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Ring flash with crossed polarizers: first tests

 
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Pau
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Joined: 20 Jan 2010
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Location: Valencia, Spain

PostPosted: Fri Apr 08, 2011 9:50 am    Post subject: Ring flash with crossed polarizers: first tests Reply with quote

Back in the 80s, when I begun to do some macros with my Olympus OM2, the T10 ring flash and its Cross polarizer were a too expensive object of desire.
Some weeks ago I was able to buy them used at a very reasonable prices and I couldn't resist.
Info about this equipment at:
http://www.alanwood.net/photography/olympus/t10-ring-flash.html
http://www.alanwood.net/photography/olympus/ring-cross-filter-pol.html
(Thanks, Alan)
No automatisms available without OM cameras, only two manual power settings, but I found easy to control the exposure playing with ISO settings and reviewing histograms.
First tests with the Canon 7D and EF 50mm f2.5 Compact macro. All hand held manual focus, f numbers between 11 and 16.

Young Ginko biloba leaf at 1:4 (aprox)


Small Euphorbia flower at 1:1 (aprox)


Eye portrait


Crop of the former image, strange interference pattern (the young man eye hasn't any square pattern!)


Self portrait of the flash against a mirror


I like the results very much:
- Almost no reflections (is what it's designed for)
- The colors are highly satured (in the Ginko I lowered a little the color saturation)
- The illumination is flat as expected but not too much for my taste
- In some pictures there is a slight blue cast, but shooting RAW as always I do it's easy to correct.

Any comments always wellcome
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Last edited by Pau on Sat Apr 09, 2011 8:39 am; edited 1 time in total
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g4lab



Joined: 23 May 2008
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PostPosted: Fri Apr 08, 2011 11:17 am    Post subject: Reply with quote

Very nice piece of kit!
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rjlittlefield
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PostPosted: Sun Apr 10, 2011 12:01 pm    Post subject: Reply with quote

In the eye, I wonder if the square pattern is somehow due to birefringence in the tissues?

--Rik
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Pau
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Location: Valencia, Spain

PostPosted: Sun Apr 10, 2011 3:22 pm    Post subject: Reply with quote

Of course you are right, it's due to the cornea birefringence acting as a curved retardation plate:
http://lo.um.es/publications/PDFs_main/AO_corneas_2002.pdf
(but my too basic physics knowledge don't allow me to understand this curious square pattern).
I never suspected it before, thinking in all the optical components of the eye as amorphous materials like optical glass.
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Craig Gerard



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PostPosted: Sun Apr 10, 2011 7:28 pm    Post subject: Reply with quote

Pau,

Interesting results!

Please post more images taken with this setup when available. Cool


Craig
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realjax



Joined: 19 May 2010
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Location: Netherlands

PostPosted: Mon Apr 11, 2011 12:11 am    Post subject: Reply with quote

Hi Pau,

I'm pretty sure I was the one who sold this particular flash to you Smile Glad to see it is serving you well!

On a side note: I had been thinking of building some sort of adapter for the olympus hot shoe so that the TTL quelch pin matched the EOS pin. In theory that should give you TTL on the EOS. I had no time to further investigate this and so I sold the flash on, but maybe you find it worth looking into?

cheers
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Pau
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PostPosted: Mon Apr 11, 2011 8:09 am    Post subject: Reply with quote

Thanks all for your comments,
Realjax: Yes, it came from Netherlands, and it's very nice Very Happy . I don't think it would be adaptable to the EOS eTTLII system because, apart of other possible electronic issues, both systems work in base at very different principles: The OM TTL measures the light reflected by the film itself during the exposure cutting it when it reaches a certain level while the new Canon system measures a preflash to precalculate the amount of light in the exposure flash.
I can't imagine any possible conversion, but in some form it's what I do manually: I check the exposure in a former test shot to adjust, not really the flash duration apart of the only two settings, but the ISO sensivity.
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realjax



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PostPosted: Mon Apr 11, 2011 11:29 am    Post subject: Reply with quote

True, its not adaptable to ETTL. But TTL should be possible. Even the newest Canons still support this. Smile
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Jacco
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Pau
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PostPosted: Tue Apr 12, 2011 9:58 am    Post subject: Reply with quote

Jacco,
The camera manual states that with other Canon flash no EX set to TTL it only fires at maximum power (i.e. no TTL mettering), do you have any reference for it?
In any case, as I'm too ignorant in electronics I never would try any modification Smile
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Harold Gough



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PostPosted: Wed Apr 13, 2011 12:38 am    Post subject: Reply with quote

Thanks, Pau.

Having gradually accumulated OM T series macro flash in recent years, I can sympathise with the difficulty in obtaining it at realistic prices.

The very last item, purchased early this year, was the cross polariser, which I have yet to use. It is very rarely offered. Your results are very informative and encouraging. I will be using mine with fully OM equipment throughout, at least for film use.

Harold
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realjax



Joined: 19 May 2010
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PostPosted: Wed Apr 13, 2011 4:37 am    Post subject: Reply with quote

Pau wrote:
Jacco,
The camera manual states that with other Canon flash no EX set to TTL it only fires at maximum power (i.e. no TTL mettering), do you have any reference for it?
In any case, as I'm too ignorant in electronics I never would try any modification Smile


Obviously you would not want to modify either the camera, nor the flash unit Smile. I was thinking of getting an EOS shoe/connector from for instance a cheap flash extension cable and a similar cheap OM flash connector. Then rewire the EOS quelch out pin to the OM quelc in pin in such a manner that the OL flash can be plugged on the OM shoe and the other end on the cameras shoe.

If I'm not mistaken on the eos the shoe looks like so

1____2

3____ 4
___X__


Where 1 is the quelch. Note: 3 needs to be covered, otherwise the EOS camera thinks it is connected to an ETTL compatible flash unit and TTL is automatically disabled. I used to have some more reading on this, if you are interested I can see if I can still find it, just let me know.

The Olympus flash connector looks like this:
(from the top of my head and valid for the ringflash)

__X__
____1

where 1 is the quelch pin.
In theory not all that difficult to do, the question remains if the quelch signal coming from the EOS will be understood by the OM flash. Basically it is just a signal that says 'stop the flash' so it can't be all that sophisticated.. Smile
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Pau
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PostPosted: Wed Apr 13, 2011 10:39 am    Post subject: Reply with quote

Jacco,
Many thanks for your sugestions and schemes.
I'm still not enough skilled (or brave) to try it, and if the camera don't allow ordinary TTL metering as I deduce reading the manual, it wouldn't work.
But, if you have the time and can do perform tests, manual settings are often as good or better than automatisms.
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Linden.g



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PostPosted: Sat Jun 15, 2019 11:21 am    Post subject: Reply with quote

Excellent images
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Pau
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PostPosted: Mon Jun 17, 2019 3:52 am    Post subject: Reply with quote

Linden, thanks for your kind comment.
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