Ray,
You can tell the camera where to focus. On the Nikon DSLR's there is a red dot/cube that you can move around the viewfinder so that it only uses the single sensor. You can use the multiple sensors to check and adjust lighting throughout the scene much like spot metering; apply it to maximize or make critical choices in DOF; and do it all without moving the camera. It is very cool.

Having said that, I'm not in total agreement that to complain about AF is to deflect blame or that AF will work in any light. There aren’t that many lenses that are F1,2 or F1,4. In good light my AF Nikon will focus as fast or faster than I can manually on an FE2. In low light I can out focus an AF. Although I own Nikon, I've shot EOS AF and it was not appreciatively different in normal light, but I have no experience in low light.

There's no replacement for a rangefinder (with a bright VF) to focus in low light (w/o any focusing aid lightsource). An SLR (digital or analogue) simply won't do it as well... And with a RF a) you don't need a fast 1.x $$$ lens to do it b) as an added bonus, you get much better / accurate focusing with wide angle or ulta wide angle lenses... Given that, I'd always rely on AF when using an AF body, since their focusing screens are crap (unless you have the opportunity to replace them with better / more accurate ones) + the lenses' focusing strokes are usually too short to focus accurately. (AF will always do the job better than MF with those bodies and lenses - tried it, that's definitive for my case.) Agree with jd on using the camera according to their design. (Such as using local focus points instead of wide focus area...)

Regards,
Loris.



... I'm not in total agreement that to complain about AF is to deflect blame or that AF will work in any light. There aren’t that many lenses that are F1,2 or F1,4. In good light my AF Nikon will focus as fast or faster than I can manually on an FE2. In low light I can out focus an AF. Although I own Nikon, I've shot EOS AF and it was not appreciatively different in normal light, but I have no experience in low light.

There's no replacement for a rangefinder (with a bright VF) to focus in low light (w/o any focusing aid lightsource). An SLR (digital or analogue) simply won't do it as well... And with a RF a) you don't need a fast 1.x $$$ lens to do it b) as an added bonus, you get much better / accurate focusing with wide angle or ulta wide angle lenses... Given that, I'd always rely on AF when using an AF body, since their focusing screens are crap (unless you have the opportunity to replace them with better / more accurate ones) + the lenses' focusing strokes are usually too short to focus accurately. (AF will always do the job better than MF with those bodies and lenses - tried it, that's definitive for my case.) Agree with jd on using the camera according to their design. (Such as using local focus points instead of wide focus area...)

Regards,
Loris.
The Leica M8 is a great choice if onne wants to stay digital.


Don Bryant

g'day Silver

could you possibly expand on this statement?

seems to me the "maker" intends that multiple point autofocus will make too many assumptions, the most obvious being that the system will decide what to focus on by assuming the subject to be the object closest to the camera

Ray, one should never allow the camera to automatically pick and choose the focus point/s. Although the makers do allow this, it is not their intended way of using their cameras.

And if one picks and choose the FP manually, one will find the best image quality is produced, in regard to critical focus and metering.

Now if the comp is fairly dark, and dark enough to cause the camera to struggle to acquire focus lock, there are speed lights that can provide AF assisting lights, even if a flash is not desired. I find the assisting lights work very well.

Ray, one should never allow the camera to automatically pick and choose the focus point/s. Although the makers do allow this, it is not their intended way of using their cameras.

And if one picks and choose the FP manually, one will find the best image quality is produced, in regard to critical focus and metering.

Now if the comp is fairly dark, and dark enough to cause the camera to struggle to acquire focus lock, there are speed lights that can provide AF assisting lights, even if a flash is not desired. I find the assisting lights work very well.


yeh, isn't most of that what i said?

why your "never" recompose comment?

yeh, isn't most of that what i said?

why your "never" recompose comment?

Recomposing after focus lock is to move the focus plain, and therefore cause less then critically sharp focus. The whole point of multi focus points is so that one does not have to recompose. Recomposing can also throw off metering too. Of course if one shoots at F5.6 or down from there, recomposing is less an issue, because of the fatter depth-of-field.

Most DSLR users don't know how to use their multi-point cameras. Even those having 10+ years with Nikon or Canon. Strange.

Hi


I've had an EVolt 500 for about a year. Truth to be told, it's the first auto focus camera I've ever owned,


ok ... its a paradigm shift I know. I still remember my first conference shoot with an EOS 630 and being frustrated that I had to center everything to focus and make damn sure that I didn't put someones cheek in the AF spot or it'd hunt and not even allow me to take a shot!



Here's what's bugging me: in what I consider to be reasonable low light conditions (early evening, cloudy, aiming toward stuff in my garden...so I'm pointing away from the sky) it won't manual focus.


I guess that you mean it won't Auto focus?




Would any auto focus DSLR behave the same way, or is my EVolt sort of wimpy in this regard? The answer -- switch to manual -- is pretty obvious, but I find that the manual focus ring does very little.


well, perhaps its because you're looking at a much smaller viewfinder and using a much wider angle lens than normal? I mean that I find it hard enough hand focusing my 24mm (even on my old Pentax MX) let alone try this with a 18-55 zoom.



In bright daylight conditions, the camera does wonderful stuff. But take a small step away from the norm and it seems to call it quits. My ancient Minoltas -- film and manual focus that works -- do what I want when I want. Why not my EVolt?


one reason is the point about the wider angles and the darker smaller view finders. Another is that some cameras AF sensors work differently with different f lenses. The wider the aperture the more contrast they can get. Also were you working with live view (focuses with a different system altogether if I recall).

If the light is low, then perhaps use just the central AF point
Just a few suggestions.

Hi


Most DSLR users don't know how to use their multi-point cameras. Even those having 10+ years with Nikon or Canon. Strange.

most people don't know how to change gears in a bicycle properly but that's not the bike makers fault

wrt the multi point AF, well do some tests and don't be stunned if you don't get focus exactly where you want it. I've found that (with my 10D and Tokina 12-24) that multiple 1/2 presses of the shutter (and the camera not altering focus anymore still result in less than optimal focus in the off center points. Heck with my 20D I got different results even with just the EF50 on different focal points.

Back ages ago (like 1990's) I tested my EOS 630 with only a single focal sensor and then checked focus with a ground glass on the film gate and found that I could do better by eye in the screen than it could at f1.8 This issue resolved itself when stopping down to f5.6 or smaller. I could not do follow focus on a runner (approaching me) with my USM lens anywhere near as well as it could though.

so ... swings n round abouts :-)

I know this doesn't help, but perhaps it helps to manage expectations?

Hi


That means that digital is no real progress:


if you mean digital in terms of AF systems well ... yes and no. Its like having an assistant, you have to learn to work with the assistant. Some people can't do that and are always over worked / late / missing things. I find that for some applications I use AF (sports and kids) and for others use manual focus.

I've leand to use my multi af points as if they're a moving split image, but to be honest I don't think its soooooo different to using my center and recomposing. The difference may be there but there are other potential errors that may make it similar anyway.

:-)

Hi
I've leand to use my multi af points as if they're a moving split image, but to be honest I don't think its soooooo different to using my center and recomposing. The difference may be there but there are other potential errors that may make it similar anyway.

:-)


When shooting close to your subject, and fast in aperture, you can be sure that locking focus then recomposing will throw off critical focus. If one has low standards one does not see much difference. For me, critical focus is very important. Do you know how thin the DOF is with a 50mm prime at 20 inches from the subject and at F1.4 or F2? Too thin to recompose and expect critical focus. Why not just learn to manually pick & choose the appropriate FP and use the camera as intended?

As to digital and progress wtih AF, well DSLR's often use the same logic and/or mechanism for AF as SLR's for respective companies.

Hi


Do you know how thin the DOF is with a 50mm prime at 20 inches from the subject and at F1.4 or F2?

I do ... but then I rarely use it at such, I often stop down to f5.6 or 8 because at 20 inches the background will still be blurred

and (as I mentioned conferences) I was thinking of a 200mm at 8 meters.


Why not just learn to manually pick & choose the appropriate FP and use the camera as intended?


I guess you didn't read what I wrote then ... I'll post it below even though you already quoted it.


I've leand to use my multi af points as if they're a moving split image,

Hi



I do ... but then I rarely use it at such, I often stop down to f5.6 or 8 because at 20 inches the background will still be blurred

and (as I mentioned conferences) I was thinking of a 200mm at 8 meters.



I guess you didn't read what I wrote then ... I'll post it below even though you already quoted it.

I've leand to use my multi af points as if they're a moving split image,


Ok, but are you MANUALLY picking the appropriate focus point? And if so, are you not recomposing after locking focus? Even at F5.6 and 20" from your subject, recomposing can soften critical focus.

Hi


Ok, but are you MANUALLY picking the appropriate focus point? And if so, are you not recomposing after locking focus? Even at F5.6 and 20" from your subject, recomposing can soften critical focus.

yes, that's correct, I move the focus points with (on my camera) a thumbpress and a quick wheel to get the one I want. But I only do this to move to the extreme focus points as the cluster more or less around the center is of such little arc that its hardly worth it.

Also (for what its worth) I find that my camera occasionally front or back focuses anyway, something not obvious in the puny APS sized finders of my 10D or 20D ... I prefer the finder on my trusty old EOS 630 (which only has one focus point anyway ;-)

I've found USM lenses lessen this effect, but (say) on my EF 50 1.8 its quite notorious for it.

Well, front/back focus issues with even L lenses and all the Canon DSLR's are an on going problem. This is the bane of Canon, and perhaps the other makes. I've finally got my stable of lenses spot on, but it took years, and packages to Canon service. My 50L F1.2 still has issues however. I think no amount of calibration will mitigate it's issues; a design flaw that started during the blueprint drawings. Unlike the other L primes, the 50L does not use a floating design (idiots).