Basics in manual mode Underwater Photography. Learn what Aperture, Shutter Speed and ISO sensitivity means and how to handle them.
Taking good underwater pictures or any pictures means you need to get away of your automatic camera mode and into your manual mode to adjust your settings. I’ll teach you the 3 most important manual modes on your camera.
We need to look at this in a very simple way so I’ll teach you this as I would teach a child don’t be offended but once you read on, you’ll see it makes a lot more sense!
The first one we learn about in Manual Mode is ISO
ISO, which stands for International Standards Organization, is the light sensitivity rating of a digital image sensor.
You can adjust the ISO not only in manual mode but in many other Camera modes as well.
It means that as the higher the ISO Number is the more sensitive the sensor is to light. And obviously in the opposite direction it’s the smaller ISO number you have the less light sensitive your sensor is.
So you might say, cool lets go into manual mode and crank up that ISO number, as for photography the more light the better. But unfortunately it’s not like that.
See, as the higher you adjust the ISO the more noise, grain and artifacts you can see on your Pictures! So the opposite is the better choice the lower the ISO the sharper the Picture.
Here are the examples of low to high ISO
As you can see on the example Pictures the higher the ISO as the more noise and grain appears on the Picture!
However with a high quality camera you can go up to 1600 ISO and the Picture is still ok to work with.
So you could probably say, outside you’d use an ISO 100 in the shade, around 200 ISO if you go Indoors, probably 400 or closer to 800 ISO.
But since we’re interested in underwater photography, sometimes a flash may not always be available and often the water is murky or you are doing a really deep dive where the light and colors fade, especially anything at depths of 30m. If there is no underwater flash, you can compensate a little with the ISO value
So if you don’t have a Strobe/Flashlight the alternative is a torch with a wideangle beam or a snoot which only lights up a small spot. Remember that especially underwater you need a lot of light, as you want to keep your ISO low and your shutter speed high to get a sharp and crisp Picture!
The second alternative is to push your ISO up to probably 1600 but try on Land before you go diving and take all your Pictures with 1600 ISO and back home when you download them onto your computer and see that they are all noisy and full of grain and the only right way is to throw them in the bin you’ll be angry and smash the keyboard into your screen.
In the Camera world you pay higher prices for light.
Remember keep your ISO as low as possible to avoid noise and grain!
The next step is Aperture
Aperture is a little confusing in terms of light.
As the higher the number the smaller the hole in the lens and the less light comes in
You can actually see this in your camera. There are blades which open as in make the hole bigger and let more light in or close and make the hole smaller to let less light in. Watch this video and see the small whole in the center it opens and closes as i turn the wheel on the Aperture.
The smaller the number the bigger the hole in the lens the more light comes in.
But Aperture is not so much about the light mainly it controls the depth of field.
What is Depth of Field
Depth of Field (DoF) is the distance between the closest object in focus and the farthest point of focus. Or in other words all what is sharp on your objects focus.
That means you can in manual mode adjust the aperture which controls how much of the foreground and background is in focus (sharp) of your actual object you focused on.
This is actually easier to understand:
The higher you set the f/stop number in your camera mode the further or higher is the depth of field focus.
The lower you set the f/stop number in your camera mode the smaller is the depth of field focus.
Here you can see example Pictures with a ruler from lower (short DoF) to higher f/stop (wider DoF) which will make it clear.
Note the higher the number the higher the Depth of Field
So if you for example shoot a Macro nudibranch underwater and you’d like to have all the focus on your nudibranch and the back and foreground blurry you’d use a very low f/stop somewhere around f/3.5
If you’d like to shoot underwater Landscape and large Fish like a Manta Ray or a shark in the distance you would crank your f/stop up to f/16 or even f/22 to get all fore and background sharp in your Picture
The next we learn about is Shutter Speed
Shutter Speed or often called exposure time is the time the sensor of your camera gets exposed to light and hence to your object, or with other words the time in between the opening and closing of the shutter.
Shutter speed is measured in seconds you can see shutter speed is displayed on your Camera screen as 1/100, 1/125 sec all the way up to 1/8000 sec in good cameras.
Which means as the longer the shutter is open as the more motion blur is in the picture. Apart from having a tripod. But for the moment we handhold our Camera.
For example for sporting events, a running dog or in underwater photography a fast swimming fish, you would like to have a high shutter speed which freezes the object and makes it crisp and clear. You’d need anything from 1/350th of a second and higher.
So basically the faster your object is moving the faster shutter speed you’ll need to adjust in your camera settings.
In case you would like to include motion blur into your picture you can slow down your shutter speed to around 1/80 sec. and you’d get something like this.
You can also go the other way with like an open shutter of 1″, 2″ or most cameras do up to 30″ sec. Which isn’t very suitable for underwater Pictures. But to make this guide complete i will also include it.
Now from 1/80 sec and longer exposure times you’ll need or should use a tripod to take pictures as you can’t hold your camera still for this long time and you would get blurry and a lot of motion blurriness in your Picture.
You would use that to shoot waterfalls and the water looks then like it’s still flowing. Or you use it to take pictures of lightning. Sometimes it’s possible to also use it in wideangle landscape photography.
Now there is one more topic I would like to go over briefly as this is another big topic.
Max. Shutter flash sync speed
This is the maximum shutter speed you can run and sync your underwater strobe to it. In most good quality cameras it’s somewhere around 1/160 of a sec.
And that’s often the problem underwater as you’d need a lot of light and a fast shutter speed to avoid motion blur.
So check the cameras max Shutter flash sync speed before you buy it if you don’t want to be disappointed with your cameras abilities if it doesn’t match your expectations.
In most DSLR cameras the max shutter flash sync speed is 1/200 of a sec. so don’t expect a too high number in normal compact cameras.
Summary for your Cameras Manual Mode
ISO Light Sensitivity of your sensor the higher the number the more noise and grain in your picture so try to keep it as small as possible.
Aperture controls the Depth of Field (DoF) the distance between the closest object in focus and the farthest point of focus. The lower the f/stop number the smaller the DoF
Shutter Speed is the time in between the opening and closing of the shutter in sec. Higher Shutter speed less motion blur lower shutter more motion blur.
And remember as the more you practice with your different modes as the better of a photographer you become!
Photography cheat sheet
And yes Experienced Photographers I know and understand that there is much more to it to take good Pictures and being a good photographer but for the complete basics and if you start doing photography i think these are the Basics you need to know.
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