Need advice on compression ratio

[Dan Rosario]

I'm shooting my first music video with the Scarlet this weekend. The final output will be 1080p but I'm going to shoot in 4k. I'd like to be efficient with my two 64 SSD's and was looking for advice on the compression ratios that might best suit my question of quality vs file size.

Dan

 

[Rob Castiglione]

Hi Dan

I seem to recall a thread in which someone did comprehensive tests on this question that you might want to look up here on Red User. Personally I have settled on 1:10 and have never had any difficulties.

 

[Roger Viloria]

Dan

Rob is right, a 64gb ssd at 10:1 compression will give you about 42 minutes of recording time and picture quality still very good, I have even pushed it to 12:1 for 50 minutes.
This is in 4K HD aspect ratio.

R.

 

[Mike P.]

8:1 is about 30mins of footage, and it takes about that long to dump a 64gb card via USB2 (the slowest). So even if you're that limited you could record continuously... Just a thought.

 

[Ayan Pratap]

If getting the maximum shoot time is your goal, then you can try 8-10 comperssion. However, I believe there is quality loss beyond 5:1. Beyond 8:1, the quality drops faster.

 

[Brett Harrison]

Correct me if I am wrong, wouldn't the download time always be much less than shoot time on Scarlet? It's not going to take 24 minutes to offload.

 

[Dan Rosario]

I'll try 8:1 and see if that is managable. Thanks for the advice fellas.

 

[Philipe Ratton]

I always shoot 6:1, download using esata to usb3 drives.
A 64 gig takes about 12 minutes.
And yes, you can shoot higher compression but in low light or very detailed scenes, the less compression the better.

 

[William Dempsey]

Hi Dan,

First let me say that everything I will say about quality here is subjective and I suggest you run a few tests of your own to see what you feel meets your own standards.

That said, I have run a number of tests over the past year on compression. The best quality is of course the lowest compression ratio you can afford to use but there are many situations where a higher ratio would not result in a substantial difference in image quality for most deliverables. When I need to get the shot and don't want to take any risks I shoot at 8:1. I have never seen a compression artifact that would be problematic for 1920 HD delivery using 8:1. I should add I do not shoot for the big screen so there may be things you would see on a 40' screen that I am not aware of.

As your compression ratio goes up there is a slight increase in apparent noise. Most of this does not appear to be that there is more noise , but rather that the pattern becomes slightly more noticeable at higher compression. Most of this noise when reduced to standard HD formats is not much of an issue. I have worked on a number of projects shot on other types of HD cameras that had more objectionable noise than things I've shot at 4K on a Scarlet set to 18:1. How much noise is considered objectionable is a bit subjective. I have been shooting film for many years and the Scarlet camera produces less noise than most of the film I've shot on when the Scarlet footage is exposed correctly even at higher compression ratios.

I have actually been doing a lot of testing shooting at 18:1 to get a clear idea of what the limits to Red Code are when pushed to the upper limit of compression. I have been quite surprised to find that 18:1 is actually a usable ratio for some applications.

To shoot at 18:1 you get the best results when:

1.) You shoot with plenty of soft light at a relatively low contrast ratio.
2.) No dark shadows or deep black subjects as they will become mushy/almost painterly.
3.) You must expose as close to clipping as possible so that the image is brighter than you want but can be graded to where you want it in post.
4.) You must reduce random moving scene noise. Example: no falling snow, waves on the ocean, blowing fields of grass , moving trees, etc, etc... Note this does not seem to be connected with complex static patterns as long as the camera remains fixed.
5.) Preferably a static camera unless the scene is visually simple. If you are shooting a person on a white seamless background then camera moves are not likely to be a problem. If you shoot a scene with complex detail and want to move the camera don't shoot at 18:1!

So what this tells me is that as you add certain conditions: High key lighting, very dark colors , low light conditions , complex moving scene, and camera movement you must use lower compression ratios .

I would be comfortable shooting an interview at 18:1 for HD delivery in the right environment . With prior testing I might be willing to shoot other types of scenes with a static camera at 18:1 for certain types of clients. Tests I've recently run with a static camera , static environment and one moving subject in the scene have demonstrated that at 4K using 18:1 compression running continuously with in camera audio I can get 57 minutes and 55 seconds of non stop recording on a single 64gig card. I got 59 minutes at 4K with no on camera audio in the same scene. Another test showed that I can record 100 minutes 15 seconds at 3K with audio onto one 64 gig card.

As part of my further 18:1 testing I shot a ballet performance on a stage with a static camera under less than ideal lighting conditions and after grading the black curtains that were off to the sides of the stage to go mostly black the image was surprisingly good.

I am not suggesting you shoot anything , much less your music video at 18:1 but rather trying to illustrate the maximum potential of Redcode at its limits and the conditions under which it tends to fail at high compression since I have found these tests informative.

I suspect a music video could be shot at anywhere from 12:1 down. If you need to maximize your recording time vary your compression by shot if you are comfortable adjusting on a per shot basis .As you add conditions that stress the codec reduce your compression. If you can run tests uder the conditions you expect to encounter in advance of your shoot ,you should do so. When in doubt use 8:1 and have a laptop and an assistant to download for you to clear space so you can cycle cards ! If there is a budget rent additional cards.

Just my thoughts on the subject,

Bill

 

[Brian Merlen]

I always use the lowest possible settings for my work. Lots of drives and fast ports is key. Or hire a wrangler

 

[Alain Vo]

I have used 8:1 for some shoots, and the last 2 shoots I shot at 5:1 and there was a significant quality change. But yesterday I could only get it to go down to 6:1 on my 128 card. But in my opinion, 5:1 is perferred, but 8:1 isn't bad.

 

[Joe Minuni]

Lots of good advice, I have only tested the waters lowest as 10:1 on a simple scene without much random motion and was fine (talking heads). At 10:1 I could see some artifacts by pixel peeping, but nothing to worry about for HD delivery.

If you have time I would highly reccomend shooting quick tests and different compressions, just take them to a station and view 1:1 to see if it will be a problem.

 

[Daniel Stilling]

I never shoot more compressed than 10:1.
if I do green screen I go 6:1 for a good key. Most of the time I do 8:1.

 

[Will Keir]

Dan,

Depends what you are doing. Shallow DOF work you can get away with higher, maybe even 10:1. If you are doing high frequency, high detailed work you'll want 5:1 or 3:1. If your doing any of this with minimal or natural light I'd suggest you go 3:1 and dump your footage often.

I've tested and tested this myself and I've only been happy with my work in the forest (dark natural light) with 3:1 compression. Before that I was using 7:1.

Hope it helps.

I'm shooting my first music video with the Scarlet this weekend. The final output will be 1080p but I'm going to shoot in 4k. I'd like to be efficient with my two 64 SSD's and was looking for advice on the compression ratios that might best suit my question of quality vs file size.

Dan

 

[Will Keir]

It's a great idea, see what your tolerance is. If you enjoy a good noisey image then don't worry about it too much.

If you have time I would highly reccomend shooting quick tests and different compressions

 

[Ryan Sims]

If your doing any slo-mo work (2k and 1K stuff at high framerates) go with lower compression ratios. For 2K and smaller, I go with the lowest compression ratio allowed most times. Extreme Example: 1K WS will do 120fps in latest builds - but I would set compression low at 3:1. Not that I'm recommending using 1K WS, just know it has limitations. I would only use it very rarely.

Most times your better off with 2KHD and above formats. My rule of thumb - 4KHD at 10:1 works well unless your shooting outside with trees, grass or water. Then I go with 8:1 or better.

 

[Paramon Ivanovich]

well lit and correctly exposed 8:1 looks good.
slow mo and low light shoot lowest possible, you'll be glad you did.

 

[Michael Notar]

all that info that william posted is really helpful. i may use 18:1 fro an artistic effect for a shot.

 

[Jude Byard]

I would do a test of various shooting scenarios and lighting setups, or if you don't have the time, buy/rent/borrow some more REDMAG cards. I generally shoot 3:1 or 6:1. Not skimming on noise on good shots.

 

[Jeff J Daniels]

I usually shoot at 8:1, which gives me a great image when properly exposed. Also gives me a very manageable shooting ratio with 2 x 64Gb SSDs.
No down time swapping between cards and dumping footage.

For keying and low light work, I always go as low compression as possible. It might slow the shoot down with only a few small SSDs, but the image is what matters.