New high bit-rates improve the GH1’s low light performance

https://vimeo.com/12718346

The new 44MBIT AVCHD is amazing in low light. It holds onto so much more detail at ISO 1600.

The GH1 needs careful handling and a great lens to perform at ISO 1600. You need to expose well, maybe a little over.

For this test I used a Contax G rangefinder lens (Zeiss T* F2 45MM). It’s rather beautiful but fiddly to focus (the guy who made the G adapter had a ‘lets make money first, think about product design later’ kind of business plan!) but this is a Leica rangefinder standard piece of glass for much less money. At F2 wide open it is really crisp and sharp, with lovely flare and bokeh.

The Canon 5D Mark II has always had a reputation for being great in low light (but not as good as the Nikon D3S) and the GH1 has usually been written off as being quite poor at ISO 1600 with noise and banding. The 5D, 7D and 550D do have an edge in terms of noise, maintaining more detail and saturation (certainly more true of 5D) and they certainly have less banding. But the performance spread of individual GH1 units is astonishing. Banding varies a hell of a lot and it seems to improve the later your serial number. My older GH1 is not a patch on my latest one.

Now we have the different flavours of video on the Jailbroken GH1 (so many flavours in fact, it’s like an ice cream parlour). I shot in 44Mbit AVCHD 1080/24p and 70Mbit MJPEG 720/30p. Quite a big difference in compression so let’s see how they do.

A quick note on resolution. I have put my 50Mbit 1080p MJPEG on the back-burner for now. The difference in MJPEG mode between the 1080p and 720p flavours is quite small. When you up-scale the 720p to 1080p in Final Cut Pro you can tell very little difference so why let the camera do the hard work? The advantage of 720p MJPEG is that you can now up the bitrate to an astonishing 70Mbit and it’s a lot more robust.

I’ve still not found a flavour of MJPEG that doesn’t occasionally crash the camera though. 720p 70Mbit roughly 10% of the time and 1080p 50Mbit 30-40% of the time. Though it depends a lot on what you’re shooting!

The MJPEG doesn’t playback in camera, although some flavours do apparently. Yet to see this. You can use a slower shutter speed than 1/30 in the 720p MJPEG mode for timelapse and a low light boost but in 1080p MJPEG mode it crashes the camera and you have to pull the battery out. This is a bit funny, because when Panasonic introduced these new slower frame rates with the first official firmware update last year they only worked in 720p mode too.

I transcoded the AVCHD in Final Cut Pro’s Log and Transfer to Apple ProRes LT and dropped the MJPEG clips straight in, upscaling them in Final Cut Pro to 1080p on a 24p timeline. Then I exported to Sony XDCAM EX 35Mbps 1080/24p for Vimeo.

What did I think of the footage?

First impression is that the MJPEG is brighter but nosier. I had the same picture profile for both (Smooth). I had noise reduction +2 but MJPEG has Bands of noise crawling all over the place. You can see it on the LCD while shooting, it’s not a Final Cut Pro thing. It looks more like ISO 3200 than ISO 1600 at times. The colour saturation seems a bit off as well.

Then when I produced the finished, rendered XDCAM footage and played it back full-screen I was astonished at how much better the detail is on the AVCHD shots at ISO 1600 compared to MJPEG or the old 17Mbit AVCHD. In good light at lower ISOs the resolution between upscaled 720p MJPEG and 1080p AVCHD is hard to tell apart but not at ISO 1600!

The new higher bit rate codec at ISO 1600 can hold onto a lot of detail and show very little noise. But only on the lighter areas of the image. When there is a dim area of greyish texture or shadow, that’s where the noise and banding can creep back in.

The AVCHD footage is very smooth for ISO 1600 though, as you can see. And it’s holding onto a heck of a lot more detail than before the patch overall.

I have always found that given a few candles or street lights the GH1’s sensor picks up a lot more of the reflected light whilst the 5D Mark II can be more muted. The Panasonic sensor is very sensitive, giving a bright and punchy image. Quite contrasty. Very typical of CMOS – nice reaction to light but not so good with shadows!

The noise reduction still does remove some detail of course. But this is a nice step up.

So is the GH1 now competitive with the 5D? At ISO 800 – yes totally. At ISO 1600? Yes but you have to treat it well. At ISO 3200? Not even close, but then neither camera is that good at 3200.

High ISO is MJPEG’s biggest Achilles Heel. I have given up on MJPEG for now. I think that until we solve the issues with a complete lack of noise control, lack of 24p and the greater aliasing and moire, 44Mbit AVCHD is the better option.

Overall, very happy with this latest high bitrate AVCHD. Show me a ‘professional’ video camera that can produce an image like this for under $1000 and I’ll eat my hat.

I don’t really agree that a DSLR is just a ‘digital bolex’. It has a larger sensor and works with all kinds of lenses from Bolex to Medium Format. It’s much more than a crash-cam for people who can’t afford a studio camera. I can shoot in places I simply couldn’t do before, be it on digital format or film. And the portability along with ISO 1600 is great.

Settings

You need PTools V3.36
Native 24p – ticked
AVCHD ‘C’ settings as recommended by Suggested Values in PTools, which are:
Video Bitrate Adjustment Simplified – ticked, set to 50000000 (instead of old value of 160000000, big increase!)
Overall Bitrate Adjustment – ticked, set to 52000000
Limiting Bitrate Adjustment – ticked, set to 60000000