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Snoot'ed boxer-crab, same exposure, but not?


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#1 MortenHansen

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Posted 17 December 2012 - 01:19 AM

Hi everyone,

I took these two images with my 7D and a homemade fiber optical snoot.
These were not the best shots (luckily) but I noticed something strange.


_mg_1436.jpg

_mg_1432.jpg


The images were taken with the same exposure: 1/250s, f14, ISO320, z240 full burst

There was a consistent amount of ambient lighting (the pictures were taken within 30sec)

Now my question is: Why does one have a black background and one is slightly lit up?


Any ideas would be much appreciated!
Happy bubbles, Morten

#2 Uli Kunkel

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Posted 17 December 2012 - 02:50 AM

Was that the snoot that I gave you?

If so I think I have an answer; .....it was sabotaged.

:D

#3 MortenHansen

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Posted 17 December 2012 - 06:10 AM

Was that the snoot that I gave you?

If so I think I have an answer; .....it was sabotaged.

Posted Image


Haha, yup, thats the one, you did a pretty good job sabotaging it since it only happens on maybe one out of five shots!? You evil genius you! :)

Have been playing around with it more and more lately, but I really don't get it why one exposure is different than the other.. Have you had the same issue?

-M

#4 Uli Kunkel

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Posted 17 December 2012 - 09:02 PM

Did you change anything between shots? Strobe position, the cap on the end of the snoot, or the camera orientation to the subject? Could also be that there was some light reflecting off of something (from one of the other holes on the snoot).

It would be interesting to do a few test shots without adjusting anything - when I used that one I noticed that the position of the end cap changed the light distribution quite a bit...

Edited by Uli Kunkel, 17 December 2012 - 09:03 PM.


#5 RWBrooks

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Posted 17 December 2012 - 10:08 PM

sun was out in one and not the other.....

Edited by RWBrooks, 17 December 2012 - 10:16 PM.

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#6 MortenHansen

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Posted 18 December 2012 - 02:24 AM

I didn't change anything on the strobe/snoot, it could of course be that I while looking through my viewfinder accidentally bumped the snoot and it changed the alignment to the flash tube, but that also would not explain why it was a regular occurrence.

It was consistently sunny, of course it could be that a cloud just passed by the sun when I took this shot- but that also doesn't explain the regular occurrence of it.

Before I started shooting I took a few images with the flash turned off to make sure that the background would indeed be totally black and at that point the sun was for sure shining.

I spent a total of 45min just with the boxer-crab on this dive and took a million pictures, quite a few of them in fast succession, and they are totally different in exposure, even when it was a matter of say, a frame/2 sec one would be good, one would not, then three would be good, one would not etc.

Anyways, as I was a bit bored while doing my safety stop earlier today I thought that maybe it could be the sun rays shimmering on the bottom, as the little critter was pretty shallow, 6-7m.

The ripples/small waves on the surface collect the light in the same way a magnifying glass does, and maybe that increased level of light would be enough to show in the images despite of the rather dark exposure, experiences anyone?

Next time I go on a cloudy day and see if I have the same problem! :P

-Morten

#7 tdpriest

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Posted 20 December 2012 - 05:40 AM

Look at the direction of the light: it's in front in one image, and behind in the other...

... the reason why, I guess, I have never been a snooty photographer: too little patience and too afraid to miss the shot by continually fiddling with my strobes!

#8 MortenHansen

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Posted 21 December 2012 - 02:40 AM

Too little patience and too afraid to miss the shot by continually fiddling with my strobes!


Hehe, for sure it it frustrating as can be! But I guess thats its one of the great things about working in a place like Bali, if I don't get the shot I was going for, I can simply go back there again the next time I have a day off :P

#9 tdpriest

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Posted 21 December 2012 - 04:14 AM

... one of the great things about working in a place like Bali, if I don't get the shot I was going for, I can simply go back there again...


Yeah...

... I can see that. I, however have to rely on Photoshop for last month's images from Seraya (plus a few days at Menjangan). And it's raining, cold and grey here...