Mr.FaHaD
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Can you please advice me with your settings
my pictures are totally flashlight
best regards
Sealife DC2000 what’s next?
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my pictures are totally flashlight
best regards
I generally use manual mode, spot metering, ISO 100, shutter 1/160s (a limitation of my A6300; on RX100 you can use 1/250s or 1/320s if you want darker backgrounds - it can go all the way to 1/2000s, but these very fast speeds are only really useful if the sun is in the frame) and then adjust aperture to balance background exposure against the foreground.
Keep in mind that when you're shooting with strobes, you have, in effect, two exposure triangles - one for the foreground, which is lit by flash, and the other for background, which is not.
If you're unfamiliar with the concept of exposure triangle, it's fairly simple. The function of the camera, at its core, is to record light levels. Each photocell on the CCD sensor, when exposed to light, builds up an electrical charge. The more light it gets exposed to, the more charge it builds up, up to a certain limit, and this directly translates into output that is rendered as shades of grey, between pure black (no charge) and pure white (maximum charge). Colored (red, green and blue) filters placed before each pixel allow for color, rather than black-and-white photography. You can control this process in three ways:
1. Aperture. In the middle of the lens, there is an iris, formed by aperture blades. Closing those blades to reduce the iris size reduces the amount of light that gets in, while opening them to enlarge the iris increases that amount. Aperture is typically measured in 'stops' which are a number that you divide the focal length of the lens by to get the diameter of the iris. For example, if you have a 50mm lens, and the aperture is set to f/2, then the iris diameter is 50/2=25mm. The basic f/stop scale is 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, with each successive number admitting half the amount of light into the camera as the previous one - i.e, f/1.4 is half as bright as f/1, f/2 is half as bright as f/1.4 and so on. Most modern digital cameras and lenses allow you to adjust aperture in 1/2 or 1/3 stop increments.
2. Shutter speed. This is pretty self-explanatory - the longer the sensor is exposed to a given intensity of light, the more charge it builds up. A shutter speed of 1/250s will admit twice as much light as 1/500s, 1/125s will admit twice as much light as 1/250s, and so on.
3. ISO. This is the electronic gain on the sensor. When the signal is too weak to be useful, you can boost it to improve the output, but boosting the signal also boosts the noise, so best results are obtained by applying as little gain as possible, as long as you have sufficient light to produce a working exposure. ISO 200 is twice as bright as ISO 100, ISO 400 is twice as bright as ISO 200, and so on. Very grainy photos shot in the dark that you're no doubt familiar with are the result of the ISO setting being pushed too high in order to compensate for inadequate light.
Taken together, these three settings form the exposure triangle. All three of them have secondary effects - aperture affects depth of field (wide-open apertures have shallow depth of field; closed-down apertures have greater depth of field) and to some extent sharpness (very small apertures reduce sharpness by diffracting the light rays), shutter speed increases or reduces motion blur for moving objects, while ISO affects dynamic range (the level of difference between bright and dark objects that the camera can capture) and noise. You can manipulate them in conjunction with one another to adjust how your photo turns out while maintaining an acceptable exposure. For example, if you want a shallower depth of field for subject isolation, you can open the aperture two stops - go from f/5.6 to f/2.8 - while simultaneously increasing shutter speed from 1/250 to 1/1000, and your overall exposure will not change. Imagine that you have a triangle, where the three points represent aperture, shutter and ISO, and as you move each point in and out, the overall area of the triangle changes - that's your total exposure.
Now, when you're shooting underwater, with TTL strobes,things get a bit more complicated. Something that you should keep in mind is that the xenon bulbs used in strobes don't have power adjustment - electronic strobes work by storing electrical energy in a bank of capacitors, then using that energy to produce an electrical discharge in a glass tube filled with xenon gas, which causes it to emit high-intensity white light. When this electric discharge is triggered, the gas goes to its peak brightness very quickly (some tens of milliseconds), maintains this brightness as long as the capacitors keep dumping electricity into the tube, and when the current stops, it fairly quickly (a few hundred milliseconds) dims back down to nothing. Therefore, the output of a strobe is moderated by the duration of the pulse, rather than its intensity, which is analogous to shutter speed.
(Wow, this got long - first time I bump into Scubaboard 10k charachters post limit. Continued in the next post)
Keep in mind that when you're shooting with strobes, you have, in effect, two exposure triangles - one for the foreground, which is lit by flash, and the other for background, which is not.
If you're unfamiliar with the concept of exposure triangle, it's fairly simple. The function of the camera, at its core, is to record light levels. Each photocell on the CCD sensor, when exposed to light, builds up an electrical charge. The more light it gets exposed to, the more charge it builds up, up to a certain limit, and this directly translates into output that is rendered as shades of grey, between pure black (no charge) and pure white (maximum charge). Colored (red, green and blue) filters placed before each pixel allow for color, rather than black-and-white photography. You can control this process in three ways:
1. Aperture. In the middle of the lens, there is an iris, formed by aperture blades. Closing those blades to reduce the iris size reduces the amount of light that gets in, while opening them to enlarge the iris increases that amount. Aperture is typically measured in 'stops' which are a number that you divide the focal length of the lens by to get the diameter of the iris. For example, if you have a 50mm lens, and the aperture is set to f/2, then the iris diameter is 50/2=25mm. The basic f/stop scale is 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, with each successive number admitting half the amount of light into the camera as the previous one - i.e, f/1.4 is half as bright as f/1, f/2 is half as bright as f/1.4 and so on. Most modern digital cameras and lenses allow you to adjust aperture in 1/2 or 1/3 stop increments.
2. Shutter speed. This is pretty self-explanatory - the longer the sensor is exposed to a given intensity of light, the more charge it builds up. A shutter speed of 1/250s will admit twice as much light as 1/500s, 1/125s will admit twice as much light as 1/250s, and so on.
3. ISO. This is the electronic gain on the sensor. When the signal is too weak to be useful, you can boost it to improve the output, but boosting the signal also boosts the noise, so best results are obtained by applying as little gain as possible, as long as you have sufficient light to produce a working exposure. ISO 200 is twice as bright as ISO 100, ISO 400 is twice as bright as ISO 200, and so on. Very grainy photos shot in the dark that you're no doubt familiar with are the result of the ISO setting being pushed too high in order to compensate for inadequate light.
Taken together, these three settings form the exposure triangle. All three of them have secondary effects - aperture affects depth of field (wide-open apertures have shallow depth of field; closed-down apertures have greater depth of field) and to some extent sharpness (very small apertures reduce sharpness by diffracting the light rays), shutter speed increases or reduces motion blur for moving objects, while ISO affects dynamic range (the level of difference between bright and dark objects that the camera can capture) and noise. You can manipulate them in conjunction with one another to adjust how your photo turns out while maintaining an acceptable exposure. For example, if you want a shallower depth of field for subject isolation, you can open the aperture two stops - go from f/5.6 to f/2.8 - while simultaneously increasing shutter speed from 1/250 to 1/1000, and your overall exposure will not change. Imagine that you have a triangle, where the three points represent aperture, shutter and ISO, and as you move each point in and out, the overall area of the triangle changes - that's your total exposure.
Now, when you're shooting underwater, with TTL strobes,things get a bit more complicated. Something that you should keep in mind is that the xenon bulbs used in strobes don't have power adjustment - electronic strobes work by storing electrical energy in a bank of capacitors, then using that energy to produce an electrical discharge in a glass tube filled with xenon gas, which causes it to emit high-intensity white light. When this electric discharge is triggered, the gas goes to its peak brightness very quickly (some tens of milliseconds), maintains this brightness as long as the capacitors keep dumping electricity into the tube, and when the current stops, it fairly quickly (a few hundred milliseconds) dims back down to nothing. Therefore, the output of a strobe is moderated by the duration of the pulse, rather than its intensity, which is analogous to shutter speed.
(Wow, this got long - first time I bump into Scubaboard 10k charachters post limit. Continued in the next post)
The question comes up then, how does the camera know for how long to keep the strobe on in order to produce a good exposure? This is solved by using what is called TTL (through-the-lens) metering. When you press the shutter button, the camera takes two photos in quick succession. First, it takes your aperture, shutter and ISO settings, opens the aperture and fires a very brief flash pulse (this is typically called pre-flash). The resulting photo is almost always underexposed, but it's not even shown to you or saved anywhere - instead, it is used by the camera's processor to gauge by how much it was overexposed, and once that calculation is complete, it can decide how much flash power it needs to add to produce a proper exposure. Once that is done, the camera takes a second photo, this time for real, using the calculated required flash power, and this is the photo that gets saved to your memory card.
When you're using off-camera TTL strobes, such as SeaFrogs ST-100, they act as a simple amplifier to the camera's flash. When the pop-up flash emits its pre-flash pulse, they also flash briefly, and when the camera emits the main flash, they stay lit for as long as the camera's flash stays lit. The camera is only aware of the increased amounts of light coming in. One point of note, however, is that if the light transmission through fiber optics between the triggering pop-up flash and the off-camera strobes is poor (as it can be with poor-quality fiber optic cables) and/or the off-camera strobe's sensor is not particularly good, the off-camera strobe can miss the brief pre-flash, causing the camera to take effectively a wrong reading and fire the main flash pulse at too high a power setting. This has a very high chance of producing overexposures.
Now, translating all this theory into practice, we come back to our settings. ISO 100 gets us maximum dynamic range, so that's a given. This gives us the first point on the exposure triangle. For aperture, f/5.6 is a decent middle-of-the-road setting, so let's start there - this gives us our second point. Now, we need to take into account foreground and background separation - while shooting with strobes, the strobe light dissipates quite quickly with distance, so only objects very close to the camera (foreground) will be lit by strobes, while objects further away from the camera (background) will be lit by ambient light only. Therefore, for the background, our exposure triangle will be formed by ISO, aperture and shutter speed. Suppose a shutter speed of 1/250s produces a level of exposure that is acceptable under your specific circumstances, which can change with time of day (angle of sun in the sky), cloud cover, water clarity, depth, etc - but let's assume 1/250s is good enough for our example.
The last and possibly most important part is the strobe output and its effect. When the subject of your intended photograph is close to the camera and strobe, the light emitted by the strobe, reflected by the subject, and carried through the lens onto the sensor will be significantly brighter than the light emitted by the sun and reflected by the subject into your camera. This is important while shooting underwater because sunlight is filtered through a large amount of water, which absorbs longer wavelengths (red and yellow) far more than shorter wavelengths (green and blue), so at depth, you get the characteristic blue/green tint. When the white light emitted by strobes, which did not travel through tens of meters of water, dominates the exposure, then you get the bright, vivid colors that you can't really get otherwise. However, and this is largely specific to underwater photography - in most cases, not all of your frame reflects strobe light. In many cases, much of your frame will consist of clear water, through which your strobe light will go out and dissipate, never to return. This is where it gets very important that you understand how the metering modes work in the camera. The default mode is Multi - it divides the frame into areas, measures the brightness of each area individually, and tries to come up with a balanced exposure. Underwater, with lots of water in the frame, this is bad, bad, bad - the camera will evaluate the water as badly underexposed, dial up the flash output, and badly overexpose the subject in its vain attempt to light up an entire ocean. The second available mode is Center - this measures the average brightness of the entire screen, while emphasizing the center - it is less bad, but still mostly unacceptable underwater for the same reasons as Multi. Finally, there is Spot - this is the setting that I use underwater with my A6300, as it only evaluates the center of the screen, and ignores everything around it. This way, so long as you compose the photo with the strobe-lit subject in the center, the camera uses the strobes to light up the subject in a way that is not too dark and not too bright. If the background is too dark, you can open the aperture to admit more light into the lens, and the camera will automatically dial down the flash power to compensate, or you can reduce shutter speed at the same aperture and this will have no appreciable effect on flash power and thus foreground exposure.
TL;DR: For clear tropical water at moderate depths in good weather, ISO 100, f/5.6, 1/250s, spot metering, TTL flash, subject in the center of the frame should produce something approximating decent results. Get as close as you can to your subject and play with aperture and shutter speeds to adjust background exposure levels. Shoot in RAW format and many mistakes can be fixed in post-processing.
When you're using off-camera TTL strobes, such as SeaFrogs ST-100, they act as a simple amplifier to the camera's flash. When the pop-up flash emits its pre-flash pulse, they also flash briefly, and when the camera emits the main flash, they stay lit for as long as the camera's flash stays lit. The camera is only aware of the increased amounts of light coming in. One point of note, however, is that if the light transmission through fiber optics between the triggering pop-up flash and the off-camera strobes is poor (as it can be with poor-quality fiber optic cables) and/or the off-camera strobe's sensor is not particularly good, the off-camera strobe can miss the brief pre-flash, causing the camera to take effectively a wrong reading and fire the main flash pulse at too high a power setting. This has a very high chance of producing overexposures.
Now, translating all this theory into practice, we come back to our settings. ISO 100 gets us maximum dynamic range, so that's a given. This gives us the first point on the exposure triangle. For aperture, f/5.6 is a decent middle-of-the-road setting, so let's start there - this gives us our second point. Now, we need to take into account foreground and background separation - while shooting with strobes, the strobe light dissipates quite quickly with distance, so only objects very close to the camera (foreground) will be lit by strobes, while objects further away from the camera (background) will be lit by ambient light only. Therefore, for the background, our exposure triangle will be formed by ISO, aperture and shutter speed. Suppose a shutter speed of 1/250s produces a level of exposure that is acceptable under your specific circumstances, which can change with time of day (angle of sun in the sky), cloud cover, water clarity, depth, etc - but let's assume 1/250s is good enough for our example.
The last and possibly most important part is the strobe output and its effect. When the subject of your intended photograph is close to the camera and strobe, the light emitted by the strobe, reflected by the subject, and carried through the lens onto the sensor will be significantly brighter than the light emitted by the sun and reflected by the subject into your camera. This is important while shooting underwater because sunlight is filtered through a large amount of water, which absorbs longer wavelengths (red and yellow) far more than shorter wavelengths (green and blue), so at depth, you get the characteristic blue/green tint. When the white light emitted by strobes, which did not travel through tens of meters of water, dominates the exposure, then you get the bright, vivid colors that you can't really get otherwise. However, and this is largely specific to underwater photography - in most cases, not all of your frame reflects strobe light. In many cases, much of your frame will consist of clear water, through which your strobe light will go out and dissipate, never to return. This is where it gets very important that you understand how the metering modes work in the camera. The default mode is Multi - it divides the frame into areas, measures the brightness of each area individually, and tries to come up with a balanced exposure. Underwater, with lots of water in the frame, this is bad, bad, bad - the camera will evaluate the water as badly underexposed, dial up the flash output, and badly overexpose the subject in its vain attempt to light up an entire ocean. The second available mode is Center - this measures the average brightness of the entire screen, while emphasizing the center - it is less bad, but still mostly unacceptable underwater for the same reasons as Multi. Finally, there is Spot - this is the setting that I use underwater with my A6300, as it only evaluates the center of the screen, and ignores everything around it. This way, so long as you compose the photo with the strobe-lit subject in the center, the camera uses the strobes to light up the subject in a way that is not too dark and not too bright. If the background is too dark, you can open the aperture to admit more light into the lens, and the camera will automatically dial down the flash power to compensate, or you can reduce shutter speed at the same aperture and this will have no appreciable effect on flash power and thus foreground exposure.
TL;DR: For clear tropical water at moderate depths in good weather, ISO 100, f/5.6, 1/250s, spot metering, TTL flash, subject in the center of the frame should produce something approximating decent results. Get as close as you can to your subject and play with aperture and shutter speeds to adjust background exposure levels. Shoot in RAW format and many mistakes can be fixed in post-processing.
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