Orquid "Phoenix"

Orquid "Phoenix"

by ceinmart

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Suppose I have to short in very low light so I have to set up shoter speed to 10-20 sec. Live view and autofocus doesn't work in this case and view finder give you a little help since it is to dark. The only thing I know for sure is distance to object, but I'm not sure how to rotate focus ring to focus on specific distance.

So there are actually two questions: 1. How to accurately focus in low light? I.e. you can't see sharpness in View finder. 2. How to accurately focus in almost zero light?

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6 Answers

up vote 3 down vote accepted

Your best option is to light the subject temporarily somehow, than use auto-focus and focus lock (or better, switch to manual focus), remove the light and take the picture.

If you can't get enough light for auto focus to work but you still get get some light on the subject than use manual focus with live view (zoom in your live view to the maximum zoom to help with focusing).

Next best option is to use the lens distance scale if it has it - just stop down a bit to increase depth of field because those scales can be a bit inaccurate (also your subject distance is probably also inaccurate because if you can just walk up to the subject with a tape measure you can also walk to the subject with a flashlight and use auto-focus)

If you can't get any light on the subject and don't have a lens with a distance scale than your next option is to focus on something else that is approximately the same distance - this tends to be very inaccurate - so stop down to increase depth of field and use a depth of field calculator to make sure you have a wide margin of error (there are DOF calculator apps for all smartphones, or you can print a DOF table from an on-line calculator if you don't have a smartphone).

And finally, if everything else fail you can use the hyperfocal distance - when you focus to the hyperfocal distance (or behind it) everything from half the focus distance all the way to infinity is in focus, any DOF calculator will tell you the distance for a given focal length and aperture

If you use the hyperfocal distance, apart from giving up on blurring the background, you will also probably have to stop down because the smaller your aperture the closer the hyperfocal distance - and if your hyperfocal distance is smaller than your subject distance you have enough margin of error to get this right in the dark using approximate distances.

Also, you want to focus a bit farther than the hyperfocal distance because if you accidentally focus even a bit nearer not everything to infinity will be in focus and you can get an out of focus subject.

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Even if shining a light on the subject does not light it up enough, if there is a round metallic part it will likely have a reflection. Manually focus to minimize the size of the reflection. –  Phil Apr 24 '13 at 4:46
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The lens focus ring is rarely marked precise enough to focus using just that.

Use a torchlight if target is in vicinity or use a handheld laser to project a dot on the target and focus through the viewfinder.

Some flash lights have a LED to help focus the image. You can use the flash only for that.

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Focus on something else, focus lock, remember the distance, turn to your subject and move make the distance identical. Aim, shoot.

Sounds silly and not reliable, but it's worth mentionning when no other solutions are possible.

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Try bumping up your ISO temporarily and focus the shot using live view mode and zoom function (if your camera has this, otherwise do your best with your eyes). Then turn your ISO back down to an appropriate exposure level to get the shot.

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I have used simple LED torchlight to temporarily light my model and using Live view focused on her eyes. And Speedlights have built-in red light to help with focusing.

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Two things I do to get better results in low light conditions:

  • Try to find more light. I know it sounds silly, but there are often brighter areas around that you can use to help set focus and metering: white objects, street lights, moon light, lighters -- anything. If you can find something to focus on that is roughly the same distance then you at least have a starting point for manual focus corrections in your desired composition.

  • Many better lenses include a distance scale to help set focus. Sometimes they're difficult to judge precise focus with, but they are great to get close. If it's too dark to see the distance scale I pull out my phone briefly and used its screen to light the lens to help me get started.

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