Video Noise testing?

[Luis Caffesse]

I'm hoping to get some time in a few weeks to do some real testing with my HVX.
One of the things I really want to get down to is the issue of noise -

Anyone have any ideas on the best way to control for noise, in terms of what I should be shooting for a test?

Am I better off shooting at proper exposure or underexposed?
Should I shoot flat subjects (meaning a flat colored wall for example) or detailed subjects (like foliage)?

Once I get the time to do this I'll post samples if I find anything interesting.
Thanks for any ideas.

[cardmaverick]

Luis, I would suggest shooting a macbeth chart, and a gray scale. Keep your test exposures high as well, and maintain them. Also test under various color temperatures, and white balances.... speaking of which, you should really try my magenta filter technique, its very good.

A little tip on keeping things on an even playing field:

Make exposure settings based off of the green channel. This channel shouldn't ever change, it doesn't in the DVX, so I'm assuming its the same with the HVX.

I would also recommend a Pedestal setting of 0 to +7, as this will give you a good look at the full dynamic range you have. As for chroma, I'm tempted to say jack it up really high too.

Hope that helps.

[Luis Caffesse]

Thanks Chris, good tips and exactly the kind of stuff I was looking for.
:thumbsup:

I'll definitely try the magenta filters - it was actually your post that really put the bug in my ear about doing some controlled testing. We'll see if I get some time anytime soon.
As it stands now it'll be sometime in the beginning of November before I have a chance to do anything serious.

[gunleik]

We record through component to AJA to ProRes to get rid of codec noise...

Works very well.

-;)

and:
I know I can tweak the camera to get less noise (though I'm a bit surprised by the saturation suggestion...)

But: You win some, you lose some...

Gunleik

[cardmaverick]

I suggest the full saturation due to some of my observations from working with RAW sensor data. I've noticed that the colors can be VERY rich, but I'm just theorizing here, the saturation might be a boost of whats already there, or it might not. Either way, saturation is something you can just throw out in post and not harm the footage, so is not really a bad thing.

If you notice the exposure getting darker after using different white balances, this is normal, as the white balance is literally boosting gain in the red and blue channels differently.

[Elton]

We record through component to AJA to ProRes to get rid of codec noise...

How are you doing this? Do you have the AJA I/O HD which might let you do this in the field with a MacBookPro, or do you simply record the raw analog signal to a computer capture station? If the latter, do you mostly shoot in-studio, or do you drag a computer around in the field?

If you're talking about P2 playback and recording via analog, I don't see how this would help with codec artifacting.

[gunleik]

Hi

This is for studiopurposes only.
(though it's mounted in a flight so that it's sorta of draggable...)

We use HVX's, but customers can hook up any HD-SDI/analogue camera they want.

We have a XSAN&XRAID/5 x XSERVE setup where we can record live through dual HD-SDI to 3 xserves and key live on the fourth while the fifth controlls the SAN.

This is hardly a portable solution -;)

And we record the live component signal.

For field recording we use P2 and/or Firestore

The reason we have landed on recording through the analogue out, is less noise and better perceived resolution (when recording directly to ProRes or uncompressed)

Gunleik

[Filip Staresinic]

I found that the most noise is in green colored subjects.
Hey Luis did you go to see Troublemaker studios there in Austin? And to have a chat with el Wizard.
I know I would if I am in Austin.

[Luis Caffesse]

Actually I have been over there a few times.
Pretty cool place.

It's amazing what can be done in a green screen studio that isn't really all that big.

[cardmaverick]

I found that the most noise is in green colored subjects.


But are you sure its coming from the green channel?

I'm a bit skeptical, as green is typically the cleanest channel. If your seeing noise in green objects, its probably actually coming from the blue and red channels. Open the footage up in After Effects, zoom into the subject, then play back the the footage with just the green channel turned on, then compare it to the other channels. I think you'll find most of the noise is from the blue channel. Sometimes its red, it all depends on what color temperature your working under, and what your white balance / optical filtering happens to be.

The only time I've ever had green be the nosiest channel is when shooting subject matter that lacks a lot of green. In your typical day to day scenes, there tends to be more green content, thus it always gets the strongest overall exposure, which means its usually the cleanest channel, and its usually the first channel to blow out.