RX1 AF - petty amazing if you remember to let enough light in...

Started Mar 17, 2013 | Discussions thread
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Ray Sachs
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RX1 AF - petty amazing if you remember to let enough light in...
Mar 17, 2013

Like a lot of folks, I read all of the early horror stories about the RX1 auto focus that started showing up when the camera had first been released. Whether Sony has done something to improve the AF in more recent production runs, I don't know - I don't think there have been any official firmware updates on it yet, but who knows if there were tweaks. But after playing with the camera for a solid two days now, I've seen the AF behave in amazing ways, both good and bad, and realized its quite easy to keep it working really well.

I did a night of shooting with the camera the first night I got it, and was incredibly pleased with the low light AF, but wasn't all that shocked because I was shooting outdoors with varying amounts of light coming from buildings, cars, streetlights, etc, and there was always plenty of contrast around to get the camera to lock onto. I posted some of those shots, on Friday, here: http://forums.dpreview.com/forums/post/51044172

Then last night, I decided to really test its limits and started trying to focus on my wife and dog and other stuff in my bedroom with just the light of a single bedside lamp on. To my amazement, it locked on quickly every time, even in quite low contrast scenes. When I say quickly, its not the fastest AF ever, but within it's normal AF speed, it would just lock right on, no drama, no hunting. My Fuji X-Pro tends to do fine with some contrast in low light, but focussing on human faces or some dull backgrounds or fabric, it'll hunt until the cows come home. So I was really impressed and then decided to really go hard towards getting it to fail. So I turned off the one bedroom light and then only some indirect light coming in from the hall was lighting the room. Frankly, lower light than I'd ever shoot in realistically. It took 1/40 of a second, wide open at f2.0, at ISO 12800 to get an exposure. But, to my amazement, it locked right on. To my wife's face, to my dog, to whatever. The only time I could get it to hunt was when I pointed it at a totally nondescript section of our comforter, with zero contrast. And with the single light on, it had locked on to that. But with almost no light, THAT'S what it took to get it to hunt.

So then this morning, I'm just playing around doing some product shots (selling a bit of gear that might go toward funding a purchase of this camera) and I started playing around with focussing at various points around the room, and damned if the camera wasn't hunting like crazy to lock onto almost anything, even pretty contrasty items. And this was in MUCH, MUCH better light than anything it was seeing last night. WHAT!?!?!? I started thinking maybe the camera came with a 48 hour good behavior dispensation built in to impress new owners but then would go back to its normal behavior! The warranty was up - we will now HUNT for you!

But it only took me a couple of minutes to figure out what I was doing wrong. I was trying to get enough DOF to get all of my product shots in focus and with this large sensor in macro mode, even f8 wasn't doing it, so I had closed the aperture down to f11. And not shockingly, once I pointed the camera away from the really well lit little product scene I'd put together, it was having trouble locking onto much of anything. Then I opened the aperture back up to a more reasonable f4 and BINGO, insta-lock.

So, it probably seems obvious to some of you - it should have to me. But if you want the AF to work well in low light, open the damn lens up. At f2 it will focus reliably in the most remarkably low-light situations you can imagine. At f11, it just might not! Frankly, when used correctly, I'm beyond pleasantly surprised with the AF on this camera - I'm actually pretty amazed. Given that its not a speed demon, it might just be the most sure footed low light CDAF system I've ever used. At least as good as the OMD, which is crazy fast in good light but can hunt in low light. And seemingly a good deal better than my Fuji gear, which I love, but which will go hunting in the right situations.


Sony RX1
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