Gamma curves for Sony's HD F900/3 camera. (I)
Cinealta curves by Sony

This is one of two articles regarding the gamma curves developed by Sony for the HD F900/3´s. This first article talks about the gamma curves developed by Sony´s for the HD F900/3 camera, which can be found at www.cinealta.com ; the second article refers to the curves developed by Digital Praxis, based on Cineon´s logarithmic format.
Sony developed these curves to emulate the look of a Kodak 250D´s emulsion with different processes and prints on Kodak Vision. To compare these, we filmed them using an Arrilaser with the LUT application called Alice. We shall now describe the different curves:


Curve 7D25NMVA44A

This curve imitates the look achieved by the 250D emulsion with normal developing. In the grey card reading given by the vectorscope we can see how the gamma curve darkens the blacks from its default setting and also increases the range of detail in the high lights. As a whole, the curve gives us a slightly more contrasted image. We can also see how the sensitivity of this camera changes with this curve. If the normal sensitivity is around 320-400 Asa, this curve will bring it down to 200-250 Asa. The curve´s latitude offers around 8 F-stops on the diaphragm with a contrast ratio of 350:1. You can specially notice the difference on the high lights, getting to see up to 3 F-stops over the average density, losing detail in a softer way.



Standard 4 grey scale



Curve 7D25NMVA44A



Grey scale comparison


In the gray card picture, you can see how the blacks are darkened and detail is gained in the whites. This curve may need some manipulation during colour-grading to correct the mid-tones that are left too dim.



Standard 4 grey scale



Curve 7D25NMVA44A



In the image we can see the values of reflected light measured in F-stops with regards to an 18% grey

In the still-life we can see how the image obtained with the curve achieves a higher contrast and loses detail in the shadows but maintains it in the high lights even while sightly overexposed. We can also see how the colours are more saturated than usual.



Standard 4 T 5.6 1/3 Grey18 45%


Curve 7D25NMVA44A T 4 1/3 Grey 18 45%


In the following image, we can see the difference in the camera´s sensitivity with the 7D25NMVA44A curve. At the same aperture we can see how the image is underexposed with loss of detail in the shadows. A larger aperture will correctly expose the curve’s characteristics outlined above.






Curve 7D25S2VA44A

This curve emulates the look offered by the 250D emulsion pushed 1 stop. We can see how both the contrast and the colour saturation increase. The camera's sensitivity remains around 200 Asa.



Standard 4 grey scale



Curve 7D25S2VA44A



Grey scale comparison


Here we see how the blacks are darker with less detail and the whites recover some of their detail, although less than with the NM curve. The image has more contrast than the standard and the NM. The latitude is around 8 F-stops. When it comes to colour-grading we have seen how its possible to recover detail in the shadows but not in the high lights.



Standard 4 grey scale



Curve 7D25S2VA44A


In the still life we can see how both the contrast and the colour saturation increase.



Standard 4 T 5.6 1/3 Grey18 45%



Curve 7D25S2VA44A T 4 1/3 Grey 18 45%




Curve 7D25S4VA44A

The curve imitates the look offered by the 250D emulsion pushed 2 F-stops. We can see how the contrast increases (the whites are closer to the standard than S2 while the blacks remain darker) as well as the colour saturation. The camera's sensitivity remains around 200 Asa.



Standard 4 grey scale



Curve 7D25S4VA44A



Grey scale comparison


Here we can see how the blacks are darker with less detail and the whites have less detail than with the NM and S2 curves. The latitude is around 7 F-stops. When it comes to colour-grading we have seen that we were not able to recover the detail in the shadows or the high lights. A slight overexposure results in a loss of detail in the high lights.



Standard 4 grey scale



Curve 7D25S4VA44A


In the still life we can see how the contrast increases compared to the other curves, as does the colour saturation.



Standard 4 T 5.6 1/3 Grey18 45%



Curve 7D25S4VA44A T 4 1/3 Grey 18 45%




7D25L2VA44A

This curve emulates the look of emulsion 250D underdevelopped by 1 F-stop. We can observe how the contrast diminishes in comparison with the curves discussed earlier, as does the colour saturation. The camera's sensitivity remains around 200 Asa.

Standard 4 grey scale



Curve 7D25L2VA44A



Grey scale comparison


In he grey scale we can see how the compression of the whites maintains darker blacks.



Standard 4 grey scale



Curve 7D25L2VA44A


We can see the lower level of the whites and the darkened mid-tones.



Standard 4 T 5.6 1/3 Grey 18 45%



Curve 7D25L2VA44A T 4 1/3 Grey 18 45%


In case colour-grading becomes necessary, these images offer great recovery in high lights. We can also see how the colours are more saturated than wih the standard curve but a lot less than in the S curves.



7D25L4VA44A

This curve emulates the look of emulsion 250D underdevelopped by 2 F-stops. We can observe how the compression in the whites is larger, diminishing the contrast and the colour saturation with regards to the other curves. The camera's sensitivity remains around 160 Asa.



Standard 4 grey scale



Curve 7D25L4VA44A



Grey scale comparison



Standard 4 grey scale



Curve 7D25L4VA44A

As we can see the image has very little contrast



Standard 4 T 5.6 1/3 Grey18 45%



Curve 7D25L4VA44A T 4 1/3 Grey18 45%


In the still life we can see the lower level of the whites, in the jug and the scale for example.
Lets have a look now at the comparison between the different curves.

In the following images we can see the values on the grey card. We can see clearly the different handling of the high lights, the gamma and the shadows by each curve.


Comparison of the 7D25NMVA44A curve with the L series





Comparison of the 7D25NMVA44A curve with the S series





Superimposition of the L and S curves with the NM


NM curve compared with L series


NM curve compared with S series


Conclusions: These curves are useful tools to give images a more cinematographic look as well as greater control of detail in high lights. In general the images do not require a thorough colour-grading process and can be viewed directly on the monitors. In my opinion the NM curve provides excellent results in exteriors, with good latitude, very little noise and intense colours.

These tests are a reference for anyone who will want to use them. In any case I recommend carrying out your own tests, adapting them to your needs. In Cinealta's website we can see different images shot using these curves and a detailed explanation of their development.