After getting a 21mm Zeiss that has a hard stop for infinity that is spot on too, I'm wondering how that still works with bitter temps. Seems most of the lenses I've had the infinity changes a good bit if the lens gets really cold. Last night for example the infinity on the Samyang 14mm seemed to be clear at the very edge, while warmer times it seemed it was definitely on the other side of the infinity line. Guess I'm not sure what I'm wondering exactly. Just what others have seen. Some lenses must be designed differently that it's not as big of an issue. First impressions is that it's not budging on the Zeiss.
Infinity and Cold
- Thread starter extremeinstability
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I often wish there was an infinity stop on my Canon lens--I miss that from my old Olympus film lens. Of course it would need to be switchable so it could be released when you need to compensate for extreme temperatures. Then of course it probably wouldn't make sense (or even be possible) to account for AFMAed lens.
I also miss the DOF scale on the lens too....just pondering here.
I also miss the DOF scale on the lens too....just pondering here.
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I must admit that I've never understood why my Canon FD lenses can have a nice convenient hard stop at infinity and never suffered from any noticeable focus shift with temperature (and I did use them over a huge range) while my EF's don't have a stop and apparently have to be that way to deal with temperature extremes?
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TAF said:
My understanding is that a lot of FD lenses do not have a hard infinity stop, which is what allows some of the longer lenses to be adapted for EOS and still be able to focus to infinity...
source: http://photography-on-the.net/forum/showthread.php?t=57023
As per the OPs comment, I think different materials allows for less thermal expansion/contraction. If the focusing element is on a plastic "rail" as opposed to metal, there would be practically no thermal expansion
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Hard stop on a manual lens is not so bad, but it WILL be affected by temperature. Hard stop on an AF lens is not so good. The focus motor will be ramming up against that stop every time focus is at infinity or the lens runs to infinity while trying to focus. It needs to have a bit of overtravel, i.e., go a bit past focus and then come back to it. What I do is make a mental note of where the line/arrow/whatever is in relation to the infinity mark when AF is at infinity. If I need to set it manually (night shots, astrophotos, because I want to, etc.) that's where I set the focus.
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Yeah that is what I feared when I first used the hard stop on this Zeiss 21 and it being the first hard stop lens I've owned. I thought, how does that work when it gets cold unless it happens to change the other direction and hard stop is in normal temps. Seems the change usually is towards the past infinity direction though. But the other night I used it without problems it was about 15F out I guess. Then again now that I think about it, I was mostly using the Samyang 14. It's focus seemed to change so far that it was pretty much hard stop well past the infinity line on there. I should just leave the Zeiss out one of these 0F mornings coming up and see if it changes much from the hard stop.
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I've been using my 24-70 f/2.8 and 16-35 f/2.8 quite a bit for night sky photography, and what I've found is, although there isn't a hard stop on either, there is a fairly consistent soft stop. what I do is, I turn until I hit the soft stop, then come back the other direction slightly, and I've been able to pretty consistently nail the infinity focus I'm looking for. I think at this point it's just muscle memory that's built up after doing it a bunch of times. it may sound wildly inaccurate or ludicrous, but you'd be surprised how finely tuned you can hone your muscle memory.
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