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Canon XH Series HDV Camcorders
Canon XH G1S / G1 (with SDI), Canon XH A1S / A1 (without SDI).


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Old July 16th, 2008, 09:36 AM   #1
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fisheye numbers

.3x or .55x etc. what do these numbers mean

and is this a pretty decent one for the price, and wht is with the decision to have a flat glass ontop of the curvature one? protection??

http://www.bhphotovideo.com/c/produc...a_Fisheye.html


thank you

pieces

Last edited by Janson Williams; July 16th, 2008 at 12:10 PM.
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Old July 16th, 2008, 09:43 AM   #2
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hey janson, noticed we posted at the same time so i'll try to answer this.
if what you see regularly is 1, then 2x is like you moved twice in, 3x is three times in etc (on the telephoto side).
when you wanna move back (via glass) so to speak, 0.5x is like you went twice as much back (wider) taking in more scenery. 0.3x is even more. the smaller the number the wider.
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Old July 16th, 2008, 09:45 AM   #3
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wrd, thanks man, your response was quick, much appreciation!!
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Old July 16th, 2008, 09:46 AM   #4
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do you use a fisheye? and any thoughts on the one i am looking at?
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Old July 16th, 2008, 10:04 AM   #5
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You have a 10x zoom lens that goes 10 mm to 100 mm (say). If you screw on a 0.5x wide converter you now have a 10x zoom that goes from 5 mm to 50 mm. Similarily if you fit a 0.3x you have a 3 to 30 mm zoom - assuming the converter lenses you fit are full zoom through lenses.

More than likely the 0.3x will be a single element (or cemented doublet) in which case you'll probably end up with a 3 to 15 mm zoom.

As is the name of the game you'll get a wider field of view but at the same time lose some sharpness and often gain some flare and barrel distortion.

Not sure what you mean about the 'flat glass'. can you explain more?

tom.
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Old July 16th, 2008, 10:18 AM   #6
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thank you very much tom

as per the "flat glass" , if you click on the link, the lens i am interested in purchasing looks as if there is no curvature to it, or the actual fisheye lens is under a protective lens (glass)
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Old July 16th, 2008, 10:28 AM   #7
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You link takes me 186,000 products, so I could be some time finding the fisheye. Very unlikely to be a protective element - much more likely that the front element is flat(ish) with a very deeply curved rear surface. At these sort of focal lengths you want to limit the number of elements used because of huge dof and the problems in hooding and keeping the front element spotless.
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Old July 16th, 2008, 10:31 AM   #8
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hey janson, actually i dont use a fisheye. i think the xh a1 is wide enough for me. i used to use one on an old elura-2. it helped there.
plus i think for my filmic taste i'd rather shoot people on the telephoto side of the lens. for outdoor scenery i would rather walk as far back as i can or find a better location( if you have the option).
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Old July 16th, 2008, 10:52 AM   #9
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The point about a powerful wide-angle is the way you can direct the viewers attention by utilising the perspective control open to you. The mild wide-angle coverage that comes as part of a camcorder's fixed zoom lens offers little dramatic interest, which is why add-on lenses are so popular.

tom.
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Old July 16th, 2008, 11:46 AM   #10
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Janson, I have a Century Optics fisheye and the glass is definitely curved. I think it is .55x but I'm not sure. It is actually the bayonet version for the Canon XL1, and when I got the XH-A1 I discovered the lens actually fits both cameras if you wiggle is just right.
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Old July 16th, 2008, 12:10 PM   #11
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my bad


LINK IS UPDATED


http://www.bhphotovideo.com/c/produc...a_Fisheye.html
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Old July 16th, 2008, 12:52 PM   #12
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From the picture it looks as if both surfaces of the lens element are concave, and as barrel distortion correction isn't required, that design should work well.
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Old July 16th, 2008, 01:03 PM   #13
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thankyou much
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