GH2 ETC-mode noise penalty

balazer

I have a 50-mm lens, which gives almost the same field of view as the Lumix 20-mm lens with ETC turned on, so I did a little experiment to see how much noise ETC adds. This was just eyeballing it, i.e., not scientifically rigorous. Tests were performed with 100-Mbps intra recording and NR at -2.

The ETC noise penalty is: 2 and 2/3 stops. Specifically, the picture with ETC off at 3200 ISO looks about as noisy as the picture with ETC on at 500 ISO.

What I find interesting about this result is that increasing the sensitivity by a factor of 6.4 increases noise about as much as using 6.76 times as much sensor area (2.6^2) reduces noise. In other words, the GH2 is making very good use of those 16 million pixels when it downsamples to 1080p, giving nearly all the reduction in noise that you would hope to have from using a larger sensor area and correspondingly larger lens aperture.

Though there definitely is aliasing in the downsampled picture. The aliasing is not as bad as in the GH1's 1080p, or in the Canon 5dmkii, but it's there, and it makes you see things that you shouldn't be seeing. I can put together a little demonstration video if anyone is interested, but that's a separate topic.

Mark_the_Harp

Really useful to see this - I've been using ex mode recently and thought it was a bit noisy.

stoney

Keep the ISO at 400 or less on ETC mode :)

Oedipax

And remember about switching ISOs and the weird glitch with them being noisier if you increment upwards rather than downwards.

Mark_the_Harp

@Oedipax @Stonebat Good advice, both.

I was intrigued though to test out what @balazar said. I just experimented with a 1.4 video lens which requires ETC mode, and compared it with my 1.4 Nikon lens which is a 35mm lens and hence uses the entire sensor. Same scene, same ISO (800 in this case), recorded at 1080p.

Here are two crops of 400 x 400 taken from a 1080p frame from each timeline. They are very similar brightness (actually pretty much identical when you look at the whole frame rather than these two crops).

But I'm slightly disappointed as I was hoping the video lens would give me similar low light performance to the Nikon 1.4 but with the additional capability of zooming. However, clearly I was wrong and yes, the ETC mode is noisier, which rather defeats the point of using my video lens for low light. You live and learn!

Mind you, the noise is still there in both, just that it looks "softer" in the full-frame version.

Mark_the_Harp

...and a portion of the two photos lined up and then split between the two, which makes it really obvious:

balazer

@Mark_the_Harp, what kind of video lens do you have? You might find that instead of using ETC mode, the image circle is large enough that you can shoot regular 1080p, and then just crop and zoom a bit. Even if you have to crop all the way down to 720p, that's not so bad.

It's appealing to try to make some use out of old and cheap video or cine lenses, but we must keep in mind that for two different lenses with the same F-number, the one with the shorter focal length has a smaller aperture. It captures less light. That's why smaller formats have more noise and/or lower resolution. It's the lenses, not the sensor sizes.

Mark_the_Harp

@balazer Nice idea - I did do a full-frame shot with the video lens, so had a go at what you suggested, and loaded it into the editor and zoomed in until the image filled the output, then flipped between that and the ETC-mode - but unfortunately there is exactly no difference on my lens, because it just barely covers the ETC-mode sensor area. I was excited for a second though!

I'm also so annoyed that I had two huge TV studio camera lenses that I basically chucked away 2 years ago. But I don't suppose they would have been any better, and they weighed a ton. Both were about 60cm / 24" long! So more a case of having a lens with a camera attached to the back.

Thanks so much for your thoughts though - the lens came from an ancient AKAI tube camera, and resolution-wise it's not so bad really (if it's that or get no usable video because of poor light). So it'll have a use somewhere. At the moment it's a bit of an oddity with an aperture lever poking out the side and a Russian adaptor screwed to the back so it fits on the camera. Just that sometimes when there's not much light around, it's nice to have the flexibility of a zoom lens which works well in low light - though maybe what I'm looking for isn't possible without spending a shedload of money.

balazer

I went through the mental and mathematical exercise of figuring out exactly how I could use every different type of c-mount lens on the GH2 with cropping and/or ETC. There are many types: 1/3", 1/2", 2/3", 1", 4/3", 8-mm and 16-mm. In the end I concluded that while I would be able to use any of them, picture quality won't benefit. It's only useful if you want a certain kind of effect. It's usually better go to for bigger format lenses, like APS-C or 35-mm!

DrDave

The ETC mode was one of the primary reasons I bought the camera--I tried it once and never used it because of the noise. But handy in a pinch, for sure. Under the right conditions, for example with decent light and a fast prime, I'm sure you can get an interesting effect.

SisterCities

Last year, Hunter Richards had a cool thread on using ETC mode w/ dynamic black and white to attain a realistic grainy 16mm look - http://tiny.cc/rbus8

Mark_the_Harp

@balazer @DrDave Thanks guys - your experience in this is really valuable, as you've found out and clearly explained what I would otherwise have spent a ton of time finding out! I did a bit of comparing last night and my Nikon 1.4 definitely looks nicer in low light than the 1.4 zoom + ETC. And yes, I'll hang on to my TV zoom lens I think, just for those special times when it's useful. Talking of which,

@SisterCities thank you for this. I'd seen it before but I really like it and it could be exactly the right look for some things. Having seen the very high ISO GH2 stuff around recently, the grain in that is a bit too "fixed" for me, and this ETC-mode grain does look very good if that's the effect needed.

On the other hand, it's also made me realise how interesting it is to work with fast primes, esp with some of the hacks like the GOP1 ones which seem to produce nicer-looking noise, and to have to recompose to get shots.

brianluce

Don't forget that another virtue of ETC is that it greatly reduces jellovision. If you need to film some handheld stuff -- especially something like a chase scene, it can be a great feature.

Mark_the_Harp

@brianluce Thanks - didn't know that, and I really really hate the jello look so useful to know.

SisterCities

@Mark_the_Harp No problem. I agree, it's a cool tip worth checking out.

zigizigi

Isn't that the same situation as with optical teleconverters where 2x tele give you 2 stops loss?

I'm wondering what's the difference in terms of noise between electronic teleconverter technology and real optical add-on lens? If I put on a 2.5x extender I guess it will give about the same amount of light loss as with decreasing the active sensor surface. But still I think that a full sensor will be less prone to intrusive noise than just a fraction of it.

There is a variety of cheap teleconverters on ebay.

So, anyone has experience with an optical teleconverter on his GH2? How does it compare to ETC?

nomad

I have tried a very good teleconverter (Minolta S-300) and it doesn't only loose light, but produces additional CA too. Most of them do.

The noise reduction at full frame is some kind of "smearing" of noise by scaling down to HD from 14 mpx, while ETC shows the true noise, which is a per pixel noise. It has a different look and good noise reducers can handle it very well. I don't consider the loss as much as a converter has.

Gerald

I baught the GH2 for ETC also. Cause my GH1 made eveything else good enough. The noise problem in ETC-Mode let me use it in good light situations only. But fortunately @ almost any daylight sport situations where i need fast pannings i do have good light. And with the1:1 crop the rolling shutter effect is greatly minimized.

Roberto

Could I ask some of you experimenters with comparable lens focal lengths but different mounts to try this at lower ISO ratings? -with image grabs showing the same content, too? @balazer 3200 iso - as much as I see your point - doesn't really make up part of my world. (also, I really thought this ETC comparison had been put to bed long ago..)

questech

Hello Everyone!

I have done a lot of testing in the past and have come to some conclusions and have many more questions as a result, and I'd like to cover some of them here.

First of all, I could find no evidence of the "ISO Bug" with my GH2. I tried everything, but got consistent results regardless of how I set the ISO.
I get noise at ISO 160. I think it's distracting and for high contrast dramatic scenes, it's unacceptable.
I purchased a nice 1/2" C-Mount lens for it's incredible low light capability, but I have to use it in ETC Mode. BTW it's one of the nicest handling lenses that I use. It is Parfocal and unlike my Nikon Prime lens, it is smooth when rack focusing in each direction without slop.
ETC Mode generates way bad noise, which renders my low light advantage of the C-Mount lens Useless.

So I can use the C-Mount lens in well lit situation, but not for the reason I purchased it. If I had the time to experiment with a GH2 before I purchased it, I probably would have purchased a more expensive option.

My question to everyone is: Do you think that Panasonic a) can fix this with a firmware update b) will they fix it if they can (with the GH3 coming out ??) ?

Is there a hack that addresses the noise problem in ETC?

Thanks in advance!

Meierhans

If noise is not acceptable in ISO 160 without ETC I guess you must have a faulty cam.

questech

Hi,

For high contrast dramatic scenes, unacceptable to me, but I've seen other GH2 footage and it was like mine, so I think it's just bad QC on Panasonic's part... hit or miss maybe.

From the many threads I've read (maybe hundreds) noise at ISO 160 is a common problem. I guess it is a subjective measure of what you can tolerate.

If my camera is faulty, well I'm stuck with it, but I was hoping that Panasonic, or some Hacker would improve the performance, especially in ETC Mode.

Post-mortem:

After all of my research I decided I had enough information to make hacking my GH2 worth a try.

I ran numerous tests and learned a lot along the way. I understand what I read and the comments I recieved much differently now than I did before.

I posted the results of my numerous tests here: http://philipbloom.net/forum/threads/gh2-hacks-noise.1814/

Thanks All!

RoadsidePicnic

"ETC does work well if you understand it has limitations. Part of what makes DSLR's good in low light even with high ISO is that the images get scaled or binned or reduced in size. Whatever you want to call it the fact is that we are never seeing a 1 to 1 ratio of CMOS pixels to recorded pixels. This helps smooth out the noise.

In ETC mode you actually are using a 1 to 1 pixel ratio so you do not gain any of those size reduction advantages. This doesn't mean ETC is bad. In fact it is no different then a normal single chip video camera. ETC basically acts like a single 1/2" CMOS 1920x1080 chip. On those type of cameras going to 9db or 12db of grain looks pretty bad. Heck some don't even like the look of 6db on some of those camcorders.

So yes ETC can visually have more noise then normal modes but not because it is inferior or a useless feature. It has more noise because it acts as a normal CMOS chip would in a regular video camera. Normal shooting modes on the GH2 just help mask some of that noise so you can push the ISO much higher and it still looks clean. In good lighting ETC is awesome. In moderate lighting ETC is decent. In low light forget about ETC. Of course in that kind of light good luck finding a tele lens fast enough anyway. If it really does get that dark your options get very limited if you still need to reach far. Just the way it is.

So you can buy a camera without ETC mode but then you have no option at all. At least with the GH2 and GH3 the option is there if you need the extra reach. If you do the kind of shooting where you want to shoot like a video camera then really you should buy a video camera. A DSLR can look awesome but it is not a 100% replacement for event work unless you want to work around the limitations. "

Thomas Smet in http://www.dvinfo.net/forum/panasonic-lumix-gf-gh-series/511979-gh3-does-have-various-crop-modes.html#post1763106

Just sharing.

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