Why doesn't the Fuji do all of it's focussing wide open?

DanFry wrote:

DaveHutch wrote:

Erik Baumgartner wrote:

DaveHutch wrote:

Tim van der Leeuw wrote:

DaveHutch wrote:

Are you suggesting using Pre-AF instead?

I wouldn't use "Pre-AF" as that does a continuous AF as long as the camera is on. What might work for you is to use back-button AF - you can put the camera in manual focus, and then use the AF-L button to focus.

Then the camera will focus with the lens wide open (presuming low light situation) and you can use the DoF preview to check focus across the whole frame instead of just under the focus-point.

Then press the shutter when you're happy.

Of course that will slow down your shooting which doesn't work for everything.

Yes, that is an option which I'd consider but you're right, if speed is required it might not work.

Do you think there's a good reason why it isn't possible to uncouple DoF from the half-press?

Doing so would increase shutter lag - if you’re already stopped down, the shutter can actuate immediately without a pause for stopping down the iris. I honestly don’t understand what sort of problems you’re having - my EVF always looks fine stopped down unless you’re in very low light where you really don’t want to stop down so much anyway. Do you not have Boost mode on? That can mess with the EVF.

I'd have thought the would improve low light continuous AF no end!?

Yes, I have boost mode on and set to 100fps. I only really noticed it when I was shooting at f8, in a darkish room and didn't have my flash modelling lights switched on.

I think for the most part I won't notice it but the question was more to get an understanding of exactly what to expect and why Fuji have done it this way.

I think I understand the reasoning now so thanks very much for your answers, and everyone else too.

Not sure that I understand the "my EVF always looks fine stopped down...." argument.

No argument, just stating that when stopping down for a DOF preview, I don’t typically experience any significant image quality problems in my EVF - but then again, I don’t often stop way down in low light and don’t use flash. The OP does.

If shutter is wide open to focus, that's in my understanding the most beneficial to achieve reliable focus as intended. What is visible in the EVF has no bearing on focus accuracy - in AF-S, focusing and releasing the shutter with one press, as proposed, what is there to see? Focusing manually with BBF, with the shutter wide open, then the EVF or screen is useful, in particular when using the focusing assistants available in MF. So Fujifilm offers in my view 2 alternatives:

- AF -S and then focus and shoot with half or full presses of the shutter button > stopped down focusing

- MF with BBF, shutter button only takes the photo, but does not focus > wide open focusing

Still don't understand why people don't use BBF mor often or exclusively.

Dan