Why doesn’t turning my Canon 18-135mm STM to infinity give sharp night shots?
Asked 6/7/2018
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I’m shooting urban night scenes on a tripod with a Canon EOS 450D and EF-S 18-135mm STM. When autofocus can lock, distant subjects look sharp. But when it’s too dark for AF, I switch to manual focus and turn the ring all the way to the infinity end, yet the image is still badly out of focus.
Is this normal? Shouldn’t the infinity end of the focus ring make distant subjects sharp? What’s the best way to manually focus this lens for night photography?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
8y ago
2 Answers
1
The problem is that on the modern lenses there is no clear point marking the infinite (it is marked as L___, so it is somewhere theeeeere). Never the less you have a few possibilities:
use a laser pointer or a torch and autofocus with that,
use the lcd screen and magnify the view 5x or 10x, then focus manually (if it is super dark, set ISO to 6400 or 12800, focus and go back to the desired ISO value),
prefocus during the day (the best from the tripod) and mark on the lens with a marker or a piece of a duct tape where the focus point is on the lens, and come back later to exactly the same spot and focus manually to the marker.
Originally by user56984. Source · Licensed CC BY-SA 4.0
user56984
8y ago
0
Generated from our catalog & community — verify before relying on it.
Yes, this can be normal. On many modern lenses, the infinity mark is not a hard stop at exact optical infinity. Focus can go past infinity, and the exact point varies, so simply turning the ring all the way may not give a sharp result.
Your EF-S 18-135mm STM also uses focus-by-wire manual focus: the ring does not directly move the optics. The camera interprets ring movement and drives the lens, and some STM lenses can reset focus position when power cycles or the camera sleeps. That means a tape mark on the ring may not stay accurate.
Practical ways to focus at night:
- Use Live View and magnify the image to 5x or 10x, then manually fine-tune focus.
- If needed, temporarily raise ISO to brighten the Live View image, focus, then return to your shooting ISO.
- Shine a torch or laser on a distant target and autofocus on that, then shoot.
- You can pre-focus in daylight from the same spot, but with STM focus-by-wire, don’t rely on a ring mark if the camera has been turned off or gone to sleep.
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AI8y ago
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