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Strobe and focus light issues

Strobe focus position

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#1 Trwen

Trwen

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Posted 05 July 2014 - 03:44 AM

My set up is: Canon S120, Canon housing, single Inon 1200S strobe mounted on 2 x 5" arms, Fantasea Nano focus LED mounted on cold-shoe top of housing.

 

Issues are: diving in fairly murky water (meaning a lot of floating plankton and debris) and this year, due to violent storms in spring, vis around 3-5m max. 

 

Current settings on camera are Manual, Auto focus on, ISO 100, f6.3, shutter speed 1/500, point AE focus, minimum flash power. On strobe the setting is Manual, with magnet in, and flash strength 5.5

 

 Exposure problems - the top third of a lot of photos is over exposed. I've read loads (feeling quite confused) about single strobe positions for macro pix and understood that the closer the subject, the closer the strobe to the camera - this makes sense. However, this does seem to produce a hotspot or flare (not sure which).

I've attached a typical photo with above problems

 

I am also having problems with backscatter - due I'm  sure to positioning of strobe.

 

I have heard that you set your camera settings before you go in and alter exposure for different shots with the strobe strength..is this the best place from which to start?

 

I tend habitually to take macro shots from around 3-6" away, most often on short animal turf on rock/boulder, aim the focus light directly at subject and use my focus light with shutter halfway pressed down to focus the camera lens ...and from there on  I'm lost about how/where to focus the strobe (which doesn't have an aiming light). Can anyone draw a diagram for me from which strobe position and distance from camera to start, given all the above criteria? When sites mention angles of 45degrees, they fail to mention 45degrees from what.

 

I know I'm probably asking too much but some help would be greatly appreciated! 

 

 



#2 TimG

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Posted 05 July 2014 - 10:07 AM

Hey Trwen

 

There's no photo attached. Do you want to give that another go?

 

You do need to get close with macro but 3"-6" seems very close indeed. 

 

The 45 degrees refers to 45 degrees from a straight line between the camera and the subject. So the subject to strobe angle is 45 degrees as is the angle from the camera to the strobe.


Tim

(PADI IDC Staff Instructor and former Dive Manager, KBR Lembeh Straits)


#3 bear35

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Posted 08 July 2014 - 12:44 AM

Hello Trwen,

 

The best advice I can give you is to get hold of a copy of The Underwater Photographer by Martin Edge. It will help your understanding of lots of different aspects. :swimmingfish:



#4 Ram

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Posted 09 July 2014 - 07:43 AM

I might be wrong, but have you tried a diffuser?

Ram