Is the Center Focusing Point always the most accurate?

[humbee]

Hi all

I recently started using a 40D (the price is really quite good, since its an outgoing model )

I just like to learn from others, whether you've found the Center Focusing Point (altogether, there are 9 of them) to be the most accurate "all the time".

Personally, I've discovered that many times, using the 9-points produces very sharp results. Sometimes, using the Center Point alone produces 'less sharp/out-of-focus' results. I don't think this is a camera or lens fault - even thought it could possibly be due to front/back focusing issues, which I guess every lens/body will have, to a greater to lesser degree.

I'm not sure if my opinions are correct:

1. Take spot metering for example. Although 'Spot' metering is suppose to be the most accurate, but the exposure can go seriously wrong if a user 'spot' on the wrong area. In other words, it is very 'narrowly defined', and very unforgiving - with little or no margin for error . Spot wrongly - picture probably gone . (and I think many users don't have enough experience to always know where to spot correctly.) I frankly think that the evaluative or center weighted mode is 'safer' in most cases - a lot more forgiving.

2. Back to the 'center' focusing point, could it be that not all areas of a subject suits the center focusing sensor - because it is too narrowly defined? (even though it is cross-type) Are the other 8 focusing points cross-type too?

I sincerely don't suspect it's a camera fault, but rather the need to understand how each camera and its sensor units behave, and capitalize on its strength. When switched to full auto mode, the results can be impressive - surprisingly good on when left on its own 'auto-piloting'

What are your experiences so far, and please do not hesitate to correct me if I'm wrong. No worries, I'm just a humbee

humbee

[rendition]

Hmmm, personally, I don't think centre is the ''most accurate" neither are the rest of the points. But of course, in a frame, if you focus say on left, there's a chance for the centre subject in frame to be OOF, pretty obvious right.

I guess most of us use centre cuz it's just the... I dunno, my primary eye is set to seeing the middle as the point of focus.

[Snoweagle]

I find all focusing points just as accurate. Center focusing point is most often used as it utilises the 'sweet spot' of lenses, which is the center part.

[chalib]

Center is faster to lock....

[jkaiser]

how come u talk about focus, then suddenly jump to exposure metering then back to focus..

2. Spot metering takes note of about... 3% of the screen..the small circle in the centre.. i think like u said, have to be careful where u meter.. for example past 2 days i've been shooting dance..with the black backdrop..if i have used evaluative, it would have overcompensated for the backdrop and blow out the rest of the picture...hence it makes more sense to spot meter... of cos in other uses, i dun spot meter as much... the thing is knowing what u need, and be prepared for that moment when u have to use it one day (read: practise 1st)

[humbee]

Hi Bro (Jkaisar)

I was actually using spot metering as an analogy. Actually, I was a little worried about people may not understand what I meant. I lack to ability to articulate well.

Thanks for posting.

[Snoweagle]

Originally Posted by chalib Center is faster to lock....

My other focusing points do lock just as fast.

[Stratix]

the center is faster and more accurate then the rest of the points on most cameras.

that is because the center point features a cross AF sensor that detects both horizontal detail and vertical details, while the rest of the points are only vertical sensitive.

[dev2k8]

hmmm...if i remember cprrectly 40D's focus points are all cross type...

[Octarine]

A single point cannot be faster than another single point. Using several points might gain some fractions of a second - but whether the focus point that locked finally is the best one for the situation is a different story altogether.
There are white papers about the focusing system and it's a good idea to read about it and understand how focusing works. Helps to prevent misunderstandings and misperceptions.
The slowest part of all focusing is the lens motor pushing the focusing ring into the right position. The sensor and the electronics do their job within such short time that it doesn't matter at all compared to the mechanical part. The main point is: can the underlying sensor detect the contrast? If not the hunting starts. The centre point can detect in two directions (horizontal and vertical) - but that doesn't make this point any faster nor will using a different point slow down the focusing. Provided the necessary pattern is there for the AF to recognize.

[Snoweagle]

I still find my 5D's AF locking on all points just as fast though.

[grantyale]

Simple - spot metering is 'accurate' when you point at a patch that averages to mid-gray in your final image, 'spot' focusing is 'accurate' when you point at the spot you want your image to be sharp at.

[chalib]

Originally Posted by Snoweagle My other focusing points do lock just as fast.

Do test on extreme situation then you will see the diff

[flyer]

Originally Posted by Snoweagle I still find my 5D's AF locking on all points just as fast though.

Originally Posted by chalib Do test on extreme situation then you will see the diff

Agree with chalib. Only the center AF sensor is cross type on the 5D, the rest will hunt more in difficult focusing situations.

[Snoweagle]

Originally Posted by chalib Do test on extreme situation then you will see the diff

Tried and tested even at low-lighting conditions. Of cos i was using my 50mm.

[twisted illusion]

Originally Posted by humbee Hi all I recently started using a 40D (the price is really quite good, since its an outgoing model ) I just like to learn from others, whether you've found the Center Focusing Point (altogether, there are 9 of them) to be the most accurate "all the time". Personally, I've discovered that many times, using the 9-points produces very sharp results. Sometimes, using the Center Point alone produces 'less sharp/out-of-focus' results. I don't think this is a camera or lens fault - even thought it could possibly be due to front/back focusing issues, which I guess every lens/body will have, to a greater to lesser degree. I'm not sure if my opinions are correct: 1. Take spot metering for example. Although 'Spot' metering is suppose to be the most accurate, but the exposure can go seriously wrong if a user 'spot' on the wrong area. In other words, it is very 'narrowly defined', and very unforgiving - with little or no margin for error . Spot wrongly - picture probably gone . (and I think many users don't have enough experience to always know where to spot correctly.) I frankly think that the evaluative or center weighted mode is 'safer' in most cases - a lot more forgiving. 2. Back to the 'center' focusing point, could it be that not all areas of a subject suits the center focusing sensor - because it is too narrowly defined? (even though it is cross-type) Are the other 8 focusing points cross-type too? I sincerely don't suspect it's a camera fault, but rather the need to understand how each camera and its sensor units behave, and capitalize on its strength. When switched to full auto mode, the results can be impressive - surprisingly good on when left on its own 'auto-piloting' What are your experiences so far, and please do not hesitate to correct me if I'm wrong. No worries, I'm just a humbee humbee

i personally prefer to centre focus then lock then re-frame... but it just me... too lazy to shift the focus point around with every frame...

[chalib]

Originally Posted by Snoweagle Tried and tested even at low-lighting conditions. Of cos i was using my 50mm.

Lucky you got 'special' cam

[Snoweagle]

Originally Posted by chalib Lucky you got 'special' cam

Yeah, damn 'special'.

[estel]

Originally Posted by Snoweagle Tried and tested even at low-lighting conditions. Of cos i was using my 50mm.

I have noticed that side focusing points can hunt or find focusing difficult if the only contrast gradient they can find is either horizontal or vertical, depending on the point. This seems to agree with the official account of focus point design.

40D, 5D II.

[Snoweagle]

Originally Posted by estel I have noticed that side focusing points can hunt or find focusing difficult if the only contrast gradient they can find is either horizontal or vertical, depending on the point. This seems to agree with the official account of focus point design. 40D, 5D II.

The point on cross-type is true but usually under normal conditions wouldn't be noticeable at all. I'll switch around focusing points to the one which is nearest to where i want to focus and so far all very snappy.