Jagged histograms

[DonaldSmkn]

I was wondering if I could get a basic explanation for the following.

Using 14 bit NEF files, and Capture NX2, after I move the whitepoint and blackpoint (ever so slightly) to the centre in curves adjustment, for photos where the majority of info is "clumped" in the middle, and then draw a mild "s" curve, I get a jagged histogram (which I'm lead to believe is posterization).

Can anyone explain why I'm getting a jagged histogram after adding the s curve?.

How can I avoid this?

Any help appreciated.

[ErikKaffehr]

Hi,

You still see the "jagginess" if you save the image and open in some other program? Could be a software bug/issue/feature in NX2. There may be a lot of processing involved in building the histogram and NX2 may reuse a precalculated histogram to save some time.

Best regards
Erik

I was wondering if I could get a basic explanation for the following.

Using 14 bit NEF files, and Capture NX2, after I move the whitepoint and blackpoint (ever so slightly) to the centre in curves adjustment, for photos where the majority of info is "clumped" in the middle, and then draw a mild "s" curve, I get a jagged histogram (which I'm lead to believe is posterization).

Can anyone explain why I'm getting a jagged histogram after adding the s curve?.

How can I avoid this?

Any help appreciated.

[DonaldSmkn]

Yes, emulating the same process in photoshop with a 16bit tiff results in the same jagged histogram!

[Jonathan Wienke]

Make sure you are converting the RAW to 16-bit instead of 8-bit.

[DonaldSmkn]

NEF's are pretty much unadultered - straight from camera, 14bit. There is no change of format or bit depth.

Typically, why do jagged histograms appear?

[stamper]

NEF's are pretty much unadultered - straight from camera, 14bit. There is no change of format or bit depth.

Typically, why do jagged histograms appear?

Every edit you make to an image degrades it. Thus it shows up in the histogram as a comb shape. Only if the gaps are wide then there is an issue. In jpeg capture there is 256 tonal bits and in 14 bit raw there is over 16,000 therefore there is less degradation taking place. Don't worry about it unless you are making massive changes to your image. Print it and look closely for posterization.

[DonaldSmkn]

Thanks stamper!

This will throw a spanner in the works though... What would you define as too wide?

[pegelli]

I think one should use histograms as a tool to spot potential posterization trouble, not as an end in itself. Since all pixels of the picture are lumped into one graph it is possible to have a smooth picture with a jagged histogram and a posterised picture with a smooth histogram. It just depends where the other parts of the image fall. In the end the printed picture is the one you need to closely inspect for the final assessment.

[bjanes]

I was wondering if I could get a basic explanation for the following.

Using 14 bit NEF files, and Capture NX2, after I move the whitepoint and blackpoint (ever so slightly) to the centre in curves adjustment, for photos where the majority of info is "clumped" in the middle, and then draw a mild "s" curve, I get a jagged histogram (which I'm lead to believe is posterization).

Can anyone explain why I'm getting a jagged histogram after adding the s curve?.

How can I avoid this?

Any help appreciated.

As others have mentioned, make certain that you are rendering into a 16 bit space. I use ACR rather than NX2, and with ACR the histogram is made from a cached image and a combed histogram can result unless one regenerates the histogram using all of the image. The same could apply to NX2.

[DonaldSmkn]

As others have mentioned, make certain that you are rendering into a 16 bit space. I use ACR rather than NX2, and with ACR the histogram is made from a cached image and a combed histogram can result unless one regenerates the histogram using all of the image. The same could apply to NX2.

That was it!! Realised this just now!

Cheers all!

On another note... Will exposing to the right reduce the risk of final image posterization?

[Jonathan Wienke]

Will exposing to the right reduce the risk of final image posterization?

Yes. http://visual-vacations.com/Photography/ex..._strategies.htm