Auto focus not working in dark rooms.

<p>Hi,<br /><br />I have been photographing many events and party's over the years. The problem I have is my auto focus finds it hard to pick up focus in dark rooms. I have up to date canon cameras and fast f2.8 canon lens. I don't have this problem when the room is in daylight or lighting is good. I use flash for 85% of my working with indoors photography.<br /><br />When I am working with a video person his lights help out with the focusing . I was wondering if any one uses a LED light attached to a bracket with your flash .<br /><br />Any help would be great. <br /><br />thanks,<br /><br />Marc<br /><br /></p>

<p>Many current flash units, probably most, including those designed for Canon systems, include an AF assist beam. Make sure your flash is set to have that beam on when needed.</p>

<p>I do see the beam working . Does not make much difference.</p>

<p>In my experience, w/ f2.8 glass, the AF assist beam is of adequate intensity to allow me to AF in virtual complete darkness... as long as there is a subject within appropriate range. <br>

You may see better results using primes, or faster glass, but maybe not.</p>

<p>Since you are using flash for these shots, I don't see that a little LED flashlight taped to the side of your flash (or something which does the same thing but is more professional looking) would have that much impact on your shooting, Of course if you are willing to put up with the limitations of a 320EX, it has a visible light LED for an AF assist which may work better for you.</p>

<p> </p>

<p>Marc,</p>

<p>First, let's just state this as a general principle: Any kind of focusing system will struggle in a dark room — just as they will struggle trying to focus on a flat and featureless wall. Autofocus relies on contrast to work; come to think of it, so does manual focus. The darker it gets, the lower the contrast, so the harder focus becomes. This is normal, and inevitable.</p>

<p>I have used a small, off-camera LED video light a couple times while doing portraits, but never at an event. If the LED were attached to the camera, say, by a bracket, I'm not sure I'd like the effect it would have on the photos. Plus, since the still photographer doesn't shoot constantly, the way the videographer does, I think it would be a bit strange to have the LED stay on all the time.</p>

<p>•</p>

<p>Every hot-shoe flash I've used for the last four or five years has an autofocus assist beam, and at least in my experience, this works quite well, at least at short distances. Fortunately, this is where it's really important. If you're shooting in low light, you've probably opened the aperture up wide, and so you have relatively shallow depth of field. The closer you are to the subject, the shallower the depth of field — and so the more important it is to nail the focus.</p>

<p>As you step away from the subject, even if you leave the aperture wide open, depth of field increases and precise focus becomes a less critical issue. At some point, you can switch to manual focus — or even old-fashioned "non-TTL" manual focus using the distance marks on your lens. I understand that you are using Canon, but I'll mentioned that for the last couple of years I've enjoyed the advantages of focus magnification through the EVF in my Sony and Olympus bodies, and this helps too. </p>

<p>You could try using the focus and recompose method: that is, focus on a high-contrast point in the scene on or very close to the focal plane, lock focus (typically by keeping shutter button half pressed), and recompose. Do be aware that, if (a) the high-contrast spot you focus on is "too far" from part of the subject you actually want to have in sharpest focus, and (b) if you're also "too close", focus and recompose can virtually guarantee out-of-focus pictures. You'll have to consult <a href="http://www.dofmaster.com/dofjs.html">a depth-of-field chart</a> and do the trigonometry yourself to figure out exactly when the focusing point is "too far" from the desired focal area or what constitutes being "too close" to the desired focal plane for focus and recompose to be (relatively) safe. </p>

<p>Will</p>

I worked an extremely dark reception a few months ago. I thought my Nikon D7100 handled it well, but not the older

bodies. So as a result I put a 35mm 1.8 on another body and the zoom on the D7100 and it seemed to be fine. I think

trying a fast lens is a good idea although I don't know Canon.

<p>Thanks for all the help.<br>

<br />I have found another post that has come up with some test i need to do on my 1DX.</p>

<p> </p>

<p>The Canon autofocus assist is nice but be aware that it only works in One Shot mode. Also, if your flash is mounted up on a bracket it may throw off the autofocus assist beam alignment.<br>

Curiosly, the fastest lenses are not always the best performers in regards to dark focusing. For example, I've always found the discontinued Canon 20-35 f/3.5-4.5 lens to be terrific at finding focus in dark locations, much better than my 50mm 1.4 and 85 1.8 lenses.</p>

<p>Focusing in the dark is always a huge PITA. Here's what I've done:</p>

<p>• Have an assistant hold a flashlight on my subjects to acquire focus.<br /> • Use a Nikon SU-800 Commander as an AF-assist light only (Nikon users only; AF-S mode only).</p>

<p>However, I've been thinking for months now how to design a better focusing aid. Something bracket-mounted, operated by a momentary switch. Ideally, something like a Streamlight tactical flashlight (but not as bright), with a remote, weapons-like, pressure-switch, Velcro'd to my camera body, operable by one of my left-hand fingers.</p>

<p>In some jurisdictions, possession of laser pointers, is an offence.</p>

<p>WW<br>

<br>

</p>

 

<i> Moderator Note: This thread has been edited, in that editing the reference to using a laser pointer was removed, but this seeminly odd comment remains as general advice to the question which was asked.</i>