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05-12-2012, 12:16 AM   #1
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How to focus in very low light

I know this is a rather ridiculous question but I just wanna fire it.

Last night I was at a friend's birthday party, which was at a bar. The environment was very dimly lit, only enough to barely see things that reflected light. I tried to give photography a shot, relying on our high ISO capability. And I actually made good frames with ISO 10000-12800 with 1/80, 1/60 speeds at f1.4. No problem with the images, but the focusing was kinda sorta astray.

The K-5 rarely found focus, and if it did, it needed a few seconds of hunting first. Although the AF assist light is made available in the menu, the camera did not use it. I even had to recheck to see whether I had disabled it some time. Anyways, I decided to focus manually. But another boomer. The environment, as I say, is so dark that even I could not distinguish in the viewfinder whether I had the focus or not. I could just realize when I was completely out of focus, and the rest of the way I had to go intuitive.

The lens was Sigma 30mm f1.4

I now realize I could also give a try to live view focusing, since it could pump up the live view ISO and enable me discern better. But other than that, what do you recommend to be able to focus and shoot in such interiors? Cuz I really want to be able to utilize this high ISO ability without using flash. And why on earth did not the AF assist lamp activate? I've seen it aid focusing at times.


Last edited by Crosshair; 05-12-2012 at 12:21 AM.
05-12-2012, 02:23 AM   #2
hcc
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In very low light, I recommend to focus manually (MF). You will get a much better percentage of good shots (or keeper rate).

I have heard of another option with quickshift lenses consisting in pre-focusing manually, to guide somehow the AF.

MF is ultimately the best option in low and very-low light IMHO.

Hope that the comment may help..

Last edited by hcc; 05-12-2012 at 02:52 AM.
05-12-2012, 02:38 AM   #3
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+1 for the manual focus
in low light there isnt much you can do. if the viewfinder doesnt help (you may install a focusing screen, but in low light... hmmm not sure it'll help), use the screen in lv, pressing the info, zooms the image so it kinda helps..
what concerns me is that the af assist didnt fire.... are you sure its activated ?
05-12-2012, 07:21 AM   #4
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a useful technique is to use a flashlight to help focus
during my experence.
it is true that it is hard to focus in very low light situation.
in some indoor event, the lighting is just so dark. many of my photo come out of focus.
so I develop a techique.
I bought a key chain flashlight (it is tiny and lightweight). and velcro it to the top of k-5 and flash (if i am using flash)
if it is too dark, I just turn on the flashlight.
it is much powerful than the focus assist light of k-5.
and works great.


Last edited by liukaitc; 05-12-2012 at 07:43 PM.
05-12-2012, 07:36 PM   #5
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The K-5 AF is specced to work within a brightness range of -1 to 18 EV.
So if it is so dark that you can barely see, the environment may simply be too dark for reliable AF.

But if you select centre-spot AF, and focus-recompose using some bright or contrasty areas that sometimes show up in even the darkest scenes, you can often get a decent AF strike rate. But otherwise manual focus and knowing the available DOF for your lens/apertures is the best way to go if it is just too dark.

Also remember using any filters on your lens - even UV or 'protection' filters - will make a lens darker and hence perform more poorly at AF.

FYI, if you want to examine the EV of a scene as the camera metering (and AF) sees it, download PhotoMe and open up a JPEG of a typical dark scene and see what the camera is working with - eg (for the K-x):

05-12-2012, 11:24 PM   #6
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Photography does not capture subjects; it captures light. 'Tis rather difficult to shoot in sub-zero light even with manual focus and ISO boosted up the wazoo. How I focus and shoot in near-darkness:

* Wide fast lens, and zone- or guess-focus. The MF Vivitar-Kiron 24/2 and Zenitar 16/2.8 are my friends. I can guess-focus pretty well with the 24/2; and focus hardly matters with the slightly fishy Zenitar and its immense DOF.

* Boost ambient light if possible. Switching-on a couple inconspicuous lights usually doesn't ruin the local mood but definitely helps MY mood, especially if I can thus avoid tripping over things, or creatures, or myself.

* Switch to my 'Nightshot' Sony DSC-V1 with the Sony HVL-IRM infrared light attached. Now I *can* shoot in absolute darkness without frying eyeballs. With a bit of PP, the results don't look so much like surveillance imagery.
05-13-2012, 03:01 AM   #7
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Original Poster
thank you. all helpful comments. making some research I found out that the AF assist lamp does not activate when using AF-C.

this was the case in Nikon also, but I forgot. using AF-S in very low light can also help, since it lights its way up, and in my tests it worked pretty well.

MF is hard because as I said in the first post, it was so dark I could even barely see something other than darkness in the VF
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