cannot focus properly?

[chenwei]

just got my camera and found out today that the auto-focus cannot work properly in some scenarios.

when i am taking dragonfly photos, the distance is around 50cm (maybe more or less? can't remember), in order not to scare away the dragonfly, i try to zoom the closest (s602 6x zoom) in normal (not macro) mode, press half for auto-focus, but it focus the background instead of the dragonfly.... anyone knows why? i was forced to get closer, do it in macro mode... too bad the dragonfly always fly away then... :cry:

or must a close up filters b4 used? :dunno:

 

[shuy]

i would like to add on....
i use an epson 3100Z, n the autofocus is really disappointing sometimes. like today at esplanade, i tried using autofocus on the theatre. it shot out at aperture of 2 n shutter speed of 1/30. the pic became blur n abit too dark. y the aperture of 2? i was taking the whole theatre for goodness sake.

in fact, my autofocus usually sets the aperture not more than 3. y is that so? does the metering mode make a difference?

 

[Midnight]

Originally posted by chenwei
just got my camera and found out today that the auto-focus cannot work properly in some scenarios.

Do note that every lens has a minimum focusing distance; for a zoom lens, this minimum focusing distance will increase at higher focal length settings. This may be the problem in your case; if so, this is where macro lenses and close-up lenses will make a real difference.

Another possible problem may lie simply in the way autofocus is done: most of the time, it works by detecting contrasts (esp. vertical lines) in the scene, so it may well be that it locks onto the background by virtue of the fact that it has more strongly contrasting areas than the foreground. I would suggest ensuring that the "autofocus area" in your viewfinder is completely taken up by some strongly contrasting area of the foreground, instead of background elements.

 

[Midnight]

Originally posted by shuy
i use an epson 3100Z, n the autofocus is really disappointing sometimes. like today at esplanade, i tried using autofocus on the theatre. it shot out at aperture of 2 n shutter speed of 1/30. the pic became blur n abit too dark. y the aperture of 2? i was taking the whole theatre for goodness sake.

in fact, my autofocus usually sets the aperture not more than 3. y is that so? does the metering mode make a difference?

I think you're referring to auto-exposure, not auto-focus. Anyway, the problem is simply the sheer lack of light; the whole discipline of photography depends on interacting with light to form the image you want, and you can't do much when there isn't enough light. Your eyes may be able to adjust to accommodate the relative lack of light, but your film/sensor isn't anywhere as versatile. In fact, it sounds like your camera's already trying its very best by selecting the widest available aperture setting so as to get the fastest shutter speed possible, but unfortunately in this case this still means a shutter speed duration of 1/30s.

y the aperture of 2? i was taking the whole theatre for goodness sake.

Btw, I'm not sure if I understand this part of your post. What does taking the whole theatre have to do with aperture size? :dunno:

 

[syncmaster]

I do not know your camera , but does it have Spot focus ? Or Spot light metering ?

 

[shawntim]

Originally posted by chenwei
just got my camera and found out today that the auto-focus cannot work properly in some scenarios.

when i am taking dragonfly photos, the distance is around 50cm (maybe more or less? can't remember), in order not to scare away the dragonfly, i try to zoom the closest (s602 6x zoom) in normal (not macro) mode, press half for auto-focus, but it focus the background instead of the dragonfly.... anyone knows why? i was forced to get closer, do it in macro mode... too bad the dragonfly always fly away then... :cry:

or must a close up filters b4 used? :dunno:

before you do that, go Settings > AF > change to AF instead of AF Area.

Then go Menu > change to Spot metering. See if it helps. When you're using the spot metering, the cursor changes to a crosshair instead of a box.

 

[chenwei]

Originally posted by Midnight
Do note that every lens has a minimum focusing distance; for a zoom lens, this minimum focusing distance will increase at higher focal length settings. This may be the problem in your case; if so, this is where macro lenses and close-up lenses will make a real difference.

Another possible problem may lie simply in the way autofocus is done: most of the time, it works by detecting contrasts (esp. vertical lines) in the scene, so it may well be that it locks onto the background by virtue of the fact that it has more strongly contrasting areas than the foreground. I would suggest ensuring that the "autofocus area" in your viewfinder is completely taken up by some strongly contrasting area of the foreground, instead of background elements.

i think the 2nd scenario better explain and descibe my situation, thanks

syncmaster, shawntim, will try ur suggestion when i back today

 

[shawntim]

you may wish to check ur settings > set adaptor ring to no or yes depending if you're using the TC.

The autofocus beam comes from the IR looking thing just infront of the flash. Apparently Fuji added this feature for users whose TCs block this beam.

 

[mpenza]

there's actually no "IR beam" shooting out from the camera. The IR sensor is passive and gives a rough gauge of subject's location to speed up focussing.

 

[mpenza]

Originally posted by chenwei
when i am taking dragonfly photos, the distance is around 50cm (maybe more or less? can't remember), in order not to scare away the dragonfly, i try to zoom the closest (s602 6x zoom) in normal (not macro) mode, press half for auto-focus, but it focus the background instead of the dragonfly.... anyone knows why? i was forced to get closer, do it in macro mode... too bad the dragonfly always fly away then... :cry:

or must a close up filters b4 used? :dunno:

all lens have a minimum focussing limit. that's why there's a macro mode for close-up shots.

if you want to use full 6x optical zoom, your best bet might be to use close-up filters. but I find that this does not give enough magnification..... check out azone's pics.... he's using the equivalent of +8 and the shooting distance is around 12cm. here's one of his threads....

http://forums.clubsnap.org//showthread.php?s=&threadid=14046

anyway, don't worry about dragonfly. they tend to come back to the same spot to rest. I've spent many a good afternoon shooting them in the past

 

[Zerstorer]

Originally posted by chenwei
just got my camera and found out today that the auto-focus cannot work properly in some scenarios.

when i am taking dragonfly photos, the distance is around 50cm (maybe more or less? can't remember), in order not to scare away the dragonfly, i try to zoom the closest (s602 6x zoom) in normal (not macro) mode, press half for auto-focus, but it focus the background instead of the dragonfly.... anyone knows why?

At full tele, the minimum focus distance is 0.9M. That's why you couldn't focus. Check the manual for the numbers and guidelines, it will help avoid such mistakes in future.

i was forced to get closer, do it in macro mode... too bad the dragonfly always fly away then... :cry:

or must a close up filters b4 used? :dunno:

Macro mode will shorten focal distance as well as reduce the focal length. Close up filters will only reduce focal distance.

A +2 will bring the range at full tele to about 0.5M. +4 will take it to 0.25M.

The passive IR sensor is just under the flash. It gives a rough gauge of distance before the contrast detection focusing fine tunes the result. This is used to speed up the focusing of the 602. If you use TCs the sensor would be blocked and the 602 would have to rely solely on contrast detection through the lens.

 

[Zerstorer]

One thing to note, focusing and metering are 2 totally separate elements. Changing to spot metering will result in only the spot metered by the centre crosshair properly exposed.

Spot metering should only be used in when a certain effect is intended, for most purposes Matrix Metering is adequate.

 

[xdivider]

Originally posted by chenwei
just got my camera and found out today that the auto-focus cannot work properly in some scenarios.

when i am taking dragonfly photos, the distance is around 50cm (maybe more or less? can't remember), in order not to scare away the dragonfly, i try to zoom the closest (s602 6x zoom) in normal (not macro) mode, press half for auto-focus, but it focus the background instead of the dragonfly.... anyone knows why? i was forced to get closer, do it in macro mode... too bad the dragonfly always fly away then...
or must a close up filters b4 used?

Juz stand there like a idiot like wat i always do and he will think u r harmless. Them pull out ur big barrel at 1cm macro range and fire.:bsmilie:

 

[chenwei]

Originally posted by xdivider

Juz stand there like a idiot like wat i always do and he will think u r harmless. Them pull out ur big barrel at 1cm macro range and fire.:bsmilie:

er... i dunno whether i dun have such a luck, normally when i get closer, they all fly away, leaving me alone standing there like idiot for a few mins... finally i gave up (is it because of my fierce-looking???)... :what:

thanks shawntim, mpenza, zerstorer and xdivider for all the suggestions and explainations!

today i went to buy a +4 close up filter, tried a few times just now, seem like whenever the close up filter is attached, there will be a distance (one and only one!) the object will get clearest, all other distance the object can't be focused properly. wondering why is this happenned...

and seem like using a close up filter, the distance cannot be too far even using tele lens at the same time... :dunno:

 

[mpenza]

close-up lens/filters change the focussing distance. divide 100cm by the power (added together if stacked) to get the focussing distance. the magnification comes from being able to use the full optical zoom under normal (non-macro) mode.

e.g. if you're using a +4 close-up filter, you can focus best at a around 100/4 or 25cm using the full 210mm zoom. if you're using a +8, you can focus best around 12.5cm using the full 210mm zoom. at lower zoom setting, you can focus over a slightly wider range.

 

[chenwei]

Originally posted by mpenza
close-up lens/filters change the focussing distance. divide 100cm by the power (added together if stacked) to get the focussing distance. the magnification comes from being able to use the full optical zoom under normal (non-macro) mode.

e.g. if you're using a +4 close-up filter, you can focus best at a around 100/4 or 25cm using the full 210mm zoom. if you're using a +8, you can focus best around 12.5cm using the full 210mm zoom. at lower zoom setting, you can focus over a slightly wider range.

i c, thanks for the explaination! :angel:

just wonder the slightly wider in lower zoom setting u said, is it means the focus area is wider, but the best focus distance still remains the same?

 

[mpenza]

hmm... e.g. for a +4, if you don't zoom in fully, you may be able to achieve focus from 20-30cm.... a wider range compared to if you zoom in fully.