Weird problem with a Ike 125. Anyone has a clue?

After coming back from Ike's shop for the second time, I have a strobe that fire properly when in TTL, 1/2, 1/4 and 1/8. It does fire in Full but the picture come out completely underexposed.

This is the test I made after trying the strobe in my pool today.

Camera on manual, 100 ISO, 1/250 sec shutter speed, f/13

Keeping the distance from subject to dome and from subject to strobe always the same.

I take a picture changing ONLY, the strobe setting, from TTl to 1/8 stoping in all stations.

I can see in the histogram of my 20D the gradual increase on exposure, about 1 stop going from 1/8 to 1/4 and then from 1/4 to 1/2.

When I try the Full position I can see the strone fires but the picture is just a black frame and the histogram shows only a very skinny spike in the very left.

The ttl works wonderful. I can go in manual from f2.8 to f32 and the picture keeps exposing nicely.

When I take control of the strobe from the housing switching the TTL control to manual, I can see in the histogram a distinctive effect in the exposure for every small change in strobe output, seems like the strobe can go FULL when comanded from the TTL board in the housing. You can see the difference in the noise of the strobe recovering, in the time it take to recover and in the histogram.

Ikelite's repair dept returned the strobe with a note that say We can not reproduce the problem. The first time I sent this sick pupy the replace the battery pack.

Does this sounds like a sinc problem? Does the strobe get's tested for output but no for timing?

IS IT POSSIBLE FOR THE STROBE TO FIRE TOO SOON OR TOO LATE AND MISS THE SHUTTER OPENING WINDOW ONLY IN FULL POWER ?

Should I run my Lamborgini over the whole rig and take on another hobby like knitting or collecting spiders?

Please help? Please???

Thanks in advance to all reading and doing the head scratching thing...

Hugo

Do you have the Ikelite housing with TTL support? If yes, you should direct cable the housing to the strobe and use the housing controller to control the strobe manually with the strobe set to TTL.

As for the problem you are having, my guess is that the Canon is firing a preflash that is triggering the strobe and the reason 1/8, 1/4, and 1/2 work is that the strobe recycles fast enough to flash for the preflash and the main flash. But at full the strobe cannot recover fast enough, nor should you expect it to.

If this doesn't seem to be the problem, please tell me more about your configuration i.e. what's connected to what.

Have had threats of using a Ferrari to demolish obstinate equipment, but never a Lamborgini. Sounds intriguing, but check ground clearance carefully.

Need to know what camera and housing you are using. I suspect Peter Schulz is correct that you are getting full dump on a preflash which needs to be turned off. Some cameras like the 5060 must be changed to Slave mode for manual strobe.

HI Ike.

Thanks for the reply.

I'm using a Canon 20D. It is no pre-flash here.

When I use the ttl circuit from the housing as manual control, every step up and down in flash output can be traced in the histogram and reacts ok.

The problem is when the strobe output has to be controllled from the strobe dial. In the TTL, 1/2, 1/4 and 1/8 positions the output adjust fine and can be traced in the histogram. When I choose Full everything goes to hell. Severe underexposure and only a thin spike in the histogram all the way to the left.

I'm looking for the keys of the Lamborgini as we speak.

Hugo

Ike, this question is for you.

When your people test strobes do they measure output with a light meter?

That would show only the lenght of the flash

Do they measure if the strobe fire too soon or too late?

Do they look at a histogram of any kind?

Thanks in advance for your reply.

HUgo

Re "I'm using a Canon 20D. It is no pre-flash here."

From the Ikelite site "Camera disables pre-flash to the hotshoe unless a correct Canon eTTL capable strobe is attached."

http://www.ikelite.com/web_pages/camcanchart.html

My guess is that with the Ikelite eTTL circuitry the strobe looks like a Canon eTTL capable strobe and thus sends preflashes that are incompatible with using the DS125 manual control settings.

That said, I don't see this as a problem as it's easier to control the strobe from the housing manual control settings.

Peter Schulz is 100% correct as usual! You are shooting with a 20D but leaving the housing in TTL and putting the strobe in manual. If the housing is in TTL then the camera is going to want a preflash, and if the strobe is set to manual full power, the preflash will be fired at full power.

If you want to control the powers with the switch on the strobe, you must put the housing in manual mode by holding both buttons down for more than one second. When the housing is set to manual, no preflash will be fired and you can use whatever strobe setting you want.

If shooting TTL, set the housing to TTL. If you want to shoot manual, set the housing to manual, and you can use either the housing (easier way) or the strobe to set strobe power level.

I'm sorry Ike but Peter is not right.

When the strobe is in TTL the housing controls it. When the strobe is in Full, 1/2, 1/4 and 1/8 the only signal the strobe counts on is the fire signal from the camera.

Furthermore, once the strobe is set other than TTL what's different between full and the other settings?

The strobe was functioning properly in all settings before. The only complaint I have is with the swich in the FULL position.

And to firther my position this start happening when the strobe was going death when set in the full position unless I start wiggling the switch back and forward. It is something wrong with this puppy.

If looking at the histogram, with the camera in full manual, Full strobe should deliver a picture overexposed compared with the picture taken with the strobe in 1/2 strobe. That doesn't happen.

I guess is time for another call to the repairs department tomorrow morning.

Thanks for trying to help Peter and Ike, I truly appreciate your coments and your time spent doing the head scratching thing.

Good night.

Hugo

Huquito: Think of me as just the typing pool, but answer was from knowledgeable type who designed the conversion circuitry and much of the strobe electronics. You are missing the fact that the conversion circuitry in the housing tells the camera what is attached and what to do. Housing set to TTL will command a preflash which strobe can supply but not recover in time for primary flash if set to full power. Strobe in ttl supplies correct preflash with most of its energy availablel for the primary flash.

Works fine when used as designed. Why reach for the strobe manual settings when it is on the housing with the 20D conversion circuitry.............?

HI.

I have to admit that I was wrong.

I had a very long conversation with one of the engineers in Ikelite this morning, after a very detailed explanation of the simptoms, I found he was nice enough to give me a very detailed explanation of WHY the strobe acted that way.

It is clear to me know that this strobe is problem free.

I was worry thinking " This strobe has a very insignificant problem now, I can live with it, but it is going to turn into a big problem for sure when I'm diving in the middle of nowhere with no back up"

Thanks again Ike and Peter for trying to help.

I can return the Lamborgini to the its legal owners.

Thanks aggain.

Hugo