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A diffuser stole my power!


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#1 Wiggsy

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Posted 06 June 2014 - 02:13 AM

A diffuser stole my power!
Hello Alex and crew. I'm off to fabulous Aiyanar Resort, Anilao in a few weeks and wanting to sort this problem out as I would prefer to use a diffuser using macro. Actually I'm leading a group of 32 and am really looking forward to some great critter dives. But....I'm having problems with the Inon .5 stop diffuser on d180 strobe. I find that, if I use this diffuser it underexposes everything by about 4 stops (not .5) but only when I use the strobe on auto. On auto this diffuser cannot work properly with this strobe. If I return the strobe back to manual function full power is restored and I get perfectly exposed shots with very little loss of power (.5 stop if fairly difficult to pick). It is as if the auto sensor gets too much light fed back into it by refraction and 'backsplash' off the diffuser. There is a small hole in the diffuser to allow the sensor to function, but I think there must be a considerable light flow backsplash that fools the sensor into shutting the strobe off prematurely. Anyone else experience this. Any comments..? I'm thinking of either drilling the hole out larger the avoid light backsplash into it, or perhaps blacking out the edges of the whole. Any comments..?


Many thanks,


Alan Wiggs

 



#2 SwiftFF5

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Posted 06 June 2014 - 03:31 AM

Since I mostly do video, I'm not really qualified to address this, but my first thought had been to insert some of tube to block the light from hitting the sensor.  Blacking the edges might be an easier way to start and see if it helps.


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#3 tdpriest

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Posted 07 June 2014 - 04:38 PM

A diffuser stole my power!

 

 ... if I use this diffuser it underexposes everything by about 4 stops (not .5) but only when I use the strobe on auto.

Alan Wiggs

 

 

 

Why on earth (or under the water) use the Auto setting? It's unreliable at best, worse than TTL. You should, however, check the magnet setting (advanced cancel circuit) and the filter on the sensor window (EV compensation switch) if you insist on using Auto.



#4 Wiggsy

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Posted 07 June 2014 - 05:36 PM

Tim - I actually find External Auto reasonably effective and have done so for around 12 years and probably well over a dozen articles in Sportdiving Magazine. The Inon d180 strobe only has 4 settings on manual and providing the strobe to subject distance is the same as the lens subject distance and the strobe orientation is accurate I get quite predictable results using external auto. I've never used TTL so can't compare.  I use the camera on full manual, tell the strobe on External Auto what aperture I'm after and the sensor generally gets very close to final exposure - maybe a tweak at bracketing or two. The magnet is another issue altogether - with my most recent 2 cameras ( Canon S95 and Olympus EPL-1) the magnet is inserted as there is no pre-flash on manual. My earlier camera (one of the early digital era cameras) was the excelent Olympus C5000z which required the magnet 'out' even when in full manual. 

I got a useful reply though from Aquaventure which confirmed my suspicions. Inon do manufacture a diffuser for external auto that has a larger hole with a ferrule around it to block light transmission through the diffuser.  I will make a few adjustments to mine as the diffuser supplied with my unit (years ago) was for full manual use only. The only difference is the hole over the sensor is slighty larger with a metal ferrule - will be easy for me to modify mine.  Cheers!



#5 Interceptor121

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Posted 08 June 2014 - 03:28 AM

If you want to use the AUTO setting you need to make sure you buy the -0.5 white diffuser external auto

 

The TTL diffuser that comes in the box or any of those not labeled as external auto will not work properly because of the size of the hole on the light meter

 

The normal TTL diffuser has a very small hole that is flat on the diffuser surface whilst the auto diffuser has a special additional part attached to it that acts as a hood for the light meter (this also prevents you using the 1/4 boost level on the strobe)

What happens when you use the normal TTL diffuser in auto mode is the light reading of the strobe light meter gives a too optimistic read and therefore tells the strobe to shut off resulting in underexposed pictures.

 

You can only use the normal diffuser with TTL and Manual mode, if you intend to use the strobe AUTO mode you need an auto diffuser. The auto diffuser works in all modes but they are only available White and Blue no other color temperature. I use two of those on my setup and I find that it works wonders combined with TTL in close shots to have different shadows (When I want them to be different)

 

Attached picture of the two diffusers side by side you will see what I mean easily

Auto diffuser left TTL/Manual diffuser right

Attached Images

  • inon.jpg

Edited by Interceptor121, 08 June 2014 - 03:31 AM.

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#6 Wiggsy

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Posted 08 June 2014 - 04:25 AM

Thanks Interceptor for your detailed and thoughtful reply....Yes , this is what I suspected and goes along with what Aquaventure suggests. I have limited time before a trip to the Philippines so might try a slight modification to the manual diffuser I have. I will drill the hole out larger and fit a rubber grommet - this should block light spill through the diffuser material into the sensor.  I'll give it a try....if I have no success I will try to source one from Manilla. Thanks again for taking the time to make this so clear.



#7 Interceptor121

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Posted 08 June 2014 - 04:52 AM

You are welcome and I hope the modding goes well. The part in contact with the light meter is plastic kept together by a metal ring

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#8 tdpriest

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Posted 13 June 2014 - 02:10 AM

Tim - I actually find External Auto reasonably effective and have done so for around 12 years and probably well over a dozen articles in Sportdiving Magazine.

 

Look: I offered an honest opinion, and one that isn't uncommon. I don't really need to be browbeaten with Sportdiving Magazine...

 

... I would note, in passing, that the Inon diffusors are very brittle and wish you luck with machining them.

 

If a photographer is interested in fully flexible strobe lighting, perhaps the Z230 would be better if manual control is limited on the D180?



#9 Wiggsy

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Posted 13 June 2014 - 03:42 AM

Tim - I did not intend to beat any brows! Just that I've never had a problem with the d180 on external auto - and I was succinctly providing evidence of that by relaying some of my publication experience. Indeed - a very low error rate if any. The only time there has been a problem is with the strobe fitted with the diffuser. I agree that it is brittle and will go very carefully. Thanks for the pointer on the Z230 - would love one, but as a teacher by trade can't find the dollars right now.  Again, I have found the combination of the camera in full manual with the strobe on external auto very successful. Cheers and thanks to all.