AF speeds on DSLR vs. Mirrorless, and is live view optional?

Started May 27, 2012 | Discussions thread
Billx08 Forum Pro • Posts: 11,373
Re: AF speeds on DSLR vs. Mirrorless, and is live view optional?

erang42 wrote:

I'm looking into moving up from a P&S to either DSLR or Mirrorless 4/3 (in the sub-$1000 range). This is for photographing my anticipated first child, where I believe speed (AF speed, shutter lag, etc.) and quality will be important.

I read that using live view on a DSLR hurts the AF speed. But on cameras that have live view, is it an option that can be turned off? i.e. Truly an "option" in that I can turn it off and enjoy fast AF using the viewfinder, as fast as cameras without live view? Or is live view vs. viewfinder a decision I need to make when I choose a camera?

There are DSLRs that use only optical viewfinders for shooting and they autofocus very quickly. Then came the DSLRs that added Live View. They focus just as quickly when Live View isn't used, and usually much more slowly when Live View is used instead. So slow that sometimes it's impractical to try to shoot without the camera on a tripod. The so-called "mirrorless" cameras don't have multiple autofocus sensors. They focus using the camera's image sensor, just as digital P&S cameras have done forever. Some are faster than others, but the fastest are still significantly slower than DSLRs in one or more ways. Into the mix comes Nikon's new Series 1 cameras, the J1 and the V1. They autofocus both ways but they don't have the excellent optical viewfinders that DSLR use or the cruddy optical viewfinders that some P&S camera have. The J1 has no viewfinder and the V1 has a high resolution Electronic Viewfinder (EVF). In dim light they focus like many mirrorless and P&S cameras. Decent, but nothing special. In better light, they focus the way DSLRs do, and they can be blazingly fast. They're also fairly small cameras. If they seem interesting, these links can provide enough information to keep a speedreader occupied for a long, long time.

Also, any advice on deciding between DSLR or mirrorless? Is the AF (or shutter lag) on mirrorless significantly slower than DSLR? Are these latencies written in the specs somewhere so I can compare on paper?

For single shot photography, the best mirrorless cameras can just about keep up with decent DSLRs. Where they fall behind is shooting long bursts of photos while continuing to track and maintain focus on quickly moving subjects. This is one of the things that the J1 and V1 do very well. No, the latencies are not found in the spec's. You'll find them in the better camera reviews, such as those from DPReview, Imaging-Resource and Jeff Keller's Digital Camera Resource website. DPReview has recently started to publish reformatted versions of some of Jeff's camera reviews. Below is an example of Jeff's Panasonic ZS20 reivew with two links, one for the beginning of the review and the other skipping to the page that lists the performance measurements. Spec's won't tell you everything. No matter what the latency is, with optical viewfinders you're able to see the subject continuously. This is important for keeping the camera pointed at a moving subject when you're shooting bursts of photos. Many P&S and mirrorless cameras either don't show the subject between shots, or only show you on the LCD or in the EVF where the subject was , not where the subject is now . This can make it very difficult to keep to keep the subject in the frame as you pan the camera.

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