I <span style="font-size: small;"]<span style="font-family: Calibri;"]own the 8mm and there are no electronics on this lens.<span style="mso-spacerun: yes;"] I understand this to be true for all the Samyan lenses.<span style="mso-spacerun: yes;"] What that means is that there is no data communicated and no camera driven aperture setting. You shoot AV or Man. There is a focus ring and an Aperture ring.<span style="mso-spacerun: yes;"] If for example the Aperture is set to 3.6 the camera records 0.<span style="mso-spacerun: yes;"] If you have the lens stopped down then focusing will be a challenge in low light conditions because the camera can't automatically open the aperture while you focus.<o></o>
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<p style="margin: 0cm 0cm 10pt;" class="MsoNormal"]<span style="font-size: small;"]<span style="font-family: Calibri;"]This would certainly account for much of the reduced price when compared to a similar, but fully automatic, Canon.<span style="mso-spacerun: yes;"] The auto focus and Aperture control are pretty complex parts of the lens (Strip these out and you've instantly saved a lot on manufacturing and R&amp;D). The Canon badge also has a price attached.<o></o>
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<p style="margin: 0cm 0cm 10pt;" class="MsoNormal"]<span style="font-size: small;"]<span style="font-family: Calibri;"]My understanding (from reviews) is that all these lenses are both Full Frame and Crop compatible (but the fisheye needs to be modified by trimming down the hood - not something I'd do personally). But make sure of this before you buy one.<o></o>
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<p style="margin: 0cm 0cm 10pt;" class="MsoNormal"]<span style="font-size: small;"]<span style="font-family: Calibri;"]I've heard people complain that it is hard to accurately focus manually with a modern SLR because the focus screen is not as bright and has no manual focus aids.<span style="mso-spacerun: yes;"] Split prism screens are available and easy to install. The best quality screens seem to be Katzeye and cost around $100-150 from memory.<o></o>