Finally pulled the trigger on my upgrade to the Canon S100

[Interceptor121]

You can save yourself some time as the Ev does not do anything when the flash is set to on
The camera assumes the flash can compensate 3 f-stops so always shoots at 1/60 or F2 or higher depending on the zoom
If instead you shoot with natural light the ev control acts on the shutter or aperture depending on the mode
If you want to really control aperture you need to shoot in manual

 

[Warmwater Wank]

F.Fish--Scott at Blue Water is being excessively modest. Take a look at his UW Photographer's Guide website. Underwater Photography Guide You'll find more answers than you have questions for. Plenty of demos, tutorials and illustrated explanations to clarify the kinds of things you are asking about.

To be obnoxiously opinionated I second Interceptor's comment: shoot in Manual exposure mode if you want better exposure control and simpler (!) shooting. Above water, manual exposure may seem a hassle w/ the ambient light always changing. Below water, different story. Working at closer distances (1m or less) there are not going to be big exposure changes when using an external strobe. Set a shutter speed as high as 1/500 then leave it alone, unless you shoot open water and want to control the back ground water color. Shutter speeds affect background areas (ie--the ambient lit areas where the strobe doesn't reach) and it's how you get black backgrounds.

On the reef and coral shot you asked about you would need to raise the shutter speed. If the bg water could add a nice effect by being blue you may not want to go to 1/500, you could try something lower but not as low as what you used. UW, w/ strobes, the shutter speeds predominately affect the background, not your foreground subject lit by the strobe. Use a high enough f/stop to get the depth of field needed for the shot then (the SECRET!) adjust the strobe output manually to give you the exposure you want on the coral. If the bg water is too bright, raise the shutter speed. Too dark, lower it. Thing is, it took way more time to read about all this then it would take to actually accomplish it, once you understand the concepts and practice a bit.

If whatever form of TTL you use works, it seems great, very simple. When it doesn't work though, you can be hard pressed to make quick corrections to get the specific results you want. When you shoot in manual you get used to the exposure tweaks pretty quick and then mostly use the strobe output adjustment knob to make corrections. Shooting in manual gives you back more exposure control options but it does not have to complicate your shooting. Especially if you "dive" into Scott's wonderful UWPG website first for more input and understanding. // ww

 

[rob1967]

I second Warmwater wank's post! Just shoot manual! I don't really understand all the effort people put in to trying to make TTL, Ev, Tv, Av, CHDK hacks, etc. work. Much better to just shoot manual. Simpler, more control.

 

[Interceptor121]

TTL works well with the camera and a DS-TTL strobe it presents several benefits
A simple one is that you don't generally need to bracket with the strobe which means you can shoot more and worry less
However on the S100 without CHDK there are severe limitations that either prevent TTL in manual or restrict it to Aperture and Shutter priority that with the camera settings produce good but not outstanding shots
TTL in itself works great

 

[rob1967]

Hi Interceptor,

I have to admit I don't really fully understand, and I know there are a lot of people who love TTL, but from a very fundamental point of view, the camera in TTL still has to make a guess-timate of the exposure and try to adjust the strobe power accordingly... It seems to me that underwater, a human can maybe do a better job. As warmwaterwanker says, light condition doesn't change that much underwater with strobes, so in full manual, it usually is just a matter of taking a few test shots, and once you are adjusted, your exposure is usually pretty close to correct, and any further fine-tuning you do is probably better (and much more artistically creative and flexible) than what the camera can do in a semi-automatic mode.

Once I made the switch to shooting full manual, I have never really looked back... I actually have never even tried TTL, and have rarely used Tv and Av, because it seems to me that manual is just better... But maybe I am missing something here, should I try TTL? But with the S100, that would mean Av or Tv mode...

 

[ivakdiver]

Back in the last century, with 35 mm, we used to bracket our exposures, estimating exposures using guide numbers, flash charts, then shooting on both sides of the suggested exposure, one underexposed, one over exposed, so that, hopefully you would end up with a well exposed image. TTL did work well under certain conditions. I am, like rob1967, finding that I enjoy working with manual mode with the S100 and I can work with apertures, shutter speed and flash power with my older Nikon SB 105 strobes. It is especially nice to view images instantly in order to make corrections,band with practise becomes easier.

 

[Warmwater Wank]

Rob, a good exposure is a good exposure--if it's what you want. TTL was a real blessing in film days and if it delivers what you want it's worth trying out. Just don't expect the photos to somehow look different than what your well exposed shots taken manually would look like. At least not if we say that a good exposure simply means the shot is not too dark or light

"Photography is a series of compromises!" as an old instructor of mine used to say. What you gain in ease and consistency w/ TTL is offset by less creative control of the exposure. Case in point is the o.p.'s question about how to shoot the reef & coral shot that is overexposed on the right side. For me that would be tough to control in TTL but easy in manual. I'd find an f/stop and strobe output setting that gave me what I wanted on the foreground at left. Then I'd raise my shutter speeds to drop the exposure values of the water on right. Eventually (like by the 2d dive) you'll have a good sense of what works for exposures, though you'll still occasionally need a few test shots. (I find those extra shots often give me other ideas to try.)

An option, if you felt TTL offered possibilities but mostly wanted to shoot in manual, is to setup the Custom function mode for what works in TTL (ie--what f/stop, what mode, what ever...) then you just have to switch the strobe to TTL.

Shooting manual works for me, it's not "best". Best is what works for you to deliver the kinds of images you want, the way you want to see them, hopefully in a fairly simple and consistent manner. Other folks have other approaches, so play with settings and decide what approach(es) you prefer for the kind of photography you want to do. // ww

ps--Fox F, I would not use auto ISO, set it for 80 or 100. Auto WB is fine, especially if (here comes that other kettle of fish) you shoot in RAW.

 

[Foxfish]

Thanks for the detailed explanations. I've gleaned the following.

- Use the strobe to control fore ground light where required.

- Working at closer distances (1m or less) there are not going to be big exposure changes when using an external strobe.

- Use a high enough f/stop to get the depth of field needed for the shot.

- Manual strobe control gives you greater control of the fore ground lighting.

- Using TTL you don't generally need to bracket with the strobe which means you can shoot more and worry less.

- Set shutter speed as high as 1/500 then leave it alone, unless you shoot open water and want to control the back ground water color.

- If the background water is too bright, raise the shutter speed. Too dark, lower it.

- Adjust background exposure using shutter speed to suit the water conditions.

- Exposure compensation doesn't work in flash mode on the S100.
- Set ISO to 80 or 100.

Lots of other good hints and information above. I'll try this out and post the results.

Am I correct is saying that CHDK gives you the ability to adjust shutter speed in aperture priority mode. Not clear about the other benefits.

 

[Interceptor121]

I have shot in manual too for most of the time but recently switched to DS-TTL and the results are exceptional
I shoot (or should I say my partner as these days I am just a coach) in Manual mode with TTL there is no way to achieve an exposure that I like shooting in Av or Tv underwater but has nothing to do with TTL but with the way the camera does the metering and selects fstops

Now exposure is composed of a number of factors to me, the first is the overall background and colour of the water. You need to reach something you like.

In most cases the flash photography that we do is really close focus wide angle as big subject are shot anyway without strobe

With a strobe if you use the cameras Av and Tv mode you usually end up with compromises.
In Av mode typically you get very light blue water colour and blurred subjects as the camera settles for low shutter speed.
In Tv mode if you set high shutter speeds to control the background and make it darker the camera goes always for wide apertures of F2-F2.8 with resulting lack of depth of field. If you have a fisheye lens this is ends up to be near to acceptable but still a compromise

So the way I recommend to shoot for close focus wide angle is:
1. Have sufficient depth of field. With a compact and a good fisheye F5.6 is sufficient in any condition
2. Choose a shutter speed that allows to freeze the subject this ranges usually between 1/125 and 1/500
3. Compose the background and choose the shutter speed that give me a background I like this may include a diver in the distance or a boat or a piece of reef or a large school
4. At this point for the foreground I let TTL do the job, considering the camera is at 1-2 feet from the subject TTL can do it. Alternatively in the past I would have bracketed manually, I had a set of positions that depending on distance and f-stop would give me a good starting point

So I am not recommending to use Av or Tv just to use TTL, on the S95 rig that we have we force TTL on manual and that is the best option this is why CHDK is essential, I also use a script I have developed this allows me to shoot with a sequence of step that are logical and maximise the number of shots

For the S100 there is now a beta of CHDK my first starting point would be to shoot in Tv overriding the Aperture with CHDK to a fixed value.
So the workflow would be set the camera in Tv and override the aperture with CHDK set the ISO to what you like for example 100. Set the flash off then half press the shutter to see what background you get adjust shutter speed. Enable the flash again and then shoot the camera in Tv will trigger the DS-TTL flash
This achieves the same of my steps on the S95 though with an additional step

If you don't or can't use CHDK on the S100/S95/S90 shoot in manual, the camera metering system and the decisions the camera makes on shutter and aperture are just good enough and would produce the same quality of picture of a normal point of shoot in P mode (I have actually tested this if you use the 'kids and pets' settings with a fixed ISO the camera produces acceptable results)

Hi Interceptor,

I have to admit I don't really fully understand, and I know there are a lot of people who love TTL, but from a very fundamental point of view, the camera in TTL still has to make a guess-timate of the exposure and try to adjust the strobe power accordingly... It seems to me that underwater, a human can maybe do a better job. As warmwaterwanker says, light condition doesn't change that much underwater with strobes, so in full manual, it usually is just a matter of taking a few test shots, and once you are adjusted, your exposure is usually pretty close to correct, and any further fine-tuning you do is probably better (and much more artistically creative and flexible) than what the camera can do in a semi-automatic mode.

Once I made the switch to shooting full manual, I have never really looked back... I actually have never even tried TTL, and have rarely used Tv and Av, because it seems to me that manual is just better... But maybe I am missing something here, should I try TTL? But with the S100, that would mean Av or Tv mode...

 

[RESCUEDIVER]

My camera and housing are on the way, so I can play...I have DSTTL (S&S) compatibe strobe

Maybe I missed something, but to use ttl (particularly DSTTL), I thought the concept was to use CHDK and force the shutter speed to something beyond (above) the abysmal 1/60 and then shoot in aperature priority...adjusting the aperature based on desired scene settings

(this was discussed in the previous post regarding the necessity of CHDK)

Hopefully the TTL script written by Interceptor allowing ttl in M will work, negating the above