P2 DVCPRO GAMMA PROBLEM

Paul Anderegg wrote on 6/30/2013, 2:37 AM

Ever since I switched to Pro from Movie Studio along with my P2 conversion, everything I render has a gamma problem, where everything gets extremely dark dark dark. I shoot everything at night, so basically, I loose all detail and contrast in my footage, and it is not usable. I have taken to upping the gamma from 1.0 to 1.25, and this helps some, but the video is still too dark, and is like viewing old tube camera footage. I shoot with an f13@2000 camera with a 100watt light, so this is ridiculous. The preview box shows dark video, but shows it correct after the gamma lift, but the resulting render is pitch black, and does not match the preview even close. I have replicated this issue on three separate PC's all running Pro 12.

When I render DVCPRO AVI ingest files, the preview is fine, and the renders look perfect, the same as the preview box. 1080p AVCHD handycam footage looks too light in the preview, but renders perfectly, no gamma issues. I am adding a link to a side by side of the rendered video left, and the preview box right. I have tried switching project properties to 32 bit, but this changed nothing. When I render the same files in FCP, I get perfect gamma, but my Vegas PC renders at twice the speed of the Macbook, so I really want this issue solved. Upping the gamma to 1.25 adds about 6db of gain grain to my footage, most of which is shot on 0db.

http://oi39.tinypic.com/2ldx3qx.jpg

And I know the preview box and WMP are bad for reference, but this video airs totally dark and inky black.

Comments

farss wrote on 6/30/2013, 5:27 PM

I think the reason you're not getting any help here is because until V12 Vegas didn't support DVCPro natively so only a few have any working knowledge of it.

I spent a bit of time trying to see what's going here with the only sample you provided which really didn't reveal all that much other than there is a shift between the two frames. What confuses me is I'm not seeing enough of a shift to turn a well exposed image black or dark, dark, dark as you've said.

As is well known Vegas doesn't correctly handle video levels and the preview monitor is incorrect, search here for more information on this than you probably want to read. Even so, the issue is not bad enough to make well exposed footage black or dark, dark, dark.

Now it could well be that V12 is making a mess of decoding DVCPro but really I'm not reading enough in what you've said so far to confirm this and you seem to be making potentially unfounded assumptions about the camera you're using. I'd suggest you need to remove one of the variables here, namely what the camera is doing shooting low light. Take your new camera and shoot something well exposed in full sun. I'd also recommend getting used to using the waveform monitor in Vegas as your go to tool for judging how well exposed your video is. If your camera has any exposure assistance metering such as zebras or a waveform monitor learn to use that. If your camera has a histogram ignore it, especially in low light with nothing more than 1x 100W light, the histogram can lead you into making bad exposure decisions.

Bob.

musicvid10 wrote on 6/30/2013, 6:20 PM

Could you repeat your test, using this?
May just be levels, not gamma.
https://dl.dropboxusercontent.com/u/20519276/dualgray1.png

amendegw wrote on 6/30/2013, 6:41 PM

The other thing that would be interesting to know is what format is being rendered to. I'm guessing the answer is indeed the "levels issue" if he is rendering to .mp4. However, if it's a .wmv render, that would be a puzzlement.

Furthermore, it would be interesting to have the OP perform the test suggested by Nick Hope, here: Survey: What min/max levels does your cam shoot?

...Jerry

farss wrote on 6/30/2013, 7:12 PM

To the best of my knowledge DVCPro cameras all conform to Rec 601 and DVCPro HD conforms to Rec 709 with the usual overshoots on highlights.

A correctly exposed grey scale chart or one with such a wedge in it would be the most useful if the problem here is gamma.

Bob.

Paul Anderegg wrote on 7/3/2013, 4:11 PM

OK, after fiddling with the color corrector plug-in for awhile, I have found that adjusting only the OFFSET level seems to work the best. I am linking several test clips below. The first 2 clips are of an interview at night with a lit subject. One is raw processing, the other has the OFFSET raised to 20.0. The second set of clips if of the greyscale chart. Again, first version is raw, the second is with 20.0 offset.

http://sandiegonewssource.com/wp-content/uploads/2013/07/VEGASTESTUNALTERED.mp4
http://sandiegonewssource.com/wp-content/uploads/2013/07/VEGASTESTOFFSET20.mp4

http://sandiegonewssource.com/wp-content/uploads/2013/07/VEGASTESTNOMODIFICATION.mp4
http://sandiegonewssource.com/wp-content/uploads/2013/07/VEGASTESTMODIFIED.mp4

I found that the offset value of 20.0 matches what the original MXF file looks like in VLC Player. For reference I shoot DVCPRO50 30P "NEWS" gamma setting, and render to 720-30p M2T for broadcast, but the MP4 test files exhibit the same darkness issue.

Thank you everyone for your assistance. As you know, the official Sony support doesn't work! :)

Paul

Paul Anderegg wrote on 7/3/2013, 4:20 PM

I would also like to mention that rendering the same footage to HDV 720-60p using FCP results in soft video, and very dull colors, as well as washed out contrast. I love Vegas compared to FCP, much easier to use, and better results IMHO. ;)

Paul

farss wrote on 7/3/2013, 4:26 PM

Your VEGASTESTUNALTERED.mp4 clip is using ComputerRGB levels.
All you need do is apply say the Sony Levels FX and use the Computer RGB to Studio RGB preset.

Bob.

musicvid10 wrote on 7/3/2013, 4:40 PM

As is VEGASTESTNOMODIFICATION.mp4, the grayscale test.
Thought so.

Paul Anderegg wrote on 7/3/2013, 4:55 PM

STUDIO RGB seems to help immensely! Thanks! :-D

http://sandiegonewssource.com/wp-content/uploads/2013/07/VEGASTESTSTUDIORGB.mp4

What other corrections would you recommend applying to bring it up to the levels of the original? I guess what I am asking is how do I brighten up the darks to the levels of the original files with the least amount of noise and grain being added. My way of testing is to wait until it airs on TV......it's the best test of true end user quality, but it's not the fastest process to make changes with! :-)

Paul

farss wrote on 7/3/2013, 5:20 PM

My go to tool for changing levels, adjusting everything come to think of it is the Color Curves FX.

I just tried a custom curve and I can get a bit more shadow detail out of the image without bringing the noise up too far. Personally I'd just leave it as is apart from correcting the levels.

The main problem is the shot is a little underexposed, the white handkerchief reads about 80% so you could open the iris maybe 1/3 of a stop which would also bring the talent's skin up just a little along with the shadows which is a lot of the frame.

For this kind of shooting you really need to get used to using the zebras in the camera if it has them. My camera has dual zebras and I have zebra2 set to 65 to judge skin exposure, in a shooting scenario like what you're shooting the talent's skin is the one thing you know how it should be exposed.

Bob.

Paul Anderegg wrote on 7/3/2013, 5:34 PM

I shoot with a Panasonic SPX800, and I have my viewfinder set, and have become accustomed to shooting with respect to my final rendered product. Since I was always boosting gamma, I tended to find highlights, such as slight zebra on a face, would show up as blown out whites. My normal SOT procedure is to open the iris all the way, and bring up my dimmable 100watt light until the subject is exposed properly. This results in brown light,a nd I keep a 2700k preset to work with that. I like to be able to see the background! When I used a 50 watt light previously, I would set the camera at 9db, and bring the light up a little, and use a 2500k preset.

Now that I have solved 75% of this issue, I will reevaluate my exposure settings. Thank you for pointing that out, I probably wouldn't have thought of it myself! :)

Paul

musicvid10 wrote on 7/3/2013, 5:42 PM

Exposure considerations notwithstanding, never judge your output by the Vegas preview window. The preview shows RGB levels, you must correct those to 16-235 before rendering to any YUV codec, making the preview look flatter than your rendered video playback.

farss wrote on 7/3/2013, 6:01 PM

Paul,
you've certainly got the right ideas.
One tip if I may.
Lose that 100W light. Firstly as you dim it as you've seen the CT goes lower. Secondly, it's using a lot of power. Thirdly cameras perform better with daylight than "tungsten". You get less noise using daylight.

I can highly recommend the Comer 1800 for this kind of shooting. I'm lucky though because my camera runs off 12V and I use batteries with a D Tap so the light and the camera can all run off the one battery.

As for [I]" I tended to find highlights, such as slight zebra on a face, would show up as blown out whites."[/I]

What are those zebras set to? Sound to me like 100% and for sure exposing skin at 100% means it is over exposed. Most say skin should be 70% but I work with dark skinned talent so I use 65% but that's pretty good for any skin type, the worst thing to my eyes is over exposed skin.

Bob.

Paul Anderegg wrote on 7/3/2013, 6:09 PM

Not sure what my zebras are set to, 85 and 100 I think? I've gotten into the habit of shooting to air and not to how it looks in the viewfinder or Vegas preview window.

As for the light, I shoot 100% at night in the field. My Lowel ID-light is powered by Hytron 140's, and with my cameras f13@2000 sensitivity, I can shoot stuff 100 feet away at 2AM at 0db gain. :-)

As for bringing up my blacks just a bit, what would be the preferable way, gamma, gain, or offset? Or "other"?

farss wrote on 7/3/2013, 6:25 PM

Try this project file: https://dl.dropboxusercontent.com/u/8841527/Vegas%20Demo/Lift%20Blacks.veg

Sorry I'm pretty busy so I'm winging it on my Office PC and the monitor on that is tragic. You might want to adjust the Curves a bit to taste whilst being very much aware that the Vegas preview monitor is wrong as Musicvid10 pointed out above.

As for your zebras, before relying on them you REALLY do need to know what they're set out.

Bob.

Paul Anderegg wrote on 7/3/2013, 7:42 PM

Thanks for the waveform info. I will plug in that veg file and play with it some.

I know the Vegas preview is useless, but is the waveform in Vegas accurate if I use it to evaluate a rendered video file that I import back into the program?

As for zebra's, my camera has a really nice 2" B&W VF, and I am taking my camera into the shop to be set-up next week, so I will have them adjusted accordingly at that time.

Thanks for the help everyone, I learned a lot, and I hope this thread can assist others with SD P2 footage rendering issues as well.

Paul

Paul Anderegg wrote on 7/4/2013, 2:37 AM

I've been playing with various filters for hours, and I think I "nailed" it. Below is a link to a short AVCHD file with several filters added, including studio RGB output start .006, unsharp mask amount 0.1/radius 1.0, and standard sharpen turned on but left at 0.0.

http://sandiegonewssource.com/wp-content/uploads/2013/07/VEGASLEVELSTEST1.m2t

I did't have to adjust the gamma, gain, contrast, or anything else. The studio RGB thing really made a huge difference, but the real improvement was the unsharp mask max radius adjustment. It not only sharpened things up, it turned the blacks DEEP BLACK, while totally maintaining the grays. Very impressive.

Thanks again for all the help, I love this forum. :)

Paul

farss wrote on 7/4/2013, 8:22 AM

That's a most interesting use of the Unsharpen Mask.
It took me a while to fathom how it would do that and I'm still not 100% certain and don't have anywhere enough time to devote to trying it out for myself at the moment.

My best guess is the convolution kernel that it's based on is spreading / smoothing the blacks. It'd be interesting to what'd happen with different images and I'd also like to check the outcome on my "pro" monitor as I know this one is toast below around 5 IRE.

Bob.

musicvid10 wrote on 7/4/2013, 8:29 AM

That's because Unsharp Mask is a low cut filter, and depending on the kernel can have some "different" effects on the near-blacks.

Maxing it out in this case seems a little much for my tastes; however, without the original camera footage to compare it to, I can't say whether it actually helps or hurts the shadow grain.

Paul Anderegg wrote on 7/4/2013, 11:10 AM

Well.........something horrible took place overnight. Every news story that was cut and aired using the new levels, somehow corrupted the Apple Compressor used to transcode the video for air. All last night and this morning, the playbacks skipped at 4x speed then went to black. It was horrible. This happened with the standard M2T files. In later testing, it was found that MP4 versions using the same levels DID work. The M2T to MOV files that had problems were able to be fixed by running them back through Compressor a second time. This is very odd, and yet another reason I hate Apple.

As for the unsharp mask levels, I am clicking that filter on and off right now, and it has amazing effects. It's like adding camera gain with no grain, while at the same time turning muddy dark areas with no detail into deep rich blacks. A very effective filter, I am glad I played around with it.

How does the test clip appear to you subjectively? Too colorful? Too sharpeninging? This camera competes against JVC HM790's that are always on 18db gain and have absolutely no dynamic range or rich blacks, so that look really gets attention.

Paul

musicvid10 wrote on 7/4/2013, 12:04 PM

With VLC player, the grain structure looks odd.
Can you upload an unprocessed version of the same footage?