Can anyone please offer any recommendations for specific models, as well as which features have the biggest practical impact on video quality? I am currently considering Canon SD4500, Canon S95, and Sony DSC-HX9V. Each of these seems to have certain unique advantages. I am not really sure what is the relative importance of these features. I should stress that by far, video recording is what I care about the most, but I am not considering a full-sized camcorder, since portability is also an important factor.
1) Max video resolution. SD4500 and HX9V offer 1080p video, whereas S95 only goes up to 720p. However, each of them has about the same 10MP of effective pixels. Is there any real benefit from packing those 10M pixels in a 1080p video format? It seems that a 1080p video has about 2M pixels on the screen. I understand that for each of these, the camera needs at least four actual pixels on the sensor (red one, blue one, and 2x green), which brings it close to the effective pixel of each of these models. Then, there is a noise factor, and the fact that compression loses some quality. Recording in 1080p does seem to result in more bits written out to the memory card, though, which cannot be a bad thing. But does it matter in the end?
2) Sensor size and type. S95 has a larger 1/1.7'' CCD sensor, whereas the other two models have smaller 1/2.3'' CMOS sensors. Some sources claim that CCD is superior as it does not waste precious space on silicon for transistors and captures more light. The specific CCD in question is also bigger, covering 50% more area. Other sources state that CMOS is a newer technology that offers better picture quality. Which is better? And how does this relate to the maximum video resolution? Better to record from 50% larger CCD sensor, but fit it into video format that saves 50% fewer bits on the memory card or record from a smaller CMOS sensor that saves more data and presumably suffers less of a quality loss from video compression?
3) Frames per second. HX9V can shoot 1080p at 60fps, the other two can shoot at 24fps at their highest resolution. I presume a human eye cannot tell the difference in terms of a video playback smoothness, but 60fps does sound like 2.5x more information. Will it result in video less noisy? Does it have a similar impact on image quality as sensor size/type or resolution?
4) Aperture. S95 has a very bright f/2.0 lens; the others start at f/3.3 and f/3.4 at their widest angle setting, which is presumably where all underwater video shooting will take place. More light presumably means less noise in the video? How does that play with other factors I have mentioned earlier?
5) Wide angle. HX9V starts at 24mm, S95 at 28mm, SD4500 at 36mm. What is a reasonable minimum underwater, does extra wide angle make enough difference in practice in terms of composition and other aesthetic factors to sacrifice a little bit of image quality? Better to have a slightly wider angle or a brighter lens? Does the answer change if I assume I do (or do not) want to use an external video light?
6) Autofocus. I was not able to find any comparison of how well these cameras can focus in low-light conditions underwater. Presumably, in most underwater situations the scene is not changing too rapidly. Anyone owns these and experienced problems? I actually used to own SD4500. I lost it in an accident before I had a chance to assess picture quality underwater. When shooting 1080p videos on the surface, it seemed to sometimes get a little out of focus when panning or rotating, but would regain it in a second or two. Is that a common issue?
7) Is there anything else that matters for getting good quality underwater video? All cameras listed above seem to have some sort of image stabilization, and claim support for shooting in low-light conditions.
1) Max video resolution. SD4500 and HX9V offer 1080p video, whereas S95 only goes up to 720p. However, each of them has about the same 10MP of effective pixels. Is there any real benefit from packing those 10M pixels in a 1080p video format? It seems that a 1080p video has about 2M pixels on the screen. I understand that for each of these, the camera needs at least four actual pixels on the sensor (red one, blue one, and 2x green), which brings it close to the effective pixel of each of these models. Then, there is a noise factor, and the fact that compression loses some quality. Recording in 1080p does seem to result in more bits written out to the memory card, though, which cannot be a bad thing. But does it matter in the end?
2) Sensor size and type. S95 has a larger 1/1.7'' CCD sensor, whereas the other two models have smaller 1/2.3'' CMOS sensors. Some sources claim that CCD is superior as it does not waste precious space on silicon for transistors and captures more light. The specific CCD in question is also bigger, covering 50% more area. Other sources state that CMOS is a newer technology that offers better picture quality. Which is better? And how does this relate to the maximum video resolution? Better to record from 50% larger CCD sensor, but fit it into video format that saves 50% fewer bits on the memory card or record from a smaller CMOS sensor that saves more data and presumably suffers less of a quality loss from video compression?
3) Frames per second. HX9V can shoot 1080p at 60fps, the other two can shoot at 24fps at their highest resolution. I presume a human eye cannot tell the difference in terms of a video playback smoothness, but 60fps does sound like 2.5x more information. Will it result in video less noisy? Does it have a similar impact on image quality as sensor size/type or resolution?
4) Aperture. S95 has a very bright f/2.0 lens; the others start at f/3.3 and f/3.4 at their widest angle setting, which is presumably where all underwater video shooting will take place. More light presumably means less noise in the video? How does that play with other factors I have mentioned earlier?
5) Wide angle. HX9V starts at 24mm, S95 at 28mm, SD4500 at 36mm. What is a reasonable minimum underwater, does extra wide angle make enough difference in practice in terms of composition and other aesthetic factors to sacrifice a little bit of image quality? Better to have a slightly wider angle or a brighter lens? Does the answer change if I assume I do (or do not) want to use an external video light?
6) Autofocus. I was not able to find any comparison of how well these cameras can focus in low-light conditions underwater. Presumably, in most underwater situations the scene is not changing too rapidly. Anyone owns these and experienced problems? I actually used to own SD4500. I lost it in an accident before I had a chance to assess picture quality underwater. When shooting 1080p videos on the surface, it seemed to sometimes get a little out of focus when panning or rotating, but would regain it in a second or two. Is that a common issue?
7) Is there anything else that matters for getting good quality underwater video? All cameras listed above seem to have some sort of image stabilization, and claim support for shooting in low-light conditions.
