Deep-blue sea

MacHeath · Jul 20, 2004

OK, like a lot of hopeless amateurs I want to get nice colourful pictures of fish with a deep-blue sea as the background.

Currently a lot of my photos are washed out and have greenish backgrounds. I think this is due to too much light scattered from the water relative to the light reflected from my fish.

So what I want to do is proportionally increase the amount of light I get from the fish, without overexposing.

My understanding is that with a manual camera I could increase the shutter speed and make the background darker all the way from green to blue and eventually black. Obviously I need to get more light onto the fish by increasing the strobe output at the same time.

As I have a Sony P9 (and external slave strobe), I can't control the shutter speed. So instead, could I set the exposure value lower and then correct with increased strobe power?

Am I on the right track? Or is a trip to the camera shop in order?

ShoalDiverSA · Jul 20, 2004

From what I see here, the water you are diving in is the issue. Depending on the conditions on the reef, I get shots that vary from green to blue. Does the water appear blue to your eyes, or does it have a greenish tinge? If it is the water, there is not much hope that your camera will fix it. You may be able to shift the colour palette on your photos in post-processing.

When you speak of the photos looking "washed out", this may be due to the shots being overexposed or excessive increases of image brightness in post-processing. Difficult to say without some pictures to evaluate.

Why not post some pics so that we can see the problem first-hand?

Cheers,

Andrew

Cecil · Jul 20, 2004

You're last suggestion is what I've been doing lately and have been getting better results. Set the exposure to -2 ev and turn up the flash. Since you can make these changes UW there's no good reason not to try it. I was going to try a couple of different options this last weekend but there was to much surge to try it.

One thing you should know, the Sonys do shift toward the green underwater. I normally shift all UW pictures back in Photoshop after the dive.

Here's a shot from this weekend using the above techniques (the water here is very green).

ReyeR · Jul 20, 2004

MacHeath:
My understanding is that with a manual camera I could increase the shutter speed and make the background darker all the way from green to blue and eventually black. Obviously I need to get more light onto the fish by increasing the strobe output at the same time.

As I have a Sony P9 (and external slave strobe), I can't control the shutter speed. So instead, could I set the exposure value lower and then correct with increased strobe power?

Am I on the right track? Or is a trip to the camera shop in order?

I posted something about this a little while back (see this). Is your external slave strobe a manual one? If so your theory is easy to test.

You can do this at home. Set up your camera and strobe as you would underwater. Setup a subject, say a soft drink can, on a table next to a window with diffused daylight. Set the camera's EV compensation to zero. Take a photo with the external strobe (adjust the strobe output till the soft drink can is correctly exposed). Keeping the strobe settings the same dial the EV compensation to -2.0 and take another photo.

Has the surrounding background become darker compared to the first picture?

kdietz · Jul 20, 2004

To get a nice blue background and a properly exposed foreground subject........decide on your desired DOF and choose an aperture setting (assuming prosumer cp5000 or c5050 ).....let's say f4 for shallow DOF and f10 for more DOF.....then meter on the background blue water to establish the shutter speed...I like to underexpose 1/3 of a stop +/_.......take a test shot and then vary the strobe output to properly light the foreground subject

IOW.....the aperture controls the DOF.....the shutter speed controls the background.....and the strobes control the foreground

If you have all three properly set, the background blue water will be properly exposed along with the foreground subject

Karl

MacHeath · Jul 21, 2004

ShoalDiverSA:
From what I see here, the water you are diving in is the issue. Depending on the conditions on the reef, I get shots that vary from green to blue. Does the water appear blue to your eyes, or does it have a greenish tinge? If it is the water, there is not much hope that your camera will fix it. You may be able to shift the colour palette on your photos in post-processing.

When you speak of the photos looking "washed out", this may be due to the shots being overexposed or excessive increases of image brightness in post-processing. Difficult to say without some pictures to evaluate.

Why not post some pics so that we can see the problem first-hand?

Cheers,

Andrew

Here is an example of my problem. These two photos (not very good I know!) were taken seconds apart. Everything is the same, shutter speed aperture etc. The only difference is on the greenish picture the strobe fired (external YS-25), on the blue one the strobe was off. Sadly I only thought of reducing the exposure value a long time after finishing diving. I will try next time, but I wondered if others were having the same problem

ReyeR · Jul 21, 2004

Looks like a white balance issue to me. Did the camera's flash (not talking about the external strobe here) fire in both the pictures? It doesn't look like something you can solve by adjusting the exposure value.

Also, re: the exposure value, this is what I found in the PDF manual for the P9 >> Advanced still image shooting >> Adjusting the exposure >> Page 56:

When the subject is extremely bright or extremely dark, or when you are using the flash, the adjustment may not work.

Looks like what I posted in the other thread is consitent with the P9's behaviour. But it's still worth a try, especially the excercise I mentioned in the post above.

ReyeR · Jul 21, 2004

Just a quick tweak with Photoshop curves with the 'greenish' picture of yours:

MacHeath · Jul 21, 2004

ReyeR:
Looks like a white balance issue to me. Did the camera's flash (not talking about the external strobe here) fire in both the pictures? It doesn't look like something you can solve by adjusting the exposure value.

Also, re: the exposure value, this is what I found in the PDF manual for the P9 >> Advanced still image shooting >> Adjusting the exposure >> Page 56:

When the subject is extremely bright or extremely dark, or when you are using the flash, the adjustment may not work.

Looks like what I posted in the other thread is consitent with the P9's behaviour. But it's still worth a try, especially the excercise I mentioned in the post above.

Hi ReyeR

The internal strobe did not fire either in the bluer shot.
What white balance should I use if I have an external strobe?
I tried a few a while ago, and Auto seemed to be about the best.

I did actually try your test, don't have the photos with me, but the background did seem a little darker, but not much.

I saw the statement in the manual that said it may not work, I wonder why it is MAY?

Sounds like I MAY need to go and buy a better camera

MacHeath · Jul 21, 2004

ReyeR:
Just a quick tweak with Photoshop curves with the 'greenish' picture of yours:

Very good! I have elements and can't seem to get it to work that well. I'll have a try tonight.

It would still be nice to get them like that out of the camera.

Deep-blue sea

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