Comments on: X-series AF performance: AF-L button focus method

By: Edmond

Edmond — Fri, 04 Jan 2013 02:42:28 +0000

I remember that before 2.01 update AF-S didn’t have a problem. Fuji told me they found the reason of the back focus and it can be fix with new firmware. Unfortunately If you bring your camera to Fuji service right now, Fuji cannot help you even they may deny the issue because Fuji Japan didn’t provide any comment about the back focus to local Fuji service. That was the why I reported the problem to Fuji Japan directly.

By: Antonio G

Antonio G — Thu, 03 Jan 2013 23:21:41 +0000

You’re right Chad, my mistake.
As you say AF-L in AF-S mode just seems to lock focus. I checked the menu entries and there is no way to prevent shutter button to AF.
TThe confusion comes from the possibilities offered by my full frame DSLR that already allows it and because I do use the Fuji in manual focus mode via the AF-L button and eventual micro adjustments with the ring.
As a matter of fact it only adjusts the frame when pressuring the shutter button half way. For me it is not a bad thing because time reasons but because this way one of the advantages of using range focusing and the OVF to anticipate the image’s framing is partially compromised as you only know where the lines are at the moment you press the shutter, and this happens even if you use also manual exposure.
This and the precision of focus range indication bar should be considered by Fujifilm for future firmware updates.

By: edvarda

edvarda — Thu, 03 Jan 2013 21:06:11 +0000

Thanks to all of you for your answers. After many many test shots I am really sure now that my 35 mm lens struggles with a back focus issue in AF-S mode. If you try to focus on “challenging” low contrast objects it gets more pronounced while AF-L in manual mode is still capable to focus accurately.

I doubt if this is a general problem since only a few people can duplicate this (see also
http://www.fujix-forum.com/index.php?/topic/6752-afl-button-focus-method/ )

Edmond,
thanks for the good news from the Fuji HQ. Did they tell you if it is an issue of the camera FW or if only some lenses are affected? Before sending the 35mm lens to the Fuji service I will wait for some more weeks until the next FW update is available and hopefully fixes the issue. By then I will work in manual mode and mainly enjoy the incredible 18-55 lens.

By: Edmond

Edmond — Thu, 03 Jan 2013 13:45:31 +0000

That’s what I reported to Fuji. Fuji told me that they need at least one month for new firmware to correct this issue.

By: Chad

Chad — Thu, 03 Jan 2013 02:21:16 +0000

Edvarda,

I cannot duplicate what you are seeing. Just a couple comments and suggestions.

When you do your test, make sure you are in EVF mode (to ensure you are absolutely focusing on the same spot). Even better, use a tripod.

The Fuji Contrast Detection system differs from others in that it excels at recognizing vertical lines as opposed to horizontal. A bookshelf has lots of vertical lines so make sure the AF spot is completely clear of any contrast or vertical lines. A plain white wall is a good torture test.

Best,
Chad

By: Chad

Chad — Thu, 03 Jan 2013 02:15:16 +0000

Are we using the same camera?

You said: At the end, using AF-L in manual mode is just the same as using it in AF-S mode. The idea to use AF-L in manual mode is only to let the camera use autofocus and afterwards to make fine adjustments using the lens ring.

Not true here. Using AF-L in AF-S does just what it says it does – lock the AF so you can recompose without changing focus. It does NOT attempt to AF like it does in manual mode.

By: Chad

Chad — Thu, 03 Jan 2013 02:09:24 +0000

Yes, I am sure. Just tested again. In Manual mode, using AF-L button does one thing only – capture focus similar to what AF-S would do EXCEPT it does not change the frame lines, that is an extra step, accomplished by a half shutter press.

So whatever perceived AF speed gains people think AF-L gives them (and I have seen none) are negated when you add the extra time needed to reframe with the half shutter.

So that leaves us with the assertion that somehow AF-L in manual mode is more accurate than AF-S. Haven’t found that to be true either.

Best,
Chad

By: Antonio G

Antonio G — Wed, 02 Jan 2013 16:13:00 +0000

Are you using “Multi” or “Area” when you select AF-S via the shutter button half pressing?

And, when switch to “manual focus” and press AF-L do you change your settings and leave the shutter button just to measure exposure and trigger or you leave it just to change to AF-S and half press to autofocus?

Did you try to set you camera in a way that AF-L is the only button to focus it and switch from AF-S to Manual using the focusing mode selector and “Area” focus? If so, do you see any difference?

By: edvarda

edvarda — Wed, 02 Jan 2013 13:16:43 +0000

I did my shots ( X-E1 + 35mm lens at f1.4) in lowlight of a bookshelf focusing on some glossy white books (with fine black lettering). For sure not an easy job but the camera managed it in the manual mode all the time while it failed in AF-S mode. I repeated this exercise this morning in daylight. Same results: no difference in focus speed between the two modes but the AF-S shots were just not 100 % sharp. So the camera seems to struggle especially with low contrast, glossy objects – but only in AF-S mode!

I did also some test shots of other objects (lowlight and daylight) where there was absolutely no difference between the AF-S/manual mode. Neither in terms of focus speed nor in the resulting pictures (all were sharp).

I couldn’t reproduce this with the 18-55 mm lens (at 35 mm and f 3.6). But maybe the larger DOF compensated the differences.

By: Antonio G

Antonio G — Wed, 02 Jan 2013 11:11:23 +0000

Are you sure that in manual focus mode the half shutter press will reframe the frame lines again?

I guess that the only effect of half press will be to fix exposure, if you are not using manual mode for it as well (meaning, you’re using A or S semi auto modes) and you “said” the camera (via menu) to use shutter only for that.

At the end, using AF-L in manual mode is just the same as using it in AF-S mode. The idea to use AF-L in manual mode is only to let the camera use autofocus and afterwards to make fine adjustments using the lens ring.

If it takes longer or not depends on the photographer and the kind of photography. Maybe if you move the focus point around within the viewfinder, instead of just focusing using the central area, will take you longer.

One of the benefits of using range focusing mode in manual mode is that you don’t need to refocus when your subject stays in the appropriate range, and this is the reason why so many street photographers use it (namely with real manual rangefinder cameras).