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What will be an easy way converting digitized negative images to positive images? - Printable Version

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What will be an easy way converting digitized negative images to positive images? - Stephen Liu - 10-26-2024

Hi all,

What will be an easy way converting digitized negative images to positive images?

Steps performed by me creating digitized negative images on films

1. Use a 12" tablet as light box
2. Mount the film on film holder
3. Place the film holder on top of the tablet
4. Take photos with a mobile phone camera mounted on a tripod

I have no problem taking digitized negative images from films.  But what will be an easy way converting them to quality positive images?

I haver tried;

1. import negative image to GIMP
2. Color -> Invert

It converts it to positive image but quality is not good.

Please help or advising me the reliable method?  Thanks

Regards

RE: What will be an easy way converting digitized negative images to positive images? - Ofnuts - 10-26-2024

You can use Curves with a NW-SE diagonal as a starting point and then tweak the curve:

[attachment=12486]

(image used in example is from Wikipedia)

And if a curve works well for you you can save it as a preset.

However, if you start from a smartphone picture, the picture has likely already been over-processed by the smartphone and useful bits of info have been lost. If your smartphone can do DNG or "raw", that could be a better optikon (and the demosaicing app could have pre-cooked curves for specific film types).


RE: What will be an easy way converting digitized negative images to positive images? - rich2005 - 10-26-2024

Have you tried the GEGL Negative Darkroom.  Tools -> GEGL Operation -> Negative Darkroom (in the drop down menu)

This a very quick photo, just made against a window, so a bit on the dark side.  Split view, negative is on the right side.

[attachment=12487]

RE: What will be an easy way converting digitized negative images to positive images? - Stephen Liu - 10-26-2024

(10-26-2024, 08:55 AM)Ofnuts Wrote: You can use Curves with a NW-SE diagonal as a starting point and then tweak the curve:

(image used in example is from Wikipedia)

And if a curve works well for you you can save it as a preset.

However, if you start from a smartphone picture, the picture has likely already been over-processed by the smartphone and useful bits of info have been lost. If your smartphone can do DNG or "raw", that could be a better optikon (and the demosaicing app could have pre-cooked curves for specific film types).
Hi Ofnuts,

Thanks for your advice.

I tried your suggestion but I found only one curve here, not 2 curves.

Channel: [Value] [Reset Channel]

I use Samsung Galaxy S24 smart phone.  I haven't appled any setting taking the photos.

Regards

RE: What will be an easy way converting digitized negative images to positive images? - denzjos - 10-26-2024

Used a negative from alexburkephoto and tried this :
- negative as layer
- Colours / Invert
- Colours /  Levels / Auto Input Levels
[attachment=12490]

RE: What will be an easy way converting digitized negative images to positive images? - Ofnuts - 10-26-2024

(10-26-2024, 09:32 AM)Stephen Liu Wrote:
(10-26-2024, 08:55 AM)Ofnuts Wrote: You can use Curves with a NW-SE diagonal as a starting point and then tweak the curve:

(image used in example is from Wikipedia)

And if a curve works well for you you can save it as a preset.

However, if you start from a smartphone picture, the picture has likely already been over-processed by the smartphone and useful bits of info have been lost. If your smartphone can do DNG or "raw", that could be a better optikon (and the demosaicing app could have pre-cooked curves for specific film types).
Hi Ofnuts,

Thanks for your advice.

I tried your suggestion but I found only one curve here, not 2 curves.

Channel: [Value] [Reset Channel]

I use Samsung Galaxy S24 smart phone.  I haven't appled any setting taking the photos.

Regards

The SW-NE diagonal is always there. But if you pull the ends it adds a second curve that will be you new transfer curve.

RE: What will be an easy way converting digitized negative images to positive images? - Krikor - 10-26-2024

It's always good to have other examples of this technique.
A good example is at:
https://www.dpreview.com/forums/post/58350160

"Get neutral WB in frame edge to remove most overall film tint" - This was a valuable tip in this case.

Otherwise, the well-known procedure of inverting the colors and applying a levels - auto input levels - was used.

RE: What will be an easy way converting digitized negative images to positive images? - sallyanne - 10-27-2024

I usually do the colour invert then levels. Not tried the curves one before will have to try it.
EDIT: Cool, It really works!

RE: What will be an easy way converting digitized negative images to positive images? - Stephen Liu - 10-28-2024

(10-26-2024, 11:47 AM)denzjos Wrote: Used a negative from alexburkephoto and tried this :
- negative as layer
- Colours / Invert
- Colours /  Levels / Auto Input Levels
Hi debzjos,

Thanks for your advice.

It seems no action here after selecting; - Colours /  Levels / Auto Input Levels

Please refers to the screenshot attached here.  Thanks

Regards

RE: What will be an easy way converting digitized negative images to positive images? - Krikor - 10-28-2024

(10-28-2024, 05:27 AM)Stephen Liu Wrote:
(10-26-2024, 11:47 AM)denzjos Wrote: Used a negative from alexburkephoto and tried this :
- negative as layer
- Colours / Invert
- Colours /  Levels / Auto Input Levels
Hi debzjos,

Thanks for your advice.

It seems no action here after selecting; - Colours /  Levels / Auto Input Levels

Please refers to the screenshot attached here.  Thanks

Regards

Just in case.

First you invert the image:

1- Colors - Invert;

Only then do you apply:

2- Levels - Auto Input - Levels