Overexposure problem using TTL (Olympus E-M1)

[morretti]

On my first dive trip with the Olympus E-M1 and the Nauticam housing, I had a problem using TTL. I think it showed up the most with medium distances using the 60mm macro lens. I was using two YS-01 strobes.

I have some examples of the problem. All of these are shot with the mode dial on manual. The metering was center-weighted. Here’s a pair of flamingo tongues that were overexposed when shot at 1/320^th and f6.3:



My reaction was to drastically change the f stop, so the next shot was OK 1/320^th at f 14.0:



Same dive, here’s a toadfish overexposed when shot at 1/320^th and f 8.0:



Again, I stopped the camera down, and the next shot was OK at 1/320^th and f 14.0:




Here’s a shot that had OK exposure at 1/160^th at f 6.3:



But then the very next shot (different subject), is way over-exposed when also shot at 1/160^th at f 6.3:



The same scene is better exposed after drastic changes to the shutter speed and aperture, this time 1/320^th at f13.0:






Any ideas what I was doing wrong? Could I have had the flash setting on “full” rather than “fill”? Would that explain this?

 

[JackConnick]

I would shoot at a slower shutter speed maybe 1/250th. Not sure what your ISO is?

 

[Incident]

I would shoot at a slower shutter speed maybe 1/250th. Not sure what your ISO is?

\

Just curious how a slower shutter speed would make any difference in the final exposure?

The attached images are so tiny I really cannot see anything in them, but the only thing a slightly slower shutter speed would accomplish is a very marginal additional amount of exposure of the ambient light. Looking at the exposures listed, going from 1/320th or 1/160th down to 1/125th would be such a small incremental amount of ambient exposure, I cannot see how that would make any difference in these results.

The slower shutter speed would have no effect at all on the strobe exposure.


To the original poster:
I would ditch TTL entirely and go with manual control of the strobes. It is very easy to learn (even using trial and error) to figure out how to dial in your strobes to provide you with reliable and most importantly repeatable results.

If you could post some larger images, someone (me) would be happy to try to provide some more detailed analysis based on your examples.

 

[Wisnu]

I have the same set-up, and always use manual control. Agree, it's easy to learn.

 

[Interceptor121]

You are not doing anything wrong. I used to have a YS-01 and it would perform fine with the canon in TTL and give me similar overexposed shots with a panasonic
Ultimately it depends on the quality of the internal flash TTL. If you try and keep the ys-01 in ttl and lower the power knob it may even go worse so it is best to set the flash in manual mode and shoot with no pre flash
Inon strobes have an TTL-Low mode to counter this situations sea and sea have much simpler logic and usually fail at dimming ttl with a number of brands
It is a pain as macro shots are what TTL is really useful for

 

[jd950]

Although I agree that using manual is often the best way to go, it may be worth noting that I have no problem using ttl with the EM1 and Inon strobes. In fact, more often than not the exposure is pretty much dead on and I have been using TTL more often. I wonder if the problem is the combination of the YS strobes with the Oly? I have never used that combination but seem to recall some people having issues. I am wondering if the strobes are simply firing at full power on each shot? If aimed directly at the subject and firing close it could produce the conditions the OP describes, I think

 

[deeper thoughts]

Interesting

 

[JackConnick]

Although the EM-1 says it will sync to 1/320th, we've seen TTL exposure issues like this above 1/250th. The OP even states that his exposures are ok at 1/180th. It has to do with they way it syncs.

Again, not sure what ISO you are using. If you are using auto-ISO, you're going to be all over the board with exposure, and it tends to over expose quite a bit, don't use it.

Make sure RC mode is off.

Jack

 

[morretti]

Sorry that the photos are so small; I can try to re-do that later. I should have said that the ISO was set at 200 the entire time. RC mode was indeed off (or at least I intended for it to be off)

As for the possible incompatibility of the YS-01 and olympus, I didn't mention that I had an EM-5 on an earlier dive trip, with a single YS-01 strobe, and I didn't have this problem. (I also generally used a slower shutter speed).

If the problem were one of synching at the faster shutter speed, wouldn't that problem manifest itself by the image being partly black or shadowed?

 

[JackConnick]

Hi;

Generally yes, you'd see a black line. But what we're seeing is some TTL exposure issues like this with the YS-01 at the highest sync speeds - to be honest not sure why. Have you tried turning down the exposure knob on the strobe a bit?