Knee point, Slope & Cinegamma questions at DVinfo.net

Simon Denny · November 28th, 2009, 08:37 PM

Ok, I'm playing around with my Sony F350 and trying to get the top end whites from clipping but still keeping enough luminance in the over all shot.

I see some beautiful footage on Australian Tv where the overall skin tones are still bright but with the top end whites not completely blown out, something I what to achieve in my shooting.

I have search high and low for some info on the Sony f350 Cinegamma's with the Knee, slope engaged but have come up with nothing that I'm after.

Question: With the knee point, turned on and at a setting of 90 does this soften the image? and what shoud the knee slope be set at?

Any other info on this subject would be great.
I have looked at the Alan Roberts setting for the 700 and thought maybe I could mimic this on the 350 or something similar.

Cheers

Alister Chapman · November 29th, 2009, 02:52 AM

The 700 and F350 are very different and 700 settings don't really work with the F350.

The Knee does not work with the cinegammas. Cinegammas are designed to be graded, they maximise dynamic range while keeping mid tones reasonably neutral to make grading easier. The images they produce, straight from the camera however often look flat and uninteresting, this is a result of taking a high contrast scene and compressing the highlights and lifting the blacks. If your after a "look" straight from the camera you are probably better off with the standard gammas.

The knee is crucial to highlight handling with the standard gammas.

The image beneath the knee will not be softened. The detail in the parts of the image being compressed by the knee is controlled by the knee aperture setting. Standard gamma 1 is a little noisy and gives an image with deep blacks. Standard 2 gives a less contrasty image than 1 but has less noise. Try bringing the knee point down to 80 or 85, I normally leave the slope at 50.

Simon Wyndham · November 29th, 2009, 05:19 AM

Quote:

I see some beautiful footage on Australian Tv where the overall skin tones are still bright but with the top end whites not completely blown out, something I what to achieve in my shooting.

Depends on how they shot it and whether they used reflectors etc to help them out and whether they graded or not.

If you are using the STD gammas then using the knee point switched on is a good idea. As Alister suggested around 85 is a good setting. But be careful to tally this with your skin tone exposure. You don't want skin tone to fall above that 85% exposure or the tonal range will be compressed.

There isn't really one gamma to use for all situations though.

Simon Denny · November 29th, 2009, 06:17 AM

Thanks guys,
I have noticed that using anything lower than 85% as you mentioned Simon produces compressed images and that using around 90% seems to retain some detail in the top end.
Yeah I realize there could be a host of other factors in producing these shows but the one show that stood out for me was a cooking show shot by channel Ten here on the beach. The
images being produced really held together over the whole range and this got me thinking that some sort of keen settings had to be used to retain such a clean image as our skies here in Oz are not very forgiving with shooting in at times and especial on the beach. Also they would have been using 2/3rd in chip cams as opposed to the 1/2" f350.

Forgot to say that using the gammas is a great place to start and that most of my shooting seems to be outdoors. I have had great success in cinegamma 1 but at times cinegamma 3 I also use

Thanks

Uli Mors · December 4th, 2009, 08:08 AM

i just invested into a field lcd + waveform monitor - very helpful, because you will see how and what elements do clip in your picture.

What I found with my pdw330 as well: my blacks were always to high, but there is no way to correct that onlocation without a waveform monitor.

Since that experience I take a battery driven lcd+wave with me if possible.

Also, german broadcasters (they start HD production now) recommend using a waveform monitor for "better" programs.

Regards

Uli

November 28th, 2009, 08:37 PM	#1
Simon Denny Trustee Join Date: Jul 2007 Location: Australia Posts: 1,409	Knee point, Slope & Cinegamma questions Ok, I'm playing around with my Sony F350 and trying to get the top end whites from clipping but still keeping enough luminance in the over all shot. I see some beautiful footage on Australian Tv where the overall skin tones are still bright but with the top end whites not completely blown out, something I what to achieve in my shooting. I have search high and low for some info on the Sony f350 Cinegamma's with the Knee, slope engaged but have come up with nothing that I'm after. Question: With the knee point, turned on and at a setting of 90 does this soften the image? and what shoud the knee slope be set at? Any other info on this subject would be great. I have looked at the Alan Roberts setting for the 700 and thought maybe I could mimic this on the 350 or something similar. Cheers

November 29th, 2009, 02:52 AM	#2
Alister Chapman Inner Circle Join Date: Dec 2005 Location: Bracknell, Berkshire, UK Posts: 4,957	The 700 and F350 are very different and 700 settings don't really work with the F350. The Knee does not work with the cinegammas. Cinegammas are designed to be graded, they maximise dynamic range while keeping mid tones reasonably neutral to make grading easier. The images they produce, straight from the camera however often look flat and uninteresting, this is a result of taking a high contrast scene and compressing the highlights and lifting the blacks. If your after a "look" straight from the camera you are probably better off with the standard gammas. The knee is crucial to highlight handling with the standard gammas. The image beneath the knee will not be softened. The detail in the parts of the image being compressed by the knee is controlled by the knee aperture setting. Standard gamma 1 is a little noisy and gives an image with deep blacks. Standard 2 gives a less contrasty image than 1 but has less noise. Try bringing the knee point down to 80 or 85, I normally leave the slope at 50. __________________ Alister Chapman, Film-Maker/Stormchaser http://www.xdcam-user.com/alisters-blog/ My XDCAM site and blog. http://www.hurricane-rig.com

November 29th, 2009, 06:17 AM	#4
Simon Denny Trustee Join Date: Jul 2007 Location: Australia Posts: 1,409	Thanks guys, I have noticed that using anything lower than 85% as you mentioned Simon produces compressed images and that using around 90% seems to retain some detail in the top end. Yeah I realize there could be a host of other factors in producing these shows but the one show that stood out for me was a cooking show shot by channel Ten here on the beach. The images being produced really held together over the whole range and this got me thinking that some sort of keen settings had to be used to retain such a clean image as our skies here in Oz are not very forgiving with shooting in at times and especial on the beach. Also they would have been using 2/3rd in chip cams as opposed to the 1/2" f350. Forgot to say that using the gammas is a great place to start and that most of my shooting seems to be outdoors. I have had great success in cinegamma 1 but at times cinegamma 3 I also use Thanks

December 4th, 2009, 08:08 AM	#5
Uli Mors Major Player Join Date: May 2006 Location: Germany Posts: 565	i just invested into a field lcd + waveform monitor - very helpful, because you will see how and what elements do clip in your picture. What I found with my pdw330 as well: my blacks were always to high, but there is no way to correct that onlocation without a waveform monitor. Since that experience I take a battery driven lcd+wave with me if possible. Also, german broadcasters (they start HD production now) recommend using a waveform monitor for "better" programs. Regards Uli