Problems with overexposing on wide angles

[Bluefish 0]

Hiya

 

I am relatively new to underwater photography and am experimenting in swimming pools with friends so I don't have much natural light. I am using two strobes, Ikelite Ds 125 and a 161 attached by TTL with a dual strobe connector. I am getting blooming over exposure problems with my subjects and an unbalanced photograph. I have my metering set to centre weighted average metering and wondered whether this might be one of the problems? If I had it set to centre weighted metering when my subject comes into frame it would be more accurately exposed?

 

Another theory that I have is that my strobes are positioned direct at the subject?

 

I am thinking that the low light and the large amount of surrounding water (wide angle of lens) and my small subjects in comparison; is making it difficult for TTL to function correctly?

 

any advise would be appreciated, I have some pooltime next week to experiment!

 

Thanks

 

B

[sdingeldein 0]

The wide angle experts here can probably give you more and better advice. So take what I say with a grain of salt until confirmed/denied by others.

 

First, don't shoot TTL, shoot manual.

Use the shutter speed to control the brightness of the background and the f-stop setting to control the foreground lighting. That rule never made sense to me photographically but works reasonably well.

Don't aim the strobes at the subject but slightly away from the subject so that the subject is washed by the penumbra of the strobe.

 

Make use of the dial on the back of the Ike housing to turn the strobes up (if not using full power) or down (if using full power). Use the manual settings on the dial with the strobe left on TTL (that essentially puts the strobe in manual and not TTL (unless you use the upper half of the dial which is TTL).

 

It took me a long time to realize that TTL underwater is not the way to go (except I use it at night).

[derway 2]

matrix mode works better for TTL, in many cams.

 

Then you can dial in negative flash exposure compensation.

 

For wide angle usually folks use manual.

 

For macro, ttl works great.

[philsokol 1]

Greetings B,

 

Welcome to wetpixel!

 

I only shoot manual, so take what I say with that in mind. And I've never done any pool work either, so I may be completely off base.

 

Contrary to your opening, I would think shooting in a shallow pool you'd have tons of natural light (vs. deep in the ocean). sdingeldein is correct in that your shutter speed will control your ambient, ie water/background exposure. Given that you're shallow in clear water, I'd set your shutter to 1/250th or as fast as your strobes will sync., the theory being that this fast shutter speed will minimize the amount of ambient light reaching the sensor. Start at f8 and meter the water or area near your subject. You want the exposure to be approx 1 stop underexposed - this varies with cameras, personal taste, artistic objective, etc., but provides a good starting point. Again, given that you're so shallow, you will probably have to stop your aperture down, maybe to f11, f14, or even smaller to get that exposure. Then you use your strobes to light your foreground subject appropriately by adjusting your strobe power.

 

You want your strobes pulled back, at least behind the port and angled out slightly.

 

More info on camera and lens might be useful, but I hope this helps.

 

Phil

Edited March 5, 2011 by philsokol

[ornate_wrasse 0]

You are spot on in your thinking that TTL doesn't function correctly in wide angle shots. The only situation where TTL works well is when the subject to be photographed fills up the frame, e.g. macro shots. For wide angle, TTL is definitely NOT the way to go. Manual, although a bit daunting to use to some who are used to TTL, is really not that difficult. It just takes a bit of practice. The results, in the end, for wide angle, are far superior to using TTL. After practicing, you'll soon know what settings (aperture and shutter) get you the results you want. Another poster has given you some great tips for shutter and aperture.

 

Another theory that I have is that my strobes are positioned direct at the subject?

 

Aiming strobes directly at the subject is to be avoided in underwater photography. It is the surest way to get a lot of backscatter in your images.

 

I highly recommend you get a copy of "The Underwater Photographer" Fourth Edition by Martin Edge. There is a whole section about lighting. One of his tips, among many, is the following:

 

"The idea is to avoid lighting the water column in between the lens and the subject. This reduces the effects of particles, and creates images that are cleaner, sharper and more colourful"

 

Before long, you'll see big improvements in your images.

 

Have fun!

 

Ellen

[Larry Gates 0]

Hiya

 

I am relatively new to underwater photography and am experimenting in swimming pools with friends so I don't have much natural light. I am using two strobes, Ikelite Ds 125 and a 161 attached by TTL with a dual strobe connector. I am getting blooming over exposure problems with my subjects and an unbalanced photograph. I have my metering set to centre weighted average metering and wondered whether this might be one of the problems? If I had it set to centre weighted metering when my subject comes into frame it would be more accurately exposed?

 

Another theory that I have is that my strobes are positioned direct at the subject?

 

I am thinking that the low light and the large amount of surrounding water (wide angle of lens) and my small subjects in comparison; is making it difficult for TTL to function correctly?

 

any advise would be appreciated, I have some pooltime next week to experiment!

 

Thanks

 

B

 

Hi Bluefish,

 

Pools are a great place to experiment in. Although I am not sure what type(s) of experiments you are doing. Just practiccng your photography, or checking the results of different strobe placements, etc. While you mention your photographs are all turning out grossly over exposed, I don't know what camera settings you are using: Aperture, Shutterspeed, ISO.

 

 

Like you I experiment in pools too. Mine are done in daylight hours, on sunny days, in an outdoor pool with depths ranging from 3 to 9 feet. I do my experiementing mainly to check different lens/ports/extension combinations. I do not use a strobe. This is because I have so much ambient light. If I were to use a strobe at all my photographs would, like yours, turn out grossly over-exposed.

 

Unless: I set my exposure manually by using the fastest shutter speed that will synch with my strobe and use a very small aperture opening (high aperture number) and the least sensitive to light ISO setting (in my case ISO 100).

 

Your strobes are both very 'powerfull' in terms of guide numbers. Plus I believe your TTL is probably functioning. But, even so, using strobes in the type of ambient light that exists in the pools that I shoot in will result in over-exposed images.

 

So, depending on your experiement, just practice or practice with strobes, either don't use your strobes at all (though mount them, just leave them turned off),or, use your camera's manual exposure controls to create a darker exposure, and then use your strobes.

 

I agree with what others posted in their replies to you. So this is just my additional twocentsworth and probably clumsily written, and realize very basic, but hope it helps, none the less.

 

lg

[Bluefish 0]

Hi all

 

Thanks very much. It all makes a lot of sense. The pools I am using are indoor pools so really don't have a lot of ambient light, It makes sense that TTL is not working on my wide angles as if i pull in to a closer shot I get better results. My settings are usually ISO 200, F4, shutter speed at 125 (fastest sync whith strobe). Strobe on TTL.

 

Am in a pool tomorrow, will start again with ISO at 100, F8 and shutter at 125, will put strobes on manual, facing away from subject (I have read the Martin Edge book! and adjust camera settings to get an accurate exposure.

 

I was worried that my TTL was not working properly, I am very reassured by your advice and will let you know how I go.

 

Thanks again.

 

B