, Paul.

It's worth having a look on the How To pages of some of the main u/w camera dealers: Reef Photo and Video, Backscatter, Bluewater. They have some good stuff.

7 minutes ago, TimG said:

Have a start with this:

https://www.backscatter.com/reviews/post/How-To-Underwater-Strobe-Flash-Placement

This is really useful.  I love the Frankenstein! This is a really great way to try and remember the positions.

9 hours ago, Sandyzoo2 said:

Hi WP people,

Having recently acquired a new camera and (so far!) a single strobe I was wondering if anyone has any advice about setting about practicing taking pictures above water. I'm not expecting anyone to coach me... Or spend too much time writing a response.  I'd settle for a link to an article or thread that covers this.  

Is it even worth doing?

SZ

If you are practising taking photos above water be careful not to overheat your strobes, If you are practising lighting you could for example use higher ISO so you can lower your strobe power.  The cooling for strobes is generally better UW.

4 minutes ago, ChrisRoss said:

If you are practising taking photos above water be careful not to overheat your strobes, If you are practising lighting you could for example use higher ISO so you can lower your strobe power.  The cooling for strobes is generally better UW.

Thanks Chris.

Mostly my strobe was on its lowest setting.  In fact I had the camera at f11.. iso at 100 and strobe at the lowest setting.  I still had to have a super high shutter speed to get a decent exposure.  

That sounds odd, ISO 100 and f11 should need about half power to expose properly.  Are you inside or out?  If you are inside (and you should be to reduce ambient lighting so you can impact of strobe position) then shutter speed doesn't come into the exposure equation if the strobe is your only light source.  What camera and strobe are you using?  How close is strobe to subject? 

17 hours ago, ChrisRoss said:

That sounds odd, ISO 100 and f11 should need about half power to expose properly.  Are you inside or out?  If you are inside (and you should be to reduce ambient lighting so you can impact of strobe position) then shutter speed doesn't come into the exposure equation if the strobe is your only light source.  What camera and strobe are you using?  How close is strobe to subject? 

I was inside.  The subject was within 2 ft of the strobe.  I have an rx100 and a retra prime.  I had no idea that shutter speed had no effect on exposure this way.  Thinking about it... It does kinda make sense.  There is only light while the strobe flashes.. so no real ambient light to worry about over exposing.  Hmm.  Thanks Chris.  This was my first attempt at ever using a strobe.  A lot to think about!

4 hours ago, Sandyzoo2 said:

I was inside.  The subject was within 2 ft of the strobe.  I have an rx100 and a retra prime.  I had no idea that shutter speed had no effect on exposure this way.  Thinking about it... It does kinda make sense.  There is only light while the strobe flashes.. so no real ambient light to worry about over exposing.  Hmm.  Thanks Chris.  This was my first attempt at ever using a strobe.  A lot to think about!

Shutter speed only impacts ambient light.  Are you pointing the strobe directly at the subject?  My typical macro exposure is about f10 ISO200 and my Z240 are about 1/4 power, but I'm only using the edge of the beam.

4 hours ago, ChrisRoss said:

Shutter speed only impacts ambient light. 

To a degree. The OP mentions an RX100 - this means they're able to sync with strobes all the way to 1/4000s, and shutter speeds above 1/320s or so will start cutting into strobe exposure as well; just by how much depends on the strobe's discharge curve, and I haven't seen one for Retra Prime/Pro.

2 hours ago, Barmaglot said:

To a degree. The OP mentions an RX100 - this means they're able to sync with strobes all the way to 1/4000s, and shutter speeds above 1/320s or so will start cutting into strobe exposure as well; just by how much depends on the strobe's discharge curve, and I haven't seen one for Retra Prime/Pro.

I suspect it's cutting into it a bit as circular flash tubes are reported to have longer duration than linear tubes, though it was mentioned being on minimum power which should be quite short durations even if the full power dump is long.  Say the duration was 1/125 then 1/4000 is 5 full stops difference.    The Retra has 13 power levels each 1/2 a stop I assume so you would need to be at 1/4000 I think to start cutting the power output due flash duration at minimum power.  Pushing the shutter way up to get a good exposure was mentioned though.

Still would you agree being on minimum strobe power at f11 and ISO100 seems a bit odd? 

Yeah, that does sound a bit odd... @Sandyzoo2, are you shooting TTL or manual? If you're shooting TTL, (mode knob in TTL position, three clicks counter-clockwise from off position) then I suggest setting the camera flash metering to center spot and having your foreground subject in the center of the frame when you take a shot. Put the power knob in the middle position ('12 0'). If the exposure is off, adjust it with flash compensation in camera and/or power knob on the strobe.

If you want to shoot manual, remember that your camera's flash only works in TTL mode (i.e. it always fires a pre-flash), and you need to use Smart SL mode on the Retra to work with that. In order to do that, load the Retra UWT app on your phone, enable Bluetooth, put batteries in your strobe, turn the mode knob into BATT / TEST position, and do a long press on the center button - the indicator light should turn blue, which indicates that the strobe is now available for connection over Bluetooth. Go into the Retra UWT app on your phone, discover and connect to the strobe, go into settings (gear wheel icon on the upper right) and make sure either U1 or U2 bank is set to 'Smart SL'. The 'Low power SL' and 'HSS' modes are useless to you, so you might as well set the other bank to 'Pilot adjust', for all the good that it does. After that is set, turn the mode knob to the setting where you put 'Smart SL' (either U1 or U2), connect the fiber optic cable between your housing and strobe, put the camera into the housing, pop up the flash and take a shot. The Retra strobe will not fire - this is normal, as it is learning your camera's pre-flash pattern. The indicator light will blink amber prior to that shot, then glow constant amber for a while after the pre-flash pattern is learned, then go to green/yellow/red battery indicator status. After that first learning shot, the strobe will fire on subsequent shots using the power level set by the power knob on the left (between 1% and 100%, in half-stop increments - i.e. one click up will increase the flash power by 50%, two clicks up will double it, and so on). Note that you will have to repeat the 'learning' shot every time you turn the strobe off and on again.

Thanks everyone for taking an interest.  I will certainly use the Retra app to check out the settings on the strobe.  It was firing perfectly well in the ON position, so I was happy.

Please ignore my statement about the high shutter speed to get a "decent exposure".  It was lazy of me to write that.  I was actually trying to achieve a black backgroud behind a bright yellow "My Little Pony" at the time.  So I suppose I was trying to control the ambient light with the shutter speed.

I'm very new to using strobes, so forgive my ignorance!

23 minutes ago, Sandyzoo2 said:

Thanks everyone for taking an interest.  I will certainly use the Retra app to check out the settings on the strobe.  It was firing perfectly well in the ON position, so I was happy. 

I'm guessing that what was happening is that the strobe was firing twice - on the pre-flash and on the main flash - but you had the power set at less than half, so there was enough charge in the capacitors to execute both flashes. At higher power outputs, this will not work - most of the charge will be wasted on the pre-flash and the main flash will be severely weakened. With an RX100, you need to use the Smart SL option for manual control of the output.

6 hours ago, Barmaglot said:

After that is set, turn the mode knob to the setting where you put 'Smart SL' (either U1 or U2), connect the fiber optic cable between your housing and strobe, put the camera into the housing, pop up the flash and take a shot. The Retra strobe will not fire - this is normal, as it is learning your camera's pre-flash pattern. The indicator light will blink amber prior to that shot, then glow constant amber for a while after the pre-flash pattern is learned, then go to green/yellow/red battery indicator status. After that first learning shot, the strobe will fire on subsequent shots using the power level set by the power knob on the left (between 1% and 100%, in half-stop increments - i.e. one click up will increase the flash power by 50%, two clicks up will double it, and so on). Note that you will have to repeat the 'learning' shot every time you turn the strobe off and on again.

Thanks for the really detailed info.  I think it makes sense.  I will do this and feed back.

59 minutes ago, Barmaglot said:

I'm guessing that what was happening is that the strobe was firing twice - on the pre-flash and on the main flash - but you had the power set at less than half, so there was enough charge in the capacitors to execute both flashes. At higher power outputs, this will not work - most of the charge will be wasted on the pre-flash and the main flash will be severely weakened. With an RX100, you need to use the Smart SL option for manual control of the output.

I think this explains why, when I fired the flash at 100%, which I only did once, although it fired, my image was not lit.

30 minutes ago, Sandyzoo2 said:

I think this explains why, when I fired the flash at 100%, which I only did once, although it fired, my image was not lit.

Yep - it fired on the pre-flash, and had no more charge left to execute the actual exposure. Digital flash TTL relies on firing a low-power pre-flash (something in the 1/128th to 1/16th power range; @Randall Spangler knows the exact details here as he develops TTL systems), evaluating the resulting exposure, calculating by how much it's underexposed, then firing a main flash pulse at a strength derived from that calculation. Some cameras use a pre-flash sequence of multiple pulses - IIRC Retras' Smart SL mode can handle up to ten. Sometimes the pulses are fired too close together to tell apart by eyeball, but other times you can observe a very characteristic double flash - especially on night dives, those pulses carry a long way, and it's plainly visible that someone is firing TTL flashes somewhere in the vicinity.

An unfortunately side effect of TTL flash (and one that you cannot get away from on Sony compacts) is that it introduces a small amount of lag to your shutter, which can complicate things when you're shooting something that is time-sensitive - a subject getting into a certain position, or exhibiting a certain behavior. When this happens, you need to anticipate them and press the shutter a fraction of a second before they do whatever it is that you intend to capture in a photo. For a fairly simple sample, this moray eel was constantly opening and closing its mouth, so I pressed the shutter while its mouth was closed in order to get a picture in which it is fully open:

After a small work-life balance issue I finally managed to revisit this.  I connected and updated the strobe.  I was actually pleasantly surprised at the ease of use and lack of options in the app.  For some reason I was expecting to see lots of configurable options that I didn't understand!

I set U1 to SmartSL and performed the learning shot as described by @Barmaglot above.  Like witchcraft... And it worked! As he said, after power cycling the Retra it requires another learning shot - but it's no big deal.  You need to remember to do it though or you will miss your first shot!