When I set my focal distance to infinity ...

[Skubagirl]

So .. I'm standing on the beach ... and I manually focus my 70-200mm lens on a boat way off shore. My lens is now focused on infinity ... should the boat be in focus? Because it's not .. I have to dial my focus ring back down ever so slightly to get the boat in focus.

Just wondering if my lens needs to be calibrated .... I thought that setting it to infinity would put things well out of the lenses range, in focus.

[LostMahbles]

Just got a new 50mm prime and I get the same thing. Would love to know if there's something wrong, and if not, what the reasoning is. Anyone?

[Doug Pardee]

Originally Posted by Skubagirl

I manually focus my 70-200mm lens on a boat way off shore. ... should the boat be in focus? Because it's not .. I have to dial my focus ring back down ever so slightly to get the boat in focus.

I think that you're missing something. You say that you manually focus on the boat but the boat is not in focus?????

If you're talking about manually focusing at infinity, which is what the message title suggests, take a close look at the focusing scale on your lens. There is an infinity symbol and an L-shaped line leading from it. Infinity focus is expected to be somewhere within that line, depending on the temperature.

Except in extreme temperatures, infinity focus will be near the hook on the L, not at the infinity symbol.

(The above info is for Canon lenses, which is what I believe you have. Some Nikon lenses are similar.)

Here's a picture of the 50mm f/1.2 from the Canon site. This lens is set to focus at infinity:

[Skubagirl]

I'm manually setting the focus on the boat, but being that it is so far away, I've turned the focus ring as far as it will go to get focus. So, with the focus ring turned as far as it will go (which I thought was infinity .. wasn't looking at the graphic on the lens) .. the boat is not in focus. I have to turn the focus down a bit to get sharper focus.

I will try testing with the instruction that you gave. Can you turn the focus ring to the infinity symbol? If the L bracket is infinity, then shouldn't the focus ring only turn to that point?

[LostMahbles]

I think what he's saying, and what I found here (for Nikon, but I assume it's similar for Canon), is that it allows you to focus past infinity because in some temperature conditions, the infinity focus would be passed the focus stop. It's better to be able to go past the "stop" and thus be covered in all temperature conditions, than to force the "stop" and not be able to get focus on a hot hot day (or cool....not really sure whether the relationship is longer travel = warmer).

Basically, you're trading the convenience of being able to just rotate until it stops, for the ability to get tack sharp focus in any conditions.

[Doug Pardee]

Originally Posted by Skubagirl

Can you turn the focus ring to the infinity symbol?

You can turn it there, but unless you're wearing a parka and taking a picture of penguins the only thing that your lens will be focused on is Buzz Lightyear after he's gone "to infinity and beyond". I'm not sure that 200mm will be enough reach for that.

If the L bracket is infinity, then shouldn't the focus ring only turn to that point?

Anywhere within that L bracket is infinity, depending on the temperature. For ordinary temperatures, the bent foot of the L is about the right spot.

[sk66]

TO INFINITY AND BEYOND!!!

bwahahaha!

(hey, it made me laugh...)