Frame coverage influences image contrast and colour cast

All about SilverFast HDR and HiRepp (48bit HDR processing)

linjie
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Frame coverage influences image contrast and colour cast

Postby linjie » Tue Sep 13, 2016 8:01 pm

Hello everyone!

I am a new user of Silverfast HDR package. My main objective of purchasing this software is to obtain a consist and faithful base negative to positive conversion of a selection of film stocks that I use. I will then import all of the conversions into Lightroom for further fine tuning and subjective image controlling. I use a DSLR to digitalise all my films and then use MakeTiff to convert them into linear TIFF files. I then import all linear TIFFs into Silverfast HDR to make conversion. However, I realised there are significant contrast, dynamic range and colour cast differences of deploying different frame coverages, e.g., frame outside the picture or inside the picture. Please see screenshots.
I understand the correct way is put the frame inside the picture but some particularly underexposed images has unnatural boost in contrast and saturation. In some cases when a well exposed film scan is converted with frame inside the picture. It often gives subtle increase in contrast and colour correction which results are satisfactory.

So my question comes back to my main objective. What is the correct way / process to obtain a consist and faithful negative to positive conversion in Silverfast HDR? Particularly with DSLR digitising method. Is there some setting that I am missing?
Many thanks
Linjie
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LSI_Ketelhohn
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Re: Frame coverage influences image contrast and colour cast

Postby LSI_Ketelhohn » Fri Sep 23, 2016 4:56 pm

Dear Linjie,

You can adjust the highlights and shadows of the input image in the NegaFix expert settings' extension tab.
That might be what you need to compensate this effect.
Generally the red frame should sit tightly around the image.
Screen Shot 2016-09-23 at 17.30.48.png
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Additionally you can adjust the transformation curves in the Curves tab and save them as individual film profiles.

Kind regards,
Arne

linjie
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Re: Frame coverage influences image contrast and colour cast

Postby linjie » Fri Sep 30, 2016 11:44 pm

Thank you very much Arne for your reply.
What do you mean by "Generally the red frame should sit tightly around the image."?
Kind Regards
Linjie

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LSI_Ketelhohn
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Re: Frame coverage influences image contrast and colour cast

Postby LSI_Ketelhohn » Fri Oct 07, 2016 4:22 pm

Dear Linjie,

The Histogram is based on the red scan frame.
If you place it outside the image you get wrong values.
In some cases this can cause color casts.

Kind regards,
Arne


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