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

Have questions about the equipment used for macro- or micro- photography? Post those questions in this forum.

Moderators: rjlittlefield, ChrisR, Chris S., Pau

MarkSturtevant
Posts: 1946
Joined: Sat Nov 21, 2015 6:52 pm
Location: Michigan, U.S.A.
Contact:

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

Post by MarkSturtevant »

I have built a fish-eye macro lens, but there is an issue with it, and I would like some advice about how to best resolve it. The lens I built is closely based on the relay lens design from John Hallman (See https://translate.google.com/translate? ... sheye.html ). I was fortunate to have most of the components already, so it was mainly a matter of purchasing a CCTV fish-eye lens and only a few of the adapters. I can post a list of parts if someone wants it, but I don’t know how much this version will need to change.

The resulting rig is shown below.
FishEye1Labelled.jpg
You can see that I follow Hallman’s design rather closely, but there are various differences. Two possibly important differences are the exact specs of the CCTV fish-eye lens and the reversed prime lens. The 50mm prime lens is one that I had on hand, and so I was hoping to sneak it in and not have to buy a new lens for this specialty purpose.
Other differences are presumably not important. One of some note is that I used an Asahi Pentax bellows for the main body of the lens since I can quickly change its length while I experimented with this thing.

But here is the issue that I am seeking advice about. It’s obvious with a sample picture taken with the above lens.
SamplePix.jpg
As you can see, the lens produces the Worst Vignetting In The History Of Optics. I’ve fiddled with the amount of extension on the skinny extension tubes near the CCTV lens, focus of the 50mm lens, and extension on the bellows. But so far the only way I can find a focused image is to extend the skinny extension tubes and also the bellows out toward their fullest distance, and only then does a focused image appear along with extreme vignetting. I am pretty dumb when it comes to optics, but seems likely that a big reason for the vignetting is the extreme extension that is needed.
I am not concerned about the off-centered-ness (the distal lens is wiggly, since the tubes mounted on the end are extended out to the point of nearly falling off), or the image softness (it was a semi-hand-held picture with a not very short exposure taken without a flash). I've taken sharper images with it.

I am sort of hoping that the way to solve this problem is to get a different CCTV lens other than the one indicated in the figure. But I suspect that the actual solution will be to replace the 50mm lens with a wider angle lens. Likely the Canon 24mm like in the Hallman rig. But I would like some advice just to be sure first.

Thanks for looking!
Last edited by MarkSturtevant on Tue Apr 20, 2021 5:05 pm, edited 1 time in total.
Mark Sturtevant
Dept. of Still Waters

RobertOToole
Posts: 2627
Joined: Thu Jan 17, 2013 9:34 pm
Location: United States
Contact:

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

Post by RobertOToole »

Hi Mark,

2.1mm? You are really going for it! I did try a 8mm f/2 preset SK Cinegon and was able to fill most of an APS-C frame. I will look for my notes, maybe it will help? I believe I used a longer main lens. I'll look for my notes.

Okay found my notes I used a Componon 4/28 as a main lens, with the 2/8 Cinegon with some space between the two. The 4/28 CPN was on 2 inches of extension from the body. Nice and sharp and filled the frame. FWIW this was the first time I was able to get anything out of that 8mm Cinegon!

Best,

Robert

MarkSturtevant
Posts: 1946
Joined: Sat Nov 21, 2015 6:52 pm
Location: Michigan, U.S.A.
Contact:

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

Post by MarkSturtevant »

RobertOToole wrote:
Tue Apr 20, 2021 1:13 pm
Hi Mark,
2.1mm? You are really going for it! I did try a 8mm f/2 preset SK Cinegon and was able to fill most of an APS-C frame. I will look for my notes, maybe it will help? I believe I used a longer main lens. I'll look for my notes.
Okay found my notes I used a Componon 4/28 as a main lens, with the 2/8 Cinegon with some space between the two. The 4/28 CPN was on 2 inches of extension from the body. Nice and sharp and filled the frame. FWIW this was the first time I was able to get anything out of that 8mm Cinegon!
Robert
I am not entirely sure what the 2.1mm means. Presumably that is the focal length. That sort of measure is pretty typical for these little CCTV lenses (1.8mm, 2.0 mm, etc.). Normally, these lenses are to be mounted onto a circuit board with a sensor array directly underneath it.
Now John Hallman says that these lenses generally have an aerial image about 7mm behind the lens. So If I understand the situation (and I might not), one needs to get the 2nd lens to focus on that aerial image.
Mark Sturtevant
Dept. of Still Waters

dickb
Posts: 342
Joined: Mon Jul 05, 2010 1:54 am

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

Post by dickb »

MarkSturtevant wrote:
Tue Apr 20, 2021 12:12 pm
As you can see, the lens produces the Worst Vignetting In The History Of Optics. I’ve fiddled with the amount of extension on the skinny extension tubes near the CCTV lens, focus of the 50mm lens, and extension on the bellows. But so far the only way I can find a focused image is to extend the skinny extension tubes and also the bellows out toward their fullest distance, and only then does a focused image appear along with extreme vignetting. I am pretty dumb when it comes to optics, but seems likely that that a big reason for the vignetting is the extreme extension that is needed.
What you are doing in essence is blowing up the tiny image circle produced by the CCTV lens and projecting it onto the your relatively large image sensor. You are getting a lot of vignetting here because the magnification of the image by the reversed 50mm plus extension isn't large enough. So you need more extension to get rid of the vignetting, not less. Or use a secondary optic with a higher magnification than your reversed 50mm. In a similar scheme I once used a 19mm Macro-Nikkor, or a reversed 23mm Xenoplan.

Before you invest too much in additional gear (I speak from experience) you should realise that the CCTV lens is the limiting factor here - it is designed to project a tiny image circle onto an equally tiny sensor with a limited resolution. Using a relay lens system you can make the image larger but the resolution doesn't increase, and all the lens flaws will be very visible. The upside down image is a hassle. It may be easier to use on a camera with an appropriately tiny sensor, Pentax Q comes to mind.

Still it's a fun exercise, but I wouldn't recommend buying any gear that can only be used for this experiment.

MarkSturtevant
Posts: 1946
Joined: Sat Nov 21, 2015 6:52 pm
Location: Michigan, U.S.A.
Contact:

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

Post by MarkSturtevant »

dickb wrote:
Tue Apr 20, 2021 2:16 pm
What you are doing in essence is blowing up the tiny image circle produced by the CCTV lens and projecting it onto the your relatively large image sensor. You are getting a lot of vignetting here because the magnification of the image by the reversed 50mm plus extension isn't large enough. So you need more extension to get rid of the vignetting, not less. Or use a secondary optic with a higher magnification than your reversed 50mm. In a similar scheme I once used a 19mm Macro-Nikkor, or a reversed 23mm Xenoplan.
Before you invest too much in additional gear (I speak from experience) you should realise that the CCTV lens is the limiting factor here - it is designed to project a tiny image circle onto an equally tiny sensor with a limited resolution. Using a relay lens system you can make the image larger but the resolution doesn't increase, and all the lens flaws will be very visible. The upside down image is a hassle. It may be easier to use on a camera with an appropriately tiny sensor, Pentax Q comes to mind.
Still it's a fun exercise, but I wouldn't recommend buying any gear that can only be used for this experiment.
Well, there are rigs that project images from these little CCTV lenses onto crop sensor cameras. You can look at John Hallman's link and see lots of pictures. Only it is evident that less extension is used, and maybe that is b/c of the wider angle prime lens used in the series.
I've looked at other options for this exploration. I already have a dedicated wide angle macro, so I'm good enough there, but I would like to include the fish-eye effect in my set of such lenses. A very simple set up would be to use a regular dslr wide angle fish-eye lens that is mounted on an extension tube. Those can give excellent results, but the lenses are pricey to me right now. I have wondered about attaching a fish-eye diopter onto the wide angle macro...
Mark Sturtevant
Dept. of Still Waters

RobertOToole
Posts: 2627
Joined: Thu Jan 17, 2013 9:34 pm
Location: United States
Contact:

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

Post by RobertOToole »

MarkSturtevant wrote:
Tue Apr 20, 2021 1:43 pm
I am not entirely sure what the 2.1mm means. Presumably that is the focal length. That sort of measure is pretty typical for these little CCTV lenses (1.8mm, 2.0 mm, etc.). Normally, these lenses are to be mounted onto a circuit board with a sensor array directly underneath it.
Now John Hallman says that these lenses generally have an aerial image about 7mm behind the lens. So If I understand the situation (and I might not), one needs to get the 2nd lens to focus on that aerial image.
Yes, exactly. I thought 8mm was extreme, but 2.1mm!

Before the experimental setup I described I was never able to get anything usable out of that Cinegon lens so thanks for reminding about it! Now I need to get working on it again so I can have some fun with it.

rjlittlefield
Site Admin
Posts: 23561
Joined: Tue Aug 01, 2006 8:34 am
Location: Richland, Washington State, USA
Contact:

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

Post by rjlittlefield »

MarkSturtevant wrote:
Tue Apr 20, 2021 1:43 pm
So If I understand the situation (and I might not), one needs to get the 2nd lens to focus on that aerial image.
Focus is only one requirement.

A second requirement is that the light rays must be coming out of that front lens at an angle such that they succeed in entering the rear lens and working their way through the rear lens's aperture. Rays in the center of the field will always do that, but rays farther out may not. If rays farther out are angled so they get blocked, then you get vignetting in the sense that not all of the front lens's field is relayed to the camera sensor.

It helps to be sure that the rear lens aperture is wide open. But aside from that, a lot depends on internal design details of the front lens, in particular where its exit pupil is located. Realistically the best you can hope for is that the front lens will be telecentric on the image side. That sort of telecentricity also plays nicely with sensors, but it's not a strict requirement so there's no guarantee that any particular fisheye lens will work the way you need it to.

One way to help diagnose the situation is to set up the front lens by itself, then look at the aerial image with a loupe which you can fly around so as to see from any angle. If using the loupe lets you see that the field extends wider than what the camera sees, then you're getting vignetting because the angles do not play nicely together.

More magnification will reduce the area of the black surround by making the image larger. It will also move the lenses a little closer together, which will help to some extent with the angles. Using a different rear lens can also help, depending then on the location of that lens's pupil.

Unfortunately the location of lens pupils is seldom specified unless you can get hold of manufacturer's documentation like those cross sections that show lens elements.

I have not done or seen any sort of study about which fisheye lenses have designs that work well with this sort of "off-label" use. So, I don't know whether you have to be very unlucky to get a bad one, or very lucky to get a good one. I suspect the people who tell us about their successful setups don't know either. They just tell us about their successful setups -- which will be successful for you too, IF you can exactly reproduce their system including the same model lenses. Using other lenses that happen to have the same focal length and F-number is no guarantee of success.

--Rik

MarkSturtevant
Posts: 1946
Joined: Sat Nov 21, 2015 6:52 pm
Location: Michigan, U.S.A.
Contact:

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

Post by MarkSturtevant »

rjlittlefield wrote:
Tue Apr 20, 2021 6:38 pm
MarkSturtevant wrote:
Tue Apr 20, 2021 1:43 pm
So If I understand the situation (and I might not), one needs to get the 2nd lens to focus on that aerial image.
Focus is only one requirement. ...
Thank you, Rik I can look into trying to find the image projected from the front lens. I don't have a loupe, but I do have a couple microscope eyepieces laying around somewhere, and maybe those can ferret that out.
For what is is worth, when I hold the entire lens rig up and peer out through it, from back to front, I see with my naked eye a lovely fish-eye image that seems focused from near to far. This is very easy to see, so it was a bit of a surprise that the camera sensor does not "see" it. Mysteries of optics, I guess.
Mark Sturtevant
Dept. of Still Waters

rjlittlefield
Site Admin
Posts: 23561
Joined: Tue Aug 01, 2006 8:34 am
Location: Richland, Washington State, USA
Contact:

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

Post by rjlittlefield »

MarkSturtevant wrote:
Tue Apr 20, 2021 10:41 pm
For what is is worth, when I hold the entire lens rig up and peer out through it, from back to front, I see with my naked eye a lovely fish-eye image that seems focused from near to far. This is very easy to see, so it was a bit of a surprise that the camera sensor does not "see" it. Mysteries of optics, I guess.
Does the camera capture what you see through the camera's viewfinder? If the viewfinder looks fine but the captured image is vignetted, then the problem is that your lens is stopping down to take the picture. In that case just be sure to shoot at f/1.8 and the problem should go away.

On the other hand, if the viewfinder shows only a partial fisheye, but you can see a full fisheye by eye with all the optics present and the camera removed, then I agree that is puzzling.

--Rik

dickb
Posts: 342
Joined: Mon Jul 05, 2010 1:54 am

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

Post by dickb »

MarkSturtevant wrote:
Tue Apr 20, 2021 4:16 pm
Well, there are rigs that project images from these little CCTV lenses onto crop sensor cameras. You can look at John Hallman's link and see lots of pictures.
You are right, it can be done, and John does it really well. All I am saying is that by using this setup you don't gain much over using such a lens on its intended size of sensor, be it a CCTV camera, point-and-shoot camera or even smartphone. The optics of the CCTV lens are the limiting factor here, so anything more demanding than photos for webpages is going to look less than stellar. Still, it is fun to do, and an interesting challenge.
MarkSturtevant wrote:
Tue Apr 20, 2021 4:16 pm
Only it is evident that less extension is used, and maybe that is b/c of the wider angle prime lens used in the series.
That is correct, a reversed 24mm lens with extension gives you a much higher magnification than a reversed 50mm with the same extension.
MarkSturtevant wrote:
Tue Apr 20, 2021 4:16 pm
I've looked at other options for this exploration. I already have a dedicated wide angle macro, so I'm good enough there, but I would like to include the fish-eye effect in my set of such lenses. A very simple set up would be to use a regular dslr wide angle fish-eye lens that is mounted on an extension tube. Those can give excellent results, but the lenses are pricey to me right now.

I tried the dslr fisheye with extension route. A 16mm won't give you the desired steep perspective, so you'd want an 8mm or less. There are two problems here, these are normally big and bulky lenses, with bulbous large front elements. If you get the subject to touch the front lens, the resulting magnification of the subject is still not very high. The main technical problem though is getting the correct amount of extension - you will need perhaps 2mm or so, and extension rings normally start at 5mm. With 5mm your focus is closer than the front element, so that doesn't work. My workaround was using a Canon FD 7.5mm fisheye plus FD/M39 adapter and a helicoid M39-Sony E adapter, giving me adjustable extension from 0 to 5 mm.
MarkSturtevant wrote:
Tue Apr 20, 2021 4:16 pm
I have wondered about attaching a fish-eye diopter onto the wide angle macro...
That won't work terribly well, as the additional bulk of the the fisheye adapter will increase the distance to your subject, reducing the magnification and with that the impressive effect.

For the most extreme result you need the shortest possible focal length (your CCTV lens) combined with high magnification of your subject (your subject just about touching the front lens) in a way that fills your sensor. Maybe the most practical way may be your current setup, but replacing the reversed 50mm with a reversed wide angle lens in the 20 to 28mm range.

MarkSturtevant
Posts: 1946
Joined: Sat Nov 21, 2015 6:52 pm
Location: Michigan, U.S.A.
Contact:

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

Post by MarkSturtevant »

So lets' try to work through the various questions and points.
@Rik: There is definitely a LOT more vignetting due to the aperture. But even if shot wide open there is still significant vignetting out toward the corners. Wide open I see a lot more of the scene as well. So aperture is definitely a big contributor, but not the whole story.
Here are examples.

At f/11:
f11 and small enuf.JPG
Wide open (f/1.8 ) :
f1.8 and small enough.JPG
And this is a cell phone picture of the lcd screen. It looks essentially like the wide open picture.
viewfinder and small enuf.JPG
Still waiting on the microscope lenses to peer into the CCTV lens. They are in our main office, and the wife is working there all day. I daren't disturb her.

@dikb: I am understanding now that the way to expand the image area is to use a considerably wider angle reversed lens. I'm reluctant to commit to purchasing the 24mm in the hopes that it solves the issue. But what I can do, proceeding in baby steps, is to rent one for a short time to see how it does. If it works, and if I like how it looks, then I can buy the lens (a used copy, no doubt).

Success though will be measured not by how large is the image area at wide aperture. What is desired is to have an image cover the sensor , or at least most of the sensor, when the reversed lens is stopped down to say f/14 - f/16 to give considerable depth of focus. A desired "look" of these pictures is to have the more distant background be somewhat in focus so that the viewer can see the environment around the subject. A strongly blurred out of focus background is less interesting for this kind of photography.
I agree too that this sort of contraption is not meant for high image quality, or even medium image quality pictures. It really is just for kicks. It's fun. I have a conventional wide angle macro and that thing is really exciting to struggle with (it not being an easy lens to use in the field)

What the fish-eye effect can bring into the hobby is that it can make the viewer feel a bit like they are in the picture; a Lilliputian standing in a land of giant, looming mushrooms and monster insects that might step on them. Sort of a fantasy of mine, I guess. :)
Mark Sturtevant
Dept. of Still Waters

dickb
Posts: 342
Joined: Mon Jul 05, 2010 1:54 am

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

Post by dickb »

MarkSturtevant wrote:
Wed Apr 21, 2021 9:20 am
@dikb: I am understanding now that the way to expand the image area is to use a considerably wider angle reversed lens. I'm reluctant to commit to purchasing the 24mm in the hopes that it solves the issue. But what I can do, proceeding in baby steps, is to rent one for a short time to see how it does. If it works, and if I like how it looks, then I can buy the lens (a used copy, no doubt).

You don't need a specific lens for this. The 24mm you mention is a good option as it is lightweight, high quality and easy to use with this reverse setup. But a reversed 18-55mm kit lens will work as well. Or any other lens in this focal range, although the lack of auto-aperture of non-EF lenses may be a bit cumbersome. Or that wide angle macro you referred to (unless it is one of the 15mm macro lenses, its magnification when reversed may be a bit excessive).
MarkSturtevant wrote:
Wed Apr 21, 2021 9:20 am
Success though will be measured not by how large is the image area at wide aperture. What is desired is to have an image cover the sensor , or at least most of the sensor, when the reversed lens is stopped down to say f/14 - f/16 to give considerable depth of focus. A desired "look" of these pictures is to have the more distant background be somewhat in focus so that the viewer can see the environment around the subject. A strongly blurred out of focus background is less interesting for this kind of photography.
I agree too that this sort of contraption is not meant for high image quality, or even medium image quality pictures. It really is just for kicks. It's fun. I have a conventional wide angle macro and that thing is really exciting to struggle with (it not being an easy lens to use in the field)

What the fish-eye effect can bring into the hobby is that it can make the viewer feel a bit like they are in the picture; a Lilliputian standing in a land of giant, looming mushrooms and monster insects that might step on them. Sort of a fantasy of mine, I guess. :)
That sounds like a very reasonable set of attainable goals. It is certainly fun, if a bit cumbersome. If your camera supports wifi control by smartphone that can really help as you can get a viewfinder image the right way up - that makes a big difference in actual use.

The most extreme version of this type of relay lens shenanigans I tried was with a lens from a dvd drive as front lens - extremely short focal length, very difficult to use but a fun experiment.

Lou Jost
Posts: 5942
Joined: Fri Sep 04, 2015 7:03 am
Location: Ecuador
Contact:

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

Post by Lou Jost »

Maybe it would be easier to build something for the smartphone's own camera?

MarkSturtevant
Posts: 1946
Joined: Sat Nov 21, 2015 6:52 pm
Location: Michigan, U.S.A.
Contact:

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

Post by MarkSturtevant »

Very good advice here, as of course is expected. I very much appreciate the many helpful comments.
I may explore the kit lens idea. The old ones can be pretty poor, but they have gotten better, I hear.

I do happen to have a set of lenses that clip onto a cell phone, and this includes a fish-eye lens. I got them many many years ago, long before I got into this hobby. The lenses are actually beautiful little things, and when put onto a cell phone they take pretty good pictures as long as you don't look toward the outer edges too closely. The fish-eye can also focus surprisingly closely and would be fun to just use in the field on a cell phone. A tiny extension tube on that would make it focus closer, I suppose.
However, I cannot get it to produce an image in the above relay system. Perhaps its being designed to deliver an image to a cell phone sensor prevents its ability to deliver an aerial image to the necessary point in the reversed lens.

But there are other fish-eye lenses out there. The larger CCTV lenses with with a "C" or "CS" mount, rather than the tiny 12mm mount like I have now, for example. Those I assume (need to check) are meant for a larger sensor so they might project a larger image circle. There are fancier CCTV lenses but they get into some cost, and I was wanting to keep a lid on that. There are GoPro lenses... I was just backing out of the driveway and realized of course the rear camera is a fish-eye lens. I was all like: Hmmm....
Mark Sturtevant
Dept. of Still Waters

rjlittlefield
Site Admin
Posts: 23561
Joined: Tue Aug 01, 2006 8:34 am
Location: Richland, Washington State, USA
Contact:

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

Post by rjlittlefield »

MarkSturtevant wrote:
Thu Apr 22, 2021 8:28 am
Perhaps its being designed to deliver an image to a cell phone sensor prevents its ability to deliver an aerial image to the necessary point in the reversed lens.
More accurately, that clip-on fisheye is designed to deliver an image to the cell phone lens, not the cell phone sensor. The image created by the fisheye clip-on is a virtual image, still focused at infinity or close to it, so that the regular lens inside the camera can do its usual job of forming a real image on sensor.

Your setup expects the fisheye to construct a small real image all by itself, so it's not surprising that the clip-on fisheye doesn't work in that setup.

--Rik

Post Reply Previous topicNext topic