Flashing in the dark

Phal · 21 Jul 2015 at 19:52

I've had my flash since before xmas but can't say I've used it very often so far...

The last time I used it (before this weekend just gone) it took me ages to remember that the infrared focus assist grid thingy didn't work with AI Servo AF on!

This time I remembered and I was also a little more sober than last time

So I was getting shots of people but I just wonder what people's experienced are when focusing with the IR assist thing?

I mostly tend to end up using my flash when I have my Sigma 18-35mm F1.8 lens on since it's quite a nice focal length for crop and it's a fast lens. The issue is that the focusing on this lens never seems to be 'that' accurate and obviously low light isn't going to help.

Do you guys notice the accuracy drop when you're relying on the IR assist for focus?

mrk · 25 Jul 2015 at 03:06

Depends on your camera body, some will favour low light AF over others. Usually the centre AF point is the strongest in low light and able to lock servo AF and track with good accuracy, but as is usually the course with this way, shoot a few bursts during servo, sure enough at least 1 will come out in focus.

The AF beam pattern won't work during servo because if it did, you'd see the pattern in your shots.

Phal · 25 Jul 2015 at 09:03

mrk said:
The AF beam pattern won't work during servo because if it did, you'd see the pattern in your shots.

Ah yes, that explains it. I had wondered why but never enough to look it up lol.

7d2 has pretty good low light focusing according to stats. I've only ever had a 70d/650d to compare it to though so it's hard to tell just how much better it translates to in real life. Also I don't often shoot people, let alone people in low light so maybe it's may fault.

I like the 18-35mm lens but the focusing on it doesn't seem all that accurate sometimes. Sadly there aren't really any alternatives when it comes to fast zooms or even wide fast primes for a crop sensor.

Vertigo · 25 Jul 2015 at 12:20

The centre point on the 6D is nuts - it'll basically focus in the dark.

Phal · 25 Jul 2015 at 13:28

Both the 6d and 7d2 seem to have the same low light focusing capabilities according to the Canon specs (EV -3 - 18 (at 23°C & ISO100)).

That being said, I'm sure focusing a prime is easier/quicker than a zoom and where a 24/35mm F1.4 prime is good for tight quarters, they're not so wide on a crop. It's a shame there's no 18mm ish fast primes to try.

Jono · 28 Jul 2015 at 11:37

Is the 6D's low light focusing (centre point) different to the 5D mkIII?

Vertigo · 28 Jul 2015 at 20:36

Jono said:
Is the 6D's low light focusing (centre point) different to the 5D mkIII?

Yes the 6D's centre point will focus in lower light than the 5D3.

The sensor on the 6D is also slightly better than the 5D3 at about half a stop better low-light/high-ISO performance. Just slightly newer tech really.

Of course the 5D3 has many advantages over the 6D but the latter does win in a few areas.

a1ex2001 · 29 Jul 2015 at 16:14

Focus performance always drops off in the dark but I find the focus assist on my flash does really help and even pretty much legless I can still get a decent in focus keeper rate at parties etc.

Phal · 29 Jul 2015 at 16:31

Yeah it definitely helps for the most part. Without the focus assist you're a bit screwed when it's that dark.

Not sure if the red grid focus assist is as reliable as the strobing that the builtin flash does but then again it's a lot less disruptive lol.