Orquid "Phoenix"

Orquid "Phoenix"

by ceinmart

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I have a particular lens in mind, but is it generally possible to do this adjustment? Of course there are a lot of lenses that don't have any distance scale to begin with. Many lenses have the scale though. I'm mostly interested if there is a way to do this adjustment by myself.

To see the amount I'm in need of adjusting, I took five shots of stars with all else kept static but nudging the focus ring a little between each shot. What I found out from the photos is that best infinity focus (the stars!) was somewhere between positions 2 and 3. That's not even near the end of focus ring rotation.

enter image description here

Naturally, I'd start by checking if the shorter distances marked on the scale match any better, but first I just want to know if lenses with a distance scale are designed to allow for adjusting of the scale. And if this adjustment is possibly a DIY-level job.

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Take a look at Why do some lenses focus past infinity? — almost all modern lenses do. –  mattdm Jan 2 at 15:11
    
Thanks @mattdm, I've read that Q/A a long time ago and it makes perfect sense. Only I am amazed by the amount of extra play in this lens, it being a prime lens too. –  Esa Paulasto Jan 2 at 15:28
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2 Answers

up vote 2 down vote accepted

Part of the problem is that you are at infinity. The reason that infinity is shown as a range is that it does not remain constant. Environmental conditions can actually impact (fairly significantly) what the actual point you need to focus the lens on to be focused on a point infinitely far away. The value that gives best results can change from one sitting to a next, which is why it is marked as a range of values.

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Okay, have to admit there is a lot of thick glass in there. I'm just amazed by the amount of extra play in the infinity range. –  Esa Paulasto Jan 2 at 15:32
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Try shooting at infinity after the lens has been out in the heat all day, then try again after the lens has been out in the winter cold all day -- there's a marked difference in many lenses! Of course, as this is probably roughly a 6-month long experiment it's a pain to try. :) –  Dan Wolfgang Jan 2 at 16:43
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As far as I'm aware the answer is no.

If its infinity that you are most bothered about, i'd find where the focus is best and mark it on the ring manually, a little bit of white paint downwards from that line to match the pointer line below would be good enough.

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