mirror lens
- Thread starter jeanie
- Start date
- Status
err.. I assumed it is understood that there must be 2 mirrors.. so conveniently left out mentioning the other mirror behind the front element..
anyway.. the 1000mm lens.. any info on the pricing? ;p
anyway.. the 1000mm lens.. any info on the pricing? ;p
In telescope there is such thing as focal reducer like 0.63x, not sure if there is same thing for cam lens. If yes, 500 x 0.63 x 0.63 will get about 200mm, at the same time the F stop get smaller.
Minolta made a 250mm CAT lens. I remember it distinctively because it was pretty much the size of an older school Nikkor 50mm 1.4 :bsmilie: Not sure if there are adapters to fit a Nikon.
http://cgi.ebay.com/Minolta-250mm-f...06393514QQihZ004QQcategoryZ3323QQcmdZViewItem
Tamron made a 350mm CAT in the old days. http://www.adaptall-2.com/lenses/06B.html There was one on e-bay http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=160308233878
Look around. I won't be surprised if the Rokkors and Tammies turn up from time to time. Also, there might have been OEM manufacturers like Spiratone producing odd-ball focal length CATS. Another possibility is to explore Soviet made CAT lenses. Apparently, they were manufacturing them before the Japanese did, so they probably had a head-start.
FYI, it seems that Sony has a 500mm AUTO FOCUS CAT lens for their Alpha range.
http://cgi.ebay.com/Minolta-250mm-f...06393514QQihZ004QQcategoryZ3323QQcmdZViewItem
Tamron made a 350mm CAT in the old days. http://www.adaptall-2.com/lenses/06B.html There was one on e-bay http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=160308233878
Look around. I won't be surprised if the Rokkors and Tammies turn up from time to time. Also, there might have been OEM manufacturers like Spiratone producing odd-ball focal length CATS. Another possibility is to explore Soviet made CAT lenses. Apparently, they were manufacturing them before the Japanese did, so they probably had a head-start.
FYI, it seems that Sony has a 500mm AUTO FOCUS CAT lens for their Alpha range.
Just a couple of points to make:
1) The donut highlight effect is partially due to the presence of the central obstruction caused by the mirror and partially due to the very shallow DOF.
2) If the donut hole is not concentric with the outer rim, it means that the lens is not collimated and is one cause for the image not being sharp.
I have not tried it before, but looking at point #1, can we create the effect, perhaps using a 135mm F2 with a piece of small round black paper placed in the centre of a protective filter in front of the lens? In the normal mirror lens, the diameter of the central obstruction (in this case the black paper) is about 30-40% of the diameter of the aperture. For example, if the filter size is 67mm, the central obstruction can be about 25mm.
Do note that the presence of the central obstruction will reduce the brightness, sharpness as well as the contrast of the image slightly.
Maybe the TS or someone else can try this out and let us know?
Kay Heem
1) The donut highlight effect is partially due to the presence of the central obstruction caused by the mirror and partially due to the very shallow DOF.
2) If the donut hole is not concentric with the outer rim, it means that the lens is not collimated and is one cause for the image not being sharp.
I have not tried it before, but looking at point #1, can we create the effect, perhaps using a 135mm F2 with a piece of small round black paper placed in the centre of a protective filter in front of the lens? In the normal mirror lens, the diameter of the central obstruction (in this case the black paper) is about 30-40% of the diameter of the aperture. For example, if the filter size is 67mm, the central obstruction can be about 25mm.
Do note that the presence of the central obstruction will reduce the brightness, sharpness as well as the contrast of the image slightly.
Maybe the TS or someone else can try this out and let us know?
Kay Heem
Aiya...just take your favourite portrait lens, cut a piece of circular black paper and past it on the center of the front element (or skylight filter better) then you simulate the center obstruction of the mirror lens to give ring effect bokeh liao mah...can experiment with different sizes some more....
Don't even know if TS is checking back on her thread, but in case ...
http://www.clubsnap.com/forums/showthread.php?t=490094
http://www.clubsnap.com/forums/showthread.php?t=490094
- Status
Similar threads
