I built a fish-eye macro lens, but I need some advice

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Lou Jost
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Re: I built a fish-eye macro lens, but I need some advice

Post by Lou Jost »

My suggestion was really about doing the whole fisheye idea with your cell phone. Cell phone attachments could get you very close to what you want to do...

MarkSturtevant
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Re: I built a fish-eye macro lens, but I need some advice

Post by MarkSturtevant »

Thank you, Rik. Of course the fish eye virtual image goes to the other lens, and not to the sensor. But that would also be the case for my set up - the fisheye lens sending its image to the reversed lens. Only it doesn't... :?
Mark Sturtevant
Dept. of Still Waters

rjlittlefield
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Re: I built a fish-eye macro lens, but I need some advice

Post by rjlittlefield »

MarkSturtevant wrote:
Thu Apr 22, 2021 3:33 pm
Thank you, Rik. Of course the fish eye virtual image goes to the other lens, and not to the sensor. But that would also be the case for my set up - the fisheye lens sending its image to the reversed lens. Only it doesn't... :?
I think you missed the point about focus. The output of the clip-on fisheye will be a virtual image at infinity, optically like the real world that the lens in the cell phone is set up to handle. But your rear lens is set up to handle a real image located just a little behind the fisheye. Totally different focus arrangements. What you had with the clip-on was like trying to shoot a landscape using just your reversed lens on bellows.

--Rik

patta
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Re: I built a fish-eye macro lens, but I need some advice

Post by patta »

A bit late in the party,
my diagnosis for the vignetting, the offender may be the narrow tube you used to mount the CCTV lens. Rest seems ok.

Vignetting should disappear if such tube is much larger. I mount the CCTV with M12 screw directly on a flat adapter,
(M12 to C mount, C mount to M42, then M42 spacing rings, then the 50mm)

Why you can see the whole fisheye when looking into the lens, my guess is that the eye's aperture (iris) is centered and smaller than the camera sensor, so can peek the whole fisheye field. Also, the eye unconsciously compensates for partial vignetting and for massive variations of illumination.

The 50mm f/1.8 is ok, do not need 24mm pancake (although, will make the whole stack shorter). A 50mm f/1.4 M42 is my favorite. Aperture must be left full open.

Have a look also at the setup of Nicky Bay, he uses a straight macro lens for relay, mount the CCTV in front of it.

As written previously, thos CCTV lenses are many and all different. But, those built for small sensors have pretty narrow 'exit angle', to be compatible with standard sensors, so all work well on relay. I tried (but not measured...)10+ of them.
On Edmund Optics catalog, they specify the exit pupil placement of their M12 lenses; it may be used as ballpark for lenses from other vendors.

MarkSturtevant
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Re: I built a fish-eye macro lens, but I need some advice

Post by MarkSturtevant »

patta wrote:
Tue May 25, 2021 2:11 am
A bit late in the party,
my diagnosis for the vignetting, the offender may be the narrow tube you used to mount the CCTV lens. ...
Party crashers are welcome. I've since re-built the lens considerably, from front to back, and as it happens that includes using a much wider set of adapters in front to get the CCTV lens on without so many narrow bits. But I also put in the reversed 24mm lens. It now works without vignetting (yea!) I've taken pictures, and feel its about as good as this one will get. It is very fun to use.
At the moment, work and other distractions have kept me away from taking it out to really test it. But I hope to post a major update on this lens in a few weeks.
Mark Sturtevant
Dept. of Still Waters

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