02-18-2012, 01:45 PM
[quote name='kwalsh' timestamp='1329570483' post='15890']
First, thanks for the great review!
There is an error though, on page two it refers to the lens being a "near-stereographic" projection (like the Samyang 8mm for APS-C). This lens definitely isn't, it is a standard equal area projection fisheye. If it was it would have to have a focal length shorter than 7.5mm to do so (6mm to be like the Samyang 8mm and 5.3mm to be a "true-stereographic").
I've measured and plotted the projection to confirm, the plot is attached to this post. You can see the projection almost perfectly matches the equal area curve and isn't anywhere near the stereographic curve.
If anyone would like to re-derive the measurements themselves here is the image I measured:
http://www.kenandchristine.com/Other/Equ...010179.jpg
The right edge of the pink post-it note marks the point at which the lens entrance pupil is closest to the wall (i.e. the line connecting the entrance pupil to the post-it is normal to the wall). The note on the post-it of 10.9" indicates the distance in inches from the entrance pupil to the wall.
From this image I also derived the lens focal length as being 7.52mm - so the specified focal length of 7.5mm is well within the measurement error of my simple setup.
As a side note, I also tested this lens for IR photography. No hot spots, but it doesn't quite make it to infinity focus. Image is just a bit soft at infinity while still sharp closer to the camera. This was tested at F/5.6 so maybe stopping down to F/8 would get infinity a tad sharper but diffraction starts being noticeable (especially at IR) as well. Don't know if I could adjust the infinity stop... Anyway, still looks great in the IR, just not quite sharp at infinity when viewed at 100%.
Again, thanks so much for the review (and all the m43 reviews especially). I'm in the U.S. (sorry about the measurements in inches by the way) so I can't contribute any lenses to be tested <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/sad.gif' class='bbc_emoticon' alt='
' /> Hopefully this post will be my minor contribution to the effort!
Ken
[/quote]
Hi Ken
Thanks for your effort - it is very much appreciated.
I must confess that my review was confusing regarding the stereographic projection.
I changed the review accordingly.
Bye Sebastian
First, thanks for the great review!
There is an error though, on page two it refers to the lens being a "near-stereographic" projection (like the Samyang 8mm for APS-C). This lens definitely isn't, it is a standard equal area projection fisheye. If it was it would have to have a focal length shorter than 7.5mm to do so (6mm to be like the Samyang 8mm and 5.3mm to be a "true-stereographic").
I've measured and plotted the projection to confirm, the plot is attached to this post. You can see the projection almost perfectly matches the equal area curve and isn't anywhere near the stereographic curve.
If anyone would like to re-derive the measurements themselves here is the image I measured:
http://www.kenandchristine.com/Other/Equ...010179.jpg
The right edge of the pink post-it note marks the point at which the lens entrance pupil is closest to the wall (i.e. the line connecting the entrance pupil to the post-it is normal to the wall). The note on the post-it of 10.9" indicates the distance in inches from the entrance pupil to the wall.
From this image I also derived the lens focal length as being 7.52mm - so the specified focal length of 7.5mm is well within the measurement error of my simple setup.
As a side note, I also tested this lens for IR photography. No hot spots, but it doesn't quite make it to infinity focus. Image is just a bit soft at infinity while still sharp closer to the camera. This was tested at F/5.6 so maybe stopping down to F/8 would get infinity a tad sharper but diffraction starts being noticeable (especially at IR) as well. Don't know if I could adjust the infinity stop... Anyway, still looks great in the IR, just not quite sharp at infinity when viewed at 100%.
Again, thanks so much for the review (and all the m43 reviews especially). I'm in the U.S. (sorry about the measurements in inches by the way) so I can't contribute any lenses to be tested <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/sad.gif' class='bbc_emoticon' alt='
' /> Hopefully this post will be my minor contribution to the effort!Ken
[/quote]
Hi Ken
Thanks for your effort - it is very much appreciated.
I must confess that my review was confusing regarding the stereographic projection.
I changed the review accordingly.
Bye Sebastian