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Wide angle and background exposure


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#1 jefdriesen

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Posted 24 April 2012 - 01:13 AM

Hi,

I'm starting to learn wide-angle photography. I'm using a Nikon D7000 with the Tokina 10-17mm fisheye and 2 YS-110 strobes.

According to many excellent guides floating around on the internet, a good start is to learn proper exposure of the background. So that's where I started, with some experimentation in the swimming pool. However due to the relative low-light conditions in the pool (e.g. evenings and thus no or very little sunlight), I either have to set my ISO very high, or end up with very slow shutter speeds (and thus motion blur) and large apertures (and thus very limited depth-of-field). But for the real photo's, I would like to use for example much smaller apertures for an increased depth of field. I know the strobes are powerfull enough to expose the foreground properly at smaller apertures.

Please note that most of my dives are at local dive sites in Belgium and the Netherlands, which have low-light and low-visibility conditions too, so just shooting under better conditions is usually not an option.

Lets say my light meter indicates a proper exposure at ISO 100, f4 and 1/30. If I would like to shoot at f11 for an increased DOF, I would have to gain 3 stops by either bumping the ISO to 800 or using an even longer shutter speed of 1/4. However, I obviously don't want such long shutter speeds due to inevitable motion blur. High ISO isn't ideal either because it isn't required for the foreground exposure with the strobes. But if I just ignore the theory and shoot at ISO 100, f11 and 1/30 with the strobes, the background is kind of okay too, so I wonder if I'm doing something wrong here?

Another thing I noticed is that in open water, I get usually get two white hotspots near the sides of my photos, where the strobes are located. I tried to pull the strobes back behind the dome port, and point them slightly outwards, but I can get rid of them completely. Also if I'm moving the strobes away too much, I'm having trouble lighting the foreground, especially with very short distances (e.g. subject almost touching the dome port). Can anyone give me some advice?

Jef
Nikon D7000 - Nikon AF-D 60mm - Tokina 10-17mm - Hugyfot housing - 2x Sea & Sea YS-110 optically triggered

#2 diverdoug1

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Posted 26 April 2012 - 06:33 PM

Hi,

I'm starting to learn wide-angle photography. I'm using a Nikon D7000 with the Tokina 10-17mm fisheye and 2 YS-110 strobes.

According to many excellent guides floating around on the internet, a good start is to learn proper exposure of the background. So that's where I started, with some experimentation in the swimming pool. However due to the relative low-light conditions in the pool (e.g. evenings and thus no or very little sunlight), I either have to set my ISO very high, or end up with very slow shutter speeds (and thus motion blur) and large apertures (and thus very limited depth-of-field). But for the real photo's, I would like to use for example much smaller apertures for an increased depth of field. I know the strobes are powerfull enough to expose the foreground properly at smaller apertures.

Please note that most of my dives are at local dive sites in Belgium and the Netherlands, which have low-light and low-visibility conditions too, so just shooting under better conditions is usually not an option.

Lets say my light meter indicates a proper exposure at ISO 100, f4 and 1/30. If I would like to shoot at f11 for an increased DOF, I would have to gain 3 stops by either bumping the ISO to 800 or using an even longer shutter speed of 1/4. However, I obviously don't want such long shutter speeds due to inevitable motion blur. High ISO isn't ideal either because it isn't required for the foreground exposure with the strobes. But if I just ignore the theory and shoot at ISO 100, f11 and 1/30 with the strobes, the background is kind of okay too, so I wonder if I'm doing something wrong here?

Another thing I noticed is that in open water, I get usually get two white hotspots near the sides of my photos, where the strobes are located. I tried to pull the strobes back behind the dome port, and point them slightly outwards, but I can get rid of them completely. Also if I'm moving the strobes away too much, I'm having trouble lighting the foreground, especially with very short distances (e.g. subject almost touching the dome port). Can anyone give me some advice?

Jef

If you NEED the DOF that f/11 gives you (although the 10-17 has pretty good DOF at lower aperatures), go ahead and bump the Iso, stay at 1/30 and use little as possible fill flash. When shooting 10mm fisheye, I bring my strobes in close and about 1 foot behind the port facing out, ohtherwise your subject will be in front of your strobes cones of illumination. Having your strobes set back a bit farther will also help with the strobe flare you are seeing on the sides of your shots.

#3 jefdriesen

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Posted 26 April 2012 - 11:18 PM

Thanks for your response. Bumping the ISO works fine of course, but the question was more about why do I still get an acceptable background when shooting at f11 and low iso? The only explanation I can think of is that the strobes also light up the background. Since I was just shooting straight into the water, with no subject at all, I would assume very little strobe light would get reflected.

For the stobe flares, I have attached an example photo of what I'm getting. A picture is worth a thousand words :-)

DSC_5990.JPG
Nikon D7000 - Nikon AF-D 60mm - Tokina 10-17mm - Hugyfot housing - 2x Sea & Sea YS-110 optically triggered

#4 diverdoug1

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Posted 27 April 2012 - 12:19 AM

Yes, you need to move the strobes farter back. You are getting 180 degrees of coverage in DX sensor mode with a 10mm fish eye (less of a problem with a 10mm retilinear lens) and the flare is being exacerbated by the amount of particulate matter in the water you are shooting in. As far as getting nice blue or green backgrounds, you must have adequate ambient light conditions (your image looks to be almost a night dive). A change of dive time or venue may be needed to get the backgrounds you are looking for.

#5 jefdriesen

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Posted 27 April 2012 - 12:41 AM

The example shot was just to illustrate the strobe flare, not the background color. It was indeed shot on a night dive, so getting a nice green background wasn't possible at all.
Nikon D7000 - Nikon AF-D 60mm - Tokina 10-17mm - Hugyfot housing - 2x Sea & Sea YS-110 optically triggered

#6 ChrigelKarrer

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Posted 27 April 2012 - 07:12 AM

jefdefriesen,
you will get e nice blue or green background ONLY if there is enough ambient light, strobes can't illuminate the infinite background, maximum they will illuminate the particles, creating a ugly backscatter.
For a nice balanced background you need to expose on the background in the right way and use the strobe to illuminate the foreground object.
You can try it at land taking pictures of something during day, sunset and night and using the built-in flash in fill-in mode. Shooting at night in the sky will not give you a nice blue sky as there is nothing to reflect the light back to the cameras film/sensor.
You can do this tests nicely - but with less fun - in a pool, but you need enough ambient light to make the water blue.
Wide Angle and strobes are a problematic situation and most of the strobe will illuminate only a few meters in front of them, depending on their guide number and the transparency of the water.

Depending on you camera you can switch the cameras exposure meter to matrix mode what should balance the exposure of for- and background in automatic. Another solution may be switching the exposure metering of the camera to spot mode, point to the "blue" hold the exposure lock and point it then to the object and press the trigger. You most probably have to regulate the strobe power down to avoid over exposure on the object, especially if of light or reflective color. The best results will be achieved driving the camera and the strobes under complete manual exposure control.,

Chris

Edited by ChrigelKarrer, 27 April 2012 - 07:15 AM.

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#7 Baumann

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Posted 27 April 2012 - 11:31 AM

To the OP...Of course you are correct in your observations and your exposure theory, and yes you need to up the ISP if the background light level dictates. However you will also see a blue background it you underexposed the background by quite some degree, in fact as with above water photography with flash it is often good to underexposed the background by one or two stops and fill flash the foreground subject to expose it correctly. So when stopping down you still saw a decent back ground colour because you would have to go a few stops before it becomes rather dark.

#8 newmanl

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Posted 27 April 2012 - 08:29 PM

Hi Jef,

Thanks for adding the photo - it is worth a thousand words! To be honest, I'm still working on the same challenges - eliminating the hotspots from the sides of the frame while at the same time getting enough light on the subject. I've done a lot of reading and found a few diagrams as to the theory on how to properly shoot wide angle - at least in landscape format. As you know, the idea is to get the stobes out to the sides and behind the dome, facing outward to some degree to avoid the hotspot issue. However, the closer the subject is the dome, the closer the strobes need to be so that the cones of light from the stobes intersect just in front of the subject. If the strobes are too far apart, there can be a gap between the cones of light rendering the subject under-exposed. The trick, I think, is to find the sweet spot for the strobes in terms of distance (laterally) from the dome, the distance behind the dome and the angle at which they're pointed away from the dome. In water like yours (and mine!), every mistake shows up as hot back-scatter! All I can suggest is to hunt up some diagrams that illustrate the theory and practice as much as you can - that's what I'm doing!

These might help:

http://www.kelpfish...._edge_light.htm

http://wetpixel.com/...a...st&id=18041

Cheers,

Lee