Outline for Tutorials: Strobes and Underwater Photography

Transcription

1 Outline for Tutorials: Strobes and Underwater Photography I - Strobes Conquering the Water Column Water column - depth plus distance from camera to subject; presents challenges with color, contrast, and clarity Loss of color and contrast Color: red is lost by feet; at 60 feet, only green and blue remain Contrast: images look faded Loss of clarity: water column reduces lighting; therefore a longer shutter time is needed to allow adequate exposure; this longer shutter time results in a blurred image from camera and subject movement Solutions to problems with water column Allow more available light by reducing the water column - stay shallow and get close to subject Restores color and contrast Restores clarity (increased light allows a high shutter speed to reduce motion blur from camera and subject movement) Use strobe Necessary for color and clarity at deeper depth and for macro Restores color and contrast Restores clarity by stopping the action; remember, however, even with high shutter speed, still must focus on subject (especially with macro) II - Issues to consider with strobes Connect with camera - slave, fiber optic cable, or hotshoe Power - guide number - the higher the better Power controls Manual power steps; on strobe, housing, and camera TTL capability

2 Histogram on camera LCD Recycle time - range can vary from less than 1 second to more than 3 seconds per full discharge Shots per full battery charge - range can vary from 100 to more than 300 Area of coverage - cone of light Angle of illumination (may vary from 70 to 120 degrees; 90 degrees or more is preferred) Quality of light Hot spot centrally; softer at edge of cone Diffuser - expands area of illumination, softens light, but reduces power Spotting light - not too helpful; generally don t aim strobe directly at subject; if is useful for backup light on night dive, however Size and weight Strobe positioning Distance from subject Position with regard to camera and subject Direction of aim with regard to camera subject Maximize aspect of subject you want to emphasize; minimize distraction Experiment with different positions, angles Most popular - overhead (mimic natural sunlight), pointed out to soften light, avoid hotspot, and not illuminate water column between camera and subject Other possibilities - one side, edge lighting, retroillumination III - Strobes: solutions to common problems Strobe too far away from subject Limited penetration (most strobes effectively penetrate no more than 3-6 feet)

3 Rapid fall off - intensity of light is reduced at a rate proportional to the square of the distance it travels from its source; even more so with particles in water Solution: get close to subject Over exposure of subject, hotspots Solution: check histogram; adjust strobe power or strobe-to-subject distance, or position and direction of the cone of light Consider diffuser (softens light; expands area of coverage; lose some power) Distracting background, light traps Solution Careful subject and background selection Compose your picture: get low and shoot up Think about strobe positioning based on subject and background; adjust cone of light; adjust strobe position and direction to minimize distractions and maximize subject Harsh shadows Solution Use edge of cone (softer light) Use diffuser (softens light and broadens cones of light; reduces power) Add second strobe Limited access (under rock or ledge) Solution: use adjustable, multi-joint arms to reposition and maneuver My main problems with strobes Backscatter Solution Adjust cone of light to make backscatter less visible Find interesting background that is not water column

4 Close crop - effectively eliminate background Set strobe at acute angle (done in the past but not much now; not practical need long arms or detachable strobe; this can also create harsh or unnatural shadows) Flooding Strobe malfunction Will not fire Gross over or under exposure Usually user error but sometimes I don t know why IV - Strobe tips for macro Macro - strobe illuminates everything in picture Use high shutter speed but still sync with strobe flash (stop the action) Low ISO - generally use the lowest ISO (ISO 100 or less) - maintains high quality and minimizes noise Adjust aperture (depth of field) for artistic effect; smaller aperture results in greater depth of field but allows less light Adjust strobe power, strobe to subject distance, or strobe position and direction to achieve proper lighting Check histogram on LCD Understand cone of light Adjust strobe position based on subject and background considerations; backscatter possibilities (see part one above) Position strobe to avoid backscatter Above camera, straight ahead Does illuminate subject with lower edge of light cone Does not illuminate intervening water column

5 Does illuminate background (can blur with open aperture) Position strobe above camera and direct light cone straight down Does illuminate subject with outer edge of light cone Does not illuminate background Does illuminate intervening water column (backscatter risk) Super macro strobe positioning Above camera, pulled close to dome port and angled down Does illuminate subject with lower edge of light cone There is very little water column to illuminate Does illuminate background (if present) V - Strobe tips for wide angle Wide angle - more complicated than macro - must balance foreground with background Adjust ISO and shutter speed for background exposure (there is less motion blur with a given shutter speed with wide angle lens than with macro lens) Adjust aperture (depth of field) for artistic effect Adjust strobe power and strobe to subject distance for foreground exposure Even low strobe power will restore some color, contrast, and clarity in foreground TTL vs. manual foreground Two strobes are often preferable for wide angle Allows even illumination over entire image Strobe positioning Both sides of camera, slightly higher than camera (conveys natural lighting from sun above) Aim strobes straight ahead or somewhat outward to minimize backscatter

6 With wide angle, you usually want to show (not eliminate) background; therefore must find good subject and good background; composition considerations are more complicated (see other tutorials) Get low, shoot up (avoid distracting background) Avoid mergers, amputations CFWA (Close Focus Wide Angle) Bring strobes in closer in order to illuminate subject in foreground at close distance Need smaller aperture for good depth of field (but this reduces light) Adjust ISO and shutter speed for background exposure Adjust strobe power and strobe to subject distance for foreground exposure Focus lock on near subject, then compose your image Composition issues - see CFWA tutorial My main problems with wide angle Back scatter Subject in foreground in blurred Uneven lighting - subject in foreground is too bright or background too dark