Timeline for Why is the main sensor not used instead of the separate AF sensor to focus a DSLR?
Current License: CC BY-SA 3.0
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| Mar 7, 2013 at 14:21 | history | edited | AJ Henderson♦ | CC BY-SA 3.0 |
Edited to reflect behavior of hybrid PD AF pixels
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| Mar 7, 2013 at 14:20 | comment | added | AJ Henderson♦ | @MattGrum - yeah. I admit that I did not know that the hybrid pixels captured useful information. I assume the color filtration is why they end up with reduced effectiveness or is there other issues with it? Is my understanding correct that a dedicated PD sensor does not capture useful information since I would suspect it lacks the color filtering necessary for anything other than metering? | |
| Mar 7, 2013 at 9:33 | comment | added | Matt Grum | You said "areas of the imaging sensor are not capturing the visible light hitting those areas" which is untrue, those pixels do receive light, convert it to charge and contribute to the image. It's only 0.1% of pixels anyway, so I would be amazed if you could see the difference. Yes they are not as good for AF, but you don't have the option of a dedicated AF sensor in a mirrorless camera so it's better than nothing. I'd be more likely to buy a mirrorless that had PDAF on the sensor than one that didn't. | |
| Mar 6, 2013 at 18:19 | history | edited | AJ Henderson♦ | CC BY-SA 3.0 |
added 328 characters in body
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| Mar 6, 2013 at 18:15 | comment | added | AJ Henderson♦ | @MattGrum - I never said it is a major deterioration, just a deterioration. When your goal is to capture the absolute best image possible, not having to make that compromise gives slightly better quality. As I understand it the hybrid pixels also don't work as well as dedicated AF. They are jack of all trades, but it is a trade off. | |
| Mar 6, 2013 at 17:37 | comment | added | Matt Grum | I don't see why the AF sensor would have to compete with the image sensor for area when exactly the same photosites can be used for both purposes. Phase detect AF pixels on the main sensor (as used by some mirrorless cameras) are capturing visible light when taking a photo and do contribute to the image. The reduced sensitivity of these pixels is not noticeable as the AF pixels number a few thousand compared to tens of millions of regular pixels. | |
| Mar 6, 2013 at 17:13 | history | answered | AJ Henderson♦ | CC BY-SA 3.0 |