Vignetting on BX53

pwnell · Post by **pwnell** » Tue Jul 31, 2012 6:19 pm

I received my magnification changer (U-CA) today. Before I had the magnification changer connected, my Canon 600D was coupled using a D-SLR series F-TV tube and a T-ring adapter to the trinocular port.

Now to keep in mind I have the FN 26 super widefield head and eyepieces. Before the magnification changer was connected I had almost no vignetting, and could fit what I see in the field of view through the eye pieces properly on the camera's sensor.

The magnification changer (set to 1x - i.e. no optical elements) raises the camera obviously. This has not affected parfocalness, however it now vignettes much more strongly and I see less of the field on the sensor than before.

What should I do? Raising / lowering the camera does not help as I lose parfocalness. Must I get a U-TV0x63x C-mount camera adapter? A U-TV1x?

Charles Krebs · Post by **Charles Krebs** » Wed Aug 01, 2012 12:05 am

Don't know the answer.

I do know that, for example, the Olympus U-TMAD adapter which takes a T-mount and has probably the largest "clear aperture" of the camera adapters gave me vignetting (Canon APS-C) on the superwide head as well as with the U-TLU. But it wasn't the head or tube-lens-unit. The vignetting was caused by a simple flare-cut diaphragm positioned in the U-TMAD which restricted the through aperture but was easily removed. (So I don't think Olympus expected people to do "direct projection" onto sensors that large). I hope your solution turns out to be something as simple as that.

Are you seeing the vignetting in the viewing eyepieces as well? Since the FN of the superwide eyepieces is 26.5mm (just about the same as the camera format diagonal) it would seem any component that was stated to be compatible with the superwide head (when placed below it in the optical "stack") should be able to "pass" a 26.5mm diagonal image, otherwise your viewing image would also show vignetting. Is it possible to try it with the fluorescence module removed?

pwnell · Post by **pwnell** » Wed Aug 01, 2012 12:34 am

I see no vignetting through the eye pieces. Also, with the magnification changer removed (once again, not using any of the lenses in it for this test - it is set to 1x), it does not vignette (well, it vignettes only very, very slightly so).

Pau · Post by **Pau** » Wed Aug 01, 2012 6:32 am

Waldo,
I like so much your direct projection setup that my question is:
is worth to put a mag changer and a relay system when you simply can crop the image at the computer?

(and my answer may be: perhaps for low mag objectives but not for hig mag ones)

pwnell · Post by **pwnell** » Wed Aug 01, 2012 8:21 am

Pau wrote:Waldo,
I like so much your direct projection setup that my question is:
is worth to put a mag changer and a relay system when you simply can crop the image at the computer?

(and my answer may be: perhaps for low mag objectives but not for hig mag ones)

I do find that at all magnifications I get a little bit extra in terms of details, and better framing in camera, with the magnification changer. It is just a bit more versatile. But I do agree one can crop, it is not as if the higher magnification objectives out resolves an 18MP sensor.

Also, I cannot do darkfield with any other objectives than 10x and 20x due to the high numerical aperture of the objectives, therefore using the 20x and the 2x magnification changer allows me more detail than just the 20x alone.

RogelioMoreno · Post by **RogelioMoreno** » Thu Aug 02, 2012 3:48 am

Waldo,

Did you try brightfield (without the analyzer) with the U-CA to check if you get the vignetting?

Rogelio

pwnell · Post by **pwnell** » Thu Aug 02, 2012 8:29 am

Yep I removed all the optics and it did the same.