ClassroomReturn to Mainreturn to scubaIC10 with Strobe


LESSON TWO: HOW TO USE A STROBE

 

In this lesson I will cover the use of the strobe.  The lessons here are based on using a single Intova ISS2000 strobe.  Strobe lesson 2 will cover dual strobes.  The strobe is necessary because water is a powerful filter of light.    As you descend red quickly gets filtered out.  Yellow is fast to follow.  There are basically three options for restoring the capturing of the colors that exist but are lost to your eye and the camera due to the lack of the full spectrum of light.  First is to use a "red" filter which is actually a balance of red and yellow and has an orange appearance.  The second is to use a strobe to enhance the flash.  Most cameras' built in flash are designed for land use and are not powerful enough to overcome the filtering effect of the water.  The built in flash will also cause "back-scatter" showing the particles in the water thus making the picture grainy. The third method is to combine these two.  You may read that some caution against using both as it can overenhance the reds.  However, I find it much easier to "cool" the color temperature in photoshop than to create it.   Here are some tips to effectively use an underwater strobe.


Strobe positioned too highStrobe set too bright

In the above example, the strobe is aimed too high.  The baby spotted stingray
is not being properly lighted.  Setting up a shot is more than lining up the subject
in the viewer, it also means aiming the strobe.  Some photographers will use 2
strobes, one for the subject and one for the background.  Shot at 27feet down
in Cozumel.
The strobe is now aimed properly so as to light the subject.  However, another
important factor is the power setting of the strobe.  In the above picture the
power was set to the maximum.  The distance of the shot combined with
ambient light created too much light essentially washing out the subject.  A
lower setting of 25% to 50% would have been enough.  Another option I have
yet to try is the new Intova Diffuser.

Strobe effectively lighting subjectStrobe shows distance and contrast

The strobe is effectively lighting the subject.  The distance to the subject is actually
only about 7 feet.  The Intova Wide Angle Lens allows being closer to the
subject.  Being closer is very important as the water contains so many
floating particles that the quality is reduced the further away you are.  The strobe
has an effective distance of about 12 feet.  This varies of course according to
the clarity of the water you are diving in.  Shot in Cozumel at 30 feet down.
The effective distance of the strobe is highighted here in coloration of near vs.
the further back branched coral.  The closer coral shows off it's soft brown with
reddish highlights brought out by the strobe.  However, the coral behind it is too
far for the strobe to effectively reach it.  This is not necessarily bad.  In portrait
photography the backgrounds are intentionally muted to highlight the subjects.
Both the aim and power level are correct.  Shot in Nassau at 65 feet.

Effect with wide angle lensCropping to lighted area

This picture can illustrate either the limitation of the strobe or the effect of
improperly aiming.  The area on the left is the focus of the picture.  Although it can
 be left this way to show the contrast, there is a less artsy feel to it.  The picture
 can be greatly improved as seen on the right.  Shot in Cozumel at 55 feet down.
Using photoshop the picture has been cropped to the area of focus.  The poorly
lighted or misaimed area has been removed.  The result is a photo that has
 good color depth and emphasizes the spineless coral.  This is where the issue
of megapixels comes in.  Having  more megapixels gives the ability to crop
photos and still retain printable quality resolution.  I switched from the 5 to the
10 megapixel Intova in order to have this ability.

strobe at wrong settingStrobe still wrong but closer

The strobe must be properly set as to its "preflash."  Many cameras use a preflash to prevent people from closing their eyes when the actual picture is taken.  If the preflash is not properly set, the strobe flash will not line up with the opening of the shutter and taking of the picture.  At 78 feet down this coral at Grand Turk appears like everything else, a greenish blue.  I took multiple pictures, one at each setting to assure the proper preflash.  The picture on the right shows an improvement in the preflash setting. However, it is still not ideal. 


 strobe set correctlyStrobe correct with photoshop correction

This picture has the correct preflash.  The true colors of the coral and the
juvenial fish are now being captured.  This is at the recommended preset of "2"
on the Intova ISS2000 Strobe when shooting with the Intova IC10.  The strobe
can be used with other cameras as well however the preset for the flash may
differ. 
Taking the image from the left and putting it into Photoshop can help restore
color and clarity to the photograph.  I will have a separate lesson on using
Photoshop to clean up your pictures.

Red filter above waterRed filter and strobe

The red filter is being used above water to give you a perspective of how
it tints the picture.  In Black and White Photography red filters create contrast
and a crispness to images.  For underwater video the red filter is absolutely
essential.  Having the red filter handy allows you to switch to the video mode
and get a much better quality video image. 
Here the red filter is being used in combination with the strobe.  The effect of
the strobe can be seen in casting a slight shadow underneath this porcupine
puffer fish.  The red filter at this close proximity helps the yellow but slightly
over emphasizes the red.  Here, the strobe without the red filter would
produce a better image.



Red filter and strobeRed filter and strobe

The combination of the red filter and the strobe worked here to bring out the
porcupine puffer.  The ambient light was poor.  Although only about 45 feet
down the large rock "finger" at Cabo San Lucas made this a darker area.
At 70 feet down the ambient light was poor and visibility cut to about 15
feet.  However, the combination of the strobe and red filter brought out the
incredible colors of the angel fish.  Shot in Cabo San Lucas.

Red filter and strobeRed filter and strobe

This starfish is brilliant and clear with the richness of its background through the
 use of combining the red filter and strobe.  Cabo San Lucas 45 feet down.
The red filter and strobe again combined to help highlight this drummer fish. 
The heavy particulate nature of the water is evidenced in the limited
background depth.  Cabo San Lucas 40 feet.


Here are a few guidelines for the use of the strobe and red filter.

1.  The red filter is essential for video, and helps in certain still shots as well including some with the strobe.

2.  Where there is enough ambient light the red filter may be sufficient without the strobe.

3.  The combination of the strobe and red filter can be useful in places where there is insufficient ambient light and high
particulate water that limits visitbility and strobe effectiveness.
4.  Practice is necessary to learn the best use of the combination.


To summarize our lesson on strobes...
1.  Strobes are essential as built in flash units are insufficient under water.
2.  The strobe must be properly aimed.
3.  The power level must be set so as to light with out washing out.
4.  The preflash must be correctly set.
5.  The strobe can be combined with red filter under conditions of lower ambient light and highly particulate water that limits visibility
and strobe effectiveness.
6.  Practice is essential.

 

Please email me with your comments or questions or suggestions.

 

email

Return to Mainreturn to scuba