Help with Canon S90 & A35 Strobes

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Postby falsebay » Fri Jul 30, 2010 4:11 pm

HELP! I have shot over 200 pics with my new canon and Ikelite strobes and I've gotten 5 good shots. What camera/strobe settings work when the background is very light and sandy? Seems like every strobe setting gets overexposure. The camera has a bad habit of NOT focusing...whether it is in macro, normal, or zoomed out about half. I do great land photography but this has me baffled. I've tried every camera/strobe setting on objects around the house... see virtually no difference between most of them. Also the focusing works above water, what am I doing wrong??? Any and all suggestions welcome!!!
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Postby seekncritters » Fri Jul 30, 2010 4:24 pm

falsebay wrote:What camera/strobe settings work when the background is very light and sandy?
.
Depends on a lot of things, but I've found it's generally easier to blow out images when the background is light and sandy.

Tell us what settings you were using on the camera and strobe, underwater. What were your photo subjects? Were the subjects high-contrast sort of subjects?

Regarding focus, for close subjects were you in macro mode with the lens zoomed out all the way (i.e., not zoomed at all)? For far away subjects, were you in macro mode?

-Dana
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Postby James » Fri Jul 30, 2010 6:58 pm

We may need a bit more info.

I am not really versed with the AF35, frankly, I would have gone Inon but it is what it is.

Macro, the S90 is known not to focus well if the lens is zoomed in macro. You may need to alter your method, go to manual focus and preset focus and move the camera into the focus zone like we used to with the Nikonos I-II-III.

The S90 Auto mode, do not use it underwater, use Program or Av/Tv or Manual.

If the AF35 is in Auto mode you use the knob on the Auto Sensor to control exposure, 1-10, 1 lowest output and 10 is highest flash output.

I do not think the AF35 is a sTTL type strobe, I believe that it is a Auto sensor and simply uses the camera strobe for a sync signal. This means the strobe is responsible for it's own exposure component and it does not boot strap the camera strobe.

Get a diffuser.

From the Manual:

"When the AF35 is in any manual setting the Auto Exposure
Selector Dial setting has no effect on the flash output."

Try this, S90 strobe in Manual at lowest power (under the Menu button), S90 in Av mode, AF35 set for no-preflash, AF35 in Auto mode, turn the AF35 flash sensor knob to lowest setting (1), set camera ISO to 100 and set f stop on S90 to f5.6.

Do these things, staying at f5.6 rotate the AF sensor knob, each click making test exposure and compare.

Next, set the AF power sensor knob to mid position and start with the S90 (set as above, Av mode, camera strobe in Manual, low power) f stop at f2.0 and work up to f8.0 taking a test shot at each.

Keep your test subject and distance consistent. Tell me what happens.

James
Swim down, swim around, swim back up

Canon S90 with FIX90 housing, 2X Inon D2000 strobes, DIY tray, Inon UFL165AD, Inon UCL165AD, Inon UWL100-67 with dome kit, ordered Fisheye UWL-04
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Postby James » Fri Jul 30, 2010 9:36 pm

Reading the AF35 manual I cannot find that it allows a pre-flash/no pre-flash setting. If this is the case, this means it always expects a pre-flash and must have a pre-flash to sync, so then try this:

S90 in Av mode
S90 strobe in Auto (Menu) and under Function Set Button go to minimum exposure (to conserve battery power is my purpose)
Set ISO 100
f stop to f5.6 and then go up and down with test shots
Set AF35 to Auto mode
Set AF35 Sensor knob to center position

Take some test shots first keeping Auto Sensor knob in center but vary your camera f stop full range

Next keep f stop at 5.6 and vary AF35 sensor knob up and down full range

Now, go with me here, set the S90 ring control to Exposure Compensation, still in Av mode, set camera exposure compensation plus two stops, no compensation and then minus two stops. Set your AF35 power knob using the best position from the previous tests and set f stop likewise.

Just trying to help figure it out. If after all of this, you see no difference in exposure as you said in your OP, then your strobe AF sensor knob/unit is possibly not functioning and the strobe is dumping full power each shot.

Do you know how to test for camera strobe/AF35 sync?

Try this, shoot into a mirror, you should see the flash in the image review, if you do not, you have a pre-flash/flash sync issue to sort out, get back with me on that.

BTW, you really, really need to block all forward light to your image from the on-board strobe or your AF35 will never function correctly.

James
Swim down, swim around, swim back up

Canon S90 with FIX90 housing, 2X Inon D2000 strobes, DIY tray, Inon UFL165AD, Inon UCL165AD, Inon UWL100-67 with dome kit, ordered Fisheye UWL-04
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Postby scottg » Tue Aug 03, 2010 8:41 pm

sand is tough.. make sure you shoot in manual mode, at a high shutter speed, and put your strobes on manual power (low power).

Once you have a basic understanding of how to control your aperture, shutter speed and strobe power getting those photos properly exposed should be quite easy.

Scott Gietler Owner/Editor, Underwater Photography Guide & Bluewater Photo http://www.uwphotographyguide.com http://www.bluewaterphotostore.com

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