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My Fish Eye looks like it had a poke in the eye.......


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My Fish Eye looks like it had a poke in the eye.......

Seeing that it is Fish Eye week, I dusted of my 4.5mm Fish Eye.

 

Oh dear how things have changed.....

Was a nice lens on my ASP-C crop cameras, but something has changed ?

 

Now on a full frame camera it has terribly diminished in more ways then one.

 

I wonder what has / is causing the deterioration in image quality ?

 

 

Oh dear, on full frame on the un-converted camera, it has diminished.

 

post-31-0-63258200-1622556232.jpg

 

 

Un-converted camera, IQ still OK.

 

post-31-0-16582800-1622556345.jpg

 

 

On the converted camera, full spectrum, still OK.

 

post-31-0-25398200-1622556430.jpg

 

 

Because of the Fish Eye & now using lens adapters, I made a 720nm IR filter to fit internally inside the lens adapter.

Uh oh, the Image Quality just went south very quickly, but why ? I was using a full spectrum flash too.

 

post-31-0-12405800-1622556648.jpg

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Some lens designs simply do NOT appreciate rear filtering. That is what you are experiencing. The Sigma 4.5 Fish can use a ultrathin gel filter, but nothing else apparently.

 

My Laowa 11/4.5 did deliver very promising output when I put the Baader U in front of it, but of course there is heavy vignetting as the filter is 48mm and the filter threads are 62mm. Yesterday I managed to mount a Baader U in the rear of the Laowa. Results were horrible. Very strong focus shift, very low contrast, and forget anything about image sharpness.

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For those very short fl-lenses the distance needed for changing focus is rather small.

Introducing a rear filter changes the optical path distance. It might be a too big change for the lens to cope with.

 

My Sunex is a fixed focus lens and I had to readjust the focus position differently for each different filter I putty mounted at the rear end.

Se more about that in the Lens Data section for that lens.

 

This might not be the case for the Laowa.

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Colin, I've always had a bad conscience, because I'm having a room with lots of stuff spread out on the table, chair, floor, etc. Seeing your room makes me feel quite relieved :grin:
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Stephan, a look at my work table (which once acted as my dinner table!) will cure you for good.
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This looks to need a critical focus distance or back glass thickness. Is this the Sigma 4.5mm fisheye?

I have it as well and it can be hard to nail focus. Since its ok on a normal camera, but not as good with either added glass or modified glass thickness (your full spectrum) than I would say that is the focusing issue.

If its a Canon version and on your adapter, than you can't do much to push it. But if not see if you can change the mounting distance less or more. I am not sure if your in macro or beyond infinity. Hard to tell from these crops.

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Thanks everybody, I'll just use this on the Sigma Quattro where more pixels will be better used.

 

Yes Dave, it is the Sigma SA mount 4.5 Circular Fish Eye.

I have the Sigma SA mount 10-20 & 8-16mm wide angle lenses, they give a vignette on the full frame fp but are sharp & clear with the 720nm filter mounted in the adaptor.

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The 10-20mm is quite an amazing lens, I have it in EF mount. Its image circle is larger than I expected. It can be mounted on a metabones EL 0.64x speed booster with vignetteing at only 10 mm.

The 8-16mm I have in Nikon mount and it covers my DF at 13mm I think. Its a great lens with a tilt and shift adapter on the m43rds. I have cut down the front hood for this, so your coverage on the Fp might be different.

My 4.5mm fisheye is also in Nikon mount, but I haven't tested it on the DF yet. I have a viltrox autofocus Nikon to m43rds mount adapter that works well with it.

Before getting that adapter it was very hard to manual focus it. Its very sensitive to focal plane. Much more than it should be. When I first bought it I thought I could just leave it at f8 and get most things in focus without adjustment. But no its very odd lens and doesn't behave as I would expect.

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