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View Full Version : Knee DR and yellow blotches..



morgan_moore
06-23-2011, 04:09 AM
I have been chipping in other peoples threads on DR and profiles,- I wont do that any more

I dont own an FS100 yet, the blotchy highlights have been holding me back

I thought I would do some tests of my EX1 to understand highlights in Sony cameras and see if I coud get a result on the EX1 and then move forward with the FS100

They are not super accurate or scientific but may be of interest..


http://www.vimeo.com/25499627

The vimeo description..

One problem I have is the nasty highlights of digital motion cameras

Sony cameras have a facility called 'knee' to hold onto highlights

The trouble I guess is that holding highlights means flattening the image

And flattening the image lowers contrast in portions of the scene

At some point colour contrast becomes low enough that changes in colour are not resolved in the 8 bit colour space

This represents as a lack of tonality or colour banding - blotches in other words

Here I try

Knee at 75 - this is designed to really hold highlights (but are they nice to look at?)

Knee off this should do 'nothing' but I guess that there is some knee built into the default curve of the camera

I then try Knee at 109, maybe this really does nothing as the knee is only flattening image that is 'off the scale'

My opinion of the footage is that the 75 knee has both the widest DR but also the most colour and tonal artifacts

No knee is better

And ramping the knee up to 109 means the least issues in the footage (at the cost of DR)

Personally I would prefer not to have the flouecent colours and have completely blown highlights

I believe those flouro colours to be virtually uncorrectable and therefore to be adding no valuable data to the image

When watching it is also worth evaluting the tonality in the lens (the subject) as well as lookng at the highlights

Do we see that 109 knee 'cures' the yellow blotching on the highs ?

Yep, but there is still some horror at the edge of the chair

Of course should I want to shoot this scene 'properly' I should light it, or control the DR in the scene in some manner

My conclusion therefore is that 'profiles and tricks' to increase the DR of 8bit cameras are probably a very double edged sword

Yes they increase DR but also introduce artifacts and bizarre tonalities banding and other issues

I would suggest therefore that they should be used with caution

And that best performance from a camera will be by keeping a low DR profile and controlling light

Yep that means grad ND on the sky and lighting and reflectors.. its called cinamatography !

More testing required

harrisoncj
06-25-2011, 11:57 AM
So that's what it's called...

nyvz
06-25-2011, 12:45 PM
I think it is a mistake to compare the EX1 knee and the FS100 knee. In my experience knee in the EX1 is always going to give you ugly highlights with hard blowouts and color shifting, in part because it overrides any curved highlight gamma and replaces it with a linear gamma which looks especially bad at the knee point and at the clip point since there is no transition. I would never use a non-cinegamma (to which knee is exclusive) if you are even thinking about having any kind of natural and smooth rendition of highlights.

With the FS100, on the other hand, knee is always on and all gamma curves including cinematone are designed with this in mind to some extent, so when knee is properly set and used in combination with a cinematone gamma and cinematone 2 matrix, no color shifting or hard clipping is visible. Hard gamma curve transitions may often still be visible at your knee point depending on your particular knee setting, but I have find several settings that make it relatively invisible. Overall quite happy with the gamma/knee options of the FS100 after some testing. It is quite comparable to an EX1 set to a cinegamma, you just have to make sure you set your knee with care to get the most out of the FS100.

morgan_moore
06-25-2011, 04:35 PM
Hopefully Ill be getting the camera next week

nearly every video posted from (from the FS100) Bloom to Zacuto to the sunset sequence here on the board has some pretty horrid banding

look at the opening frame of this http://vimeo.com/25457250

(steps in tones at the top end) rather than a smooth roll off

The AF100 appears as bad or worse BTW to my eye

Ill be intersted to play but am far from convinced

I think the camera has other strengths of course

To give a sense of context here is a still from my 5d, being able to blow mean you can open up for the darker areas of the image..

Thats the look Ill be trying to get

http://dslr4real.tv/smmspace/webimages/dslr4real/reelstills/1.jpg

S

morgan_moore
07-02-2011, 03:05 PM
Got my FS today but no lens adapter !

Tested SuperKnee DR crush profile..


http://www.vimeo.com/25911268

cheezweezl
07-02-2011, 05:40 PM
is that you just hand holding a lens in front of the sensor? trippy.

in regards to blowout, blotching, etc. ANY digital video camera will produce this effect if pushed too far. the cure is to avoid blowout at all cost. expose for the highlights and use light to expose the shadows. if youre afraid of shooting too dark, try to get over that fear. this camera holds a ton of info in the shadows and if properly graded, you can pull it out with little or no noise.

morgan_moore
07-02-2011, 10:45 PM
Yep - 'free lensed' - no adapter yet

I dont think you can avoid blowout at all cost (unless you have a million bucks to throw at lighting)

What is needed is a PP that blows out well

Ive seen a stack of dodgy colors in other peoples vids with them IMO using too much knee and chasing to0 much DR

Im pleased with the look (tonally) from the second vid because its almost handling the blowout

S

David G. Smith
07-03-2011, 12:35 AM
is that you just hand holding a lens in front of the sensor? trippy.

in regards to blowout, blotching, etc. ANY digital video camera will produce this effect if pushed too far. the cure is to avoid blowout at all cost. expose for the highlights and use light to expose the shadows. if youre afraid of shooting too dark, try to get over that fear. this camera holds a ton of info in the shadows and if properly graded, you can pull it out with little or no noise.

I have to agree with this. While of course you can not avoid blown highlights in every situation, the DR and ability to maintain shadow detail on the FS100 is amazing, and exposing for the highlights will leave you a lot of room at the bottom end. To be honest, I am kind of freaked out by the DR of this camera. I have been doing a lot of picture profile testing over the past few days, mostly in bright sunlight, and I have found the camera to be amazing. I started on film but have not shot any since about 1997 when every thing got swept up in DV revolution, but, I swear, shooting with the FS100 is almost like shooting with the original T-grain color negative stocks that were introduced in the early nineties. Of course, shooting with color negative film, you could expose for the shadows, and then let the highlights fall off as they may (within reason of course). Shooting reversal film was the opposite, since it was designed for direct projection and had higher contrast and lower DR. Exposing reversal film meant exposing for the highlights, and bring in enough fill light to make a good image. Every since switching to shooting digital video I have always treated it like reversal film and exposed for the highlights. Being a guerilla/bottom feeder shooter, this means that I have sometimes had to compromise my shadow detail to keep from blowing highlights and ended up with footage that was way too contrasty for my tastes. Now the FS100 is a godsend. I have no problems exposing for the highlights and letting this camera pick up as much detail as it can in the shadows.

Morgan, I think you will be pleased with the camera, and will be able to deal with the highlights. The issue to me is really not the knee setting. It is getting the right black level and black gamma settings. I have been playing with some extreme black and black gamma settings and noticed that it is not hard to introduce noise in the shadows. My goal now is to dial those settings down to where I can get the most shadow detail, without noise. This way, I feel I can expose for the highlights, have enough shadow detail without noise and still have leeway in post to bring the shadows back up, if need be.

morgan_moore
07-03-2011, 12:44 AM
I am pleased with the camera

Personally I think my profile looks great

I think 'superknee' brings smooth roll off - not blotches and banding flourecents and plastic skin we have seen in nearly every one else videos

They have been stretching DR at massive cost to image quality IMO

Supeknee is about getting pleasant roll off

Yep its compressing the DR but used with reflectors and lights and intelligent exposure it will sing

IMO shooting to grade in an compressed 8bit space is not the path to image quality

Do you think my second vid looks good? (apart from the shake, lack of story etc) - I do

S

morgan_moore
07-03-2011, 12:54 AM
Here is an example - deakins - of the images im after

Its full of white and has no halo or edge artifacts - which make it work

I think it is a myth that people expose left to protect all highlights - film is known to roll to blown, something vid has done badly for years

36199

David G. Smith
07-03-2011, 01:41 AM
I did like the second video, aside from the shots of the direct sun. As for matching that shot from "Jar Head", wow, that is a pretty tall order to ask of a $5000.00 camcorder, considering that the original image was made on 35mm color negative film with Cooke S-4 lenses. Mr. Deakins is also not shy about using the proper lighting, so I am sure that they had more than enough light to expose the talent against bright skies in the desert. My issue with that, and I thought so when I saw the film, is that the talent is, to me, way overexposed. I understand it for this film, but that is not a look that I particularly care for.

Also, exactly what do you mean by "Super Knee"? Is that the knee at 109 in the video? See, of the examples, I preferred the knee at 75. While the colors were funky, I like the fact that there is some detail there. I think we may have aesthetic differences, but can both work with the FS100.

morgan_moore
07-03-2011, 02:09 AM
Yep knee cranked right in the second vid; Super Knee

On my Ex1 vid I hate the funky colours and dont mind loss of detail - aesthetic differences

I agree with the bright Jarhead look not being right for everything

As for the lighting - he did not have to compete with white cos blown is blown,

I think a lot of lighting is actually simple but done with great cameras - maybe hit lit with a single board and a net - even though he had access to trucks of stuff

As for the level of the talent - indeed its not 'right' its the look for the film - I just wanted to show a respected cinamatographer bleeding to white - its the first image I found

Here is a pic of mine where the 'talent' is much darker but there is still white in the frame and an extremely challenging roll off round her ankle

(Its my 16bit 5k raw hassy btw)

Indeed - im pleased and you are pleased - thats great - I think people should however not just crush the top end of the camera (FS100) without checking other options out just because it creates some reults in dark room on a test bed

S
36202

David G. Smith
07-03-2011, 02:24 PM
Yep knee cranked right in the second vid; Super Knee

On my Ex1 vid I hate the funky colours and dont mind loss of detail - aesthetic differences

I agree with the bright Jarhead look not being right for everything

As for the lighting - he did not have to compete with white cos blown is blown,

I think a lot of lighting is actually simple but done with great cameras - maybe hit lit with a single board and a net - even though he had access to trucks of stuff

As for the level of the talent - indeed its not 'right' its the look for the film - I just wanted to show a respected cinamatographer bleeding to white - its the first image I found

Here is a pic of mine where the 'talent' is much darker but there is still white in the frame and an extremely challenging roll off round her ankle

(Its my 16bit 5k raw hassy btw)

Indeed - im pleased and you are pleased - thats great - I think people should however not just crush the top end of the camera (FS100) without checking other options out just because it creates some reults in dark room on a test bed

S
36202

Ok, Super Knee, gotcha. I love the attached photo. So far, I have been pleased with the FS100 highlight handling, but I have only shot tests in day light. I am interested in getting into some available light night time environments and see what happens to bright lights (like lighted signs and such) in regard to blown highlights.

morgan_moore
07-03-2011, 02:52 PM
So far, I have been pleased with the FS100 highlight handling.

I know this is not yours but even the opening frame one can see stepping in tonality in the sky .. http://vimeo.com/25457250

I see that a lot everywhere from Bloom/Xacuto (F3) test, the harley video etc

Obviously we know little of the exposure or post track on any of the vids

S

morgan_moore
07-03-2011, 02:59 PM
I hope the poster doesnt mind but check the graduations (or not) here for example..

36219

Rick Burnett
07-03-2011, 03:16 PM
It made the image too small, can't see it!

maarek
07-04-2011, 03:58 AM
Why don't you just disable knee? 5D has no knee so just disable it and see what you get?

p.s How do you know those Soleil Springs images were not graded?

MazingerZ
07-04-2011, 05:32 AM
5D has no knee
As you know, the Canon cameras allow you to customise the entire curve.
This is even better than knee and black gamma adjustments.

morgan_moore
07-04-2011, 06:23 AM
p.s How do you know those Soleil Springs images were not graded?

i dont..


I

Obviously we know little of the exposure or post track on any of the vids

David G. Smith
07-04-2011, 11:57 AM
I have done some more testing and you can really "Funk out" the image from the FS100 with extreme settings in the picture profiles; with increased banding very noticeable. I have run across it particularly when pushing the color depth settings around. However, with moderate adjustments to the picture profiles, I have not run across much banding and have been very please. I have been evaluating my images after the first step of transcoding to ProRes, and not taken them to delivery codecs yet and have not shot in every possible extreme of lighting condition of course. The camera is far from perfect, and extremes of image control, in-camera or in post, or extremes of lighting when shooting can definitely cause some issues. However, it is still a very good camera, and very flexible. I like it.

morgan_moore
07-05-2011, 12:26 PM
I tried to test roll off today here we see super knee (105%) vs 80% knee, certainly "SN" loses a stop or two DR (the images are not the same exposure level) but I think the highs do roll off a little better

First out of the camera and then with the blacks crushed in PS levels

What we really see both images basically drop off a cliff

I do however think my therory that flat profiles have a cost in the 8bit space is correct however

SN
36307
80
36308
crushed SN
36309
chushed 80
36310

Postmaster
07-05-2011, 12:50 PM
Now that´s scary.

Just came back to my computer after shooting a paper roll with different knee settings including your super knee - and than I saw your post Morgan.
Had the same results.

I starting to sort my PPs with different knee settings now.

Frank

nyvz
07-05-2011, 01:07 PM
Looks like the hard vertex in the gamma response at the knee point is pretty visible in both of those settings, all contrast and detail above the knee point looks pretty screwed up and unnatural. You might want to try some new settings... I played around with this for a while on my FS100 and am pretty sure the knee settings I settled upon and posted in another thread perform better.

morgan_moore
07-05-2011, 01:23 PM
Postmaster : interesting

nyvz - Ill hunt

- you realise this is serious overexposure on purpose ?

S

nyvz
07-05-2011, 02:44 PM
Postmaster : interesting

nyvz - Ill hunt

- you realise this is serious overexposure on purpose ?

S

I'm not sure what the part you addressed to me means, but as to overexposure clearly this simple test is used to show how the knee performs and is not representative of a real world scene, but the highlight gamma it exposes is clearly indicative of how one might expect natural highlights to perform in a real scene with any kind of significant contrast. Also, sometimes we overexpose scenes for a particular look or effect, so a test of highlight gamma performance is hardly irrelevant in understanding what to expect from a particular camera or knee setting.

I did a similar test live with a black and white ramp chart and my tvlogic monitor zoomed into 80% near the area of clipping with wfm on to really understand how various knee/gamma settings perform in varying situations. What it really pointed out to me was that there were really only two knee settings for cinematone 1 that I felt were optimal and still neither were perfect and cinematone2 matrix is necessary for maintaining detail and avoiding oversaturation of colors in highlight areas.

morgan_moore
07-05-2011, 03:13 PM
Indeed im looking at getting the best performance as the camera rolls to blown overexposed white

I place a lot of white in my scenes (see the feet above)

I see the ability to have blown windows and the like as a big part of my low profile filming style

I have seen lots of dodgy highlights in other users films and wonder if they have been cranking the other way in search of wide DR (a reasonable thing to do)

I dont really want wide DR at the cost of tonal artifacting

This is CineTone 2 BTW

Ill seek out your settings unless you fancy posting them again

S

David G. Smith
07-05-2011, 03:24 PM
I appreciate your posts morgan. Let me ask, with your Super Knee, have you modified the range (Low, Middle, High) or the slope? If so, what variations, if any, are you seeing? If you haven't, what effect do you think it might have?

morgan_moore
07-05-2011, 03:37 PM
105 + 5 slope blows the highlights quicker than 105-5, (and would have a steeper curve and less artifacts in my theory)

Franky Im a little lost now beyond being convinced that the 85 area knees PP are creating plastic

NYVS post in the other thread is worth a read, he is a t 105/0 I think

But he has dialled up the color, while I have dialled all colours down to -3

im not sure I know what low/med/high you are refering too

I dont really have the toolset to do close analysis (or time)

S

morgan_moore
07-05-2011, 03:45 PM
I think its about trying to tune the setting to the native of the chip (105-0?)

Its obvious that the camera comes with setting that are non native being tuned towards DR by default (and creating artifcats)

BTW - I think the camera is a real step up from my 7 or EX1 - just trying to get the best

S

David G. Smith
07-05-2011, 06:45 PM
105 + 5 slope blows the highlights quicker than 105-5, (and would have a steeper curve and less artifacts in my theory)

Franky Im a little lost now beyond being convinced that the 85 area knees PP are creating plastic

NYVS post in the other thread is worth a read, he is a t 105/0 I think

But he has dialled up the color, while I have dialled all colours down to -3

im not sure I know what low/med/high you are refering too

I dont really have the toolset to do close analysis (or time)

S

Sorry, I got confused. The High, Medium and Low settings are for the black gamma settings. The auto knee setting has a sensitivity switch that is only High or Low. The auto knee also sets the slope automatically, which I am going to avoid.

morgan_moore
07-06-2011, 01:40 PM
Cintetone 2, Knee 105/0 colours -3

Did my first interview today.. pleased

(£49 nikon series e 35 f2.5 at 4)

Recompression by DVXuser seems to ad a little color moire that is not in the original -forehead)

36374

S

David G. Smith
07-06-2011, 01:48 PM
Cintetone 2, Knee 105/0 colours -3

Did my first interview today.. pleased

(£49 nikon series e 35 f2.5 at 4)

Recompression by DVXuser seems to ad a little color moire that is not in the original -forehead)

36374

S

Looks good. What are you doing with your black levels? I love the Nikon primes BTW, I have a set including an E series 100mm F2.8. I think the E series lenses are highly underrated.

morgan_moore
07-06-2011, 01:50 PM
cant remember black levels - camera is on charge - nothing major

S