Opteka 0.2X Super Wide Fisheye Lens adaptor

[ericmark]

I bought this Opteka 0.2X Super Wide Fisheye Lens adaptor second hand from a lady I know it's not that often I need more than my 18mm with standard lens and I have been stitching with both CS5 and Hukin both reasonable so was doing this on the cheap cameras standard lens is 52mm so fitted straight on.

However focus seems to be a slight problem I have found centre is spot on but to the sides not very sharp. However realised that often it will not fit direct onto camera lens often one needs an adaptor ring so thought maybe too close.

Tried fitting the circular (not really circular) polarising filter between the adaptor and original lens this seems to work well and up to now can only test with inside photos and it seems better. What I want is to test outside just wonder if able to reach infinity?

At 18mm the result is a circular image zooming out to 35mm I get full frame with any item at sides curved as one expects. Zoomed out to 55mm the results compare with lens without adaptor set to 20mm.

So looking at rectangular image no corners cut off it about doubles my angle of view. Getting the fish eye round look then about 4 times area but this is really just an effect rather than any good for general photography.

Camera is a Pentax K10D host lens is the standard Pentax SMC DA 18 - 55mm. CCD size 23.5 x 15.7mm

I have a fixed 28mm lens for full frame camera, but 55mm filter thread, however holding the adaptor against the lens there is about the same corner cut off as with the 18 - 55mm set at around 28mm so corner cut off is not due to host lens being designed for a cut down sensor.

It does what I want but a little upset about focus outside where edges were not sharp. Not simply focus picture of local pond very noticeable but picture of crib in camera club and seems nearly A1. Since lady has a Canon not Pentax I do wonder about the space between adaptor on host lens and if adjusting this using empty filter rings may correct it?

Has anyone else used these adaptors?

 

[Lucid]

I'm puzzled as to why you're surprised that the fisheye adapter is soft on the edges. Surely you realise that in bending light in such an extreme way there has to be quite a lot of distortion in the process as the angle becomes more extreme. Put very simply, towards the edges of the lens the light bend is akin to going through a prism.

Even the best fisheye lenses produce greater amounts of image distortion and chromatic aberration as the angle becomes greater. Some of that distortion can be engineered out with a complete fisheye zoom lens, but what you have is an add-on lens which attaches on top of an existing lens. Also, it's one of the widest angle lenses of its type, so that means even greater amounts of distortion.

 

[ericmark]

Distortion I expected out of focus I did not. Anyway today I will re-try with filter between lens and adaptor and see if the results change. Not due to filter but due to larger gap lens to adaptor. Person I bought it from had a lens with larger filter thread so had an adaptor between mine is 52mm so no adaptor ring so that may be the reason?

 

[Dave54]

Generally the wider you go lens wise, the softer the corners and edges of the image will be. Similar with the Tamron 10-24 lens I have, and use with my K5. At the wide end, the edges of the image are soft.
Any converter is inevitably going to be worse than a complete lens I'd have thought.
Depends whether you feel you can live with it or not. I've never had any problem with "focus" submitting output from that lens to an agency.

 

[ericmark]

Think I have bought a toy. It does not matter if base lens set to 18 or 55 mm the edges are always out of focus. Clearly no point being set to 55mm as result is not as wide as with the base lens. I need to talk to original owner and find out what she found. It may be there is some difference between Canon and Pentax causing the problem or it may be simply a duff lens.

 

[Lucid]

Think I have bought a toy.

Hallelujah! The clouds parted and sense rained down.