video lenses for macro?

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soldevilla
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video lenses for macro?

Post by soldevilla »

Hello. Has anyone tried using a video camera lens for
an optical assembly for macro?

I own some lenses, Tokina 8mm f / 1.4, Tokina 8mm f / 1.3 and 16mm Rainbow. f / 1.4 ... and I can do some testing.

lauriek
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Post by lauriek »

A member here (linden.g) has used Canon video lenses at 17x mag with very nice results. He's on flickr too if you don't get any more responses here... http://www.flickr.com/photos/13084997@N03/4145527263/

soldevilla
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Joined: Thu Dec 16, 2010 2:49 pm
Location: Barcelona, more or less

Post by soldevilla »

Thanks Lauriek.
Encouraged by what I read, last night I tried the 16mm inverted with a extension tubes. I am delighted with the results! I would rate the outcome as the best I've found. Wulfenite I used as a "model"is not the best, but I'm surprised the growth of tiny crystals on the front and had not seen through the binocular. Add a line like scale. The image is a reduced image size so that it can post on the forum, but has no cut.

Interestingly with the diaphragm full open there is much loss of contrast but it seems that to close diaphragm does not affect the definition.

Image

rjlittlefield
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Post by rjlittlefield »

soldevilla wrote:Interestingly with the diaphragm full open there is much loss of contrast but it seems that to close diaphragm does not affect the definition.
It would be surprising if a general purpose f /1.4 lens gave overall best results wide open. Usually they have aberrations that degrade both contrast and resolution, so that best results are obtained stopped down some. See HERE, second panel, for some examples.

Probably there is some very fine test pattern that would look "better" wide open, but this really means "not quite as awful" because it would be way out on the end of the MTF curve, possibly past a point where the lens would produce no image at all for some less fine tests. See http://www.bobatkins.com/photography/te ... ution.html and consider the curves for 0.75 and 1.0 wavefront error.

--Rik

soldevilla
Posts: 684
Joined: Thu Dec 16, 2010 2:49 pm
Location: Barcelona, more or less

Post by soldevilla »

Very interesting. tomorrow, if I have time I try to test several diaphragms and extensions with this objective to find (or try at least) the optimum operating point. I guess I could try to mount something to check the quality of the wave (I have some experience in optical astronomy), but if I can not influence the quality, I'd rather not know about that ...

soldevilla
Posts: 684
Joined: Thu Dec 16, 2010 2:49 pm
Location: Barcelona, more or less

Post by soldevilla »

Hi, I have waited to make a lens adapter for the video before doing the test. I am very pleased with the outcome of this inexpensive objective and I think this is the first time I get this quality in a FOV of only 2mm.
I have made the comparison in the same conditions, closing diaphragm and shooting in AV. I have discarded the image f / 1.4 because it was awful, the rest are f / 2, f/2.8, f / 4, f/5.6, f / 8 and the last is with the diaphragm almost completely closed (video lenses completely close the passage of light). From what I see, this lens works well with f5, 6 f / 8. These images have no treatment except the crop at 25%.

In these circumstances I made my first serious test and this is the result, a Zalessite

Image

Image

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