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Author Topic: Odd things I found today  (Read 1346 times)

Offline bones615

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Odd things I found today
« on: June 12, 2011, 02:41:51 PM »
Raining outside so I got the light tent out, playing about with a reversed 50mm on my macro lens. 1st odd thing is the curve in the area in focus below. I assumed (maybe wrongly) that it should be straight.
The second odd thing is a needle i found in the wifes sewing box. 2 holes & a "v" in the top, whats that for?




Offline Beaux Reflets

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Re: Odd things I found today
« Reply #1 on: June 12, 2011, 03:07:01 PM »
V in the top may be for unpicking  :D and I guess the curve is due to light refraction being altered - could be useful or annoying  :legit:
:beer: Andy

"Light anchors things in place and gives perspective meaning."

The choices we make are rooted in reflection.

http://beauxreflets.blogspot.com/

Offline bones615

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Re: Odd things I found today
« Reply #2 on: August 08, 2011, 06:38:48 PM »
Found a strange insect today, any ideas???
No more than 25mm long including the tail.



Simon

Edit, Found out today its a type of mayfly. Should rename it august fly.
« Last Edit: August 09, 2011, 02:26:37 PM by bones615 »

Offline Paul Montgomery

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Re: Odd things I found today
« Reply #3 on: August 09, 2011, 03:47:11 PM »
That curve is odd - is it a flat surface ?
Or, just thinking aloud, I'm guessing that with a reversed lens mounted on a dedicated macro, you're looking at a fairly large magnification - does the plane of focus end up being a constant radius from the centre of the sensor, rather than the usual plane parallel to the sensor?

Offline Paul Montgomery

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Re: Odd things I found today
« Reply #4 on: August 10, 2011, 02:22:51 PM »
Hmm just thinking a bit more about my theory...
A 50mm lens has an angle of view of around 40 degrees according to the inter web. So, when its used the right way round, light from a 40 degree angle is bent to come out of the lens parallel. Does this mean that when its used reversed, parallel light going into what was the back is bent outwards though an angle of 40 degrees (20 either side of central) leading to a curve in the plane of focus ?

Offline bones615

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Re: Odd things I found today
« Reply #5 on: August 10, 2011, 03:24:05 PM »
All sounds a bit technical Paul, picture is an Ipod ear phone so it has a slight curve at the edge which might exaggerate the effect.

Simon

 

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