Under exposure

Same problem as last time. I use an Oly C4000z with PT10 housing. I recently bought an Ikelite DS50 strobe with TTL slave. No matter what I try and I've tried all the advice posted here before, my shots come out under exposed. Does anybody own the same set up, what do you do, any further specific advice would help.

No matter what I try and I've tried all the advice posted here before, my shots come out under exposed.

Can you list what you've tried and maybe post a sample image?

Here's what I would do:

Set up the camera and the strobe on a table or desk. Use a subject a few feet away and once you've framed the shot, don't move either the camera or the subject. Test the setup as follows:

1) Take a pucture with your normal setup.

2) Make sure the slave sensor is pointing backward at the camera, not toward the front at all as sometimes it will pick up the DS-50 light output and get confused. When I was sorting out similar issues with my DS-125s, I jury-rigged a little cap and fiber optic setup to make sure I was sensing only the camera's internal flash during my tests (it worked so well that I now have a jury-rigged fiber setup for underwater use as well). Turn the sensor sensitivity to MAX. Take a test shot -- any difference?

3) Increase the camera's internal flash exposure compensation (not the overall exposure compensation) to +1.0EV or more. Test shot(s) Does it make a difference?

4) Open up the battery compartment of the strobe sensor and move the little switch inside to the left position per: http://www.ikelite.com/web_pages/dsenswitch.html. Test shot -- does it make a difference?

5) If you do all these things and you still get underexposures, send the strobe and sensor back to Ike for testing. Maybe they aren't working properly.

Mike

FWIW I had exactly the same problem with C5050Z and DS50/TTL. After a lot of messing around I have given up on the TTL, and I'm expecting the manual controller to arrive next week (24 hours before I leave for my next trip, I hope).

However I have the impression that I have seen lots of other people report great results with this combo. So maybe I'm just unlucky with strobes ...

On the plus side, I learnt quite a lot about how to get some pretty good shots just using the DS50 on full dump all the time. B) Should stand me in good stead when I have the manual controller.

-David

I suspect the pre-flash duration switch in the TTL sensor provides very course settings. I find I have to dial the flash intensity to -2.0 when the switch is to the left and +0.3 when to the right. Perhaps an incremental dial would do the trick. See this http://wetpixel.com/forums/index.php?act=ST&f=1&t=2393 for sample pics.

Maybe Ike would like to comment on this?

I find I have to dial the flash intensity to -2.0 when the switch is to the left and +0.3 when to the right

Wow, that's interesting. With the switch to the left, I usually have to have the flash intensity set at +1.0! Hard to believe that there could be that much variation, but I have proof it works! (what's the little smiley thing for "scratching my head" . . .)

Mike

After some days off contact with Ike I have finally discovered that the following works on land - Aperture priority F5.6 slave switch to the right and +2 on the internal flash. I hope to jump in our pool this evening and see if that works otherwise I will try it when I dive tomorrow morning. The strange thing is that i have tried similar settings only to find that in a series of 5 or 6 shots no 2 are exposed the same!!! By the way I have my doubts that these settings will work underwater.

I have a Powershot G2 with Ikelite housing and DS125 strobe with TTL sensor, so a comparable set-up. My pictures where also all under-exposed, even following the advice I found here.

During my last dive this weekend, I think however I found another possible issue: one thing mentioned before is that the sensor must not see the light coming from the strobe, so you need to point the sensor backwards, which I did, but you should also be carefull that the sensor does not pick up reflections of the strobe light, from the ground for example.

I was taking close-up pictures near the ground and think that the sensor could have picked up light from the reflection of the strobe on the ground, even when the sensor is pointing backwards (but a downward too). When I took pictures from above the subject instead of from the side, taking care that the sensor was not pointing to the ground, I had the impression that the lighting was much better.

This was only my third dive this weekend with my camera, so I will need to do some more dives to confirm, but this could be an idea if you dive in similar circumstances.

I am diving in Zeeland in Holland, where waters are dark (under 10m) and full of dust, so you need to take close-up pictures and it is probably easy for the sensor to pick up reflections.