The curious case of the Spiratone 180 degree Fish Eye Auxiliary Lens
This auxiliary lens screws onto the front filter threads of a host lens and gives you 0.15X the original host lens focal length. It gives a true 180 degree angle of view having fair center sharpness and fairly exaggerated CA, increasingly so out to the outer edges. It's constructed of 10 elements in 6 groups.
When I was a wee lad I'd drool over these in the back of the popular photography magazines of the day.
You'd see them advertised like this Right next to the Joe Weider adds like this!
I could never afford the $49.95 Spiratone Fish Eye growing up. And I certainly never became Joe Weider!!
But when I found one of the 180 degree Fish Eye's on ebay, I just had to fulfill that childhood dream. It's kind of like the Marantz gear I've also collected as my adulthood has worn on .. as if in some way trying to fill some slight or loss incurred when growing up! Insert smiley face here!
And here it is, the Spiratone 180 degree Auxiliary Fish Eye Lens
The way this works is you screw the Spiratone onto the filter end of your host lens. You'll see in the pic above a metal flange protruding at the bottom. That's a 52mm male adapter and you don't want to lose that. There are some of these Fish Eye adapters for sale without that adapter. You can't connect the Fish Eye to your host lens without this adapter and in spite of some sellers saying they are easy to come by. They aren't!
The Spiratone has two correlated rings that work in tandem with each other. One sets the focal length of your camera. Setting that augments the other rings settings which are the resulting f stops that are available on the Fish Eye once the focal length is set. It has focal length settings to accommodate any host lens from 30mm to 200mm.
I was expecting that in setting the focal length, it would adjust the image size so it would be somewhat constant depending upon host lens focal length. However on mine that's certainly not the case. Other than changing the available f stop settings for the Fish Eye, I can't really tell if its doing any other type of compensation. However, as you go longer in focal length, light transmission proportionally goes down. This results in high light transmission with wide angle lenses acting as the host, down to much less light transmission for longer hosts lenses up to the 200mm.
Here are some of the images I shot with the Fish Eye adapter today just checking it out!
50mm lens as the host and cropped in Photoshop to approximately to the image circle size.
Mounted on the front of the 50mm host lens on a full frame 35mm camera, this gives you about the equivalent of a 7.5mm lens. The image circle is natively about 20% smaller on the frame than here. Remember, I've cropped the frame to the image circle here.
85mm lens here. The cropping here is optical, exactly as shot.
This should be the equivalent of a 12mm native lens.
Here with a 100mm lens as host. Note the cropping which is optical and exactly as it was shot.
With the 100mm host lens here this is about equivalent to a 15mm native lens.
Again here with the 100mm. Cropping is as it occurred as shot.
Back with the 50mm lens as the host again here and once again this was cropped in Photoshop to approximately to the image circle size.
For reference, the 50mm lens was a Russian Zenitar 50mm 1.7. The 85mm was a Russian Jupiter 9 f2. And the 100mm was the highly sought after Meyer-Optik Görlitz Trioplan 100 f2.8.