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Author Topic: Experimental use of Biotar 2/25mm  (Read 6479 times)

Bjørn Rørslett

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Re: Experimental use of Biotar 2/25mm
« Reply #15 on: January 23, 2016, 14:55:29 »
OK, so it works. Good on you. This will as a side effect show you that your sensor isn't as clean as you thought :D

By looking at your setup, it is obvious more extension would improve the final result because you improve the relationship of conjugate distances to become more "normal" seen from the perspective of the lens.

Don't stop the lens much down if at all, and be aware of sources for stray light. Illuminating the scene with a flash is usually a good starting point for nice photomacrographs. In fact, studio flashes can be ideal because they are "large" light sources.
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Frank Fremerey

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Re: Experimental use of Biotar 2/25mm
« Reply #16 on: January 23, 2016, 14:59:58 »
this is more like it really looks like. and I found the smaller apertures to be better for the purpose too...
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Bjørn Rørslett

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Re: Experimental use of Biotar 2/25mm
« Reply #17 on: January 23, 2016, 15:15:53 »
You cannot increase depth of field much by stopping down, and at these magnifications only serves to destroy image sharpness due to diffraction.
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Frank Fremerey

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Re: Experimental use of Biotar 2/25mm
« Reply #18 on: January 23, 2016, 15:24:25 »
my money seems to be dirtier than my camera sensor...

yes, the god of stacking has to buy a macro slider first or a micrometer holder/mover...
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Thomas G

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Re: Experimental use of Biotar 2/25mm
« Reply #19 on: January 23, 2016, 20:40:10 »
Frank,
that looks promising  8)
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Bjørn Rørslett

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Re: Experimental use of Biotar 2/25mm
« Reply #20 on: January 23, 2016, 21:28:39 »
Is this a lens originally intended for cine? Such lenses can often deliver pretty good results for photomacrography because they were designed to have high resolution over a small format. In contrast, lenses for video usage have much lower resolution and tend to perform poor for high magnification, whether they be reversed or not.

Frank: do shoot a ruler so as to be able to calculate the actual magnification. My guess is that a reversed 25 mm lens should deliver 7-8 X or more for it to be in a more appropriate conjugate relationship.
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Frank Fremerey

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Re: Experimental use of Biotar 2/25mm
« Reply #21 on: January 23, 2016, 22:05:07 »
Yes. Cinema. Yes. Ruler. Tomorrow.
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Frank Fremerey

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Re: Experimental use of Biotar 2/25mm
« Reply #22 on: January 24, 2016, 19:24:22 »
a ruler shot for Bjørn:

(note that the rectangle is 5 x 5 sqmm)
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Bjørn Rørslett

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Re: Experimental use of Biotar 2/25mm
« Reply #23 on: January 24, 2016, 19:27:31 »
That's only around 3.5X, assuming the entire FX frame is shown. Try to get at least 7X and the quality should be better.
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Frank Fremerey

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Re: Experimental use of Biotar 2/25mm
« Reply #24 on: January 24, 2016, 19:34:31 »
OK, I will get some more extension rings.
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Erik Lund

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Re: Experimental use of Biotar 2/25mm
« Reply #25 on: January 24, 2016, 21:47:11 »
Please note just for info that Gaffer tape is not very light proof....
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Erik Lund

Frank Fremerey

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Re: Experimental use of Biotar 2/25mm
« Reply #26 on: January 25, 2016, 09:34:28 »
It is a temporary measue, Erik. The reducer ring from 52 to 49 is in the post...
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Erik Lund

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Re: Experimental use of Biotar 2/25mm
« Reply #27 on: January 25, 2016, 12:46:32 »
That doesn't make Gaffer tape light proof Frank  ::)
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Erik Lund

Frank Fremerey

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Re: Experimental use of Biotar 2/25mm
« Reply #28 on: January 25, 2016, 17:47:32 »
No. Better. That leaves is out of the picture.
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Erik Lund

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Re: Experimental use of Biotar 2/25mm
« Reply #29 on: January 25, 2016, 20:49:06 »
That still doesn't make Gaffer tape light proof Frank   ::)
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Erik Lund
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