ronchappel wrote:
If i understand this right you did always have at least one layer of tape between the last 2 elements?If so then the smearing is almost certainly gum from the tape-it should easily come off
Yes, but you should know that the coating itself has limited hardness. And I did press (lightly) and rotate the element to check for direct contact. So even after washing with ethanol the mark is still there.
ronchappel wrote:
I finally found my notes from when i measured the 5d mirror clearance:
EOS flange to mirror front (when mirror is up): 7.2mm
I also measured the mirror when it was partly down ,at a slight angle.At this point it has LESS clearance because the mirror is thick and so one edge naturally comes closer to the mount at that point.here it only gives 6.8mm ! (please note i cant remember what method i used to measure these.allow 0.1mm inaccuracy to be safe)
These numbers tally up well with actual testing.If i have my rear element set much more than 6.5mm back from the EOS mount surface,the mirror starts brushing it
Well, I also found that when the element approaches 7mm protrusion it would collide with the mirror of 1Ds Mk2. But I have seen remarks that the 1D series retracts the mirror towards the sensor when it is swinging up. When I manually move the mirror up there is really some backward movement. So this may be the real reason why 1D series is better than 5D in alt. lens compatibility.
ronchappel wrote:
First i must explain that my rear element holder has a slight forward extension which contacts the outer edge of the 2nd last element,stopping the glass parts of the two elements from touching.The point is-is this extension too long?
I use flange-less M39 to M42 adapter, and the 2nd element can pass through its opening well enough to collide with the 1st element.
ronchappel wrote:
After measuring the tape thickness i knew the gap had to be between 0.12mm and 0.24mm .
And due to the easily noticeable rocking motion i mentioned in the testing above ,it\'s most likely closer to the lower number.
So.. less than 1/4 of a mm gap! Pretty cool huh?
Since then i\'ve had a little time to experiment with how far i can move the rear element forward and still achieve genuine infinity focus.
Sadly it seems to be no less than exactly 7mm -which is likely just a little too much for use on a 5D
When the brother visits with his 5D body this weekend i\'ll try it again but from past experimentation i\'m guessing it wont work
From my record, infinity can be achieved with 6.9mm protrusion when the element separation is slightly larger than 0.05mm (more than one layer of tape thickness but less than 2). YMMV
Oct 29, 2009 at 07:14 AM
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