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lens idea (unobstructed mirror) and color-correction idea
Reading about telescopes, I discovered a kind called an unobstructed reflector. Basically, light goes in the tube, bounces off an aspherical miror, and is diverted out of the tube, where a secondary mirror focuses it onto a lens. The mirror is shaped so as to prevent image distortion. This kind of telescope provides essentially perfect color (because light is bounced off mirrors, not refracted), with no reduction in brightness or distortion due to a central obstruction. One of the specific types of designs based off of this is the Yolo. I wonder if one could make one of these adapted to digital photography.



Another thought I had was for refracting lenses, a map of color-distortion produced by the lens at various parts, thus allowing for color correction. Has anyone implemented something like this?..

Comments (5)

David J Heinrich wrote:.

Another thought I had was for refracting lenses, a map ofcolor-distortion produced by the lens at various parts, thus allowingfor color correction. Has anyone implemented something like this?.

Some camera bodies do this. It seems it's easier/cheaper to do it in software than to design/build lenses that control it well..

Charlie DavisNikon 5700, Sony R1, Nikon D300HomePage: http://www.1derful.infoBridge Blog: http://www.here-ugo.com/BridgeBlog/'Experience: Discovering that a claw hammer will bend nails.Epiphany: Discovering that a claw hammer is two tools...'..

Comment #1

Http://www.photozone.de/...-f8-sp-macro-adaptall-to-nikon-reviewtest-report.

Basically thats what this is. They've been around for a while, and are a inexpensive way to get very long focal lengths. Not the most desirable design side effects like no aperture control and out of focus objects look like donuts and poor contrast...

Comment #2

BA baracus wrote:.

Http://www.photozone.de/...-f8-sp-macro-adaptall-to-nikon-reviewtest-report.

Basically thats what this is. They've been around for a while, andare a inexpensive way to get very long focal lengths. Not the mostdesirable design side effects like no aperture control and out offocus objects look like donuts and poor contrast..

That's not it really. As you say, the normal mirror lens design has the odd ring-shaped bokeh due to the central mirror which obstructs the front lens opening..

What the O.P. is asking about is a design where there is no central obstruction, and hence no strange out-of-focus effects. I've not come across this in normal photographic use, it might be something which is a speciality for astronomers.Regards,Peter..

Comment #3

Sherwoodpete wrote:.

BA baracus wrote:.

Http://www.photozone.de/...-f8-sp-macro-adaptall-to-nikon-reviewtest-report.

Basically thats what this is. They've been around for a while, andare a inexpensive way to get very long focal lengths. Not the mostdesirable design side effects like no aperture control and out offocus objects look like donuts and poor contrast..

That's not it really. As you say, the normal mirror lens design hasthe odd ring-shaped bokeh due to the central mirror which obstructsthe front lens opening.What the O.P. is asking about is a design where there is no centralobstruction, and hence no strange out-of-focus effects. I've not comeacross this in normal photographic use, it might be something whichis a speciality for astronomers.Regards,Peter.

Yes, you're right...what I'm talking about has no central obstruction...go to this wiki and look at the designs of off-axis designs: http://en.wikipedia.org/wiki/Reflecting_telescope#Off-axis_designs.

These are rare even for telescopes, so it's just an idea...

Comment #4

And actually, there are some German manufacturers of these types of devices:.

Http://www.wolterscope.de/produkte/index.html.

The smallest one has the following specs:.

140 mm objective diameter34 mm photographically usable image field1540 mm focal length11 kg weight (25.3 lbs)..

Comment #5

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This question was taken from a support group/message board and re-posted here so others can learn from it.

 

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