Official Low GOP topic, series 4

cafeteriacarlos

If I can add something to the high ISO conversation, I will note that being fearful of going higher than 1600 can occasionally ruin your shot more than noise will on a hacked GH2.

I shot a performance the other night at mostly 1600 (old Canon habit of never daring to go above it) and switched 3200 for the last few tracks. Oh, how I wish I'd done it the whole time. When we're talking about GH2 couscous grain instead of Canon Rice Krispies - an underexposed shot is a much worse fate.

L1N3ARX

Well I'm in love w/ this new quantum 9vb patch (not that new anymore); this was the first test I was able to put together this afternoon. Loving it! Thanks again Driftwood.

proaudio4

Thank you for the info, I thought this was the case, I just wanted confirmation. Yes, I tend to stay away from ISO1600 and beyond.

Fortunately , the hack has enabled the GH2 to display fine more natural grain-like noise. It actually cleans up well in post if you choose to remove it. Of course, we all know this! lol

driftwood

Beyond 1600 ISO dynamic range drops significantly.

LPowell

@proaudio4 Sensor data published by Sensorgen shows that GH2 read noise drops about 12% at ISO 800, and then remains pretty flat until it drops again at ISO 12800:

http://www.sensorgen.info/PanasonicDMC_GH2.html

As you point out, dynamic range inevitably decreases as ISO increases. If you expose your highlights as close to the right of the histogram as you can, the decrease in DR at high ISO will make shadow noise more noticeable than at low ISO.

However, if you don't have enough light for full exposure at low ISO, raising the ISO will give you more latitude at the dark end of the histogram. But given enough light at low ISO, there's no advantage in using a higher ISO - it will only reduce your overall dynamic range. Of course, there's also the infamous GH2 ISO bug to avoid:

http://www.personal-view.com/talks/discussion/comment/37083

proaudio4

@driftwood Interesting find on the GH2.

OK, just to clarify that ISO1600 appears to be the "sweet spot" for minimum noise levels.

We all know the even using ISO160 under a lot of light and with a perfect exposure (reported by the GH2), shadows can still show noise.

So under the same lighting, If we set the ISO to 1600 and then used an ND filter to arrive at the perfect exposure (same as above), shadow noise would be lower?

Of course using 1600 under this condition would offer lower dynamic range. Is this correct, I just want to make sure I understand this?

sanzadez

@driftwood Sorry, just want to clarify. By sweetspot, you mean the highest possible ISO to use in low light that is useable, correct? You don't mean it is the Best ISO to use? Just want to clarify.

B3Guy

@driftwood

the exception I would say is when shooting in a B&W mode. some of those look killer in higher ISO settings.

brudney

Macalincag-> lol, thanks, haven't noticed;)

driftwood

@ricker Read the post... I said 'The last ISO setting before that rise is your sweet spot for low light exposures'.

Macalincag

@brudney

The same thing here: http://personal-view.com/talks/discussion/2078/gh2-iso-noise-tests.-lows-mids-highs.-magic-iso-/p1

JDN

@ricker, thanks. I can confirm with various low gop patches (well, really just quantum 7 and 9) that as per that above post, ISO 640 was really doing great and can confirm from field tests that it totally kicks the ass of anything around it for lack of noise. Find I shoot 160 when I want shallow DOF, 640 when I don't (or do 720p) and 1600 or 4000 for super low light/bit of noise/super slow motion, etc.

ricker

http://www.laesieworks.com/digicom/panasonic-lumix-gh2-noise.html

Lol help if I posted it ;)

ricker

Interesting article here on best ISO setting. Certainly doesn't seem to be agreeing with ISO 1600 as the sweet spot. Seems to be 160 or 320 with greatest dynamic range.

driftwood

@sohus In low light situations it is advisable NOT to go above 1600 ISO unless you want a lot more noise - see shadow noise. And if you use noise reduction it will just make it more blobby. Q X is still being finalised...

ricker

Hey lads! All my new gh2 gear is on its way and I'm super excited to jump into the micro 4/thirds world! Just wanted to say thanks to driftwood and vitality for all their amazing work in what to most of us is a black box of information! Brilliant stuff! Looking forward to loading up Quantum! Interesting stuff in regards to iso, gonna do my own research now.

sohus

@driftwood So you shouldn't go above 1600 ISO or if you have to pick between 800 and 1600 ISO pick the latter? I want to make sure I get it right.

When do you think Quantum X will be out?

driftwood

@sohus As in sweet spot for low light exposures

The magazine reports that the ISO sweet spot can be seen on a read noise curve graph. The Panasonic G3 noise curve (the closest to our GH2) was said to have levelled out at ISO 1600, while the Nikon D7000 is almost a straight line across the entire ISO range, making the base ISO (100) its sweet spot. By using this sweet spot ISO setting and overexposing just before the point of clipping, noise can be kept to a minimum and the tonal range of a low-light image maximised. Overexpose as much as possible before highlight clipping for the lowest levels of noise.

Read noise is the electronic noise added by the camera to the image captured by the sensor(which already has 'built-in' photon-shot noise) It provides a constant noise background, so tends to be the noise that can be seen in the shadows.

When the light is low (low number of photons) and is then processed by the camera to achieve full tonal range, the digitiser read noise signal is brightened resulting in more noise in shadows. A way around this is that the ISO control boosts (gain) the sensor signal. At the top ISO end though the digitisation system cannot deal with as high a light level and the dynamic range drops.

To find the sweet spot on a GH2; the point at which the camera stops adding 'gain' (boosting the signal) as the ISO is raised is as follows. Manually set the exposure to nominal for the highest ISO setting on the camera.Then take a series of images of the same subject (with the same lighting), reducing the ISO one (1) stop at a time wihout changing the exposure. Process the captured images to the same brightness range and then compare the sequence. As the ISO setting lowers, there will often be a point at which the shadow noise starts to rise. The last ISO setting before that rise is your sweet spot for low light exposures.

I tried this last night and found it to be 1600 ISO too for the GH2.

sohus

@driftwood what do they mean with sweetspot? As in best image quality? Or maximum good quality iso?

B3Guy

@driftwood

I do really like the look of both ISO 1600 and 800. If I'm not up there, I'm down at 160. Its not like I've ever paid close attention to why, but its mostly a grain thing. Anything over 1600 for me is no good unless it is going to be very desaturated or is in black and white.

Nameless

@driftwood The anticipation is killing me fella....can't wait to go to work with Quantum X... This was mostly shot on Seaquake:

So you can imagine my impatience but i can wait lol.....Ready whenever you are mate!!!!

Thanks to everyone for the fantastic work ethic and development - you're changing lives!!

mozes

@balazer thx, i just updated to
Driftwood Aquamotion ver2 AQ2 all round and spanning - great for EX TELE and 80percent recording

mozes

nope.

driftwood

Anyone else noticed the sweet spot for Panasonic cameras exposure is 1600 ISO as seen in a Popular Camera Weekly magazine ?

Tifose

@RJH Thanks A lot yes Quantum V9

LOve your work 60Sec

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