Epic Compression Test

[Adam Rosenbloom]

I did a compression test on our Epic today, and I wanted to share my results, and see if this seemed right to all of you.

What I found, in short, was that on difficult scenes, 3:1 was great, 5:1 was good enough, and after that blocky compression started to appear.

Here is a link to download and below is a description of the shoot:
Tiffs: http://www.filesanywhere.com/fs/v.as...8b5866737c6b9a
R3D: https://www.filesanywhere.com/fs/v.a...8b5d6374b6a5ad

Scene: I shot a streetscape filled with trees, including some foreground bark, and a more isolated shot of the trees. I was hoping for a sunny day, because I read that some others had compression trouble in high contrast scenes. However, from seeing the results, a slightly overcast day worked fine.

Lens: I used a Zeiss cp.2 35mm lens. The aperture remained small (about f/15 to f/16) because I wanted a sharp image that would really test the compression. I did not use an ND filter.

Camera Settings: The ISO was 640. The frame size was 4K HD (this is just because it's how we intend to shoot an upcoming project). The framerate was 29.97 and I used a 180 degree shutter angle. All other settings that I can think of were set to their defaults (except white balance).

Notes: All of the jpegs in the link above were made from the raw tiffs out of RedCine X Pro, and I've verified that there is no visible difference between the jpegs and tiffs. I applied no post-processing as you will see, except I've blurred some signs and license plates in the 1st shot (sorry, I just wanted to be safe). I want you to know also that even though the jpegs are all the first frame of the video, I played all of them and the frames in the rest of each shot look the same.

The compression really showed the in bark. I know this is a rough test to put a camera through, but we intend to shoot some scenes like this in the future.

I would love to hear any of your analysis. Are these results expected? Did I do something wrong in my test?

Thank you in advance!

Adam

[Andy White]

Shooting with such a small aperture isn't a good idea (IMO). You're reducing the light transmission to the sensor - you'll also loose performance from the lenses themselves at such an extreme.

You've starved the sensor of some light, so you'll add to any compression artifacts. You'd have been better shooting at 800 (or 320 if you prefer), T5-T8 with ND, so the sensor get's a nice even spread of light.

I'm sure others will chime in with their thoughts too.

BTW - what did they look like on motion? Was the camera locked off? - Just interested :)

[Matt Ryan]

From this example I think I would be fine with up to 8:1 but probably not higher. Especially with all the detail in these shots.

5:1 seems like the most logical and practical choice based on these shots.

[Gunleik Groven]

This is one of the better compression tests I have seen. The deep focus does of course not starve your sensor for light, and exposing at 640 only makes you expose higher, if anything...

The leaves is where I have most interesting results.

I'd love to see the RAW files from this, and would suggest you sent single RAW frames to RED for analysis.

Thanks a lot for the effort!

[Adam Rosenbloom]

Thank you all very much for your helpful responses.

I guess I did go a little too far with the aperture. I probably won't be able to do another test today, but maybe over the weekend.

In motion, the video at 3:1 really looks nice, clean with a subtle film-like grain. At 6:1 and above the grain turns to blockiness and is just ugly noise.

I would love to post the RAW R3D files, but they're obviously huge. The 3:1 shot of the street is 2.43 GB, and it's only 25 seconds long! Do you think trimming them in REDCINE X to 3 seconds each would be work? Any ideas on which particular clips you would like to see? I'll look for a way to transmit them.

When you say send the raw R3D snapshots to RED, do you mean just email a link to their tech support?

Thank you all very much again,

Adam

[Gunleik Groven]

Just need an r3d snapshot from rcx.
And frankly I don't need them, but would urge you to send them to RED directly.

The aperture is not what is happening here, and this is exactly what needs to be adressed.

Goodone!

G

[Adam Rosenbloom]

EDIT - DOWNLOAD LINK IS FIXED.

So here's a link to the R3D snapshots from shot 2: https://www.filesanywhere.com/fs/v.a...8b5d6374b6a5ad (I have added these to the original post)

If it's okay I'd rather not post the RAW of the first shot because of license plates and signs, but if it will really help, I can upload them as well.
I am sending all of my R3D snapshots to Red.

Also, I forgot to mention that yes, the shots were locked down.

Thanks!

Adam

[Paul Nordin]

Shooting with such a small aperture isn't a good idea (IMO). You're reducing the light transmission to the sensor - you'll also loose performance from the lenses themselves at such an extreme.

You've starved the sensor of some light, so you'll add to any compression artifacts. You'd have been better shooting at 800 (or 320 if you prefer), T5-T8 with ND, so the sensor get's a nice even spread of light.

Andy, Your respose here, stated in a very authoritative tone, is total bull-shit. Light is light. A small iris, used to create deep focus, does not in any way starve the sensor of light if the exposure is right, its right!. Get a light meter, learn about proper exposures, before you spout off non-sense again!
You were somewhat correct in that extremely small iris openings can intruduce lens artifacting as a result of diffraction. But the degree of that is lens-to-lens dependent.

[Andy White]

Andy, Your respose here, stated in a very authoritative tone, is total bull-shit. Light is light. A small iris, used to create deep focus, does not in any way starve the sensor of light if the exposure is right, its right!. Get a light meter, learn about proper exposures, before you spout off non-sense again!
You were somewhat correct in that extremely small iris openings can intruduce lens artifacting as a result of diffraction. But the degree of that is lens-to-lens dependent.

Hi Paul. No problem :) I did say IMO in the post, but thanks for the authoritative and absolute response in your reply.

[Paul Nordin]

Sorry for the tone of my post, Andy. I could have been more politically correct, a la Gunliek's reply. Exposure as relates to tstop, and theoretically to fstop, is not an opinion. Its a mathematical fact. Nuf said