Saturday, April 10, 2010

F80EXR and F70EXR – Quick AF Mode Issue

The F80EXR has a few issues with auto focus. One of them is an issue it shares with the F70EXR and indeed, I’d bet with most Fuji cams. This is the tendency of Quick AF mode to overlook the most contrasty object in the scene.

This is an understandable failure, but you must be aware of it when working with this camera, or you will be in for a lot of confusion.

I first noticed the issue when testing the camera in Quick AF mode, thinking that this would be a nice way of working. But right away I found that there were scenes it could not focus on. Through a window, specifically.

It turns out that the EXR cams (and perhaps most Fujis) drastically shorten their focus range when in Quick AF mode. Here is a classic scene showing the issue.

f80_f70_quick_AF_issue[1]

Now, I’m not trying to say that this is somehow an error on Fuji’s part. I’m quite sure that this is the appropriate behavior for anyone who uses this mode. But it will catch you when you don’t expect it, so I would suggest that you only use quick AF when you are shooting fast moving objects with nothing confusing in the foreground. The cam gets easily confused.

4 comments:

Larry said...

Thanks for the tip about Quick AF. I checked my F72 settings and found I had set to Quick AF, since I value rapid focus. Any idea how much quicker it is?

I'd also noticed the camera didn't focus as close as I thought it should unless it was set to Macro. After checking the manual, I found the following info about focus range:
Normal, wide angle, 1.5 ft-inf
Normal, tele, 6.6 ft-inf
Quick AF, wide, 3.3 ft-inf
Quick AF, tele, 13.1 ft-inf
Macro, wide, 2 in-8.2 ft
Macro, tele, 3 ft-8.2 ft

Presumably the tele numbers vary with the amount of zoom.

This also explains some of my focus problems at distance when set to Macro. Other cams I've had would focus to infinity when in Macro mode, I think, so I often left them in Macro mode. Fortunately, Fuji resets the F70/72 Macro mode to OFF when the camera is powered off.

Kim Letkeman said...

Larry: Quick AF feels at least twice as fast when I use it. This because it shortens the range. But it happily leaves you unfocused without saying anything, so I think I'll forget about that. The F70 is pretty quick about focus even without Quick AF. And makes few errors. And macro mode makes a big difference ... 3ft versus 6ft for max zoom, but of course infinity focus goes away. Which is unfortunate.

Ellis said...

My wife lost our F72EXR. (grrr...) I note that it is no longer for sale at our local camera retailer. Instead they have an F80EXR.

Is this a reasonable substitute? Will I be giving up anything?

Kim Letkeman said...

Ellis: My bottom line on the F80EXR is that it works well in most light. Shot using my recommended settings, it looks great. Even at 1600 ISO. But, watch out for bad light ... orange light from compact fluorescents or incandescents will give it fits. You will see blue channel contamination creeping in and it is important to avoid trying to correct the color with custom white balance or even in photoshop unless you want to take it to black and white. But shooting normally in auto white balance leaves usable images even in bad light. So ... the F80EXR makes a very nice cam if you liked the F70EXR. But if you can get an F70EXR somewhere, I'd still take that one instead.