Zoom tests: Sony HDR-CX900 camcorder 

Hi Gert. I think you're going to be disappointed in this, the gain (ISO) on the camera does not, as far as I know, have a smooth change between steps. PS I presume you've locked the iris as wide open as you can make it? Also, are you aware of the "E" exposure mode which you can switch the iris and gain into - the way this works is that as you turn the dial, it first opens the iris to maximum, then starts adding gain (and vice versa). That way you never add gain unnecessarily, which can add noise to the image.

Haha, thank you!

Even when using the exposure mode as described (shown on the camcorder by the 'E' next to whichever settings you wish to be modified by the dial - remember you can still lock individual ones such as the shutter), the gain (ISO) will still adjust in incremental steps, just as it did with your ealier example. I agree you need to work with the iris as much as possible rather than the gain, this is always good practice. In my tests though (see my low light video test at Low light test: Sony HDR-CX900 camcorder vs Panasonic x920 and Canon HF-G30 (XA20/XA25)) the Sony does a reasonable job of adding gain without too much noise, at least compared to other camcorders.

Thank you. Feedback like that is extremely encouraging and a great boost. Cheers.

NZVideoGuy Yes, I'm sure of that and indeed page 119 of the (European) manual confirms it. I can't see any reason the NZ version would be crippled so my only guess is that you've turned on one of the options that prevents it going into 50p mode; trying to track down which one, of course, might be time-consuming...

UKAirscape Ah yes!! Thank you!! I had been selecting frame rate first, but after selecting XAVC-S, sure enough there was the option for 25P and 50P. Excellent news as I was initially disappointed. One other thing I'm a little confused about is the Clear Image Zoom. It seems that this feature is directly linked in to the steadyshot feature, and by selecting different steadyshot options, it simultaneously selects different Clear Image Zoom settings. There is no separate Clear Image Zoom setting in the menu. Correct? This makes shooting an event on a tripod a bit handicapped, because selecting steadyshot whilst on a tripod is not always desirable. You tend to get image drift at the end of a pan. Comments?

NZVideoGuy Glad you got that sorted. Yes, you're right about the CIZ and steadyshot being linked. If you want CIZ (and I'm not a fan myself, I can see the image degrade when it's switched in) then you have to have the steadyshot on.

I can't give you those exact readings as there's no measurement on the camcorder screen as to exactly how far in you have zoomed (there's just a very basic bar showing progress from wide to telephoto). What I would say is that it does ramp the iris pretty quickly, so that by approx 2/3 of the zoom range, it will be at f4

Hi. I take your point but I don't agree. Firstly, if you watch my "Stabiliser test" video (Stabiliser test: Sony HDR-CX900 stabilizer), you'll see that I did indeed shoot something that didn't move and it's noticeably poorer using the CIZ. Secondly, you can't expect whatever you're going to film to kindly stay still for you just so that it looks good. Thirdly, digital zoom is inherently bad since the camcorder has to interpolate the missing data and that's nothing more than educated guesswork. Fourthly, even unzoomed, in HD on my monitor, the softness IS noticeable. And fifthly, the reason I zoom it up in the edit for RU-vid is twofold, partly to compensate for RU-vid's compression which will degrade the image itself and partly to highlight the level of degradation in a more obvious form. It's not suggested that this is how you'd actually view it.

UKAirscape Hi, I am not sure if it is correct to say Extended Zoom uses interpolation to replace missing data; Doesn't seems to be the case; Remember there is a digital zoom that can extend even further, up to x100? What I feel is that Extended Zoom crops into the the sensor. When u switch to 'Active Stabilization', u see the camera zoom in slightly even at wide angle. That means it uses a cropped portion of the sensor to record the actual video, allowing the outer part of the sensor for more stabilization. Which means that over all, lesser resolution of the sensor is used to record video when u choose 'Active Stabilization'. At wider angle, u still get better quality because of higher resolution/larger area. But when u zoomed in to the end, u get lesser resolution, hence the slightly degraded image. But this does not means , u don't get the Full HD resolution at the far end. It could still be 1920 x 1080. It's just that getting image at the centre spot of the sensor isn't quite ideal ( small individual light sensors & the resolving power of the lens help to degrade the image further) U also start to see larger grain due to cropping. Remember the sensor's resolution is somewhere about 8 megapixels or even higher. This allows extended zoom to take place by cropping in & yet still getting full HD images. Canon's camcorders didn't have "extended zoom"; Their sensor is only about 2 million pixels in their older models. And even now, the newer models have only 3 million pixels. It's all optical zooms. Their digital zooms will degrade the image much faster than 'extended zooms'. Just some of my thoughts.

Hi again. Those are very fair points, made well. Certainly true about the Canon. My stabiliser tests do indeed exhibit the cropping as you describe (slight loss of wide angle). When I wrote that comment, I'd forgotten how many pixels were on this sensor, so you're right it could well be 1920x1080 albeit using tiny pixels. That said, I still reckon that the quality loss from switching in the CIZ is noticeable on an HD screen (even without my additional zoom to highlight it in the video). Thanks for the comments, it's appreciated - always good to have someone knowledgeable keep me on my toes...

UKAirscape This reminds me about the comparison between Canon's top of the line camcorder(1/3 inch sensor) & their cheaper models(1/5 inch sensor). Someone made a video about the image quality. Bigger sensor size does give extra definition & better color than smaller size sensor. Opting for 'Active Stabilization' and then fully zooming in, is equivalent to using a smaller size sensor.

Not one of mine, I don't think? I've done the HFG30 (XA20) and HFG25 but they've both got 1/3" chips if I recall correctly. As you mentioned already, Canon doesn't go in so much for the mega-megapixel sensors in its camcorders, preferring bigger photosites with fewer pixels.