Af-d primes focus for infinity

Started Mar 2, 2013 | Discussions thread
Marianne Oelund Veteran Member • Posts: 7,077
I trust neither infinity hard stops, nor focus scales

primeshooter wrote:

D800 liveview is sh££ in the dark lol. It is hard for stars I find.

It certainly is.  For critical astro work, I've yet to find a lens where I can trust the focus scale or infinity hard stop.  Even if a lens has a hard infinity stop that looks like it's calibrated to infinity, it really isn't.  There must always be an allowance for manufacturing tolerances, and I've found that such lenses also need to be manually focused, to achieve optimal results.

The only approach I've found to work is to manually focus-bracket, then examine the results to find the best focus setting.  You must also be careful about which direction you've been turning the focus ring.  Best to rotate it away from infinity since the camera's usually pointed up and this will use gravity to help keep the focus group seated against the focusing helicoid.

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Qualities possessed by God in infinite proportion: Love, Grace, Power, Righteousness, Wisdom, . . .
Qualities possessed by humans in infinite proportion: Ignorance.
- Marianne

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