Can someone explain "knee" & "slope"

[Leonard Levy]

The thing to be aware of is that optimal knee, point & slope settings vary for every shot so don't just dial in an extreme setting because it saved your overexposed window in one shot. it may screw up another one. An overzealous knee looks awful.

The problem with the auto knee in the EX-1 is that it reacts too much, and can create changing highlight exposure when panning past bright objects. Most auto knees are OK but the EX-1's sucks.

Lenny

[George Kroonder]

Just want to mention that Stu Maschwitz is doing a multi part post On Clipping, Part 1 that may be relevant.

George/

[Tom Roper]

Originally Posted by Paul Kellett

Ok this is what i did.
My willing participant (the missus) stands with her back to the window, i expose correclty for her with 65% zebras on the skin, window behind has 100% all over it, so i lower the knee point till the 100% zebras disappear, which is about 76 (originally 90).
Did i do this correctly ?

When i flick between std and this new PP i can definately see the difference when the zebras are off/out of the way.
With the std PP,from my same original position, looking out of the window is almost white,nothing there, however with the modified std PP i can see detail such as house roofs,hills in the distance etc.

Thanks guys.

Paul.

Beautiful Paul. Don't be concerned about getting it wrong. If you don't try, you won't advance your skills. You did just fantastic. And your numbers are consistent with my observations for that situation.

To build on what you just obvserved, you can try repeating the experiment with a few variations. You were already successful recovering detail that was buried in the white of the window. Now, will you attempt to enhance the contrast, the outlines within that detail? I would start where you left off with the knee point at 76. Next bring up the Knee Sat level to about 65-70 or so. You may not immediately see much change. Next, start dropping the Slope into the negative numbers, and watch for enhancement of outlines within the recovered detail. Don't worry if the 100% zebras start coming back, just work on definition of the outlines in the recovered detail for now. If you don't get any enhancement, go the other way with it. Whether you are able to enhance the outlines is about 50-50 on the probability. Don't worry, it just depends on what's there to recover. When you think you have the outline definition within the recovered details as good as it can be, move the knee point and slope together, or in combinations to get the 100% zebras back under control. Going up (into the positive numbers for the slope) makes the 100% zebras go away, but along the slope as opposed to the knee point which moves the clipping point. You also may find that when the slope and sat level are right, you can increase the knee point back up into the 90+ numbers, increasing the overall punch, while not losing the highlight detail.

I agree with Leonard that the optimal settings vary for every shot, however the sun moves predictably, and as long as you are shooting in the same direction in the same general period, the characterization that you can get really overzealous and awful with it (on the EX1 anyway) seems actually fairly hard to do.

Cine1 is a versatile, safe gamma but you can fine tune a custom look using Std3 and manual knee adjustments.

[Piotr Wozniacki]

Tom,

This has been one of the best posts ever on this forum :)

Using a very precise language, in just a few sentences you have confirmed and defined what I (not a professional videographer) managed to comprehend myself through a quite lengthy process of trial & error.

Thanks!

[Tom Roper]

Thank you Piotr, I'm blushing...but no one has done more than you to create awareness about the unique characteristics of the EX1.

About the trial and error, I applaud your diligence. In my first days with the cam, I really messed up what should have been gorgous footage at sunset. To prevent the sky from being blown out white, I reduced exposure using iris and shutter speed, but the landscape went black. Using trial and error, I adjusted gamma, black gamma and black in various combinations to brighten the landscape. What a mistake!

Since that time, some beautiful sunset footage shot straight into the sun with full tonality of the landscape, by using manual knee adjustments.

[Paul Kellett]

Tom.
Have you got a Picture Profile which you use ?
If so could you share it with us.

Thanks.
Paul.

[Ethan Piliavin]

You may find this sony info helpful as well..

http://pro.sony.com/bbsccms/assets/f...r-exposure.pdf

[Tom Roper]

Originally Posted by Paul Kellett

Tom.
Have you got a Picture Profile which you use ?
If so could you share it with us.

Thanks.
Paul.

Not too much to "share" Paul. The emperor has no clothes. I have some experience with the manual knee settings, because the need was urgent. All the other settings are a work in progress subject to change. So with a few exceptions, they are mostly the defaults. (I have learned more from your backfocus video.)


***************************************

Profile Name: Outdor 24

Matrix
Setting: On
Select: Standard
Level: +4
Phase: 0
R-G: 0
R-B: 0
G-R: 0
G-B: 0
B-R: 0
B-G: 0

Color Correction
Setting: Off

White
Offset White: Off

Detail
Setting: On
Level: -13
Frequency: 0
Crispening: 0
H/V Ratio: 0
White Limiter: 0
Black Limiter: 0
V DTL Creation: Y
Knee APT Level: 0

Skin Tone Detail
Setting: Off

Knee
Setting: On
Auto Knee: On (by default if no problems)
Point: 90
Slope: 0
Knee SAT Level: 50

Note: Manual adjust if situation dictates it, backlighting, shooting toward the sun etc.

Gamma
Level: 0
Select: STD3

Black: -5

Black Gamma: 0

Low Key SAT: 0

[Tom Roper]

Originally Posted by Ethan Piliavin

You may find this sony info helpful as well..

http://pro.sony.com/bbsccms/assets/f...r-exposure.pdf

Thanks Ethan.

That's the best explanation for the adjustments. It's very simple after reading.

[Dennis Schmitz]

Originally Posted by Tom Roper

Profile Name: Outdor 24

Matrix
Setting: On
Select: Standard
Level: +4
Phase: 0
R-G: 0
R-B: 0
G-R: 0
G-B: 0
B-R: 0
B-G: 0

Color Correction
Setting: Off

White
Offset White: Off

Detail
Setting: On
Level: -13
Frequency: 0
Crispening: 0
H/V Ratio: 0
White Limiter: 0
Black Limiter: 0
V DTL Creation: Y
Knee APT Level: 0

Skin Tone Detail
Setting: Off

Knee
Setting: On
Auto Knee: On (by default if no problems)
Point: 90
Slope: 0
Knee SAT Level: 50

Note: Manual adjust if situation dictates it, backlighting, shooting toward the sun etc.

Gamma
Level: 0
Select: STD3

Black: -5

Black Gamma: 0

Low Key SAT: 0

My suggestions:

Try to set Matrix to OFF: less CAs!
Or/and lower knee saturation to 0-20: less CAs!
Try to set Detail to OFF: much more organic feeling, less artifacts, more film-like
Try using a Cine Gamma: eliminates white halos around high contrasty objects
Try to use a higher Black Gamma (and black saturation): much more shadow information


Dennis

[Bob Grant]

Great thread. I've read all of it and hope I've understood all of it. Now where I'm still a little confused is there's 8 gamma curves available. What's the difference between say starting with STD1 and tweaking all the adjustments to produce a desired curve and starting with say Cine4 and tweaking away.

[Piotr Wozniacki]

Originally Posted by Bob Grant

Great thread. I've read all of it and hope I've understood all of it. Now where I'm still a little confused is there's 8 gamma curves available. What's the difference between say starting with STD1 and tweaking all the adjustments to produce a desired curve and starting with say Cine4 and tweaking away.

As far as tweaking the KNEE portion, the CINE curves are fixed so this leaves you with the 4 STD ones :)

[Piotr Wozniacki]

Originally Posted by Ethan Piliavin

You may find this sony info helpful as well..

http://pro.sony.com/bbsccms/assets/f...r-exposure.pdf

BTW, if you go up one level from the page Ethan gave us the link to, you will find a lot of other useful info, too.

For instance, explanation of the KNEE APERTURE setting (to stick to this thread main subject), can be found here:

http://pro.sony.com/bbsccms/assets/f...ture_Edges.pdf

Also, those who hate edge enhancement but don't like to loose any bit of the EX1's great resolution by turning Detail off, should consider leaving DETAIL on but compensate for it only where needed, such as noise, with the CRISPening function:

http://pro.sony.com/bbsccms/assets/f..._Sharpness.pdf

Last but not least, when you want punchier image and decrease BLACK GAMMA down to the negative territory, remember to de-saturate the colours in areas affected by also decreasing LOW KEY SATURATION:

http://pro.sony.com/bbsccms/assets/f...urturation.pdf

All in all, the creative picture composing capabilities of the EX1 are anormous, but very disappointed will be somebody who believes the 6 PP's that can be saved are enough for every occasion! This is why I have my 6 PP's ready, but only use them as good starting point for further tweaking in some typical - yet not identical - lighting conditions...

[Piotr Wozniacki]

Only part of the information on the web pages linked to above, applies directly to the EX1 (they are addressed mainly to the full-pro, highest-end, Sony cameras' users). On the other hand, in the EX1's PP setting menu there are options not mentioned directly in these articles; since I cannot imagine too much of discrepancy between the tweaking capabilities of the EX1 and those of other Sony models, I GUESS this might be just a matter of the nomenclature used.

I believe I'll be expressing the needs of all EX1 users if I ask those having access to the pro models to help us identify which is which. For example:

The Y BLACK GAMMA, or LEVEL DEPEND discussed on the site in question, may have their counterparts in the EX1's BLACK LIMITER...

But wee need some firm confirmation, TIA!

[Bob Grant]

Did you manage to find the directory page to those articles?
I'm left taking stabs in the dark trying to find an index of them on that Sony site.

Yes, no Crisping in the EX1 that I can find.