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#21
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Did Canon decide to profit on bodies?
Robert Coe wrote:
On Sat, 30 Jun 2012 13:04:07 +0200, Wolfgang Weisselberg wrote: : Robert Coe wrote: : On Fri, 29 Jun 2012 13:22:17 +0200, Wolfgang Weisselberg : : Me wrote: : : Not sure how the auto focus point select system works on the higher : : end nikons. Despite 51 AF points, there's surely not enough data : : for full face detect, : : The 1DX does have a rather high resolution exposure sensor, : : which has more than enough resolution for face detect ... : : a fact that Canon has cleverly engineered in and uses. : Isn't the crux of the matter that face detect can work only in live view mode? : No. : Because if the image of the subject is being deflected into the viewfinder, : it's not available to the sensor for analysis. Which would seem to make it : useless for AF if the camera is used for action photography. : Is the exposure sensor able to get data when the mirror is down, : and if not, how is metering done? I believe there's a special metering sensor built into the viewfinder. But it seems unlikely that it would have either the resolution 100.000 Pixel-RGB or the computing power A DIGIC 4 just for the AF --- that used to drive whole cameras! to be useful for face detection. That said, I have no expertise at all in this area; I've never had occasion to use a camera with face detection. Looking at the published data for the 1DX could have told you all that. No claims on how good it is, though, and no claims that Nikon didn't do it first. -Wolfgang |
#22
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Did Canon decide to profit on bodies?
"Trevor" writes:
"David Dyer-Bennet" wrote in message ... Today, I can place *a chosen focus point* on a musician's eyes and count on AF-C to keep the eye in focus as his head bobs to the music. Exactly my point, you don't need 61 AF points to do that. That's precisely the case where I *DO* need 51 AF points, or even more (at least, I'd like some closer to the frame edges). I mean, I'm only using a few, in the area of the eye -- but depending on the framing, that eye could be almost anywhere, so I need AF points over the whole frame. How the hell do you select the right one from 51, how long does that take you? And isn't it easier to just use a single central AF point, place it on the eye, half press the shutter, and reframe? Works for me anyway. Takes a couple of seconds to set up (two dimensional movement, not one). Focus and recompose is easier for one shot, but not so clearly easier for a series of shots. Also, focus and recompose is less accurate; when you recompose you rotate the camera around some point, and you end up with their being a triangle with apex at the subject and the other two points where the sensor was in the two positions of the camera, and those two distances aren't identical. Focusing just once for a series of shots works fine so long as the subject and the camera don't move much. Stopping down for more depth of field works fine so long as you have the light and ISO to support it, and so long as you don't mind the background being sharper (sometimes that's actually desirable, sometimes it's undesirable). When shooting at f/1.4 and wider, you've got quite limited DOF. -- David Dyer-Bennet, ; http://dd-b.net/ Snapshots: http://dd-b.net/dd-b/SnapshotAlbum/data/ Photos: http://dd-b.net/photography/gallery/ Dragaera: http://dragaera.info |
#23
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Did Canon decide to profit on bodies?
Me writes:
On 29/06/2012 1:55 p.m., Trevor wrote: "David Dyer-Bennet" wrote in message ... Today, I can place *a chosen focus point* on a musician's eyes and count on AF-C to keep the eye in focus as his head bobs to the music. Exactly my point, you don't need 61 AF points to do that. That's precisely the case where I *DO* need 51 AF points, or even more (at least, I'd like some closer to the frame edges). I mean, I'm only using a few, in the area of the eye -- but depending on the framing, that eye could be almost anywhere, so I need AF points over the whole frame. How the hell do you select the right one from 51, how long does that take you? And isn't it easier to just use a single central AF point, place it on the eye, half press the shutter, and reframe? Works for me anyway. Trevor. It's pretty easy/fast to do using the 4-way selector, and with very shallow DOF, "focus & recompose" is very unreliable - as people move. There's also the auto focus point selection mode which tries to identify the subject by pattern, and while not perfect, is surprisingly reliable in putting the selected focus points right where you'd want them. It's something I will miss if I shift to an FX Nikon, as the 51 points are far more bunched up in the middle of the frame. In fact, they're in exactly the same positions in an FX Nikon -- but the frame has been expanded around them. Sigh. I don't know the Sony SLT system well, but one I was looking at in a camera store seemed to have good face recognition, and pretty quick AF, as well as a superb EVF. This may be the future - if not in a pellicle type camera. The D4 and D800 do face-detect AF, which would be somewhat useful to me sometimes -- but sometimes I need to nail actual eyes due to shallow DOF. -- David Dyer-Bennet, ; http://dd-b.net/ Snapshots: http://dd-b.net/dd-b/SnapshotAlbum/data/ Photos: http://dd-b.net/photography/gallery/ Dragaera: http://dragaera.info |
#24
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Did Canon decide to profit on bodies?
Me writes:
On 29/06/2012 7:03 p.m., Trevor wrote: "Me" wrote in message ... It's pretty easy/fast to do using the 4-way selector, and with very shallow DOF, "focus & recompose" is very unreliable - as people move. There's also the auto focus point selection mode which tries to identify the subject by pattern, and while not perfect, is surprisingly reliable in putting the selected focus points right where you'd want them. Not in my experience with many Canon camera's unfortunately. You need face detect for that, and that still only works for people of course. It's something I will miss if I shift to an FX Nikon, as the 51 points are far more bunched up in the middle of the frame. I don't know the Sony SLT system well, but one I was looking at in a camera store seemed to have good face recognition, and pretty quick AF, as well as a superb EVF. This may be the future - if not in a pellicle type camera. Right, I've used an OM-D and that was one feature I liked. (not enough to make me buy one though) I'm expecting Canon to add proper face detect at some point. Trevor. Not sure how the auto focus point select system works on the higher end nikons. Despite 51 AF points, there's surely not enough data for full face detect, but if there's a face taking up a reasonable part (1/3?) of the VF, chance are very high that the AF sensor or sensors will light up right over the eyes. The D4 and I think D800 don't use the primary AF points for face detect, that's a secondary sensor (the same one used for matrix metering I believe); it has enough resolution for face detection, and then it knows which AF point to turn on based on where the face is. (This is book knowledge, not actual experience.) -- David Dyer-Bennet, ; http://dd-b.net/ Snapshots: http://dd-b.net/dd-b/SnapshotAlbum/data/ Photos: http://dd-b.net/photography/gallery/ Dragaera: http://dragaera.info |
#25
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Did Canon decide to profit on bodies?
Robert Coe writes:
On Fri, 29 Jun 2012 13:22:17 +0200, Wolfgang Weisselberg wrote: : Me wrote: : : Not sure how the auto focus point select system works on the higher : end nikons. Despite 51 AF points, there's surely not enough data : for full face detect, : : The 1DX does have a rather high resolution exposure sensor, : which has more than enough resolution for face detect ... : a fact that Canon has cleverly engineered in and uses. Isn't the crux of the matter that face detect can work only in live view mode? Because if the image of the subject is being deflected into the viewfinder, it's not available to the sensor for analysis. Which would seem to make it useless for AF if the camera is used for action photography. Not as I read the descriptions and user reports. The D4 for example is using the matrix metering sensor for face detect, and it can do that in reflex viewring mode. -- David Dyer-Bennet, ; http://dd-b.net/ Snapshots: http://dd-b.net/dd-b/SnapshotAlbum/data/ Photos: http://dd-b.net/photography/gallery/ Dragaera: http://dragaera.info |
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