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Re: [OM] T32 for Macro--question

Subject: Re: [OM] T32 for Macro--question
From: Mike Gordon via olympus <olympus@xxxxxxxxxxxxxxxxx>
Date: Fri, 11 Jul 2014 18:57:06 -0400 (EDT)
Thanks for that great analysis,  Chuck.  I pored over every word.  It confirms 
empiric evidence  of the ND3 utiltiy for macro.  I have no clue how moving the 
ISO slider
can actually alter the flash function.  One potential obfuscating variable is 
possible slow recycling time w/o the bounce grip.  I recall Tim saying
the recharged light comes on well before it is really up to full steam.  By the 
time you moved the rig closer it may have topped itself off. 
IIRC the auto sensor is behind the "O" in the Olympus. I don't see how the 
flash will not just punch through the filter-- the flash duration will be 
longer allowing for proper quench signal.
I wonder if fresh batteries with 3 minutes between tests would alter the 
results.  Use of the BG-2 would speed it way up as well. 

Regards to Dr. Flash,

Puzzled  Mike





The instance of 1/50 second shutter speed below is a typo.  All shutter 
peeds were 1/60 second.
Chuck Norcutt

n 7/11/2014 4:53 PM, Chuck Norcutt wrote:
 Here's the true skinny on the T32 for macro question.  This is based on
 pure observation and real data.  No speculation or computer models
 involved.  Dr. Mike had asked the question... how close can you get to
 the subject with a T32 wearing an ND3 filter in auto mode before the T32
 goes bonkers and screws up the exposure.

 I first double checked the spec of the T32 in auto mode.  If you are
 working with ISO 100 the three auto mode settings on the T32 relate to
 apertures f/4, f/5.6 and f/8.  At f/4 the distance range is given as 1-8
 meters. At f/5.6 it's 0.7-5.6 meters and at f/8 it's 0.5-4 meters.

 Since I was working with my E-M5 I had a lower limit of 200 ISO which
 moves the three auto ranges up to f/5.6, f8 and f/11.  My test platform
 was my Bogen tripod with head and camera tilted down toward the floor.
 The target was a color advertising flyer surrounded by my large medium
 gray white balance target.   The head was wearing a macro slider to help
 vary the distance. I was shooting in subdued daylight in my house with
 the the lens set at f/5.6 and shutter speed 1/60 sec.  According to the
 camera that was 3 stops down from the ambient light.  In other words the
 flash was going to have to provide most of the light.

 My first test was to try and validate the T32's specs without using a
 filter.  My test setup was going to make it difficult to shoot from as
 far as 1 meter so I decided I'd start with 1/2 meter at ISO 200, f/5.6
 and see if it worked.  By the specs that should be pushing it a bit. And
 it turned out it was but not by much.  The resulting exposure was a bit
 bright but certainly not enough to blow the highlights.  I also tried
 the exposure with my Sekonic L-358 flash meter which reported that the
 proper exposure should have been 1/60 at f/6.3.  Since I had the camera
 set at 1/50 and f/5.6 the meter was telling me the flash unit was 1/3
 stop too bright.  My eyes would agree with that.  Close enough.

 Next up, change nothing except add an ND3 filter to the flash head.  My
 first thought was that the flash ought to keep huffing and puffing
 through the filter to get the exposure correct.  But no way did it do
 that.  What I got was an exposure that was about 2-3 stops down.  Don't
 ask me why it doesn't try to push through the filter.  My first thought
 was maybe it tries to but doesn't have enough power to do it.  But I
 don't think that's the case.  Just remember the data point even if, like
 me, you can't make sense of it.

 So, the flash doesn't push out any more light just because you've hidden
 the flash head behind a filter.  So let's try and lie to the flash using
 the ISO slide.  I put an ND3 filter on so I'll tell the flash that the
 camera is using a ISO 25... three stops slower than ISO 200 to
 compensate for the filter.  When you do this the aperture indicator on
 the flash also moves down by 3 stops to f/2.  Ignore it.  Leave the
 camera at f/5.6 as it was.  Take the shot.  Whoopee.  This is a better
 exposure than the first one which was a bit bright (probably from being
 too close to the target at 1/2 meter).  But this one's at 1/2 meter too
 and the exposure looks dead on.  Strangely the Sekonic says the correct
 exposure is 1/60 at f/3.2 when we just took it at f/5.6  So much for the
 Sekonic.  I have no idea why it says 3.2.  That means it believes there
 was 1-2/3 stops less light than was actually there.

 OK, can we get closer with this same setup.  Yes.  I moved the flash
 head down to 1/4 meter from 1/2 meter.  Same thing.  A very good
 exposure, no blown highlights.  I didn't try the Sekonic.

 Then I moved the flash head down to 0.16 meters.  I couldn't go any
 closer than this without some major adjustments to my setup.  I also
 decided it was unwise to go closer than this since I had had to tip the
 T-32's flash head in to try and keep the target illuminated.  I also had
 to change the m.Zuiko 12-50 to macro mode to get it to focus.  But once
 again I got a very good exposure.  I tried the Sekonic again which said
 the correct exposure was 1/60 at f/6.3. and this time only 1/3 stop away
 from the actual.

 Anyhow, the bottom line is the T32 with ND3 will deliver proper
 exposures to as close as you can get and still keep light on the target.
   To get the correct exposure slide the ISO dial to a 3 stop lower ISO
 but keep the same aperture.

 Chuck Norcutt








 On 7/10/2014 6:09 PM, Chuck Norcutt wrote:
> I haven't found it yet but I now know there is an ND3 filter somewhere
> in the house.  I'm still thinking about how to do this... I think it's a
> non-trivial task.
>
> Chuck Norcutt
>
>
> On 7/9/2014 8:16 PM, Mike Gordon via olympus wrote:
>> Dr. Manual Flash writes:
>>>> Eventually, it went about a stop beyond the recommended aperture which
>>>> I attribute to a relatively high ambient light level and/or maybe too
>>>> close to quench.
>>
>>
>>>> I'm going to have to rethink my fill flash completely. I may have to
>> go
>>>> back to fully manual. :-)
>>
>> As long as Dr. Flash has his meter out I wonder if he can put the 3 stop
>> ND filter on the T32 and see how close  one can get before it starts to
>> overexpose  in auto mode compared to baseline .
>>
>> I wish the ISO setting on the T32 would really change the flash output.
>>
>> Student of Dr. Flash, Mike
>>
>>
>>
>>
>>

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