UV fisheye lens Fujinon 2.7mm f1.8

[dabateman]

I have been playing with smaller lenses, which lead me getting back into fisheye lenses. An expensive Fujinon 2.7mm f1.8 is available with aperture control, but the older version that can be obtained very cheap has a fixed aperture. This fixed aperture, version can be pulled out from the Axis 212 security camera. These cameras can be bought very cheap from ebay, I got mine for $50 shipped to my door.

 

The trick with this C-mount lens is fixing a filter to it. The rear element is about 15mm in diameter, but just fits inside a M43rds camera. The front of the lens is bulbus and about 54mm in diameter. A 52mm filter can just be stacked in front and held in place with some loss of the outer circle. The image circle is about 9mm on the sensor without a filter.

 

Here is an full frame color image to show the image circle on my full spectrum EM1:

 

This is the full frame Baader venus image shot at fixed f1.8, ISO 200, 1 second shutter speed. The flower is illuminated with two 365nm LEDs.

 

Here is a square crop of the above Baader image:

 

 

There are better outside images then my above basement image to show off its sharpness and detail. These ones I really liked:

http://nikongear.net...hp?topic=6215.0

[OlDoinyo]

The filter costs you a lot of FOV with this lens, perhaps leaving you with the equivalent of a 5mm lens. The question becomes whether it would not be just as well to use a longer lens to begin with, which might have easier filter attachment and better bandpass. But I am no expert on C-mount lenses. A worthwhile test to run, nonetheless.

[dabateman]

Yes I don't have an ideal set up here. I have a 52mm spacer, a 52mm to 48mm step down ring and then the really thick baader ring holding the Baader venus filter. So this is not slim optimized. The best would be to a get a 15mm diameter 330WB80 improved filter and tape it to the rear element. That would be ideal, I haven't measured the maximum clearance inside my Em1, but my 25mm filters are too big. I next will see if I can get a better slim filter combination using my 1mm or 2mm Ug1 and 2mm S8612 filters. Stacking in the same ring may work out better.

 

Also I am way too far away from my subject in these images above. Which really is the point of using the lens in my mind. This lens can focus with the subject touching the front element and still include most of the subject. This can be a fun but over used effect. I will play around more with this.

 

The purpose of this post was just to let people know there is a wider option that will work on a m43rds camera. Wide lenses seem hard to come by. My Wollensak 25mm has similar field of view as my Sigma 30mm f2.8 art lens. These are the widest afordable lenses I know of with decent response, both limited to 365nm. This lens, even with the heavy loss is still much wider than both of these. So offers an other tool to play around with if I ever see the Sun again. There is hope that it may come out tomorrow. I also may test the range on this lens. I have no idea how many elements it has. But my Peleng 8mm f3.5 Fisheye with 11 elements can only see to best 390nm. Sad as this fisheye is an all star for filter addition. I can screw my 25mm filters on the back or use cut gels in the back 1.25" filter or even screw in Astrophoto filters.

 

I also forgot to mention that the shutter speed is about the same as my UAT set at f8, using the same lights and subject. So about 3 to 4 stops slower. But that doesn't actually matter as with the angle of view I don't need slower aperture to gain similar infocus area. But you do need to be much closer. I will have to play around with getting flashes or lights close and try for some extreme close ups.

[nfoto]

There is another fisheye option that will might be of interest: the Sunex 5.6mm f/5.6. This is a fixed-aperture fixed-focus lens, but easily made focusing by loosening the grub screws that hold the optics into the outer casing.

 

I used it a lot on my UV-modified Nikon D3200 (DX format) and it should work on a smaller format cam too. Internal camera filtering, or using rear filters, would be optimal.

 

Here the Sunex easily captures the familiar UV signature of the little Colt's Foot (Tussilago farfara) flower heads.

 

 

Hand-held shot, by the way. Anything else is hardly feasible with the immense field of view provided by this Fisheye.

 

I purchased the Sunex second-hand from a local dealer and paid around 100$ for it.

 

For a wide lens with rectilinear view, the Tamron 21mm f/4.5 is a surprisingly decent UV performer. The rear filter of the lens must be removed, as it blocks a lot of UV. On my Nikons, the Tamron will focus to infinity even in UV.

[Cadmium]

Da Bateman, If you have UG1 or U-360 that are the right size to fit, then using U=1mm and S8612=2mm will work for a UV+VV (visual violet), otherwise, you could use UG11 1mm + S8612 2mm (even 1.75mm but that is getting close to the suppression danger zone).

You will get a faster exposure time with the UG1(U-360) 1mm + S8612 2mm stack, with better Red/IR suppression than the UG11 stack, but with some VV.

If you stack in the same filter, you need to keep the glass separated from each other with an air gap, just not touching, or else you will get Newton's Rings,

no Newton's rings if you glue the stack.

[dabateman]

Thank you Cadmium. I had forgotten about the Newton ring problem.

[OlDoinyo]

If I were looking for rectilinear wide-angle lenses to use on a M43 system, I might be investigating the bandpass of the 10mm C-mount offerings from Kern, Angenieux, Zeiss-Jena, or Nikon. Back in the day, my father had a Bolex 16mm camera, and he may actually have had the Angenieux lens. There have been some much cheaper specimens dumped on Ebay by Boeing Aerospace recently, but they appear to have been used hard and would probably need servicing (though it would be a cheap way to get one for a bandpass test.)

 

The Meopta 12 is a bit longer in focal length, but also much cheaper.

 

There was also a Schneider offering in the same focal length, but they are eye-poppingly expensive, for some reason.

 

In terms of fisheyes, there is also a Canon 3.5mm that looks as though a front filter might be possible; I have no idea what its bandpass is.

[nfoto]

I have the 10mm Nikon cine lens referenced above, and it cannot do UV. Its performance otherwise is excellent.

[dabateman]

I think its a bad idea to just buy a bunch of c-mount lenses hoping to find a good performance. Also I think igoriginal did just that and only found the Wollensak 25mm to work.

 

The Sunex looks good. I am not sure how much of the circle would translate over on a M43rds camera. Birna, can you post a full uncropped image from the sensor?

In a recent ebay search, this lens is going for over $500, which is outside my fisheye budget.

For full sensor coverage at just under 180 degrees I have the Peleng 8mm f3.5. Too bad its not good for UV. This Fujinon is very sharp, has a 190 degree view and its a full circle on a M43rds camera. So quite a nice bargain if you pull it from a cheap security camera.

 

[dabateman]

I tried a filter test on the back of the lens yesterday. Using a 12.5mm diameter filter that was 5mm thick. I can tape it to the back and it clears the sensor. However it will not clear the shutter and I did hit it once when not careful. Fortunately, I didn't break the shutter mechanism. But learned that the electronic shutter slowest speed is only 1/8 on the first Em1. This now really has me eyeing the Em1mk2, as its electronic shutter is the full 1/32000 to 60 second range and with 1/60 first curtain. The Em1mk1 first curtain is only 1/13.

 

But adding a 14mm diameter 2mm U360 + 2mm S8612 will not be possible on my camera. Due to the electronic shutter limitation. I was hoping this could work. Since the lens rear element extends 6mm into the camera a maximum filter thickness of 2mm will be safe for my camera.