Why all the fuss about multiple focal points?
Discussion
Cameras seem to be getting more and more focal points. The new Nikon D4 has 51... And this is supposed to be a good thing? The reviews I've read seem to think so...
I don't get it.
My Dslr has 3. Centre and points just off to the left and right of the centre. I use one. The centre. I focus on the point I want in focus, keep the shutter slightly pressed and recompose to how I want the shot.
Why would you need 51 points for the camera to select from and focus wherever it wants to? Makes no sense, or am I missing the point?
I don't get it.
My Dslr has 3. Centre and points just off to the left and right of the centre. I use one. The centre. I focus on the point I want in focus, keep the shutter slightly pressed and recompose to how I want the shot.
Why would you need 51 points for the camera to select from and focus wherever it wants to? Makes no sense, or am I missing the point?
Well thats fine, but still doesn't explain why anyone would need the use of 51 focal points.
Surely it is more time consuming to use the screen to select the focal point you require than just using a centre point and using the view finder to pick out your focal point, then re-compose.
Maybe it's just the way I picked up photography, using fully manual film SLRs, that has made me work this way, but I just can't see the advantage of using any other point than the centre to focus...
Surely it is more time consuming to use the screen to select the focal point you require than just using a centre point and using the view finder to pick out your focal point, then re-compose.
Maybe it's just the way I picked up photography, using fully manual film SLRs, that has made me work this way, but I just can't see the advantage of using any other point than the centre to focus...
Also if you are shooting with very narrow dof (say 0.5cm) you can find that focus-recompose creates too many miss-focused shots - from you moving the camera or your subject moving.
An off-centre af point can help in that situation, though it is worth keeping in mind that on many models the off-center points can be less accurate also
An off-centre af point can help in that situation, though it is worth keeping in mind that on many models the off-center points can be less accurate also
Edited by flat-planedCrank on Saturday 4th February 21:55
flat-planedCrank said:
Also if you are shooting with very narrow dof (say 0.5cm) you can find that focus-recompose creates too many miss-focused shots - from you moving the camera or your subject moving.
An off-centre af point can help in that situation, thought it is worth keeping in mind that on many models the off-center points can be less accurate also
Was going to mention this. If using really wide apertures with very shallow depth of field, focus and recompose just doesn't work. A lot of focus points are handy in this scenario.An off-centre af point can help in that situation, thought it is worth keeping in mind that on many models the off-center points can be less accurate also
Deluded said:
Cameras seem to be getting more and more focal points. The new Nikon D4 has 51... And this is supposed to be a good thing? The reviews I've read seem to think so...
I don't get it.
The 51-point system started with the D3 and D300. I don't do sports so can't say how much of an advantage it is; 11 is enough for me, and quick enough to scroll round. You can of course group the 51 into various groups if you prefer. Rather stupidly IMHO, on FX they're all remarkably central.I don't get it.
Simpo Two said:
Deluded said:
Cameras seem to be getting more and more focal points. The new Nikon D4 has 51... And this is supposed to be a good thing? The reviews I've read seem to think so...
I don't get it.
The 51-point system started with the D3 and D300. I don't do sports so can't say how much of an advantage it is; 11 is enough for me, and quick enough to scroll round. You can of course group the 51 into various groups if you prefer. Rather stupidly IMHO, on FX they're all remarkably central.I don't get it.
The AF points on my full-frame Canon are very central compared to crop as well - maybe it's a technology issue?
Eg.
1.3x crop 1D mk4: http://www.dpreview.com/reviews/canoneos1dmarkiv/p...
Full-frame 1Ds mk3: http://www.dpreview.com/reviews/canoneos1dsmarkiii...
Eg.
1.3x crop 1D mk4: http://www.dpreview.com/reviews/canoneos1dmarkiv/p...
Full-frame 1Ds mk3: http://www.dpreview.com/reviews/canoneos1dsmarkiii...
Gad-Westy said:
The grouped central thing on FX is infuriating. I have a D700 and D2XS at the moment. 51 points vs 11, yet the 11 on the D2XS are in some way far more useful as they get very close to the edge of the frame rather than being tightly packed around the centre.
When using a D700 and D200 side by side for a few weddings, I found that sometimes the D700 refused to find/lock focus (and no it wasn't on AF-C). So I got the D200 out for the same shot and it just worked. Weird.Simpo Two said:
Gad-Westy said:
The grouped central thing on FX is infuriating. I have a D700 and D2XS at the moment. 51 points vs 11, yet the 11 on the D2XS are in some way far more useful as they get very close to the edge of the frame rather than being tightly packed around the centre.
When using a D700 and D200 side by side for a few weddings, I found that sometimes the D700 refused to find/lock focus (and no it wasn't on AF-C). So I got the D200 out for the same shot and it just worked. Weird.I would guess that the benefit or otherwise of a lot of focus points is very dependent on what your subject matter is an how you ae shooting it.
Not just sports (action vs static subjects either).
With very wide angle lenses shooting landscapes, say, once you nearest point of almost focus is more than about 6ft away (14mm lens for example), focus per se is probably not much of an issue UNLESS you are going to be cropping really deep or printing very large. In which case there may be some special approach required to deal with the lens/sensor/resolution characteristics.
However if part of your image is in close focus at wide angle these things can start to matter as a slight re-positioning can make a big difference to what is on and out of the true plane of focus (much like taking a full head and shoulders portrait or a macro shot).
With software stacking technologies too there could be a strong case leaving a set up exactly as it is once the subject has been framed and changing the point of focus to achieve different levels of sharpness in the subject. I recall a blog post from Drew Gardner describing the process he went through to get a composited shot of a board of directors for an annual report (or something.) There was no way he couold get them all in one place let alone at a field location in the middle of London. So he shot the background with a structure in mind and then the individuals in specific positions related to the camera but at different places at different times using the same lighting set up. That made it easier to composite a consistent final image and each subject, at varying distances from the camera, could be shot in focus despite having preset 'the scene' format and the subjects 'mark'.
There are many similar examples of people chosing an offset focus point in order to get a subject in focus but still have a good view of the total image. News reporting would be one example - a moving image potentially, but not as fast as the more obvious sports requirement.
As fo rthe Full Format centralisation question - I suppose it might be that they are, historically, trying to keep the focus measurement in the sharpest part of the lenses. Using the same part of the income light on a crop body would allow the sensors to be spread wider in the viewfinder even though probably much the same physically in the focus system.
The multiple sensors around the 'primary' focus points are really there to provide more data to make a better decision or, more pertinently to spoarts and action stuff, focus predictions for movement to try to overcome the AF system focus tracking lag that would otherwise limit the successful hit rate.
Such a different challenge to the old Manual Focus days.
Not just sports (action vs static subjects either).
With very wide angle lenses shooting landscapes, say, once you nearest point of almost focus is more than about 6ft away (14mm lens for example), focus per se is probably not much of an issue UNLESS you are going to be cropping really deep or printing very large. In which case there may be some special approach required to deal with the lens/sensor/resolution characteristics.
However if part of your image is in close focus at wide angle these things can start to matter as a slight re-positioning can make a big difference to what is on and out of the true plane of focus (much like taking a full head and shoulders portrait or a macro shot).
With software stacking technologies too there could be a strong case leaving a set up exactly as it is once the subject has been framed and changing the point of focus to achieve different levels of sharpness in the subject. I recall a blog post from Drew Gardner describing the process he went through to get a composited shot of a board of directors for an annual report (or something.) There was no way he couold get them all in one place let alone at a field location in the middle of London. So he shot the background with a structure in mind and then the individuals in specific positions related to the camera but at different places at different times using the same lighting set up. That made it easier to composite a consistent final image and each subject, at varying distances from the camera, could be shot in focus despite having preset 'the scene' format and the subjects 'mark'.
There are many similar examples of people chosing an offset focus point in order to get a subject in focus but still have a good view of the total image. News reporting would be one example - a moving image potentially, but not as fast as the more obvious sports requirement.
As fo rthe Full Format centralisation question - I suppose it might be that they are, historically, trying to keep the focus measurement in the sharpest part of the lenses. Using the same part of the income light on a crop body would allow the sensors to be spread wider in the viewfinder even though probably much the same physically in the focus system.
The multiple sensors around the 'primary' focus points are really there to provide more data to make a better decision or, more pertinently to spoarts and action stuff, focus predictions for movement to try to overcome the AF system focus tracking lag that would otherwise limit the successful hit rate.
Such a different challenge to the old Manual Focus days.
If I'm composing on thirds/off centre then focus/recompose is a really bad way of doing things, as is MF - just not interested in twisting and fine-tuning at anything over F8
I hardly ever use multiple focal points on one exposure, but I like the ability to be able to choose from a good few of them around the range to be sure I have what I'm aiming at in focus
I did try 3D focus today, but it was a macro shot of some icicles and it just freaked out at the depth of field
I hardly ever use multiple focal points on one exposure, but I like the ability to be able to choose from a good few of them around the range to be sure I have what I'm aiming at in focus
I did try 3D focus today, but it was a macro shot of some icicles and it just freaked out at the depth of field
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